GASOLINE

RC engines that use gasoline are no different in operation as those in chainsaws and leaf blowers. If you treat them properly and set them up correctly, they will run reliably. Gasoline engines come in a variety of displacement sizes, and all of them are easy to start and are user-friendly. One of the more important tasks is to set up the throttle linkage and the throttle servo’s endpoints (travel) so that the carburetor opens and closes completely over the entire throttle stick’s travel. Avoid setups where the carburetor is fully open when the throttle stick is not at full power. And remember, if your engine begins to act up and run erratically, land immediately or, if still on the ground, don’t take off. Make sure that all the screws and bolts for the carburetor and muffler are tight and then check your fuel lines, filters, and carburetor.

NO BREAK-IN NEEDED

Gasoline engines have been around for a long time, and they are viewed by many as the best choice for ease of operation. The best thing about gasoline engines is that they are designed to be run without first having to be broken in like glow engines. Bench running is not so much about breaking in your engine as it is about getting to know your engine and not being rushed at the flying field.

PROPER FUEL MIXTURES

When it comes to lubrication for gasoline engines, just like with any 2-stroke, you need to mix oil into your gas. The best thing to do is to read the instructions and follow the manufacturer’s recommendations. Typical mix ratios are from 25:1 to 50:1, depending on the oil used. Some specialty synthetics can be mixed at 100:1. There are lots of great-performing, high-quality standard 2-stroke engine oils to choose from, and if you can’t find something at your local hobby shop, you’ll find them in small-engine shops and motorcycle- and marine-equipment outlets.

“I have been flying with gasoline engines since the late 1980s, and I have enjoyed excellent performance and extended engine service while using Honda HP2 high-performance synthetic 2-stroke engine oil. I have never had any fouled carburetor passages, and even after the engines have sat idle for years, they fire right up.”—Gerry Yarrish

Regardless of the fuel-to-oil mixture ratio you use, it is important to use good-quality oil. Cheap oil can risk the health of your engine. The 40cc RCGF 40T engine is shown at the lower left.

It is very important to keep your gasoline engine fuel clean and stored in a container that has a filter in the supply line.

“After 24 years of servicing giant-scale gas engines, we strongly recommend Redline Two-Stroke Racing Oil, mixed at 40:1 for all Desert Aircraft engines. It leaves little to no residue in the engine, while lubricating extremely well. Ring grooves stay clean, eliminating stuck ring issues, and bearing life is excellent.” —Dave Johnson

CARBURETOR ADJUSTMENTS

Even when using gasoline-grade fuel tank hardware and fuel lines (Sullivan Products shown here), be sure to secure the fuel line inside and out with some clamps or cable ties, as shown here.

We all know that you don’t want to run any engine lean! This overheats your powerplant and can lead to expensive engine damage or, even worse, the loss of your entire airplane. With new engines, it is wise to use a test stand before bolting the engine to an airplane. This way, it’s easy to work out linkage setups and fuel-line clearances and to test various propellers using a digital tachometer. Set the top end for maximum rpm without going too lean in the fuel mixture. For the idle adjustment, adjust the idle setscrew for as low and reliable rpm as possible while maintaining a smooth transition to full power.

SPARK PLUGS

“Our common 2-stroke gas/oil mixture engines used in giant-scale models are pretty simple to troubleshoot. All they need are air, fuel, and spark to make them come alive. If an engine won’t start or even “pop,” you may have a spark issue. There are two types of spark-producing accessories on our engines, Magneto and ignition module, but before you dig any deeper, check out the spark plug. Is there fuel present on the electrodes? Also, what is the condition of the spark plug? There have been times when my engine would not start due to carbon bridging—a carbon deposit between the ground and center electrode. This is a good indication that you are running an oil-rich mixture. Once removed and cleaned, you’re back in business.”—Sal Calvagna

PROPER FUEL LINES

“Always use only a gasoline-grade fuel tank, fuel lines, and fittings. You might get away with not doing so once or twice, but if you use a silicone ‘glow fuel’ system setup, the gasoline will degrade it. Eventually, the tank stopper and fuel lines will begin leaking, or worse, the goo in the tank will clog your carburetor. Always use Tygon or other fuel line specifically designed for gasoline. Even when using the correct type of fuel line, remember that, over time, they will become hard and lose flexibility. It is a good practice to change internal fuel tank ‘clunk’ lines because of this. Don’t forget, also, to secure your lines with tie wire or zip-ties.”
—Kevin Siemonsen

If your gas engine suddenly becomes harder to start and the carburetor more difficult to adjust, check the internal fuel screen under the side plate. Chances are that it is dirty. So clean it or, better yet, replace it with a new one.

While setting up your gasoline engine and adjusting the carburetor settings, it is best to bench-run the engine before installing it in your giant-scale airplane.

MULTIENGINE SUCCESS

“The most important thing to consider when flying twins is engine reliability. I have hundreds of flights on my P-38 and my Black Widow and have never suffered an engine-out. This is because I take the time to set the engines up properly. To keep the engines running reliably, you must supply them with clean fuel. I see it all the time at the flying field: An engine quits because the filter screens inside the carb are clogged and fuel flow suffers. I always use two filters in my fuel container: a felt clunk filter and an in-line paper filter. Clunk filters backed up with in-line filters between the engines and the model’s fuel tanks are standard equipment on all my models. Clean, well-filtered fuel is also very important for glow-engine aircraft. I use industrial-grade filters that you can buy at most small-engine and lawn-mower shops. They are good insurance and should always be used.” —Nick Ziroli Sr.

GLOW

The typical model airplane engines used for decades, glow engines using methanol-based fuel are the gold standard for all sizes of model airplanes. From small .049ci to over 2ci (and larger) displacements, glow engines get the job done. In simple terms, 2-stroke glow engines are popular because they have relatively few moving parts, do not require a separate ignition system, and are easy to start and maintain. When properly broken in and tuned, they produce amazing power.

The proper care and feeding starts with the break-in, and this will take several tanks of fuel, depending on the type and brand of engine. The type of engine you have is usually identified with three letters (ABC, for example), which refers to the kinds of materials that the engine’s piston and sleeve assembly are made of. “ABC” means an aluminum piston (A) fitted into a brass sleeve (B) that has been chrome-plated (C). Another popular type of glow engine is an “AAC,” which refers to an aluminum engine (A) fitted into an aluminum sleeve (A) that has been chrome-plated (C). Some engines use simple aluminum pistons, while others can be equipped with a steel piston ring, so it is always best to follow the engine manufacturer’s recommendations for break-in.

BREAK-IN

Glow engines come in various sizes and setups. This Evolution .60 2-stroke comes with a separate high-end needle valve behind the engine. It is connected to the carburetor with a short length of glow-fuel-compatible fuel line.

Engine break-in is the process of slowly conditioning the internal parts of the engine so that they fit more precisely together. Even though some manufacturers suggest that you can break in your engine while flying your model with a rich fuel mixture, it’s a lot safer—and you will have more control over the first few initial engine runs—if you run it on the ground with the airplane secured by the tail. Keep your glow engine fed with clean, filtered fuel. Install a fuel filter between the engine and the fuel tank, and use another filter in your fuel-supply container.

At the end of the day, empty your fuel tank and run out the last bit of fuel in the tank by running the engine. Never leave old fuel in the tank for long periods of time. Also, use some after-run oil after the last flight of the day. Adding a few drops down the carburetor and into the glow plug hole will lube the piston and sleeve assembly and prevent corrosion. And if your engine has been running properly and suddenly quits or it won’t readily start up, replace the glow plug.

Once your airplane is built and your engine installed, be sure to use a quality fuel and use the same nitro percentage during break-in that you intend to fly with.

Regardless of the size or brand of glow engine that you install in your airplane, it is very important to break in the engine before you use it to power your model.

“For break-in, use fuel with the same nitro percentage as you plan to fly with. Why? Generally, the more nitromethane a fuel contains, the higher the cylinder-head temperature will be. Higher cylinder-head temperatures mean greater expansion for the upper cylinder and, to some degree, the piston. If you break in an engine with 5% nitro fuel, it will actually be too loose when 15% nitro is used because the cylinder expands faster than the piston as temperatures increase.”—Dave Gierke

CARBURETORS

When breaking in an engine, it is important not to run an ABC engine excessively (slobbering) rich. This is because the engine will run far cooler then designed to at normal operation. The engine’s internal clearances are tighter when cold. Running the engine below designed operating temperature will promote premature wear. It is best to use a tachometer to read the engine’s speed while leaning out the high-end mixture. When you get to a point where further leaning creates no further increase in rpm, stop leaning the needle. Now, turn the needle clockwise to richen the mixture to produce a 200 to 300rpm drop.

“If you don’t have a tachometer, you can also perform the ‘pinch test.’ At full power, start leaning out the fuel mixture and then pinch the fuel line. The engine should momentarily speed up. Keep doing this until the engine stops speeding up when you pinch the fuel line. Now richen the needle setting a few clicks richer, and you are good to go. As a last resort, you can raise the nose of the airplane vertical and see if there is any difference in engine rpm. If the engine rpm lowers (‘sags’) with the nose up, the engine is too lean. Richen the needle a few clicks, and repeat.” —Kevin Siemonsen

PROPELLERS

“To minimize vibration, always balance your propellers and never try to repair or glue a damaged one. Vibration increases wear and tear on the engine’s bearings as well as the rest of your airplane’s parts and radio equipment. Also be sure to select the correct propeller from the recommended range specified by the engine manufacturer. Running a prop that is too big can lead to overheating, while a propeller that’s too small can allow the engine to over-rev, further affecting overall performance. Again, follow the instructions, and experiment with size and pitch values to fine-tune your airplane and engine combined performance. For safety while starting your engine, use an electric starter or a chicken stick.”—John Reid

ELECTRIC

The best way to keep your glow engine happy and running reliably is to use a quality fuel and install fuel filters in both the model between the tank and the engine as well as in the fuel supply line used to fill the tank. A Du-Bro Products filter is shown here.

More than ever, we are today enjoying a true golden age of RC electric flight. The amount of quality motors, batteries, controllers, and connectors seems limitless as are the types and sizes of airplanes you can fly with electric power. Even though there are plenty of ready-togo packages where you get everything needed in one box, some can find it difficult to get started. If you’ve never tried an airplane with clean electric power, here are some basics points that you need to know.

To be successful, you need to look at your model’s entire power system as a whole—one that will work together for maximum power and efficiency for the plane you are flying. And you have to understand how much power is needed to fly your plane safely. Whether you’re flying a lightweight microflier or a large 3D aerobatic plane, its performance is based on the amount of power that it develops relative to its ready-to-fly weight. If you are putting your plane together with a separate airframe and power-system components, then you have to know what will work together.

WATTS PER POUND

If a nitro-burning glow engine had a heart, it would be its glow plug. There are several types available, so start with your engine manufacturer’s recommendation.

This categorization is a loose, flexible way to estimate the amount of power that you’ll need for a specific-size airplane while giving the performance required for safe flight. The rule is really just a guideline to determine how many watts of power are needed per pound of airplane weight and is expressed as W/lb. Here are some commonly accepted numbers (fast fact: 746 watts = 1hp):

• 50 W/lb. or less—very lightweight micro RC and slow fliers
• 50–75 W/lb.—sport powered sailplanes and gliders, basic trainers, lightweight scale planes, vintage RC fliers, and RC Assist-Free Flight designs
• 75–100 W/lb.—basic sport fliers, intermediate aerobatics, scale low-wing designs, and medium-size warbirds
• 100–150 W/lb.—advanced aerobatics, pattern flying, 3D planes, larger warbirds, and jets
• 150–200 W/lb. or more—unlimited 3D aerobatics, warbirds, and large jets

Brushless motors have all but eliminated the use of older, brushed motors. When it comes to setting up your electric airplane, the motor that you use needs to be compatible with the rest of your power system.

CHARGING AND C RATINGS

Compared to the NiMH and NiCd, the lithium polymer (LiPo) battery packs have totally altered our definitions for power and flight duration. Where the older types of batteries offered 1.2 volts per cell, (1V under load), LiPo cells offer a nominal voltage of 3.7 volts per cell, and they provide much larger capacities (C ratings) along with an impressive weight saving. More voltage, more capacity, and lighter wing loadings have really improved our airplanes’ flight performance.

Unlike other types of batteries, LiPo batteries can be stored for one to two months without significantly losing charge. LiPo batteries should not be trickle-charged, and the typical maximum and minimum voltage for LiPo cells should be 4.23 and 3 volts per cell, respectively.

Great care is required when using LiPo battery packs. Overcharging a LiPo battery can cause the pack to burst and vent violently and can cause the pack to catch fire. As for overdischarging, most speed controls allow you to set a low-voltage cutoff or use the default, which varies by manufacturer. Three volts is the absolute minimum anyone should use as allowing LiPo cells to go below this voltage will damage them. As with any high-energy electrical equipment and battery packs, you should always carefully follow the manufacturer’s instructions for proper use.

“LiPo batteries must be properly charged with appropriate chargers to extend their life span and optimize their capabilities. Many manufacturers now produce packs that can be charged at very high rates and discharged at extreme rates. It’s common to see charge rates listed as 5C or higher and discharge rates at 45C continuous and even 90C bursts. For the absolute best service from your packs and to increase their longevity, it’s still best to charge at the 1C rate (example: 3.3A for a 3300mAh battery). Discharges are best kept within the continuous discharge rating and bursts only used for emergencies. Proper chargers should provide constant cell monitoring and balance charge capabilities.”—Greg Gimlick

The fuel tanks for electric-powered airplanes are the battery packs. They are available in various voltages and capacities. Knowing their C-ratings is also very important.

For electric-power systems, the speed control that you use needs to match the requirements for your motor and the type of airplane performance you are looking for.

BALANCING BOARDS

“Never charge a LiPo pack without the balancing board plugged in. There is no reason to charge without balancing a pack. This keeps all the cells even, allowing them to work together with less stress on each. A balanced pack will always outlast a pack that has never been balanced. Keep this in mind: Almost every new charger has balancing ports for keeping the packs balanced.”—John Reid

ARMING SWITCHES

An excellent way to make operating your electric airplane safer is to add an arming switch to your power system. It is a simple way to safely install your battery pack without bringing the speed control online until you get to the flightline and are ready to fly. These switches and plug-in connectors are made by a number of manufacturers and are easy to install.

“While working on the workbench, another excellent safety tip is to remove the propeller from the motor. This way, should you accidently switch on your power system or bump the throttle stick while the radio is on, the propeller won’t cause any damage or injury.”—John Reid

BOTTOM LINE

Always use a balancing board when charging LiPo battery packs. There are several types available, so matching the connector to your battery pack shouldn’t be a problem.

As with anything else about our hobby, before you make a major purchase, you first need to know the basics. It is always good to ask friends who have used the power system that you are thinking about and see how they liked it. And when it comes to accessories and hardware, don’t be price-driven; look for the best recommendations and pick the best quality you can use within your budget. Match your engine- or electric-powered system to the airplane that you want to fly, and treat it with care so that it lasts a long time.

The post Pick your power: electric, gas or glow! appeared first on Model Airplane News.

Poorly constructed motors can throw magnets and cause extreme current spikes that will destroy a speed control.

Quality Matters
This pretty much covers everything. Quality motors, connectors, speed controls, installation, solder joints, etc., but let’s talk about components. When encountering speed control problems, we don’t often think about whether they might have been caused by a cheap (poorly made) motor, but it can and does happen. I recently experienced a catastrophic failure in a foam jet that caused the speed control to melt and actually burn its way out of the bottom of the aircraft. Parts of it were left inside, but it unsoldered itself and melted completely. Upon post-mortem inspection, I found that the magnets inside the motor were unevenly spaced and one had actually come loose and been chewed into pieces as the motor spun. The funny thing about electric motors is when something starts to go wrong, the motor will just ask for more current so it can work to overcome it. My on-board data logger showed normal current at takeoff and shortly after, it began to climb until it spiked off the scale. This is an indication that the motor was failing and the binding of the magnet chunks caused the excessive current spike that subsequently melted the speed control. Some speed controls have over-current protection and others don’t. Look for one that does! This doesn’t guarantee that it won’t be damaged by a sudden failure like mine, but it just may help save the speed control. This was an expensive failure due to a poorly made motor.

BE COOL!

The speed control in this foam jet is jammed into the nose, so it’s fully insulated and gets no cooling air. With the heavy load from the motor and too many servos, this will overheat and die quickly.

Install your speed control in a place where you can get maximum airflow across it. Remember that if you let cool air into the fuselage, you have to provide a place for the air to get out too. That exit hole should be about twice the size of the inlet hole. Heat is the enemy, so the cooler you keep your speed control, the happier it will be.

Eleven servos and an onboard LED lighting system overtax the speed control’s BEC.

SIZE MATTERS
The quickest way to get experience buying speed controls is to buy them too small for the application—meaning the motor voltage and current requirements along with the BEC (battery eliminator circuit) requirements if you’re using one. If you’re sizing your speed control based on the maximum requirements of the system and you’re just barely meeting them, go to the next size up. If you can use one with a heat sink, do so. If your BEC requirements match or exceed the ratings of the speed control’s BEC, then choose a different speed control or disable the BEC and use appropriate receiver power. Remember, if your BEC fails, you lose the airplane.

Proper Soldering

A good soldered joint between the wire and 6mm bullet will handle a lot of current. Note that there is no excess solder running all over the outside of the bullet and the joint is shiny clean.

Many of the connectors in our electric power systems need to be soldered to wires. Always use properly sized wire gauges and quality connectors. Even the best soldering job can’t make up for bad wire and poorly made connectors. A properly soldered joint is shiny! Your components can’t be too clean, so clean the components before trying to solder them. Your fingers will get oils on everything, so be careful with what you touch. Tin both surfaces before joining them and then use just enough heat to let the solder flow between the two pieces. If the iron is oversized and too hot, it will end up being a dark, burned joint. If the solder flows and ends up nice, shiny, and bright—you’ve been successful.

Wiring Basics

This is a big motor requiring a large speed control and unfortunately, this one isn’t up to the task. Adding to the problems is the small gauge wire and adapter using uninsulated bullets. This system was caught and changed before there could be a problem.

A question I often hear is, “Is it better to lengthen the wires from the battery to the speed control or to lengthen the wires from the speed control to the motor?” Online forums are full of ideas, opinions, conjecture, and debate over this question. Let me give the simple answer first; it is better to lengthen the wires from the speed control to the motor and keep the battery wires as short as possible. That’s it, plain and simple.

The debate arises over resistance and inductance. It’s argued that using a larger gauge wire reduces the resistance, making Recipe for a Cooked longer battery wires acceptable. While it does reduce resistance, it doesn’t take into account the increased inductance it causes. Proponents of lengthening the battery wires say that can be overcome by adding additional capacitors to the front of the speed control. This is a patch, not a fix. The speed control comes with capacitors installed as determined by the manufacturer for its intended application. Without specific knowledge on current and how good the flyback diodes are, along with the switching speed of the FETs, voltage rating of the FETs, and types of FETs, you’re grasping at straws. If you do know those things, you’ll still need to do a lot of math to figure out the appropriate caps to add.

Here are quotes from AstroFlight’s Bob Boucher on the topic of which wire to lengthen:

• •Wire resistance may rob you of a bit of power, but it will not destroy your speed control or motor.
• •Wire inductance will not damage your motor nor will you be able to detect any effect even with 100 feet of wire.
• •Wire inductance will kill the mosfets in your controller and may even blow the caps. Ed. Note: Bob is comparing inductance in the motor to speed control wire with inductance in the speed control to battery wire.
• •You must keep battery wires as short as practical. Short means one foot or less, brushed or brushless makes no difference.

Bob is better known as “AstroBob,” former owner of AstroFlight and holder of a patent on electric flight. When AstroBob talks, I listen. Always lengthen the wires from the motor to the speed control if needed. The best possible solution is to keep all wires as short as possible, but we know that’s not always easy when you’re doing that special scale project.

NEATNESS COUNTS

All of these unsecured wires flopping around right over the receiver antenna will cause trouble. There is also 18 inches of wire from the battery to the speed control, and that’s WAY too much!

Remember what your mother told you, “neatness is important.” A jumble of wires just stuffed into a fuselage can cause many problems, especially if they are unsecured and flopping around on top of your receiver antenna. We have become overly secure with our robust 2.4 systems, but wires moving around in close proximity or touching the antennas can and will cause reception problems. If you have so much wire that you need to bundle them or tie them up, take the time to trim them to the proper size. This makes the plane safer, but also shortens wires and decreases resistance. This counts whether it’s for your motor/speed control or servos.

Mismatched connectors are ALWAYS a bad idea.

Connectors & Adapters

Note the securely attached speed control for this big power system and how the connections are well insulated and secured. Short wire runs and a protective grommet in the firewall, where the wires pass through, ensures no shorts over time.

An improper extension made by jamming a bullet into the EC5 connectors. Great connectors ruined by a bad idea.

A homemade parallel battery connector in a plane; wire nuts belong at home, not in your plane.

There is no standardization between connector types, so most of us end up using an adapter at one time or another. Be sure to wire and solder them carefully. Double check the adapter before using it. The goal in electrics is to reduce the possibility for increased resistance in our circuits. This causes heat and wasted power. It’s best not to use an adapter, but if it’s necessary, be sure it’s properly sized and constructed. Wire nuts have their places in home wiring construction, but NEVER belong inside our aircraft.

Check your manufacturer’s website to see the limits of their connectors. If you’re pushing the limits of your 4mm bullet connector, then go to a 6mm size. The same applies when you’re using EC3s or whatever brand. You want the most surface contact and least amount of resistance you can get for maximum efficiency from your system.

NEVER mismatch connectors. I’ve seen Dean’s Ultras jammed into female bullet types and that is a recipe for disaster. I’ve also seen spade plugs shoved into the grooves between the contacts on a male bullet connector. Likewise, alligator clips have no place in an electric airplane. They may seem like a universal fix, but it’s actually a universal mistake. All of these things can be inefficient, but more importantly—they are all dangerous and create a fire hazard.

MOUNT IT SECURELY

It’s not always easy to find the right place to securely mount the speed control, but it’s absolutely necessary. Some larger controllers come with mounting brackets so they can be screwed to the front of a firewall, etc. Most smaller controllers depend on you to figure it out. Velcro is the usual method of choice and works well. Be sure it is secure though. If in doubt, use industrial strength versions or rigid lock tabs. Whatever you do, don’t allow it to flop around inside your plane held only by the wires.

BOTTOM LINE

No one wants to cook their speed controllers! As with everything else involved in our hobby, it’s the small details that matter the most. Avoid these common mistakes and you’ll maximize your airplane’s efficiency and greatly lengthen its lifespan.  –BY GREG GIMLICK

The post Don’t cook your ESC! appeared first on Model Airplane News.

Even though there are plenty of plug n play packages out there where you get everything needed in one box, the newcomer can find it difficult get started. Whether you are a beginner or an experienced RC pilot, if you’ve never experienced an airplane with clean, quiet electric power, there are some basics you need to know to be successful. Let’s get started.

Today, there are all types and sizes of electric powered models, take your pick.

The first thing that you need to understand with electric airplanes is you have to look at the entire power system as a whole. One that will work together for maximum power and efficiency for the plane you are flying. And with that, you have to understand how much power will be needed to fly your plane safely. Whether you’re flying a lightweight micro indoor flyer or a large 3D aerobatic plane, its performance is based on the amount of power it develops relative to its ready to fly weight. If you get an ARF model airplane, then everything will be included and you’re good to go, but if you are putting your plane together with separate airframe and power system components, then you have to know what will work together.

From trainers to sport planes, gliders and electric ducted fan jets, the choices are endless.

Power

Electric motors, propellers and battery packs along with a suitable electronic speed controller make up your power system. But you have to use the correct combinations of equipment for your system to operate properly. To determine the power of your model’s power system, you need to measure the voltage and current while the motor is running. The three important parts of the power formula are amps (A) , volts (V)  and watts (W). But before we can talk about selecting power systems, we need to understand some very basic things about electric power.

Picking the proper electric motor and propeller is a very important first step.

A watt is the unit of electric power in the same way that horsepower is used to express power for an internal combustion engines. You produce a certain number of watts by moving electricity through a device that converts it to power. Movement of electricity through a power system is described by the term ampere (amp), and the force that causes it to move is the volt. The basic relationship between these units with the equation Watts = Volts x Amps (W=VxA.). The most important thing for modelers to understand is that you can produce watts by using a lot of volts and just a few amps or you can use a small amount of voltage and lots of amps. It all works together. What this means is you can use a small amount of battery voltage and a large propeller diameter/pitch size or a larger battery voltage and a smaller propeller depending on the requirements of your model. And to properly power our models we can use a simple rule called the “Watts per Pound Rule”.

Watts per Pound

This categorization is a loose, flexible way to estimate the amount of power needed for a specific size airplane while giving the performance required for safe flight. The rule is really just a guideline to determine how many Watts of power are needed per pound of airplane weight and is expressed as W/lb.

•             50W/lb. or less.  Very lightweight micro RC and slow flyers.

•             50 – 75W/lb. Sport powered sailplanes and gliders, basic trainers, lightweight scale planes, Vintage RC and RC Assist Free Flight designs.

•             75 – 100W/lb. – Basic sport flyers, intermediate aerobatics. scale low-wing designs and medium size warbirds.

•             100 – 150W/lb. – Advanced aerobatics, pattern flying, 3D planes, larger warbirds and EDF jets.

•             150 – 200 plus W/lb. Unlimited 3D aerobatics, warbirds and large jets.

–Fast Fact: 746 watts = 1 horsepower

Batteries and Charging

Having a quality multi-type battery charger is an important part of the electric modeler’s workshop.

Compared to the NiMH and NiCad (nickel metal hydride and nickel-cadmium,) battery packs we used just a few years ago, the new generation of lithium Polymer (LiPo) battery packs (often referred to as Li-poly) have totally altered our definitions for power and flight duration. Where the older types of batteries offered 1.2 volts per cell, (1V under load), Lipo cells offer a nominal voltage 3.7V per cell and they provide much larger capacities along with an impressive weight saving. More voltage and more capacity and lighter wing loadings have really improved our airplane’s flight performance.

C-Ratings

LiPo batteries must be charged carefully and with chargers designed specifically for LiPo battery packs. Though there are many new Lithium battery packs on the market with extreme charge and discharge ratings, for the best longevity of your packs you should use a 1C charge rate. (1 times the capacity of the battery) Example: 3.3A for a 3300mAh battery capacity.

Lipo battery packs are the most common used today. It is important to pick the correct one for your model’s power system.

As with most things in RC, extremely high performance RC Lipo batteries with very large capacity ratings have become very popular. Some of these high performance packs have very high charge and discharge ratings up to 5 to 15C charge rates and 45C (continuous) and 90C (burst) discharge ratings.

Safety Warning: Because of their internal chemistry, extreme care is required when using and operating LiPo battery packs. Overcharging a LiPo battery can cause the pack to burst and vent violently and can cause the pack to catch fire. As for over discharging, most ESCs allow you to set a low voltage cutoff or use the default which varies by manufacturer. 3.0v is the absolute minimum anyone should use as allowing Lipo cells to go below this voltage will damage them. As with any high-energy electrical equipment and battery packs you should always carefully follow the manufacturer’s instructions for proper use.

Fast Facts: LiPo Packs

• Unlike other types of batteries, lithium polymer batteries can be stored for one to two months without significantly losing charge.
• Lithium batteries should not be trickle charged
• Typical maximum and minimum voltage for Lipo cells should be 4.23V and 3.0V volts per cell respectively.

Another battery type of battery used today are the  LiFe or A123 (3.3V per cell). Also referred to as Lithium Iron, these are relatively more safe than LiPo cells and are often used for powering RC receivers.

Connectors

Like airplanes, battery connectors come in several styles and ratings.

Connectors are an important element in any electric power system, and you’ll find them in between motors and ESCs and between the ESC and the battery pack. The most important thing to remember is to use the proper size connector for the battery and power system being used. Most of the battery manufacturers today include connectors already attached to the power leads or at least include them in an accessory bag. Using a low quality connector or one that’s too small increases resistance in the wiring and this translates to heat and lose of power. As a rule, you should use as few connectors as you can to maximize efficiency. Many experienced modelers will eliminate the connectors between the motor and ESC by soldering the power leads directly together.

Adaptor cables help you manage your battery charger

Most brand name electric equipment has its own brand and type of connector and you need to use the matching type to charge your battery packs. You can however, simplify your life by switching all of your battery and ESC connectors to a generic one. This will then allow you to mix and match battery packs between airplanes and you can use the same charger to service your battery packs. If, the charger has the proper settings to match your packs. The most common at Deans Ultra T-configured connectors and Anderson Powerpole (APP) (also referred to as Sermos connectors). The Deans require soldering and some heat shrink tubing, while the APP connectors can be soldered or crimped onto the power leads with a special crimping tool.

At the annual NEAT Fair the electric power airplane hobby is highlighted in a very big way.

Glossary:

Ampere (Amp): The standard unit of electric current. The current produced by a pressure of one volt in a circuit having a resistance of one ohm.

Battery Eliminator Circuit (BEC): – A circuitry that allows the battery that runs the motor to also power the receiver and the servos. This is often built into the ESC

Brushed Motor: The traditional type of electric motor where brushes make contact between the rotor and the stator. The touching of the brushes essentially creates the timing and current to make the motor spin correctly.

Brushless Motor: Type of electric motor used in RC electric aircraft. Brushless motors are much more powerful than traditional brushed motors, and are commonly used in electric aerobatic aircraft. They can be inrunner or outrunner motors.

Current: The flow rate of electrical energy. Measured in Amps

Capacity:  Is a measure of how long you can draw a specified current from a battery. It is measure in Amp Hours (Ah), or more commonly for the scale of equipment used for electric flight, mill-Amp Hours (mAh).

Electronic Speed Controller (ESC):  The thing that controls how much current is given to the motor and hence how fast the motor runs. Often they have a BEC (see above) built in.  There are two main types – brushless and brushed.

Horsepower (HP): A measure of the rate of work. 33,000 pounds lifted one foot in one minute, or 550 pounds lifted one foot in one second. Exactly 746 watts of electrical power equals one horsepower.

Inrunners: Get their name from the fact that their rotational core is contained within the motor’s can, much like a standard ferrite motor. They run inside the can.

Li-Po: Stands for lithium-ion polymer battery. These are the most modern kind of battery pack being used in electric aircraft. They provide enormous amounts of power for their size, especially when used in conjunction with a brushless motor.

 mAh (Milliamp Hour): A measure of a battery’s total capacity. The higher the number, the more charge a battery can hold and usually, the longer a battery will last under a certain load.

NiCD:  Abbreviation for nickel cadmium. They are a form of rechargeable battery cells used in radio control gear as well as motor battery packs. NiCDs are being used less and less these days, as NiMH and Li-Po batteries take over.

NiMH: Abbreviation for nickel metal hydride batteries, they are the successors to NiCDs with much better performance and up to 3 times the capacity for an equally sized battery. Only Li-Pos top NiMHs.

Outrunner: The other type of brushless motor, where the outer shell, or ‘can’, of the motor rotates with the shaft. The extra inertia produces more torque, so outrunners are more powerful than inrunners and rarely are geared.

Power:   For electric models this is a product of voltage and amps and is measured in watts.

RPM (Revolutions Per Minute): The number of times an object completely rotates (360 degrees) in one minute

Voltage: A unit of electromotive force that, when applied to conductors, will produce current in the conductors. Voltage is also referred to as electrical pressure.

Watt: The amount of power required to maintain a current of 1 ampere at a pressure of one volt when the two are in phase with each other. One horsepower is equal to 746 watts. Watts are the product of volts and amps.

A power meter is a handy piece of equipment to have to check how your airplane power system is operating.

The post Getting Started with E-Power appeared first on Model Airplane News.

THE BASICS

Fuel tanks come in all shapes and sizes.

Fuel filters are worth their weight in gold! Clean fuel means no trash in the tanks.

Whenever possible, pad your fuel tank with foam rubber-it helps prevent “foaming.”

Just like the family car, the fuel tank contains the engine’s fuel supply. The tank is connected to the engine’s carburetor with flexible fuel line (plastic tubing), and a rubber stopper seals it. For a tank to operate properly, it must have a vent line that allows air to enter the tank as fuel is drawn out. It relieves the vacuum left in the tank. Model airplanes don’t always fly straight and level. To allow the fuel to flow at different attitudes, the tank has a flexible internal pick-up tube. A heavy “clunk” fitting is attached to the end of the pick-up tube to always keep the end of the tube at the lowest part of the tank. If the pick-up tube wasn’t flexible, once the fuel level dropped below the pick-up tube, the supply of fuel would stop and the engine would die.

Lengths of brass tube pass through the tank’s rubber stopper, and the fuel lines that carry the fuel to the engine slip over the ends brass tubes. The rest of the fittings and accessories help the fuel system work properly and make it easier to maintain and operate.

BAD VIBES

Making your fuel tank easy to get to makes maintenance of your fuel system easier to do.

The removable fuel tank tray can also secure your battery packs.

One common problem that can lead to your engine running lean is fuel foaming in the tank. Vibration causes this and it forms tiny bubbles in the fuel. The bubbles cause erratic fuel flow and the air in the bubbles causes the fuel mixture to lean out. The simple solution to this is to make sure to properly pad your fuel tank with soft foam rubber. Also, make sure that after time, you check the padding to see if any part of the unprotected tank is coming in contact with the model’s inner structure like a former or engine mount bolt or nut. I prefer to use rubber bands to hold the foam padding in place but you can also use tape. Make sure you don’t compress the foam too much as this will lessen its ability to isolate the tank from the vibration.

Regular maintenance is key to keeping your entire model in top condition. One way to keep a better eye on your fuel system is to make the tank removable. When there is no fuel tank compartment hatch, I make a slide-in tank tray from lite-ply and a matching set of rails inside the fuselage. This way, I can slide the tank into place and secure it with a couple of small screws. You can save more space by attaching your battery pack to the tray as well.

This system works extremely well, especially with large airplanes.

To choose the correct size fuel tank for your airplane, check your kit’s directions or check the engine manufacturer’s recommendations. You’ll want a tank that can hold enough fuel for a 15 to 20 minute flight.

TWO-LINE SETUP

Adding a fuel filter to your fuel supply line gives you double protection.

A two-line fuel system is the simplest and almost foolproof way to go. The setup requires only two pieces of brass tube, a clunk, a rubber stopper and a short length of silicone tubing. Bend one tube 90 degrees to form the vent and insert it through the stopper. The vent lets outside air in as the fuel is drained out, and it acts as an overflow indicator when you fill the tank. The second tube is the fuel-supply for the engine and the interior pick-up tube and clunk are attached to it. To fill the tank, the fuel supply tubing is removed from the carburetor and attached to your filler pump line. When the tank is full, you simply reattach the line to your carburetor. The vent line is often attached to a pressure fitting on the engine’s muffler. This arrangement helps pressurize the tank to enhance fuel flow to the engine.

2-line setup

The simplest and most trouble-free setup is a two-line tank.

THREE-LINE SETUP

In a three-line tank, the setup is just like for a two-line arrangement, but a third line is added and used to fill the tank. The third line doesn’t need an interior pick-up line and clunk, but many do add them to allow the removal of fuel at the end of the day. Before running your engine, you must seal off or cap the third line to prevent fuel from leaking out. Fuel line plugs called “Fuel Dots” are available commercially to do this, but you can also use a tight-fitting machine screw or a short piece of ?-inch-diameter brass rod material as well. In a pinch, you can use a one-inch length of ?-inch dowel.

3-LINE SETUP

Three-line tank setups allow convenient tank filling without removing the fuel line from the engine.

ILLUSTRATIONS BY FX MODELS

TROUBLESHOOTING

Properly installed, your glow engine fuel system will last a very long time and may never need to be changed. In a hard landing, however, some of its parts may be dislodged or a line can become kinked or pinched. Here are some common fuel-flow problems and fixes.

After a hard landing, the flexible pickup tube and clunk inside the fuel tank can be forced all the way forward. This can go unnoticed until the next flight when the tank stops delivering fuel to the engine in a nose-high attitude. To prevent this, solder a short piece of brass tube to your clunk. This decreases the pick-up tube’s flexibility a bit but still allows it to draw fuel in normal flying attitudes.

If your engine starts to run lean for no apparent reason, check for small pinholes in the fuel-supply lines. Check closely where ever there is a tight bend or where the fuel or line comes into contact with the firewall. To help prevent chafing at the fire-wall pass-through, drill a small hole in the firewall and use a length of brass tube in the holes. Slip the fuel lines over the brass tubes to complete the system.

If your engine begins to run erratically, debris may have gotten into your fuel system. It usually finds its way into the model’s fuel tank from your fuel storage jug, and if it blocks fuel flow, your engine will die. To prevent this, use an in-line fuel filter in the fuel supply line just before the carburetor. Install another filter in your fuel-pump line so you fill your tank with clean filtered glow fuel. Add a combination fuel clunk/filter, and you have a triple defense against dead-sticks.

The post Model Airplane Fuel Systems Explained appeared first on Model Airplane News.

Charge rates are just what they sound like. It is the amp rate at which you are capable of charging a specific battery pack. Most commonly you will see this at 1C, 2C, and all the way up to 5C. Well what is “C” in this scenario? It is the amp hour of the battery packs. While most are familiar with the milliamps, the amp hour is that number divided by 1000. So for a 5000mAh battery, 1C would be 1(5) or a 5 amp rate, 2C would be 2(5) or a 10 amp rate, and 5C would be a 25 amp rate. A 1C charge or discharge should be an hour long process. 2C cuts that time to about 30 minutes. Balancing can extend the overall time but this gives you a ballpark in terms of the time it will take at any of these rates.
Your charge rate used to make a big difference in overall performance in the days of NiMH and NiCad cells. The faster you charged the more punch you would get. This also tended to lead to less cycle life. With LiPos the difference really isn’t that obvious. It’s not a night and day performance difference charging at a faster rate. Opposed to charging packs at faster rate you would see more benefit from charging your packs just before use because you would maximize capacity. The main reason to charge at a rate that’s higher than 1C at this point is to reduce charge time: 1C = 1 hour, 2C = 30 minutes, and 5C =12 minutes. Balancing tends to be an equalizer here, though. At a 5C charge rate, it is more likely for cells to get out of balance. The farther they are out of balance the longer it takes to balance at the end of a charge cycle. This can, in turn, increase overall charge times.
Higher grade batteries can handle these rates at little to no degradation but lower grade cells have a much higher probability of failure at higher charge rates. Make sure to charge your battery according to manufacturer recommendations to ensure long life and great performance.
Joshua Barker, MaxAmps

The post LiPo C-Ratings and What They Mean appeared first on Model Airplane News.

The lithium polymer (LiPo) batteries that we use today in our electric RC aircraft are typically described using several standard electrical terms: “voltage” or “cell count”; “storage capacity”; and “current” or “discharge rate limits.” Take a look at any LiPo label and you’ll see at least these three items. These terms aren’t unique to the batteries we use in RC; they’re terms that are used in all electrical fields, so it’s important to know what they mean and to use them properly. TEXT & PHOTOS BY JOHN KAUK

VOLTAGE

A battery is composed of cells, which are connected in series and/or parallel to make up the battery. The voltage of any battery is determined by the chemical composition of the material within the battery’s cells. Nickel cadmium (Ni-Cd) batteries have a reference, or nominal, voltage of 1.2 volts per cell. Lead-acid batteries have a nominal voltage of 2.0 volts per cell. A typical LiPo cell has a nominal voltage of 3.7 volts per cell.

A battery’s total voltage is given as a multiple of the cell voltage, so six lead-acid cells make up the 12-volt battery we carry in our cars. A three-cell series-connected (3S) LiPo is labeled “11.1 volts,” and a 6S battery’s label is “22.2 volts.” At a state of full charge, a LiPo battery’s voltage will be near 4.2 volts per cell, and the cutoff, or minimum allowable, voltage is 3.0 volts per cell.

Two 5000mAh battery labels show different C-rates. The Pulse battery shows a single 45C rate, while the Turnigy shows a range from 25C to 50C. While it’s not stated explicitly, I’d treat the lower as the continuous rating and the higher as a 30-second rating. Note that neither label specifies a charge rate.

The labels for these batteries both show energy capacity in watt-hours in addition to the storage capacity in amp-hours. The E-flite label specifies a charging voltage, while the ElectriFly specs the charge current.

STORAGE CAPACITY

A battery’s storage capacity (C) is described as the amount of charge that it can deliver over a period of time while staying above the cutoff voltage, and is basically determined by the size of the battery. In general, bigger LiPo batteries have more capacity, as do bigger Ni-Cds. Capacity is measured in amp-hours (Ah) or milliamp-hours (mAh), and those are defined by the number of hours that a battery can provide a given discharge current. This means that a battery with a capacity of 1Ah is capable of providing a current of one amp for one hour before it gets to its cutoff voltage. It can also provide 500mA of current for two hours, or two amps for half an hour. Josh Barker of MaxAmps confirmed for me that the industry standard for labeled capacity is a one-hour discharge rate.

Storage capacity varies; it isn’t a constant. Increasing discharge current will decrease a battery’s capacity as will temperature extremes. It’s also worth noting that we rarely use a battery’s full capacity anyway as doing so might cause damage to it and shorten its lifespan. I time my flights so that I land when the battery is near storage voltage: 3.8 volts per cell. That leaves about 45 percent of the capacity unused, but it allows a safety margin for failed landing attempts and it’s easy on the batteries. It’s also easy on me because I don’t have to charge or discharge to storage levels once I’m done flying.

USES OF “C”

In all batteries, capacity is used to define several other rates, such as charge and discharge rates, and this is where things can get a little confusing.

Charging a battery incorrectly can damage it, so manufacturers specify a safe maximum charge rate in multiples of C. With the LiPos we use, a 1C charge rate is almost always safe and easy on the batteries. Some manufacturers specify higher charge rates. For instance, Pulse Batteries and MaxAmps specify a 5C charge rate, so I’d be comfortable using that rate from time to time. For routine charging, I stick to the gentler 1C rate because I think that it helps the batteries last longer.

The term “C-rate” is used to define the discharge current for a battery. As with charge rates, this number is specified as a multiple of C, such as 20C. Sometimes the label will show a range, like 25–50C, and sometimes it will show continuous and pulse, or 30-second rates. A continuous C-rate is the maximum discharge current that the battery can provide for the full discharge, from full charge down to the cutoff voltage, without damaging the battery. The 30-second C-rate is the discharge current that the battery can supply for short-term pulses up to 30 seconds without damaging the battery. For a 5000mAh 25-45C battery, that means a continuous current of 125 amps and a pulse current of 225 amps.

This old Astro Flight Whattmeter has served the author well over the years. Knowing current, voltage, and power allows a modeler to confirm that a power system is within its battery’s specs to avoid damage. Watt meters are available at many RC vendors.

How these maximum discharge currents are determined is a bit of a mystery to me. I’ve talked with people at various companies about it, and there isn’t a consistent answer. In most cases, the limits are defined by the cell manufacturer to prohibit excessively high currents that would damage the battery. Things like cell chemistry, cell construction, intercell connections, internal resistance, and wire size all have an impact on the final maximum current rating for a battery.

This data log from the Castle Creations Edge HV 120 in the author’s Top Flight Corsair shows voltage and current graphs for its first flight. A maximum current of about 58 amps and maximum power less than 3000W mean that the power system is well within its limits on this flight.

I try to set my models up with moderate current demands, for reasons I’ve discussed before. An advantage of doing this is that I don’t have to worry about fanciful C-rates causing problems for me. If I keep my maximum current to 75 amps or less, a battery rated at 25C is sufficient for larger planes. They’re less expensive and last a long time because I don’t stress them much.

If you’re interested in more general information about batteries, there are plenty of reliable sources on the Internet. One that I’ve found helpful from time to time is batteryuniversity.com, and MIT’s Electric Vehicle Team has a nice guide to battery definitions as well (web.mit.edu/evt/summary_battery_specifications.pdf). A more in-depth discussion of LiPo lore that relies heavily on Internet forum sources is “Learning About LiPo Batteries” by Ken Myers, available at theampeer.org.

BuddyRC AB Clips

One of the most annoying things about charging batteries is getting the JST-XH balance lead plugged into and out of a balance board. The plug bodies are small and fairly thin, and when they’re stuck in a socket, they can sometimes be hard to grip well enough to pull out easily. Resorting to a firm pull on the wires risks pulling them out of the plastic plug and causing a short circuit in the balance leads. Trust me, I’ve done it and it’s no fun.

BuddyRC’s AB Clips solve that problem, and they do it cost effectively. The one-piece molded polypropylene clip snaps tightly around the balance plug and its wires, forming a larger piece that’s much easier to grip. That makes it simpler to connect and disconnect the balance leads with no risk of damage. I’ve got them on all of my batteries now, and I haven’t pulled a wire out of a plug in a long time.

Available to fit 2S through 6S balance plugs, the AB Clips come in packages of five for a regular price of $1.95. buddyrc.com

BY JOHN KAUK

The post Battery Talk: What the Numbers Mean appeared first on Model Airplane News.

WHAT SIZE?

Starting at the top of the engine is the cylinder head. It is bolted into place and has a threaded hole in the center for the glow plug.

The area between the bottom surface of the cylinder head and the top of the piston is the combustion chamber. The bottom of the glow plug and the platinum element can also be seen here.

All model kits and ARFs have a recommended engine size range. Typically this will be something like .25 to .32, or .40 to .60, etc. You should choose an engine that is within this range, and for better climb performance you should pick an engine closer to the higher side of the range. When it comes to choosing a propeller for your engine, you should also follow the recommendations found in the engine’s operation guide.

ENGINE SPEAK

If you have never owned or run a 2-stroke engine then some of the terminology needs to be explained. Here’s a glossary of 2-stroke engine terms:

ABC– refers to the materials that make up the engine’s piston and sleeve; an aluminum piston (A), fitted into a brass sleeve (B), that has been chrome plated (C). An AAC engine is one with an aluminum engine fitted into an aluminum sleeve that has been chrome plated.

Case -the engine’s main body. Most are cast in one or two parts from aluminum, though some specialty engines are made from fully-machined aluminum stock.

Connecting rod -also referred to as a “conrod,” this is the part of the engine that connects the piston to the crankshaft. The conrod has bushings at each end and is connected to the piston with the wrist pin (top end), and is connected to the crankshaft with the crank pin (bottom end).

Cylinder head- the top part of the engine usually bolted into place with either four or six bolts or screws. A threaded hole in its center is where the glow plug is installed. The underside of the cylinder head is machined to form the top of the combustion chamber.

Ports– openings and channels machined into the sleeve and engine case that allow the transfer of the air/fuel mixture from the engine case into the combustion chamber and, after combustion, out through the exhaust.

Sleeve– the cylinder’s internal lining or ìliner.î A tubular, brass structure that houses and guides the piston, the sleeve has a flat rim flange that fits between the engine case and cylinder head to hold it in place. Port openings are machined in the side of the sleeves that align with the transfer channels in the engine case.

ENGINE ASSEMBLY

The part of the engine that the piston fits into and is guided by is the sleeve. Made of brass, it has openings (ports) machined into it to allow the flow of fuel mixture.

The crankshaft converts the up and down motion of the piston into rotation force to spin the propeller. The opening in the middle of the crankshaft is the intake port. It aligns with the carburetor’s venturi and allows the air and fuel mixture to enter the engine case through the holes in the back of the crank web.

TYPICAL TWO-NEEDLE CARBURETOR EXPLODED VIEW

With most engines, the case usually has three parts: the front housing that houses the crankshaft and main bearings, the crankcase that is the main case that the cylinder is attached to, and the back plate that seals the back of the engine. It is usually held in place with four bolts or screws and can be sealed with either a thin gasket or an internal O-ring.

The crankcase is supported in the front housing with a large rear bearing and a smaller front bearing. In less expensive engines, solid bronze bushings can be used in place of the ball bearings. A prop nut and a thrust washer hold the prop securely to the front end of the crankshaft and at the rear is a large counter-weighted web and crankpin used to connect the crankshaft to the conrod. The conrod is attached to the piston with the wrist pin and the piston fits within the sleeve, which fits into and is supported by the cylinder part of the engine case. The head fits on top of the sleeve and the space between the top of the piston and the bottom of the head forms the combustion chamber.

Depending on the design of the engine, the piston can be sealed with either a piston ring that fits between the piston and the sleeve, or the piston can be sealed with a slight taper (smaller at the top) in the sleeve. This is how an ABC engine is set up.

CARBURETOR

The piston is connected to the connecting rod with the wrist pin. A spring wire clip holds the wrist pin within the piston body.

BARREL-TYPE THROTTLE CARBURETOR

The engine’s power is controlled by its carburetor. The carburetor is made up of the main body, the throttle barrel, the high-end and low-end needle valve assembly, the spray bar and the venturi. Air enters the carburetor through the venturi opening and the amount of air is controlled by the rotating throttle barrel. A throttle arm is attached to the barrel so it can be rotated open and closed by the throttle linkage and servo.

The fuel enters the venturi through the high-end (main) needle valve and it sprays into the venture through a hole in the side of the spray bar. By turning the main needle valve in (clockwise) you lean out the fuel air mixture by lessening the amount of fuel relative to the air. By turning it counterclockwise you richen the mixture by letting more fuel flow in. The low-end (idle) needle valve is usually located at the center of the carburetor’s throttle arm and it adjusts the mixture while the engine is operating at idle to about º throttle.

It may require a thin screwdriver to adjust.

GLOW PLUG

The glow plug lights up when you energize it with a glow driver battery. It ignites the fuel mixture in the combustion chamber.

The glow plug
is used to ignite the fuel mixture within the combustion chamber. The glow plug has a 1/4-28 thread and it screws into place in the hole in the center of the engine head. In the middle of the glow plug is a coiled element made of platinum wire. The glow plug is first energized with a 1.2V glow driver battery, and then the compression of the fuel mixture and the heat generated by that compression causes the glow plug to ignite the fuel charge, much like how a diesel truck engine operates. Once the engine is started and warms up for a little while, remove the glow driver battery and the engine will continue to run. Catalytic action between the methanol fuel and the platinum in the glow plug element as well as the engine heat keep the element glowing once it has been lit with the starting battery.

BASIC 2-STROKE ENGINE OPERATION

A 2-stroke engine makes one revolution for every power cycle. As the piston moves upward in the sleeve, it compresses a fresh charge of fuel/air mixture. The compression heats up the fuel mixture and is ignited by the glow plug. As the piston travels upward it also creates a negative pressure zone in the crankcase below the piston. This draws air and fuel into the crankcase from the carburetor and into the intake port. The intake port is machined in the side of the crankshaft and it lines up with the carburetor’s venturi and it opens up to the hollow center of the crankshaft. The air and fuel travel through the hollow crankshaft to enter the crankcase.

As the piston travels downward after the fuel mixture is combusted, the con rod turns the crankshaft and this closes the intake port. The piston continues downward and starts to compress the new charge of fuel mixture. When the piston passes a bypass port this opens the port to allow the compressed mixture to flow up the transfer channel between the engine case and the sleeve. This happens just as the spent fuel mixture charge exits the exhaust port. The piston goes back up and closes the exhaust port and starts to compress the new fuel mixture charge thus opening the intake port so another new fuel mixture charge can enter the engine and start the cycle all over again. A complete power cycle requires 2-strokes of the piston in the sleeve.

CATALYTIC ACTION BETWEEN THE METHANOL FUEL AND THE PLATINUM IN THE GLOW PLUG ELEMENT AS WELL AS THE ENGINE HEAT KEEP THE ELEMENT GLOWING

ENGINE STARTING AND BREAK-IN

By removing the engine’s back plate you can see the piston’s conrod attached to the small crankpin at the rear of the crankshaft.

Don’t just bolt a brand new engine into the airplane and go flying. To produce maximum power, a fresh-out-of-the-box engine needs some special handling. The piston and the sleeve need to be gradually fitted together for a precise fit. This procedure is known as “breaking in.” If you don’t take the time to break-in your engine, excessive heat built up from friction can cause internal damage and the piston and sleeve will never seal properly.

First, install a new glow plug (the proper length and type is indicated in your engine’s instruction manual), tighten it with your fingers then tighten it down about ? turn with a glow plug wrench. Connect the fuel lines to the carburetor and fill the tank with fresh glow fuel. Use fuel with the same nitro content (typically 10 to 15 percent) that you plan to run the engine with and be sure your fuel contains at least 18 percent lubricating oil. Install the recommended prop and prop washer then tighten the prop nut with a 6-inch adjustable wrench. Close the main needle valve completely by turning it clockwise, and then open it about four full turns counterclockwise. Open the throttle fully then prime the engine by placing your thumb over the carburetor opening and flipping the prop several times. Continue until you see fuel flow through the fuel line and into the carburetor.

Close the throttle to about 1/4, attach a glow driver battery to the glow plug and use an electric starter to turn the engine over. Don’t use your fingers; if you don’t have an electric starter then use a “chicken stick” available from the hobby shop. Once the engine starts, let it warm up a little then open the throttle fully and let it run with a very rich needle setting for about 5 to 7 minutes, and then shut the engine down and let it cool off for 10 to 15 minutes. Repeat this process several times while gradually leaning out the needle-valve mixture a few clicks each time. Don’t run your engine at full throttle with a lean setting until you’ve run at least six to eight tanks of fuel through the engine.

A properly broken-in engine will run consistently without overheating and will transition smoothly from idle to full power. Try to avoid the temptation of leaning your engine to get every last ounce of power. This leads to overheating. It is always better to adjust your model for peak rpm (using a good digital tachometer), and then backing down the main needle to richen the mixture until you lose about 200rpm.

LOW-END NEEDLE VALVE

It is also very important
to adjust your engine’s low-end (idle) needle valve so your engine will operate smoothly and consistently while at idle. A properly set low-end needle valve allows the engine to transition smoothly from idle up to full power. If the engine hesitates and dies when you open the throttle, the low end is too lean. If the engine burbles, coughs and has a rough transition, the low-end needle is too rich. Make your adjustments by ? turns at a time until your engine operates smoothly and consistently.

CARE AND MAINTENANCE

Here’s a list of things to do to keep your engine happy:

• ï Use fresh, clean fuel.
• ï Install a fuel filter in your engine’s fuel system and in your fuel container.
• ï At the end of the day, empty your fuel tank and run the last bit of fuel out of the tank by starting and running the engine.
• ï Never leave fuel in the tank for extended periods.
• ï Use an after-run oil after the last flight of the day and before you store your engine for an extended period of time. Add a few drops down the carburetor and remove the glow plug so you can add a few drops into the piston and sleeve assembly.
• ï Always balance your propellers and lightly sand the leading and trailing edges to remove any sharp flashing.
• ï Never use a nicked or damaged propeller.
• ï If all of a sudden your engine won’t start up readily, replace the glow plug.

Flying model airplanes powered with 2-stroke glow engines is exciting and very satisfying. Once you learn how to operate and properly maintain these impressive little powerplants they’ll continue to earn their keep for many years to come. They are a very good investment and can be used to power several different planes.

For detailed information on 2-stroke glow engines, see Dave Gierke’s excellent books: “2-Stroke Glow Engines for R/C Aircraft, Vol. 1” and “2-stroke Glow Engines Vol. 2: Power Beyond the Basics,” available from rcstore.com.

The post Your first 2-stroke: a basic guide appeared first on Model Airplane News.

UNDERSTANDING C-RATING (IT ISN’T JUST A PASSING GRADE!)

The C-rating designation on a battery pack lets you know just how much energy you can safely pull from that pack. LiPo battery packs can release amp draw based on the requirement of the power system. However, because there is no regulator to limit the amount of power draw from the battery, the system can actually pull too much from the pack, causing it to puff up or be destroyed. This is why understanding C-rating is so critical to maintaining the health of your battery pack. The other key essential is that you need to have some way of monitoring the amount of amperage being pulled from the pack.

The designated C-rating on a pack tells us how much amperage you can safely pull from that power source. The most common one is 20C, which means that you can pull out amperage up to 20 times the size of the battery pack. A 4200mAh battery that is rated at 20C can discharge up to 84,000mA, or 84 amps.

The C-rating will be clearly marked on the label of the battery so that the pilot will know exactly what they are buying.

KNOWLEDGE IS POWER!

Using a watt meter allows you to get real-time power usage of your aircraft while the system is in use. Of course this reading is done on the ground. If you want data reading during the flight, telemetry systems are the way to go.

How do you know how many amps your power system is pulling? Purchase a watt meter and measure amperage draw of your system when it is first installed. A better way is to take advantage of many radio systems out there that are capable of real-time telemetry. By monitoring the pack throughout the flight you can easily see exactly what the power system is pulling and when it requires peak performance from the battery pack.

PRO ADVICE

Here is Mike getting his latest electric plane ready for its first flight.

Our long time contributor Mike Gantt has this to say about C-rating: “Most of us want more power, and a higher C-rated battery will ‘deliver more energy,’ and that means higher performance. The most important difference between batteries with a different C-rating is the fact that the higher rated batteries suffer less from voltage drops under load. This ability to maintain a higher and more consistent voltage is what typically generates the high performance we enjoy. This is also where my speed controller’s cut off came into play. When a lower C-rated battery’s voltage dropped down to a certain level, my speed control is programmed to shut down, which helps to save my batteries from dipping into too low of a voltage.”

Save your battery by not running at full draw all the time. While it is possible to run your battery at full C-rating, you shouldn’t. By keeping the amp draw to about 75% of the full C-rating amount, the battery will run much cooler and will last longer than if you constantly pull the amps at maximum level. If possible, try to match the battery pack to a power system that will constantly pull amps at about 75-80% of the pack’s C-rating.

In order to charge over 1C safely the charger will have to be rated for rapid charging and have a balance board for your pack.

BATTERY STORAGE

Although it is a good idea to label your batteries when they have a storage charge, it is also a good idea to always charge the battery pack with a storage charge. Then top them off the night before use at the regular charge rate.

There are some other things you can do for long-term LiPo storage that will prolong the life of a battery pack. How and where the packs are stored is perhaps the biggest factor in prolonging their performance. Keep batteries in a cool dark environment and not in a place with temperature extremes such as a car, a trailer or a non-insulated storage shed. High temperatures will destroy a battery in short order, so always keep battery packs out of the sun and heat. The other extreme is allowing packs to freeze; this will also damage them beyond repair. A refrigerator that maintains a temperature of about 40 to 45 degrees is the perfect place to store packs (but don’t use the kitchen refrigerator that has food in it!). Allow the packs to come to room temperature before using or charging them.

LiPo batteries will self-discharge at a very slow rate; but over time, they will lose their charge. Packs that go completely dead, or fall below 2.5 volts per cell, can be damaged beyond repair and become useless. Never store a discharged battery for a long period of time. Also, don’t store a fully charged battery because the cells will drift and discharge at different rates; this will result in a pack where the cells have become out of balance from one another. If left unbalanced, the cells in this battery pack will continue to drift farther apart after each charge and discharge cycle. The best thing to do is put the batteries away with a “storage charge” of about 3.85 volts. This gives each cell enough voltage to keep it stable for long-term storage. Now the cells will discharge at a similar rate and maintain a better-balanced pack over time.

Many packs get a little puffy; this can come from them getting a little hot during the flight, or many other reasons. However, a little puffiness will not harm them; the key information on the health of the battery is how well it charges and holds on to that charge. If the pack is charging ok and the battery seems to perform normal, keep an eye on it and make sure it does not get overheated. Check the temperature of the pack after the flight, and make sure there is enough airflow over it as needed. If the pack is puffed up so that all of the wrapping is very tight, with no give when you push on it, then that is a different story. In that case the battery will most likely not be performing as well as it used to with a fair drop off in charge input and discharge output. Then you likely have a bad battery that will need to be replaced.

PARTING THOUGHT

All battery labels should have a complete description of the battery size and chemical makeup, C-rating and voltage.

These tips from our pros should give you a few more good flights from your battery packs. Try them out and remember knowledge is power, or in this case more power and a longer life.

The post Increase Battery Life appeared first on Model Airplane News.

Occasionally, you may want to change the component percentage of an existing fuel, such as increasing its castor oil content. This would be advantageous for the break-in and normal operation of certain engine types (e.g., ringless iron/steel pistons/cylinders; plain-bearing crankshaft support). What are the requirements? You must know the existing oil percentage, and the quantity of the fuel to be changed.

Example

If 1 gallon (128 ounces) of the existing fuel blend contains 18% castor oil and you want to increase it to 22%, the oil content needs to be increased by 4%. \Here’s a formula that tells you exactly how much castor oil to add:

                            (F – I) x A
Ounces To Add = ————
                             100 – F

F is the final percentage of oil desired
I is the initial percentage of oil already in the fuel
A is the number of ounces you are treating.

Example:

If you have 1 gallon (128 oz.) of 18% synthetic oil fuel, and you
want to add castor oil to bring it up to 22%, then find the following:
F = 22; I = 18; F – I = 4
In the numerator portion of the formula, because there are 128 oz. in a U.S. gallon, multiply 4 x 128 = 512
In the denominator portion of the formula, 100 – 22 =78
             512
Finally, —— = 6.6 oz. (195.2 ml)

             78

There might not be enough room in a gallon can to accept the 6.6 ounces of additional castor oil. You may have to mix everything between two 1-gallon jugs. You can also use this formula for increasing a fuel’s nitromethane or methanol content. Of course, when you increase the percentage of these chemicals, the total volume of the fuel may change significantly; so recalculate the lubricant percentage based on the new total volume and modify as necessary.

ADDITIONAL INFORMATION

Many technically minded modelers may want to consult my book, “Power: Beyond the Basics (available at the rcstore.com) for additional information and techniques concerning glow fuel; some of the topics addressed include:

·         Determining an existing fuel’s lubrication content

·         Mixing your own fuel (getting the chemicals, obtaining the hardware, calculating the volumes, transferring the fuel blend, fuel use tips)

The post CHANGING THE COMPOSITION OF FUEL appeared first on Model Airplane News.