R/C models are powered in a variety of ways. Sailplanes, for example, need no power source other than nature. But they're the exception. Nearly all R/C vehicles, aircraft, boats and helicopters require something to propel them into action.
- Engine Basics
- Aircraft Engines
- Car & Truck Engines
- Boat Engines
- How To Order
What is a Glow Engine?
Electric models use small motors, powered by battery cells. Those motors should not be confused with glow engines — which are actual internal combustion power plants that form the heart of any "gas" or "nitro" powered R/C model.
Most nitro R/C models use a 2- or 4-stroke glow engine, sized specifically for that model. Typically, they range in displacement from .049 cu. in. to 1.2 cu. in. (80cc to 20cc) — a variety that satisfies virtually any model's power requirements.
Glow engines cannot be operated with the same gasoline you'd get at a filling station pump. They require a special fuel, called "glow fuel." It contains methanol as the base, with varying amounts of nitromethane to increase the energy that the fuel can provide. Oil, pre-mixed into the fuel, lubricates and protects your tiny engine as it pounds out amazing power. When you get your new engine, first examine it carefully for any obvious defects. Read the operating instructions closely. If the manufacturer suggests a specific procedure for breaking in the engine, by all means, use it!
Two-Stroke vs. Four-Stroke
You'll quickly notice that many R/C models give you the option of installing a 2-stroke OR a 4-stroke glow engine. How do you know which is best?
Two-Stroke simply means that the engine "fires" (ignites the fuel in its combustion chamber) with every revolution of the piston. Generally, they're a good place for new nitro modelers to start. Two-strokes are easier to operate, less vulnerable to problems if misused, and deliver more power for their size and weight.
Four-Stroke engines fire once with every two revolutions. They consume less fuel, sound more realistic, and provide more torque — but cost more, are harder to adjust and require more maintenance.
How does a glow engine work?
Most glow engines have a simple ignition system that uses a glow plug rather than a spark plug — so there's no coil, magneto or points. The glow plug is heated by a battery-operated glow starter; meanwhile, the modeler uses a recoil starter, Electric 12V Starter or Starter Box to turn over the engine. When fuel enters the combustion chamber, it's ignited by the heated glow plug — and with that, the engine springs to life, instantly gaining the momentum to continue running after all the starter accessories are removed.
The engine's carburetor supplies the fuel and air needed for combustion. It has several adjustments. A rotating throttle arm controls the AMOUNT of fuel and air that enters the combustion chamber. The high-speed needle valve controls the MIX or proportions of fuel vs. air at mid- to high-speeds. The idle mixture screw is similar to the high-speed needle valve, except that it controls the mix of fuel and air when the engine is only idling. When you've adjusted the high-speed and idle mixtures properly, your engine should operate smooth and steady throughout its speed range.
Tower Hobbies has many books available with helpful information about glow engine operation and maintenance.
How do I care
for a glow engine?
If you take good care of your engine from day one, it will reward you with a long life of optimum performance. Proper maintenance is not difficult. Some of the best tips include:
- Keep your engine clean.
- Keep your engine dry.
- Use an after-run engine oil.
- Use a brand-name fuel that contains at least the amount of oil recommended by the engine manufacturer.
- Use fuel with the proper percentage of nitromethane, as recommended by the engine manufacturer.
Other types of R/C engines
Models designed for first-time R/C hobbyists will not require any power plant other than an electric motor or 2- or 4-stroke glow engine. Other types of engines are used at more advanced levels of the hobby, however. For example, some R/C jets are powered by ducted fan engines, and some large-scale aircraft use genuine gasoline engines similar to those found in chainsaws and "weedeater" lawn tools.
What accessories will I need?
For whatever engine that you order (or is included with your model), check the "Accessories Needed" link on its towerhobbies.com product page. There, you can quickly find out what additional items are required to run it.
All glow engines will require glow fuel, fuel line and spare glow plugs. You may also need a muffler or tuned pipe. Most model airplanes require an engine mount, which may or may not be included with the kit. All model airplanes and many boats will also require propeller(s).
To get off the ground, your R/C airplane or helicopter needs power — whether from an electric motor, a gasoline engine, or most frequently, a glow engine. The size and type of engine will be determined by the size and type of aircraft. Helicopter engines are designed specifically for the space, weight and power requirements of R/C helicopters...airplane engines are engineered for the same criteria, applied to fixed-wing aircraft.
Choosing your aircraft engine
Some trainer models, such as the Tower Hobbies Tower Trainer 40 MKII RTF, come already equipped with a perfectly matched glow engine. That's one less decision you have to make — a big plus for many beginners!
If the model you want doesn't already come with an engine, however, you need to find out what kind to buy.
Many R/C planes as well as helicopters have names that contain a number. That number designates the class of engine which is required. Planes that are "40 size" use a .40-class engine, which includes those in the .40 to .53 cubic inch displacement range (for your convenience, all of Tower Hobbies' product descriptions list the appropriate engine range in full).
Too much power is not a plus!
R/C trainer planes are usually designed for .40-class 2-stroke glow engines, and often fly best with engines from the lower end of their recommended ranges — a .40 cubic inch engine will work fine with a "40 size" trainer. The plane's requirements might indicate that a .46 or even larger size is acceptable. But in this case, bigger is not necessarily better — the larger engines will require more throttle control from you. And you have enough other things to learn!
By contrast, seasoned pilots often gravitate toward the middle or higher end of the engine displacement ranges recommended for their "sport planes." That's because the added power gives their aerobatic maneuvers more oomph...and the pilots themselves have the experience to handle it.
What to consider?
2-Stroke or 4-Stroke?
Refer to our engine basic section for a comparison of these engine types. In brief, 2-strokes are cheaper and easier to operate, but 4-strokes offer better fuel economy and a more realistic sound.
Ball Bearings or Bushings?
Some aircraft engines feature crankshafts that are supported by bushings...others use ball bearings instead. If low cost is your priority, go with the bushing-equipped engine. If you're willing to pay a little more for an engine that will run smoother and last longer, look for an engine with ball bearings.
Ringed or ABC?
An engine's piston and cylinder assembly can have either of these types of construction.
Ringed engines use an aluminum or iron piston that moves inside an iron sleeve. The piston is surrounded by a ring that provides compression. Advantages include economy, easy starts and good power. Disadvantages? The possible need for a longer break-in period, and greater susceptibility to damage if your carburetor is not adjusted properly.
ABC engines use an aluminum piston that moves inside a chrome-plated brass sleeve. The fit of the piston and cylinder is perfected at the factory to provide excellent compression. Advantages include easy starts, shorter break-in, greater power, longer life and less susceptibility to damage from improper carburetor settings. Disadvantages? Higher price — and costlier repair, if the piston/cylinder assembly ever needs to be replaced.
What accessories will I need?
For whatever aircraft engine that you order (or is included with your model), check the "Accessories Needed" link on its towerhobbies.com product page. There, you can quickly find out what additional items are required to run it.
All glow engines will require glow fuel, fuel line, spare glow plugs and perhaps a muffler or tuned pipe. With airplane engines, you'll also need propellers — and possibly an engine mount and spinner.
Propellers come in many different sizes and shapes. Your engine's instructions will recommend appropriate sizes (as will the Accessories Needed link on towerhobbies.com for that particular engine). Sizes are given in two numbers (6 x 3, 10 x 6, etc.). The first number is the diameter of the prop in inches. The second number is the pitch, or twist, of the propeller. The larger the number, the greater the pitch — a prop with a pitch of 4 will move forward 4 inches during one revolution.
Spinners are the cones you see on the "nose" of model airplanes. Though they offer some aerodynamic benefits, they're primarily cosmetic. Spinners are available in white, black, and some colors, as well as with a polished aluminum finish. Choose whatever makes your model look best!
If your airplane kit is not equipped with an engine mount, perhaps the simplest solution to mounting is a Great Planes Adjustable Engine Mount. Their design offers enough flexibility for you to get an exact fit for almost any 2- or 4-stroke glow engine. Many engine manufacturers also offer mounts that are custom-made for their engines.
The most punishing conditions that a glow engine endures may well be those faced during R/C off-road racing.
Airplane and helicopter models soar high in the air — so, for the most part, Aircraft Engines escape abuse from the elements. But R/C car and especially buggy engines have to perform right down in the dirt.
Under normal use, all glow engines must be able to handle the stress of high operating temperatures. High-nitro car fuels turn up the heat. Add in the punishing effects of rough terrain and flying dust, and the going gets even tougher. Boat engines? They face the challenge of performing in water.
In many ways, car and marine engines are very similar to those used in aircraft. But they are not interchangeable. Many of the differences you'll see are there to give "land and sea" power plants the ability to survive harsh conditions.
Also, your options for how to start the engine include a few choices. Lots of car and buggy engines, as well as some marine engines, come equipped with a built-in recoil starting unit. This is just like the "rope" you pull to start your lawnmower — a great convenience that saves you from having to buy a 12V Electric Starter or a Starter Box.
Type and Size
Unlike R/C airplanes, cars and trucks come in a fairly narrow range of sizes — the most popular choices are 1/10 scale and 1/8 scale. So it's not surprising that there are also fewer different engine sizes to consider when you set out to equip your R/C vehicle. The 1/10 scale models most often use .10, .12, .15 or .18 cubic inch engines. Drivers of 1/8 scale machines use a .21 to .30 cubic inch displacement.
Nevertheless, there are still many different versions to choose from. For example, some chassis require an engine with a side-mounted exhaust system, while others are designed for a rear-mounted exhaust.
Engine styles also differ in the design and color of their cylinder heads. The cylinder head is the portion of the engine with "fins" that increase surface area, enabling more air to pass over the engine and carry away heat. Car and buggy power plants quickly become hot, so effective cooling is critical. But air must be able to REACH the head. So in most cases, the cylinder head sticks up and out from a hole in your vehicle's body. Because it's visible, how the head looks is only slightly less important to some drivers than how well it cools. Car and buggy engine manufacturers aim to satisfy everyone by offering a variety of cylinder head shapes, fin configurations and colors.
A few newer glow engines, have a "laydown" design that allows the engine to be fully concealed inside the body. A built-in fan unit helps cool the engine, whose reduced height lowers the car's center of gravity so it can better grip the road.
Finally, car and buggy engines must be protected from dirt and dust. If those get inside your engine, they'll cause grinding in the working parts — which increases wear and shortens engine life. Air filters must be used to trap such debris.
What accessories will I need?
For whatever car or truck engine that you order (or is included with your model), check the "Accessories Needed" link on its towerhobbies.com product page. There, you can quickly find out what additional items are required to run it.
All glow engines will require glow fuel, fuel line, spare glow plugs and perhaps a muffler or tuned pipe. With car and buggy engines, you'll need an air filters with replacement elements.
It's true with R/C cars and trucks, and it's equally true with model boats: Nitro power offers greater speed and performance than electrics — and, thanks to their sound and smoke, greater realism. Two main types of engines are used in marine modeling.
Outboard engines, found primarily on high-performance racing boats, bolt directly to the rear of the hull. The propeller, rudder and drive system are already integrated into the engine's design.
Inboard engines, such as the O.S. 18CV-RMX Marine Engine, are mounted within a compartment inside the boat's hull. They require a more elaborate drive system, called "running hardware," to get the engine's power down through the hull and out to the propeller.
Inboard Running Hardware
Running hardware can be a mystery to the novice. Power produced by the inboard engine is transferred to the propeller by a drive shaft. The shaft exits through a "stuffing box" — a tube filled with grease, which lubricates the shaft and keeps water out of the hull. Some boats use a flexible, cable-type drive shaft that eliminates a few linkages beneath the water. Other components of the system include a strut that supports the drive shaft and provides a solid mount for the propeller. Behind the propeller is the rudder, used for steering, and the water pick-up tube. This tube captures water expelled by the propeller and routes it through the engine's water jacket. Like cylinder head fins, a water jacket is a mean of cooling. It surrounds the cylinder head with cool water, which absorbs heat and then is expelled overboard.
What accessories will I need?
For whatever marine engine that you order (or is included with your model), check the "Accessories Needed" link on its towerhobbies.com product page. There, you can quickly find out what additional items are required to run it.
All glow engines will require glow fuel, fuel line, spare glow plugs and perhaps a muffler or tuned pipe and boat propellers..
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