Ball bearing engines are also more expensive, but if you can afford the difference, they are worth it. One of the nice things is that there are several new brands of ball bearing engines on the market that are very good and still in a more affordable price range. More on that later.
What Size Engine Should I Get?
In the "Airplanes" section, we advised getting a 40 - 60 size plane, but keep in mind that these numbers are only used as a reference. For a 40-size trainer, a bushed 40 engine will fly it well, likewise a bushed 60 will fly a 60-size trainer well, but if you advance in the sport, you will soon find these engines collecting dust on a shelf somewhere. For a 40-size airplane, a much better choice would be a 46 ball bearing engine. In the case of a 60-size plane, a 60 - 65 ball bearing engine would be a good choice.
The main reason for this is that with these engines you will be able to move up to more advanced planes as your skills progress. Many times I have seem a person come out to the field with a nice Sig "Something Extra", Goldberg Tiger, or other intermediate-level plane with a bushed 40 engine on it, and hear them lamenting about how they wished they had more power. So if it won't break the bank, go for a good engine.
Here is a list of engines, their street price, and a brief description:
Ball Bearing Engines (.46)
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O.S. 46AX: Price: $110 - This is the engine that is the benchmark for 46-size engines. If there's a "Cadillac" of model airplane engines, this is it.
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Thunder Tiger Pro 46: Price: $95 - The TTPro is another excellent choice. It is a close reproduction of the OS 46FX, which is the predecessor of the OS 46AX above.
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Evolution 46NT: Price: $90 - The Evolution 46NT is another excellent choice. I have used several of these with great success.
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Magnum XLS-46: Price: $70 - Magnum is another company that makes a very good engine for the budget-minded flier. At $70, it's a very good value.
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Ball Bearing Engines (.61)
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O.S. 61FX: Price $160 - Again, the Cadillac, but I wouldn't be surprised to se O.S. update this engine soon to their AX line.
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Evolution 61NT: Price: $120 - I've never personally used an Evo 61, but I have heard very good things, and with a $120 price tag, it's going to be a good buy if you're looking to save some bucks.
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Magnum XLS-61: Price: $100 - Again Magnum comes in with a good engine at the lowest price.
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Bushing Engines
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O.S. 46la: Price: $68 - OS quality in a less expensive engine. These engines are real workhorses. They don't have the power of their Ball-Bearing counterparts, but they are as dependable as they come.
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O.S. 65la: Price: $110 - Like the 46la, you get OS quality in a less expensive engine. These engines are real workhorses. They don't have the power of their Ball-Bearing counterparts, but they are as dependable as they come.
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FUEL TANKS
Let us now assume that you have installed the engine of your choice; the next step is to get fuel to it. If your plane is an ARF you were most likely supplied with a tank. If you built a kit, you probably had to purchase a tank separately, but in either case the basic setup is the same.
The tank components consist of: A tank, a rubber stopper, a clunk, two or three brass or aluminum tubes, a piece of fuel line, a cap, and a metal or nylon back plate. Some tanks will also include some soft wires for securing the fuel lines and/or a piece of plastic tubing, which is used to stiffen the clunk line.
You will notice that most tanks have three holes in the rubber stopper (aside from the center hole which is for the tightening screw), but only two of them go all the way through. This is in case you want to use a 3-line setup, but we'll discuss that later. For most trainers, a 2-line setup is all you will need.
The first step is to push the two metal tubes through the rubber stopper. They should protrude about 3/4" passed the stopper on the outside of the tank. Now you need to slide the back plate onto the tubes on the inside of the stopper and the cap or front plate on the outside end. Insert the screw through the cap and stopper and screw it into the back plate but DO NOT tighten it.
One of the tubes (on the inside) will now be bent toward the top of the tank and the other should get cut off to about 3/4" long (You can do this before inserting it into the stopper, but measure carefully!). The bent tube will be for the tank vent, which gets connected to the muffler's pressure fitting. It should come very close to the top of the tank without touching it (Some tanks even provide a little bubble in the top of the tank for the vent line to sit).
Next you will attach the piece of supplied fuel line to the feed tube and lay the assembly along side the tank. This will be the feed tube that brings the fuel to the carburetor. Cut the fuel line about 1/2" shorter than the tank and add the clunk to the end. Now insert the assembly into the tank (This may take some doing as it is usually a tight fit). Once the stopper is properly seated in the neck, hold the tank upright (Stopper side up) and make sure that the clunk is close to the back of the tank but does not touch it. The clunk should swing freely to the top, bottom and both sides of the tank. This is so it can pick up fuel if to plane is sharply banked or even inverted, but if held so the stopper is facing the ground, the clunk should NOT swing toward the opening in the front of the tank where the stopper is. In fact, we strongly recommend adding a piece of stiff tubing to the feed line inside the tank to prevent the line from swinging forward in the event of an abrupt landing (This happens a lot more often than you might think). If the tank didn't come with a piece of stiff tubing, inner tubing from a flexible pushrod works well for this.
When you are satisfied with the fit, it's time to tighten down the screw in the cap to seal the tank - but be careful - if you really tighten this screw down tight it can burst the seam and cause a fuel leak! Tighten the screw just until you can no longer turn the stopper, and then go another 1/4 to 1/2 turn.
INSTALLING THE TANK
Tank installation varies from one plane to another, but the basic setup is pretty much the same. The tank should be located directly behind the engine and if there's enough room, the tank should be padded with foam rubber to keep the engine vibrations out (In some cases, engine vibrations can cause the fuel to mix with air in the tank and become a frothy foam, which will lead to your engine running very lean or quitting). If there's no room for foam padding, don't be too worried about it, but in the event that you should have a problem with fuel foaming, you may have to make some changes to allow for some padding.
The two lines that come from the tank must now come through the firewall. Again, each plane is different - some planes will have a hole in the firewall for the lines to pass through, or you may have to drill them yourself.
A piece of fuel line that is attached to the feed line from the tank goes to the engine's carburetor, and the vent line attaches to the pressure fitting on the muffler. A nice little trick here is to cut one of the lines and add a piece of tubing to connect the two pieces. With this setup, when you're done flying for the day, you can use the tubing to connect the two tank lines together which will prevent any residual fuel from leaking out (See diagram above).
To fill the tank, you just remove the line from the carburetor and plug it into your pump or squeezeball. Then remove the vent line from the muffler and start pumping until fuel comes out of the vent. At that point, stop pumping and reconnect the lines.
One more word about filling your tank - there are many manufacturers out there who make special "Fuel Filling Valves" - Avoid them. With an exposed engine and muffler it is easier to fill the tank as we have stated, and those fuel valves will cause you more headaches than you need.
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3-LINE SYSTEMS
3-Line systems are used for engines that are enclosed inside of a cowl. Since the line to the carberator is difficult to access, a third line is added to the system to allow for fueling/defueling the tank. Inside the tank, the third line can have a clunk attached, or it can just be aimed toward the botton rear of the tank since it will only be used when the plane is sitting upright. The "Filling End" of the line is often plugged with a "Fuel Dot", which is a nice little plug that attaches to a convenient location on the outside of the plane.
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PROPELLERS
When you're starting out, there's no need to get too concerned about which propeller you should use. While it's true that some are better than others, with a 40 or 60 size trainer, you'd be hard-pressed to notice a difference. The props we recommend are Master Airscrew Brand, because they are good, durable and cheap. You'll be nicking and scraping a few props during your training, so you might as well get the ones that will take some abuse and "Keep On Ticking", or be inexpensively replaced if broken.
One thing to note about these props - and this goes for many molded props - there is a VERY sharp "Flashing" all around the edges which is left there by the mold they were formed in. You really owe it to yourself to scrape this off BEFORE installing it on your engine. The reason for this is that when you install the prop, you want to check that it is in a comfortable position for flipping. Even though you should never start an engine with your fingers, it's just human nature to flip the prop a few times after you've tightened it down. Well, those few flips will leave your fingertips with a nice slice for each time you flipped it. It's so sharp you may not even feel it. Like many modelers, I learned this the hard way. I didn't even know my fingers were slashed until I got a little fuel on them, and then - WOW!
PROP SIZE
What size prop do you need? That depends on your engine size. Your engine's manual should have a list of recommended sizes, but generally, for a 46-size engine, you'll need a 10x6, 10x7, 11x6 or 11x7. For a 60-size engine, a 12x6, 12x7, 12x8, 13x6 or 13x7 would be a good choice.
What do the numbers mean?
In a number like "11x7" the "11" is how long the prop is - in this case, it's 11 inches. The "7" refers to the prop's pitch or how far forward it will travel in one revolution - in this case, it's 7 inches. So which one is best for you? You're the only one who can make that decision. A smaller diameter prop will "spool up" more quickly than a prop with a large diameter, but won't move as much air. And a lower pitch prop will have less speed but more pull than a prop with a higher pitch. Think of it as the difference between 3rd and 4th gear in a car. A lower pitch will also allow you to slow down easier for landing. So for a beginner with a 46 engine, we recommend an 11x6 Master Airscrew prop.
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Here is a chart you can use to determine the size of the prop you need. It is from the O.S. FX engine manual, but the sizes apply to most engines in these size ranges.
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PROP BALANCING
The next thing to consider is prop balancing. We both are in complete agreement on this - Don't worry about it.
We're not saying that you shouldn't balance your props, we're just saying that it is not a MUST DO item before you can fly your plane. Prop balancing will become very important if and when you ever start to fly planes with very large props (Over 16") or run extreme speed engines. But right off the shelf, most molded props are balanced closely enough for a trainer.
Now if you have money to burn and like to have everything perfect, go ahead and buy a balancer, balance your props, and have a nice time. But if your wallet will allow you to buy a balancer or a gallon of fuel, I'd get the fuel - or the glow igniter, fuel pump, or any number of accessories that we can spend our money on.
I have a prop balancer. It has been sitting on a shelf in my shop for the last 5 or 6 years with a propeller on it. It makes a dandy conversation piece, or paper weight, but the truth of the matter is, I never use it. But everyone is different.
PROP INSTALLATION
Ok, so you've picked your prop, scraped or sanded the flashing off the edges, now it's time to bolt it in place. Start by checking to see if the prop will fit on the shaft. Most of the time the prop will slide on perfectly with very little or no slop. If it's a sloppy fit, you can wrap a band of tape on the shaft. If it's too tight, you may need a prop reamer (There's another birthday present in the making). You CAN use a drill, but unless you are experienced in drilling precision holes, buy or borrow a prop reamer.
Now, with the prop on the shaft and the engine on the plane (or sitting in the position it will be in when it's mounted in the plane), turn the engine's thrust plate CCW until you feel the compression. Without letting the shaft move from that position, rotate the prop until it is at approximately a 2 O'clock and 8 O'clock position. Place the front washer on the shaft and tighten it all down with the nut. (Note: Some people prefer an 11 O'clock and 5 O'clock position. The choice is totally up to you)
Now you can flip the prop a few times and see if it's comfortable for you. If not, loosen the prop and rotate it a little. Repeat this process until the prop is where you like it. Once you have it where you want it, make it TIGHT, but don't go medieval on it.
SPINNERS
If you're using a spinner (Nose cone) you will need to put the spinner's back plate on first (before the prop). Most spinner back plates come with a large hole and a set of different size rings that will make the hole fit your engine's drive shaft. Find the ring that fit's your engine, slide it all the way back to the thrust washer and put the back plate over it. Then add the prop, washer and nut, and finally, put the spinner on.
Two things to note here: First, different manufacturers have different methods of attaching the spinner to the back plate so you may need to align the back plate attachment holes with the prop. The other thing worth mentioning is - Many times the prop holes in the spinner will not fit over your prop. This is not unusual. The prop holes will have to be enlarged with a round file or Dremel tool. Don't have a Dremel tool? Put one on your Christma/Chanu/Kwans/ica list. They are worth their weight in gold in this hobby!
STARTING THE ENGINE
Speaking of accessories, it's time to list a few things you'll need before you can start your engine.
- Fuel
- Fuel Pump
- Glow Driver
- "Chicken Stick" or Electric Starter
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Fuel:
Different engines will benefit from different types of fuel. Check your manual for what the manufacturer recommends. If you don't have a manual, look for a fuel with 18% oil and 5-10% nitromethane. I run mostly 4-stroke engines, so I buy Cool Power brand fuel with15% nitro, but I also use it in my 2-strokes. I have been doing it for years without any problem regardless of what the Manufacturer recommends. So basically, whatever your Local Hobby Shop (LHS) carries should work, but stick to 5-10% nitro only because it's cheaper than 15% and you just don't need all that nitro for a 2-stroke.
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Fuel Pump:
Here's another one of those perfect gift items to add to your list. There are 3 common types of fuel pump: A squeeze ball, a hand-cranked pump and an electric. You'll find that most fliers agree that the hand-cranked pump is the best. The squeeze ball is cheap, but they can take forever. The electrics are ok, as long as you remembered to charge your battery, but the hand-cranked type is quick, easy and always ready.
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Glow Driver:
To start the combustion cycle, you must heat the glow plug. This is done by applying a small voltage through it. If you have a power panel on your flight box, you can plug a glow driver into it, or you can use a portable clip-on type of glow driver. They both have their advantages and disadvantages, and in fact many fliers have both types.
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Chicken Stick or Electric Starter:
Starting the engine requires that you spin the propeller. Fingers should NEVER be used for this. Many people like the ease of an electric starter, but all that is really needed is a stick. This can be anything from a store-bought "Chicken Stick", to a piece of broom stick, to a stick that fell off of a nearby tree. I've got a rubber-handle screwdriver that I often use - and one look at the scars on that rubber will tell you why you should never use your finger!
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STARTING PROCEEDURE:
Start by filling the tank. Remove the fuel line from the carb and plug your fuel pump into it. Now remove the vent line from the muffler and start filling. When you see fuel squirt out of the vent, stop filling, and replace the two lines to their original positions on the carb and muffler. And make sure that the plane is restrained from moving forward.
Lean vs. Rich:
An internal combustion engine will run best with an air/fuel mixture of approximately 15 - 1 (Fifteen parts air to one part fuel). When there is too much fuel, the mixture is said to be "Rich" - Adversely, when there is too little fuel, the mixture is said to be "Lean".
An engine that is running rich will have lower RPM at peak, and it will blow an excessive amount of oil out of the muffler (But 2-strokes are notorious for spitting oil anyway). Running an engine slightly rich really won't hurt it at all, but you're also wasting fuel and not getting the most out of your engine.
On the other hand, an engine that is running lean can overheat and wear out due to lack of sufficient lubrication. So you DON'T ever want to run your engine lean for any length of time.
Chicken Stick Method: Turn on your radio and bring the throttle to full open (Note: the glow driver is NOT on yet). If the engine has never run before, close the needle valve and open it about 2 turns. Place your finger over the carb opening and (using the stick) flip the prop (Counter Clockwise) a few times until you see fuel come up the feed line. Once the fuel has reached the carburetor, flip the prop 3 or 4 more times to prime the engine.
Now remove your finger and bring the throttle down to low. You will see the barrel inside the carb rotate to the closed position, but it should not close all the way (A 1/16" opening is average at low throttle). If the fuel in the feed line recedes back to the tank, that's ok. Attach the glow driver. Make one last check that the area is clear and that you don't have any loose clothing that can get sucked into the prop! Flip the prop through its compression. Repeat as necessary. If the engine won't start, try priming again.
Electric Start Method: With an electric starter, priming is not necessary, but it won't hurt. With the radio on and the throttle at LOW, turn the prop CLOCKWISE until you feel the compression. The starter will turn the prop COUNTER CLOCKWISE, but by turning it the opposite way first, the prop will spin freely for about 1/3 turn which will give it a "running start".
Attach the glow driver and be sure everything is clear. Press the starter firmly against the spinner and turn the starter on. Do NOT spin the starter first and then jam it against the spinner!
Both Methods: Once the engine starts, it may run for a few seconds and quit. This is often a sign of fuel starvation. Open the needle valve about 1/4 turn and start over. Once the engine is running, slowly increase the throttle to full wide open. If it dies in the process, you may need more needle valve adjustment. Once it is running full bore, adjust the needle to peak RPM (Most people can hear this), then richen the mixture until you hear a slight drop in RPM. (Note: if the engine is new, refer to your manual for proper break-in procedure. If you don't have a manual, Run the engine very rich for one tank of fuel, and then run it fairly rich for the first 3 or 4 flights. This is how I have broken in every engine I have and they all run great.
Tuning The Engine:
Once your engine is broken in, it is important to get it running properly. To do this, start the engine and bring the throttle to full open. Once it is running full-bore, remove the glow driver and slowly turn the needle valve IN (Clockwise) to lean the mixture. As you do this, you will hear the RPM increase. Eventually, it will reach its peak - take notice of where the needle is at this point. Continue to turn the needle in until you hear the RPM start to drop again. At this point, the mixture is too lean, so you'll have to turn the needle valve OUT again.
As you turn it out, the RPM should come back to peak. Keep turning slowly until you hear a very slight decrease in RPM. This is where you want it to be.
The next test is to pick the plane up and point the nose straight up in the air. The RPM should either not change, or slightly increase. If you hear the RPM sag, you may need to richen the mixture. (Note: When doing this test, bring the engine to full throttle with the plane level and allow a few seconds for the engine to "settle in" to its throttle setting before pointing the nose up. I have seen people who are starting to point the nose up before the engine has reached its full RPM. By doing this, you can't hear any change since it's changing as you go. So hold it level, let it spin up to full RPM, and THEN point the nose up).
Low-End Adjustment:
Now that the engine is running properly on the high-end, you'll want to check the low-end. This is usually set pretty good right from the factory, but not always so you will want to know how to do it. But be careful, this adjustment is a little tricky and it's rare that you will ever need to turn it more than 1/2 turn from the factory setting. So take note of where it is before you turn it so that you can always return it to the factory setting.
There are two kinds of low-end adjustments. One is called a "Low-End Needle" and the other is called an "Air Bleed" and they work exactly opposite one another. A Low-End Needle is just like a needle valve in that as you turn it IN, you decrease the amount of fuel. But in an Air Bleed setup, the screw adjusts the amount of AIR, so as you turn it in, you're allowing less air into the mixture. So to avoid confusion, I will not say "Turn the Needle IN or OUT". Instead I will say "Rich" or "Lean".
Just remember:
Rich: Needle = turn OUT - Air Bleed = turn IN
Lean : Needle = turn IN - Air Bleed = turn OUT
Ok, your engine is running at full bore, bring the throttle down to full idle and adjust the trim so that it is purring as slow as it will run reliably. Let it sit there for about 30 seconds. Did it keep running, or die out? If it kept running, make sure the plane is restrained, and quickly bring the throttle to full bore. If the engine responded nicely, no adjustment is needed. But if it died at idle, or when you went to full throttle, OR if it hesitated when you raised the throttle, you'll want to adjust the low end.
So which is it, rich or lean? There are a few simple tests you can do to give you a clue. First, with the engine at idle when you remove the glow driver, if you hear a significant drop in RPM, this can be a sign that the low-end is rich. But a better test is called the "Pinch Test".
Bring the engine to idle, let it run for a few seconds to acclimate itself, and then, using a pair of long-nose pliers or a hemostat, pinch the feed line that goes to the carb.
If the low-end is set properly:
The RPM should slightly increase, and then the engine should slowly die out - Leave the mixture alone. If you are having problems with transition from low to high throttle, make only minor adjustments to the low-end (Like 1/16 turns of the adjustment screw or needle)
If the mixture is lean:
It will die in only a few seconds with little or no increase in RPM - Richen the mixture in 1/8-turn increments and try again.
If the mixture is rich:
The RPM will slowly increase and the engine will run for a few seconds before dying out - Lean the mixture in 1/8-turn increments and try again.
When you are satisfied with the results, remember that the low-end adjustment effects the high-end as well, so you will need to go back and re-adjust the high-end.
We have a video of us starting an engine for the first time which is available here: Videos.
And as always, if you have any questions that we have not answered here, please stop by the RCUniverse Beginner's forum and we (RC Ken and MinnFlyer) will be happy to help.
Now, let's move on to the next section: Radios
Home Airplanes Engines Radios
Simulators Videos Links About Us
Copyright GettingAirborne.com; 2008 All rights reserved. The materials contained within this page may not be reproduced without the express written consent of GettingAirborne.com, Inc. The information contained herein is believed to be accurate and timely, but no warranty as such is expressed or implied.
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