Combustion engines
Combustion or nitro engines, who does not know them? until a few years before it was nearly the only method to fly a model with enough power. Until today, the sound of this engines is linked directly to model planes. With the appearance of affordable brushless engines and LiPos the nitro engines become a minority on the flying field, also they are not allowed anymore on some clubs. It is just not reasonable to fly with a nitro engine today. But we won't need for all a reason, or? ;) Still up today, nitro engines have some magnetic characteristics which will let you addict to them. Can you imagine a Warbird or a aircombat without that sound? Exactley, works, but not good ;).
They already have some kind of comeback on many flying fields, and yes, they are just a real good thing...
But lets do a summary:
Disadvantages:
Noise
Fuel cost
Waste gas
Many things you have to bring with you (Startbox, fuel, glow etc...)
Cleaning of the plane at the end of the day
Less power then up to date electric engines
Higher weight
Advantages:
Sound
Smell
As you can see, there is nothing reasonable to fly a nitro, but who is saying that a hobby always needs reasons?
There are not anymore much different engines on the market, I will not go into detail on the different types, but I will tell you some things that every beginner should know.
They already have some kind of comeback on many flying fields, and yes, they are just a real good thing...
But lets do a summary:
Disadvantages:
Noise
Fuel cost
Waste gas
Many things you have to bring with you (Startbox, fuel, glow etc...)
Cleaning of the plane at the end of the day
Less power then up to date electric engines
Higher weight
Advantages:
Sound
Smell
As you can see, there is nothing reasonable to fly a nitro, but who is saying that a hobby always needs reasons?
There are not anymore much different engines on the market, I will not go into detail on the different types, but I will tell you some things that every beginner should know.
Basics:
On model combustion engines, there are two different types:
Gas engines: Will be driven by a mixture of gas and oil and they have a seperate ignition.
Normaly there are displacements of 30ccm up to 150ccm as two stroke types used. i will not go into detail on that engines, because I have there a lack of experience.
Glow engine: The typical model combustion engine, will be driven by a mixture of methanol, oil and nitromethane and does not have an ignition, only a glow plug. Displacements are typically between 2,5ccm and 20ccm, also there are two and four stroke types. We will go into detail with that ones:
Gas engines: Will be driven by a mixture of gas and oil and they have a seperate ignition.
Normaly there are displacements of 30ccm up to 150ccm as two stroke types used. i will not go into detail on that engines, because I have there a lack of experience.
Glow engine: The typical model combustion engine, will be driven by a mixture of methanol, oil and nitromethane and does not have an ignition, only a glow plug. Displacements are typically between 2,5ccm and 20ccm, also there are two and four stroke types. We will go into detail with that ones:
Fuel:
The fuel consists always of a big amount of methanol. methanol is the easiest and cheapest way to produce alcohol. The lubrication will be done with the fuel, thats why it is necessary to add 11% - 20% oil to the fuel. Also a little bit nitromethane can be added to increase the power, decrease the heat and get a more save idle speed.
As you can maybe guess already, the most expensive part of the fuel is the nitromethane. Normaly there are 5% to 20% added. Who wants to be on the cheap side needs to mix the fuel on his own. The price for a bought mixture with 20% nitro is around 12€ per liter, if you are mixing on your own and without nitro, you are around 3€ per liter. Personaly, I fly 0% nitro by my own conviction with self mixed fuel with 13% oil. Also the cost are very low because of that.
Generally, a high nitromethane amount is used if the engine needs to bring a lot of power, with four stroke types to have a better idle speed or in small and helicopter engines to reduce the probability of a shut off.
As you can maybe guess already, the most expensive part of the fuel is the nitromethane. Normaly there are 5% to 20% added. Who wants to be on the cheap side needs to mix the fuel on his own. The price for a bought mixture with 20% nitro is around 12€ per liter, if you are mixing on your own and without nitro, you are around 3€ per liter. Personaly, I fly 0% nitro by my own conviction with self mixed fuel with 13% oil. Also the cost are very low because of that.
Generally, a high nitromethane amount is used if the engine needs to bring a lot of power, with four stroke types to have a better idle speed or in small and helicopter engines to reduce the probability of a shut off.
Engine construction:
Beside some special types, the construction of a glow engine is always the same:
Carburetor: The carburetor is needed to mix the fuel with the air to get a ignitionable mixture. The necessary underpressure to suck the fuel through the carb is done by the piston in the housing. Every carb has at least two adjusting needles which are controling the mixture ratio. One for the idle speed up to about 70% and a second one for about 70% up to full throttle.
Throttle is done through the choke part which reduces the diameter for the airflow.
Housing: The housing contains the most important parts of an engine, which are the shaft, the piston including the rod and of course the glow plug. With a opening in the shaft, it is designed when the motor will suck air, with the piston it will be compressed until it is ignition able and with the glow plug it will be ignited and the waste gas can leave through the exhaust.
Exhaust: The Exhaust is a very important part on a two stroke engine, according to his function, he is responsible for a good filling of the combustion chamber. Also there is the pressure hose to the tank connected at the exhaust, so that the fuel will be pushed to the carb. The exhaust can be built as standard exhaust, or as tuned pipe. The tuned pipe brings the advantage of a power increase at the maximum rpm and also brings down the noise a bit. On the other hand, it is more uncomfortable to transport and mostly a little bit more heavy. Also the length must be adjusted according to the expected maximum rpm.
Fuel tank: the tank does not belong to the engine, but it is at least as important get in the air. According to the displacement of the engine, the tank usualy has 125ccm up to 500ccm and lasts normaly for about 8-10 minutes flight time at full throttle. He has three connections: 1. The carb connector which is connected over a hose and a small filter with the carb, inside the tank is also a hose with a more heavy filter which is called the tank pendulum which is responsible that fuel can get to the carb in every flight position. 2. The pressure conenction which is connected to the exhaust and which is pressing the fuel to the carb. 3. The filling hose which is needed to fill up and empty the tank. There it is important, that the pressure connection inside the tank is showing up and the filling connection is showing down. Only in that configuration a flawless flight and filling is possible.
Carburetor: The carburetor is needed to mix the fuel with the air to get a ignitionable mixture. The necessary underpressure to suck the fuel through the carb is done by the piston in the housing. Every carb has at least two adjusting needles which are controling the mixture ratio. One for the idle speed up to about 70% and a second one for about 70% up to full throttle.
Throttle is done through the choke part which reduces the diameter for the airflow.
Housing: The housing contains the most important parts of an engine, which are the shaft, the piston including the rod and of course the glow plug. With a opening in the shaft, it is designed when the motor will suck air, with the piston it will be compressed until it is ignition able and with the glow plug it will be ignited and the waste gas can leave through the exhaust.
Exhaust: The Exhaust is a very important part on a two stroke engine, according to his function, he is responsible for a good filling of the combustion chamber. Also there is the pressure hose to the tank connected at the exhaust, so that the fuel will be pushed to the carb. The exhaust can be built as standard exhaust, or as tuned pipe. The tuned pipe brings the advantage of a power increase at the maximum rpm and also brings down the noise a bit. On the other hand, it is more uncomfortable to transport and mostly a little bit more heavy. Also the length must be adjusted according to the expected maximum rpm.
Fuel tank: the tank does not belong to the engine, but it is at least as important get in the air. According to the displacement of the engine, the tank usualy has 125ccm up to 500ccm and lasts normaly for about 8-10 minutes flight time at full throttle. He has three connections: 1. The carb connector which is connected over a hose and a small filter with the carb, inside the tank is also a hose with a more heavy filter which is called the tank pendulum which is responsible that fuel can get to the carb in every flight position. 2. The pressure conenction which is connected to the exhaust and which is pressing the fuel to the carb. 3. The filling hose which is needed to fill up and empty the tank. There it is important, that the pressure connection inside the tank is showing up and the filling connection is showing down. Only in that configuration a flawless flight and filling is possible.
Correct set up:
I've described here how to set up a nitro engine correct.
Storage:
Fuel for model engines contains mainly methanol and oil. Methanol evaporates normaly after a short time, oil, dosen't. it sticks inside the engine and makes it unusable. If I know that I won't fly for the next 6 months, then I'm trating it with Nanoversal which can be bought in every weapon shop. Just disconnect the hose from the carb, spray a little bit inside, close the intake socket with the thumb, oben the throttle and turn the prop a few times and the engine is conserved for the next few months. If you want to start again, just do it as you would do it normaly.
Engines used by me:
Manufacturer: Magnum
Name: XL 25
Displacement: 4ccm (0.25 cubic inch)
Tank size: 125ccm
Runtime on full throttle: 12 Minuten
Fuel: 87% Methanol, 13% Oil
Prop: 9x5
Exhaust: Original
Carb: Rotary slide, original
Model: Spitfire
Name: XL 25
Displacement: 4ccm (0.25 cubic inch)
Tank size: 125ccm
Runtime on full throttle: 12 Minuten
Fuel: 87% Methanol, 13% Oil
Prop: 9x5
Exhaust: Original
Carb: Rotary slide, original
Model: Spitfire
The Magnum engines does not have a good reputation on our flying field. Supposedly they should not be able to set up correct and run reliable. This I can refute definitely, the small magnum runs excellent! Only on idle speed, he needs little bit love and a very fine tuning. Beside of that, he just runs and runs and runs...
Manufacturer: Webra
Name: Speed 40
Displacement: 6,5ccm (0.4 cubic inch)
Tank size: 250ccm
Runtime on full throttle: 8 Minuten
Fuel: 87% Methanol, 13% Oil
Prop: 10x6
Exhaust: Webra manifold & Webra tuned pipe
Carb: Dynamix flat slide, original
Model: Bolero
Noise: 87dB(A) in 1,5m distance and 10cm above ground, 90° right.
Name: Speed 40
Displacement: 6,5ccm (0.4 cubic inch)
Tank size: 250ccm
Runtime on full throttle: 8 Minuten
Fuel: 87% Methanol, 13% Oil
Prop: 10x6
Exhaust: Webra manifold & Webra tuned pipe
Carb: Dynamix flat slide, original
Model: Bolero
Noise: 87dB(A) in 1,5m distance and 10cm above ground, 90° right.
The good old Webra engines, maybe the best ones which can be bought for money. Unfortunately they aren't produced anymore... This engine is a real screamer which has plenty of power, not much less then a 10ccm one. According to the tuned pipe (which is not really a silencer) and the dynamix carb, this engine has a sound which you can find nowhere else and an acceleration that every motorcycle would like to have. The set up needs to be done with care, the high speed needle has a very wide range, but the idle speed needs to be on one click. On starting he is, because of the Dynamix carb, a small princess and needs most time the electric starter.
Manufacturer: Webra
Name: Speed 61
Displacement: 10ccm (0.61 cubic inch)
Tank size: 420ccm
Runtime on full throttle: 8 Minuten
Fuel: 87% Methanol, 13% Oil
Prop: 12x6
Exhaust: Weston UK custom manifold & Webra tuned pipe
Carb: Dynamix flat slider, original
Model: Curare
Noise: 82dB(A) in 1,5m distance and 10cm above ground, 90° right.
Name: Speed 61
Displacement: 10ccm (0.61 cubic inch)
Tank size: 420ccm
Runtime on full throttle: 8 Minuten
Fuel: 87% Methanol, 13% Oil
Prop: 12x6
Exhaust: Weston UK custom manifold & Webra tuned pipe
Carb: Dynamix flat slider, original
Model: Curare
Noise: 82dB(A) in 1,5m distance and 10cm above ground, 90° right.
Webra engines are good. Really good. But the good ones have become rare. This one I found used on the internet when i was searching an engine fpr my new Curare. I love the Dynamix carb, the acceleration is sensationel and if you are a technican, then you especially like the concept of it.
The engine itself runs as reliable as you can imagine, but as every other engine with Dynamix carb, you can neraly only start it with an electric starter. This mainly comes from the concept of the carb and also Webra itself is writing that the carb will only work with a pressure tank. If you take care about the few characteristics, then you get one of the reliablest running motors with a lot of power ever produced.
The engine itself runs as reliable as you can imagine, but as every other engine with Dynamix carb, you can neraly only start it with an electric starter. This mainly comes from the concept of the carb and also Webra itself is writing that the carb will only work with a pressure tank. If you take care about the few characteristics, then you get one of the reliablest running motors with a lot of power ever produced.
Manufacturer: GMS
Name: 2000 61
Displacement: 10ccm (0.61 cubic inch)
Tank size: 300ccm
Runtime on full throttle: 6 Minuten
Fuel: 87% Methanol, 13% Oil
Prop: 12x6
Exhaust: Original
Carb: Rotary slide, original
Model: P51 Mustang 1,5m
Name: 2000 61
Displacement: 10ccm (0.61 cubic inch)
Tank size: 300ccm
Runtime on full throttle: 6 Minuten
Fuel: 87% Methanol, 13% Oil
Prop: 12x6
Exhaust: Original
Carb: Rotary slide, original
Model: P51 Mustang 1,5m
The GMS engines are a secret tip, but unfortunately not aivailable anymore. if you can get one used, you should buy it. They are running flawless and have more power then most other 10ccm engines. This is mainly caused by the exhaust, colleagues found that out and are using the exhaust also on myn other engines. Also set up is quite easy and the engines runs good overall.
Manufacturer: OS
Name: FS 91 II
Displacement: 15ccm (0.91 cubic inch)
Tank size: 350ccm
Runtime on full throttle: 12 Minuten
Fuel: 87% Methanol, 13% Oil
Prop: 14x7
Exhaust: Original
Carb: Rotary slide, original
Model: P51 Mustang 1,7m
Name: FS 91 II
Displacement: 15ccm (0.91 cubic inch)
Tank size: 350ccm
Runtime on full throttle: 12 Minuten
Fuel: 87% Methanol, 13% Oil
Prop: 14x7
Exhaust: Original
Carb: Rotary slide, original
Model: P51 Mustang 1,7m
Four strokes have the reputation that they are not running very well on idle speed without permanent glowing and nitromethane, this i can clearly decline on this engine. It runs flawless with 0% nitro and also the permanent glowing is not needed. But when using a four stroke, you should also use the permanent glowing, because it is a high gain of safety in low rpm's. The sound fits perfect to a Warbird and there is nothing negative to say about that engine.