strutter
PH-SAM
Hallo Jeroen,
De Camel is vliegklaar
Vertraging zul je zelf moeten uitwerken
Hier wat info van Mick Reeves:
TORQUEMASTER for Zenoah Titan 62
This unit bolts onto a Zenoah 62 engine and provides a belt driven reduction drive to a new prop shaft set in front of the cylinder. This enables a larger propeller to be driven, which is more efficient and gives greater thrust.
Why is a Reduction Drive needed and what advantage does it give? This is a difficult question to answer fully but a simple analogy will help. It's rather like the gear box on a car. Try pulling away in top gear and you will find that it is a great struggle and acceleration will be very slow until you reach a reasonable speed when the clutch can be fully engaged and the car will then accelerate to high speed. This situation can be compared to an engine fitted with a small diameter prop, or ducted fan or turbine. Acceleration from rest can be poor but performance is good once a high speed is reached.
The propeller or fan in this case is very inefficient at low speeds. Most of the energy is wasted in turbulence behind the model. Modern ducted fan models overcome the slow acceleration problem by using a very powerful engine, perhaps four times the power used in a similar sized propeller model.
The opposite case, pulling away with the car in bottom gear gives very good acceleration from rest but, of course, the car will not go very fast. If you are pulling a very heavy trailer uphill then bottom gear might be just right for the situation. The equivalent case for a model aircraft (or full size aircraft come to that) is a large, heavy, slow flying machine, where a high ratio reduction drive could turn a large prop to give the thrust needed to fly the model. But you don't get this extra thrust for nothing - the theoretical top speed available will be proportionately lower, although the model can actually reach a higher speed in practice because of the improved efficiency.
Most large scale models would lie somewhere between these two cases and most of these would benefit from using a reduction gear.
Propeller efficiency. This concept is rather difficult to explain. The propeller thrust must equal the drag of the model at a particular speed and the thrust is obtained by the propeller throwing back a column of air faster than the model is flying. The thrust is calculated from the mass of air x change in velocity.(MV) Therefore, a large prop, moving a large column (and mass) of air, can throw the air back at a low speed to achieve this thrust, whilst a small prop would need to provide a much higher speed column of air to get the same thrust. The difference between the rearward speed of the air from the prop and the forward speed of the aircraft is referred to as propeller slip and the greater the slip, the less efficiency.
Mathematical explanation:- Thrust is given by M x V , BUT the energy lost in the slipstream is given by 1/2MV2. Work it out and you find that the smaller prop with higher velocity change has much higher losses for the same thrust.
Deciding on whether a particular model would benefit , and deciding what prop size would be appropriate, is quite a problem. It is possible to calculate this provided all the facts are known but normally we do not have enough information available to make calculations worthwhile. You would need to know the speed and drag of the model; the torque curve of the engine; the thrust and torque absorption curves of various props etc. A more practical way to decide is to look at existing models which are successful with the standard engine and then look at slightly larger heavier models which can fly on the straight engine but where the performance is marginal during takeoff and climbing. This is where the torquemaster can be a real benefit. My 1/3 scale Camel is 112" span and weighs 3Olbs. The King 100 engine used in this model turned a 28 x 14" prop. at 42-4400 rpm. This gave good performance but fitting the Zenoah 62 and Torquemaster resulted in an extra 200 rpm on this prop and vertical performance with the much smaller engine.
A rule of thumb for deciding what propeller pitch to use is to aim for a 30% propeller slip. So if the model is flying at 40 mph it will require prop pitch equivalent to 57 mph ( 40 /0.7) At 5000 rpm this needs 12 inch pitch. ( MPH X 1056) RPM One would then adjust the prop diameter to reach the required rpm. The Manufacturers' power graphs for the Zenoah 62 suggest that maximum power is 4 BHP at 8500 rpm (silenced), and my engine appears to run quite happily at 9500 rpm. If you want maximum performance then you should select a prop which will allow the engine to reach these speeds, but a bigger prop might be preferred to reduce noise, engine wear and fuel consumption. My approach with the Camel was to prop for around 8000 engine rpm at full throttle, giving near maximum power but only using full throttle very rarely in flight. Level flight requires only 1/4 throttle and scale aerobatics can be done on about 1/2 throttle. It's nice to have the extra performance in hand for use when you want it.
I believe that use of the Torquemaster will give great improvements in models over 251bs and will give the impression that a larger engine is being used. Takeoff runs will be much shorter, climb outs can be steeper with good control authority, where using the standard engine would have meant a struggle to get airborne and a slow climbout near the stall.
Succes, Ralf
Verder weet ik dat een ZG45 met een vertraging van 2,5:1 een prop van 32x18" rondslingert met ca.3000 rpm
Dit komt redelijk overeen met je 50cc denk ik
De Camel is vliegklaar
Vertraging zul je zelf moeten uitwerken
Hier wat info van Mick Reeves:
TORQUEMASTER for Zenoah Titan 62
This unit bolts onto a Zenoah 62 engine and provides a belt driven reduction drive to a new prop shaft set in front of the cylinder. This enables a larger propeller to be driven, which is more efficient and gives greater thrust.
Why is a Reduction Drive needed and what advantage does it give? This is a difficult question to answer fully but a simple analogy will help. It's rather like the gear box on a car. Try pulling away in top gear and you will find that it is a great struggle and acceleration will be very slow until you reach a reasonable speed when the clutch can be fully engaged and the car will then accelerate to high speed. This situation can be compared to an engine fitted with a small diameter prop, or ducted fan or turbine. Acceleration from rest can be poor but performance is good once a high speed is reached.
The propeller or fan in this case is very inefficient at low speeds. Most of the energy is wasted in turbulence behind the model. Modern ducted fan models overcome the slow acceleration problem by using a very powerful engine, perhaps four times the power used in a similar sized propeller model.
The opposite case, pulling away with the car in bottom gear gives very good acceleration from rest but, of course, the car will not go very fast. If you are pulling a very heavy trailer uphill then bottom gear might be just right for the situation. The equivalent case for a model aircraft (or full size aircraft come to that) is a large, heavy, slow flying machine, where a high ratio reduction drive could turn a large prop to give the thrust needed to fly the model. But you don't get this extra thrust for nothing - the theoretical top speed available will be proportionately lower, although the model can actually reach a higher speed in practice because of the improved efficiency.
Most large scale models would lie somewhere between these two cases and most of these would benefit from using a reduction gear.
Propeller efficiency. This concept is rather difficult to explain. The propeller thrust must equal the drag of the model at a particular speed and the thrust is obtained by the propeller throwing back a column of air faster than the model is flying. The thrust is calculated from the mass of air x change in velocity.(MV) Therefore, a large prop, moving a large column (and mass) of air, can throw the air back at a low speed to achieve this thrust, whilst a small prop would need to provide a much higher speed column of air to get the same thrust. The difference between the rearward speed of the air from the prop and the forward speed of the aircraft is referred to as propeller slip and the greater the slip, the less efficiency.
Mathematical explanation:- Thrust is given by M x V , BUT the energy lost in the slipstream is given by 1/2MV2. Work it out and you find that the smaller prop with higher velocity change has much higher losses for the same thrust.
Deciding on whether a particular model would benefit , and deciding what prop size would be appropriate, is quite a problem. It is possible to calculate this provided all the facts are known but normally we do not have enough information available to make calculations worthwhile. You would need to know the speed and drag of the model; the torque curve of the engine; the thrust and torque absorption curves of various props etc. A more practical way to decide is to look at existing models which are successful with the standard engine and then look at slightly larger heavier models which can fly on the straight engine but where the performance is marginal during takeoff and climbing. This is where the torquemaster can be a real benefit. My 1/3 scale Camel is 112" span and weighs 3Olbs. The King 100 engine used in this model turned a 28 x 14" prop. at 42-4400 rpm. This gave good performance but fitting the Zenoah 62 and Torquemaster resulted in an extra 200 rpm on this prop and vertical performance with the much smaller engine.
A rule of thumb for deciding what propeller pitch to use is to aim for a 30% propeller slip. So if the model is flying at 40 mph it will require prop pitch equivalent to 57 mph ( 40 /0.7) At 5000 rpm this needs 12 inch pitch. ( MPH X 1056) RPM One would then adjust the prop diameter to reach the required rpm. The Manufacturers' power graphs for the Zenoah 62 suggest that maximum power is 4 BHP at 8500 rpm (silenced), and my engine appears to run quite happily at 9500 rpm. If you want maximum performance then you should select a prop which will allow the engine to reach these speeds, but a bigger prop might be preferred to reduce noise, engine wear and fuel consumption. My approach with the Camel was to prop for around 8000 engine rpm at full throttle, giving near maximum power but only using full throttle very rarely in flight. Level flight requires only 1/4 throttle and scale aerobatics can be done on about 1/2 throttle. It's nice to have the extra performance in hand for use when you want it.
I believe that use of the Torquemaster will give great improvements in models over 251bs and will give the impression that a larger engine is being used. Takeoff runs will be much shorter, climb outs can be steeper with good control authority, where using the standard engine would have meant a struggle to get airborne and a slow climbout near the stall.
Succes, Ralf
Verder weet ik dat een ZG45 met een vertraging van 2,5:1 een prop van 32x18" rondslingert met ca.3000 rpm
Dit komt redelijk overeen met je 50cc denk ik
