Zenoah ZG38 Geardrives
Toni Clark makes the reduction gear in two versions, side mounted and inline. The side mounted gearing has the drive shaft running alongside the carburetor and is for ring cowls, such as our Sopwith Pup and horizontally opposed twins. The inline version has the driveshaft over the crankcase, this is for models such as the Tiger Moth.
The distance between the drive and crankshaft is 70 mm center to center. The length of the motor fitted with reduction gear is the same as the standard motor with our standard motor mount. A Zenoah G38 with the 2,8:1 reduction gear weighs 2700 grams. The reduction gearing uses two miniature Polyflex vee belts, these belts have been developed by the American company Gates and they are the best belts available.
These Gates Polyflex belts are completely different in style and composition to all existing types of Vee belts, they are as revolutionary as the original vee belts were. These Polyflex belts are more flexible, smaller, thinner and in spite of this can transfer more power as well as requiring a lot less space. This description you will find in the catalogue from Gates who were the company that invented the Vee belt in 1917.
The life of these Polyflex belts is unusually long, Toni Clark has had it in their Tiger Moth a 2,8:1 gear that has been flown regularly most weekends during the summer and it was six months before the belts needed replacing. They often hear from customers who have been flying for several years with the original set of belts. Because they fit two belts it is highly unlikely that the belts fail simultaneously. When a belt fails one can carry on flying without noticing anything until the next start. With only one belt it is nigh impossible due to slippage to start the engine, but a pair of new belts are easy and quick to refit.
The Zenoah G38 with our stainless steel silencer turns the 32x18" propeller 2,700 rpm. They developed the reduction gear for their Sopwith Pup so as to be able to fly a model with scale size propeller. But to test the gearing they first put this into their Tiger Moth which weighed 14 kilos (30.8 lbs). If they try to tell you the possibilities that their Tiger Moth possess with such a power unit it will be impossible to believe unless you have seen it yourself. Many who have seen that setup for the first time with the reduction gear installed have all said the same, they would have never believed it unless they had seen it for themselves. In level flight the Tiger reaches ac considerable speed and sounds exactly like the newly restored Me109 with the original Daimler Benz engine or pull the nose up and you can have a fantastic wing over.
As she goes down with motor cut right back, the large propeller acts like an airbrake and slows the model right down. But the most impressive is the sound. The propeller rpm of 2,700 is the same as for full size, and this you can clearly hear. Flying the Tiger Moth or Sopwith Pup level over the landing strip most people would be easily convinced that it was a full-size aircraft they heard.At 1000 rpm the Tiger Moth performs as the full-size, but it is so quiet, you have to listen very carefully.The gearbox is supplied with assembly instructions on DVD. It can be installed inline or as a sidewinder.
We recommend using a intake bend and intake flange to maximize performance and lower noise emission. By breathing cold and fresh air in from inside the fuselage instead of being fed hot air from underneath the cowl the engine’s performance will be increased immensely. We stock replacement v-belt sets.