Prop conversion

june 2002

For the aerial robot, I need 2 clockwise turning props, and 2 counter clockwise turning props (aka pusher props). I have been unable to find a supplier of carbon ccw props, so I had to convert cheap nylon ones.

The chief-engineer A.L. Stolk, well-known for his work on F16 fighting falcon and the Hawk and Patriot projects, helped me convert the cheap low quality Tornado pusher props.

The nylon props I have feature a bore which is to large for my Faulhaber engine, so we glued an adapter to the nylon prop. This adapter uses micro inbus screws to fasten the axle. However, the adapter did not fit in the bore of the nylon prop, so we had to sand of the flange of the adapter.

clamp
The adapter

tornado-mod
After conversion

We converted four nylon adapters for use with the faulhaber engine. Two tractor props, and two pusher props. The engine turns in a single direction only, so we need to mount the engine in front of the pusher props, and behind the tractor props.

Test report

Testing the two pusher props yielded a similar result: The engine that features extremely smooth operation when using carbon props, now shakes violently during operation with the converted props.

Also, a wobble effect is observed, as the blade tips seem to oscilate in and out the plane of rotation. What causes this wobble, and the violent vibration? Would this be a simple case of a lack of ballancing? I don't know.

Needless to say, the nylon converted props provide no thrust. Using carbon props, I observe high thrust. Maybe this is a dead end, and I should have some carbon CCW props be custom made for me. This is the expensive option.