Home Made Gear Box for Model Ornithopter

Have you considered using tiny chain drives....

They give you more flexibility on the location of the shafts.

You might also want to look at cogged belts, flexibility like a chain but lower weight.

Hi,

They are ok, but perhaps they are too far one from each other. It is better to have more similar ratios between the steps (the efficiency grows). If you need to increase the torque, it is a good idea to have the bigger ratio in the last step (because the wheel diameter is going to grow and, with it, the tangential force in the teeth is going to be reduced).

Be careful with the distances between the shafts and its paralelism, if you use the pure theoric distances perhaps you are going to have problems, because normally the needed clearances are not calculated. A good aproximation for having the clearances is to separate the wheels 0.1 times the module. But be careful with it, because if you separate too much the wheels you have the possibility to have an engaging coefficcient under the minimum (1).

If the shaft are not paralels, while the wheels are working it is going to be a very big force between them that it is going to try to separate them and is going to cause very big waste in the teeth and to decrease very much the gearbox efficiency. It could cause the colapse of the system. It is because the geometry of the teeth. It is the most normal problem in home made prototipes. If you have these two problems solved, the gearing is going to work correctly (if the the endurance is big enough)

Good luck.

If I was building an ornithopter I would not use electic motors or gears at all. I remember the craze circa 1980 for rubber powered ornithopters. The wings made an unrealistic sound as they were essentially polyester film. They flew for about 10 to twenty seconds, the final glide was the most impressive. I would use compressed air and a peristalic roller acting on a flexible tube myself, to make the wings flap. If electric flight was the option, then a reciprocating 'linear' motor would be my choise. There are some very cheap high power neodymium magnets about. Ready made for you are the ultra-strong magnets to be obtained from salvaging an old 'Hard Drive' some of those might just be the 'ticket' for you. Best of Luck It sounds a wonderful project. Takes me back to the ending of the film 'War Games' we had a pre-release showing at the UK RAF Lakenheath Airbase, when the hero pulled the plug on the wretched machine, all the United States Air Force Lads shouted 'HOORAY' at the top of their voices. Happy Days, The film coincidentally reflected reality.