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This motor is used by many people to power indoor R/C scale models. I first encountered it when I discovered the 'Tiny', an indoor aerobatic model designed by Todd Long. The model was designed for use with the DC1717 motor and 11.8:1 integral gearbox by WES -Technik. Further investigation showed that this is a 3 volt motor (although other windings are available), yet an 8 cell battery pack is specified for the Tiny!
I emailed Todd Long about this and he confirmed that the 3 volt motor was the correct one. Specification sheets for the motor are available from Faulhaber-Minimotor the manufacturers.
These show that the critical factor is a maximum current of 1.2 amps. Using an 8 cell 50mAh battery pack, it takes a surprisingly large prop to get anywhere near this figure. The no-load speed is given as 14000 rpm. At the 11.8:1 ratio of the gearbox, this means a maximum possible propellor speed of 1186 rpm! Obviously, high pitch props are needed.
The specified prop for the Tiny is a 9 x 5 and I couldn't even get mine airborne with that size. A 9 x 7 proved to be better. Cutting this down to 7" dia produced a further small improvement.
The Tiny is a low aspect ratio model with a thick symmetrical wing. What I find surprising is that this unit should have been the one recommended for that model. A lightly loaded model with a lifting section wing (in other words, slow flying) should present no problems.
If you want to persue the aerobatic route, it would be a good idea to investigate the use of propellors designed for rubber powered models. The gearbox output shaft is 2 mm dia and you will probably need to make your own adaptor.
GWS supply a range of rubber spinner adaptors (1.5, 2.0 & 2.3 mm dia) which can be used to fit props designed for these. It is possible to use them for the larger GWS propellors if you thin down the prop hub and drill out to suit. However, there is a limit here because this system will not cope with a lot of torque.
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Weight: 21g (0.75oz) |
6 cells = 6 x 300 mAh NiMH
7 cells = 7 x 300 mAh NiMH
8 cells = 8 x 50 mAh Nicad
Clearly, that 14000 rpm no-load speed is on 3 volts. 4000 rpm from an 11.8:1 gearbox is impressive!
