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A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.

Cable brake

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The Sky Dart
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Cable brake

Post by The Sky Dart » Mon Nov 23, 2009 8:54 pm

Input: An object slides upward on a metal cable. Let say 3...5 mm. Object mass is 0.5...2 kg. Speed - 30....200 m/s

Needed: A brake system that will decelerate the object on the top of the cable (1...2 meters) and won't allow it to drop back dawn. Otherwise it should create minimum resistance to the upward movement.

Any suggestions :W


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The Sky Dart
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rockets-in-brighton
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Re: Cable brake

Post by rockets-in-brighton » Tue Nov 24, 2009 5:33 am

The Sky Dart wrote:Input: An object slides upward on a metal cable. Let say 3...5 mm. Object mass is 0.5...2 kg. Speed - 30....200 m/s

Needed: A brake system that will decelerate the object on the top of the cable (1...2 meters) and won't allow it to drop back dawn. Otherwise it should create minimum resistance to the upward movement.

Any suggestions :W
I'd go for a passive system, variable friction. Thicken or roughen the cable starting where you want the deceleration to begin and increasing towards the top end. What you use would depend on what you have got for a sleeve on the cable, which obviously can't be too tight-fitting. You could try: painting layers of PVA glue or similar over the last 2 m, thicker at the top than the bottom; wrapping tape around the cable, more layers as you go up.

I also thought about magnetic eddy currents (aluminum foil wrapper on the sleeve and strong rare earth magnets arranged around the cable, or vice versa) but you want it to stop - so have to contrive a one-way 'valve' on the cable to stop the load slipping back down, a flap of plastic could do that.

Good luck, report results.


Cheers
Steve
Rockets-in-Brighton
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