hi,

I need to design a gear system which uses the linear motion of a descending mass (20 kg) and convert it to rotary motion.The required output speed is 150 rpm.

It would be of great help if someone could help me with the following.Thanks in advance.

 

i.The technical specifications of the gears i can use in this case.

ii.How can the mass (20 kg) be coupled with the gear system.

The problem is not adequately specified.

What output torque do you need?

 

It will probably help if you tell us what you are trying to achieve.

@John Cuthber, I'm trying to replicate the gravity light described in the following video:

for scientific study.

A shaft would be attached to the gear system and connected to a generator to power the LED.

Hope this makes thing clear.

The best design I see is like at the video: wind the weight's rope around the input shaft, then have a series of simple gears.

 

To me, the design challenge is rather to keep dust out of the gears and bearings, protect the first shaft from shock if the weight falls from a few decimetre height, ensure lubrication - or dry run capability, which is usually worse. Also unusual with a series of gears: make it simple to assemble and repair. Ensure safe operation for users and hardware on open and short circuit.

 

Try to find an old clock powered by a falling weight, and observe it.

 

You could consider tooth belts instead of gears. They resist dust better.