Low cost planetary gears

[thlights]

I am looking for a supplier who sells planetary gearsets for very low prices ($10 or less). I need an inexpenive solution whose maximum diameter does not exceed 35mm, with a reduction around 125 or so. I don't have a spec yet for how much backlash can be tolerated, and may be able to use plastic gears instead of metal. I would greatly appreciate any recommendations.

 

[Metalguy]

Do you mean 125% or 125-to-1?

 

[thlights]

125-to-1 reduction ratio

 

[Metalguy]

That's a HUGE speed reduction! However, there just happens to be a way to get this with 3 gears--3 simple straight-cut spur gears (pinions).

What you do is use one gear with 125 teeth, and one with 126. Arrange them so they are side-by-side, each with its own axle. Then make a simple counterweighted bracket (unless the speed of the input is low) to hold the third, wider gear. It doesn't matter how many teeth it has, but you'll probably want a small gear with about 10 teeth (all gears have same pitch). Mount the third gear so that it meshes with BOTH of the larger gears. Hold the axle connected to the 126 tooth gear. When the motor/whatever spins the fat gear around the OD of the bigger gears, you'll have 125-to-1 speed reduction in a positive, non-slip drive.

Keep the motor running, release the axle (brake) on the 126 toother and hold the 125 toother, and you have the very slow output running in the opposite direction!

BTW, this arrangement is known as Ferguson's Paradox, and I have stumped MANY mechanical engineer types when I ask them to arrange 3 simple gears in a train to get the most speed reduction!

 

[ielivaz]

Hello thlights:

I am a gear maker, if you wish we could discuss your requierements.

ielivaz@oxxo.femsa.com.mx