View Full Version : Motor Speed reduction gearbox

10-04-2013, 08:52 AM
Iím looking for a speed reduction gearbox to reduce the rpmof a ľ hp AC 1725 rpm motor to about 40 rpm. I have searched online and pricesare amazing.
The application is a sand muller for my foundry. Anyone know a good source for said gearbox?Anyone have plans that a novice could follow to build one?

10-04-2013, 08:57 AM

Or make one using v-belts, I would guess you will need at least a double reduction for that.


Lew Hartswick
10-04-2013, 08:58 AM
Gear boxes with that big a reduction are by the nature going to be expensive unless you can find one in
military surplus somewhere. It's too large for a reasonable belt drive reduction. So that leaves a "home
built" reducer. A worm drive would be my solution. A 1/4 HP would not be too difficult to build. Still
will cost a bit for the gears.

Bob Ford
10-04-2013, 10:01 AM
If you have to buy gears it would be cheaper to buy finished product. I have bought and used the reducers from Surplus center found nothing wrong with the reducers. Have also cut my own gears and made reducers, but by the time you add in the case, bearings, gears and time Surplus Center is cheap.


10-04-2013, 10:18 AM
Lots on ebay, some of the ideal ones are planetary by Bayside or Alpha gear etc.

10-04-2013, 01:39 PM
Transmission from an old wringer washing machine.

The Artful Bodger
10-04-2013, 03:18 PM
All the old wringer washing machines around here have been made into power hacksaws!

10-04-2013, 03:41 PM
Depending on how much space you have for the pulleys, a pair of 2" and 12" would give you 47.5 rpm.

10-05-2013, 01:05 AM
Unless you need to go straight through, look for a 'right angle drive'. They are compact and use a worm/wheel arrangement, and are often sold surplus for under $50. A 40:1 ratio is fairly common and would get you close.

10-05-2013, 01:09 AM
a used car windsheild wiper motor and gear box assembly, certainly cheap !!! might be able to use just gear box, as motor is 12V.or just use a 120V to 12V inverter.Or try a FWD self propeled lawn mower gear box,most already come with one pulley mounted.Both of these are dirt cheap and continuous duty use.

10-05-2013, 02:40 AM
For a sand muller Id just go with the belt reduction. Keep it simple. Its a dirt op :) JR

10-05-2013, 08:18 AM
If you have the space for it and don't mind a junkyard solution, you can get a large speed reduction using an old car engine flywheel and the pinion from the matching starter. I saw that done once to gear down the drive on a bandsaw for metal cutting, worked great. The most direct route is still likely an ebay or surplus center worm drive though.

Let's see pictures when you have you muller done!

10-05-2013, 08:33 AM
For a sand muller Id just go with the belt reduction. Keep it simple. Its a dirt op :) JR

A 43:1 reduction with multi stage belts would not be all that simple!

J Tiers
10-05-2013, 09:03 AM
A 43:1 reduction with multi stage belts would not be all that simple!

Either 2x 6.5:1 reduction, or 3x 3.5:1 reduction.

The Artful Bodger
10-05-2013, 03:29 PM
One of the problems with a multi stage belt reduction would be the torque to be handled on the slower stages. The suggestion of alanganes of using a starter pinion and flywheel is a good one. One belt reduction to drive the pinion at the required speed.

10-05-2013, 05:05 PM
Either 2x 6.5:1 reduction, or 3x 3.5:1 reduction.

I wasn't referring to the simple mathematics required.