Slowing down a motor for a tumbler

[nuge]

I have my tumbelina built and hooked up a 1 h.p. d.c treadmill motor. Not enough oomph, even with a .106 drive pulley ratio.

So I need some schooling on gear reducers. How are they rated? For example, here's a badge off a 15:1. Do I have to be within a horsepower value to match a particular reducer? How much torque would one expect to gain? Any other tips for the uninformed?

[pkrankow]

Torque goes up by your speed reduction, in a perfect world, there are losses in the real world but the often can be ignored. So if you have 1 ft-lb going in, you get 15 ft-lb coming out, but at 1/15 the speed, using your 15:1 reducer. The losses will show up in extra speed loss more than torque loss.

If you feed too much horsepower through a gear box you break the gearbox.

Phil

[HWooldridge]

I ran a 55 gal barrel with a 1750 1/2 hp cap start motor and one short jackshaft under the frame to get about 20 rpm on the barrel. Bought the V-belts, pulleys and pillow blocks at WWGrainger; motor was out of a washing machine.

[Yetti]

one of the simplest ones I have seen was a 55 gallon barrel with a clamp on lid. it had a belt driven motor hangin off a limb that added tension at the back center of the barrel. the rig sat on a set of caster wheels so it would just roll in place. wasn't fast but it worked.

[clinton]

I would go with what HWooldridge said- use a jack shaft. Pillow blocks, sheaves and a shaft. Probably cheaper than a gear reduction box. Here is a link to a handy calculator that will assist you in figuring speeds and pulley size
http://gadi.agric.za/software/renting/pulley.php

[nuge]

Here is what I have going. I was all psyched about the dc motor with the speed control from the treadmill. Originally I had it hooked up to a 6.5 inch pulley but it was spinning too fast and bogging. Using the drum as a sheave works, the rpms are good at 30, but still not enough power. I am learning that maybe the motor does not have enough torque. Badge says 25 in/lbs. I am still trying to find some real world values for those numbers. I understand the bolt tightening aspect but don't really have a good feel for what kind of a value would be suitable for this, or other, applications. Do you all think a jack shaft would make 'er go? Might have to source a better power source.

On the gear reduction devices. So, if i have a 1/3 h.p. motor and a 40:1 reducer I am increasing the torque (and h.p.) by 40 times? I see gear boxes all over ebay, seems like a clean way to go and I wouldn't have to use as big of a motor.

[pkrankow]

HP remains the same.

HP = (torque * rpm) / 5252

5252 is a correction factor to make horsepower

http://www.ajdesigner.com/phphorsepower/horsepower_equation_rotating_torque.php

Phil

[clinton]

I would just find an AC motor, maybe 1 hp. Look at garage sales I find them all the time and you can pick them up cheap 5- 10 dollar range. Then go with the jack shaft to get the rpm you need

[Rich Hale]

Gear reductioon boxes take some power to run..Depending wot it was bult for it may have large bearings and gears inside that add to that. LAst one I took apart had about one inch shafts with appropriate roller bearings to hold it together. It was mated to a one and a half hp motor.. your little motor does not have much power. If you had a torque wrench rated in inch pounds and put it in a vice so you cold move the dial to 25 you could feel how little that takes. One of the posts above told you wot is working with a 1/3 hp motor and those are cheap. The jackshaft and pulleys and pillow blocks are going to run you some bucks..but it will work.

[gearhartironwerks]

Nuge,
Nice tumbler!
JE

[timgunn1962]

A smaller motor pulley, or even driving directly from the shaft, might help. Alternatively (or additionally) attaching a larger diameter to the drum and driving that? It would only need to be wood or MDF, and it looks like you could go at least 50% bigger than the present drum diameter without hitting the frame, giving a 50% torque increase.

I can't make out the belt or pulley details. If you're limited on the small pulley size by the belt section, you could try a polyvee belt. They tend to be used a lot in tumble dryers over here. I think the automotive ones tend to be a larger section, so might not work as well on really small pulleys.

If you can't do it on a single-step drive, an intermediate shaft is likely to prove cheaper and easier than a gearbox.

It looks like you have a nice heavy axle for the drum, so driving it with a cement mixer gearbox might be worth considering. They seem to give around 30-50 RPM at the drum and are worm drive so I'd guess at a reduction of between 25:1 and 50:1.

[ThomasPowers]

In general you don't want to put more HP into a gear reducer than it's rated for as it can be bad for the reducer. Putting less horsepower in may be rougher on the motor. However if you have more HP than you need for the tumbler then having a bit less than the gear reducer is rated for should be fine.

My advice: try it for a while and then check the temperature of the reducer and of the motor---if one is running hot find out why!