1/2 HP 3-speed motor too big for small homemade tumbler?

[digitalblue]

My logic was that under less load I could turn it slower, I guess that doesn't make sense now that I think about it again... but that's why I'm here asking!

The amount of torque/load you demand from the motor is what heats it up, running the motor at a lower RPM doesn't decrease the amount of torque required to turn the drum.

You can either go with a more powerful motor (so that you're using a smaller percentage of it's max output torque) or you can increase your mechanical reduction ratio.

Obviously there's is a point of diminishing returns when it comes to increasing mechanical reduction ratio, drum speeds below ~30RPM will result in unacceptably long tumbling times so it's all a balancing act.

 

[mactroneng]

You don't need a big motor to power it.

Mine is pretty small (breadmaker motor and belt speed reducer) but does the trick. I use a 6 inch pvc pipe drum that holds 4.5 liter and is for sure big enough.
Also made a drum from 10 inch pipe and the moter can spin it no problem but a big drum gets uncomfortable to handle (very heavy when full of pins, brass and water) so if I have a larger batch I prefer to run my 4.5 liter drum twice.


Here are some more ideas. Mine is in post 33 and 35.
Good luck!

https://www.canadiangunnutz.com/forum/showthread.php/1487550-Homemade-tumbler-Who-s-made-one

Thanks, looked quickly at your post but will check out that thread in more detail.

I'm not really worried about the size of my motor, I figured that half a HP should be plenty, it's just what I had laying around. And at 1050 RPM on high speed, running at low speed should make it easy to slow the drum down enough, and give an allowance to upgrade in the future (multi-drum setup maybe?).

My other option is the blower motor that I pulled out of the old furnace, it says it's 120V/0.75A so it'd probably due fine from a power requirement, but it's rated at 3450 RPM and only single speed so I'd need a lot more gear/belt ratio to get the drum down to a proper speed.

 

[Ed Smurf]

Has anybody used a VFD (variable frequency drive) instead of the reduction gear set up?

 

[VinnyQC]

Thanks, looked quickly at your post but will check out that thread in more detail.

I'm not really worried about the size of my motor, I figured that half a HP should be plenty, it's just what I had laying around. And at 1050 RPM on high speed, running at low speed should make it easy to slow the drum down enough, and give an allowance to upgrade in the future (multi-drum setup maybe?).

My other option is the blower motor that I pulled out of the old furnace, it says it's 120V/0.75A so it'd probably due fine from a power requirement, but it's rated at 3450 RPM and only single speed so I'd need a lot more gear/belt ratio to get the drum down to a proper speed.

Either way you're gonna need a gearbox of some kind to reduce the speed/increase torque. I would target something like 40-80 RPM.

 

[mactroneng]

Either way you're gonna need a gearbox of some kind to reduce the speed/increase torque. I would target something like 40-80 RPM.

For sure, it's just a matter of ratios that have to be used. What I fear with the smaller, much faster motor is that I'll need an additional step down to make it work.

 

[digitalblue]

Thanks, looked quickly at your post but will check out that thread in more detail.

I'm not really worried about the size of my motor, I figured that half a HP should be plenty, it's just what I had laying around. And at 1050 RPM on high speed, running at low speed should make it easy to slow the drum down enough, and give an allowance to upgrade in the future (multi-drum setup maybe?).

My other option is the blower motor that I pulled out of the old furnace, it says it's 120V/0.75A so it'd probably due fine from a power requirement, but it's rated at 3450 RPM and only single speed so I'd need a lot more gear/belt ratio to get the drum down to a proper speed.

Do not bother with the 3450RPM motor, you would need ridiculous pulley sizes to reduce this down.

Take for example my tumber with a 1/3HP 1750RPM motor, here are the calculations:

Motor pulley (1.5"OD x 1/2" Bore) spinning the roller pulley (4"OD x 3/4"Bore) results in a 2.66:1 Reduction.
The 3/4" Dia roller spins an 8" OD drum, resulting in a 10.6:1 reduction.

The overall ratio (motor : drum) is 28.2:1 which results in a drum speed about ~61 RPM.

You cannot find a pulley smaller than 1.5" OD that'll still fit on a 1/2" bore, so your motor pulley is likely one of the constraints you'll need to work against.

 

[mactroneng]

That makes sense, looks like my motor is going to be fine, just gotta source some parts.

In the meantime I have to source something to use as bearings for the rollers... this is very much going to be a cheapy-cheap redneck contraption.

 

[digitalblue]

That makes sense, looks like my motor is going to be fine, just gotta source some parts.

In the meantime I have to source something to use as bearings for the rollers... this is very much going to be a cheapy-cheap redneck contraption.

If you're willing to wait, princess auto occasionally runs sales on their pillow block bearings, you can usually pick them up for about $6 a piece then.
Since your drum weight is going to come around 5lb, you can get away with using 1/2" dia round stock as rollers, this smaller dia will actually help with the reduction.

 

[VinnyQC]

Do not bother with the 3450RPM motor, you would need ridiculous pulley sizes to reduce this down.

Take for example my tumber with a 1/3HP 1750RPM motor, here are the calculations:

Motor pulley (1.5"OD x 1/2" Bore) spinning the roller pulley (4"OD x 3/4"Bore) results in a 2.66:1 Reduction.
The 3/4" Dia roller spins an 8" OD drum, resulting in a 10.6:1 reduction.

The overall ratio (motor : drum) is 28.2:1 which results in a drum speed about ~61 RPM.

You cannot find a pulley smaller than 1.5" OD that'll still fit on a 1/2" bore, so your motor pulley is likely one of the constraints you'll need to work against.

Can use a gearbox instead of just pulleys to reduce speed. A planetary gearbox with a ratio of 1:50 would take that motor to 69 RPM, a speed that OP can work with easily.

 

[mactroneng]

If you're willing to wait, princess auto occasionally runs sales on their pillow block bearings, you can usually pick them up for about $6 a piece then.
Since your drum weight is going to come around 5lb, you can get away with using 1/2" dia round stock as rollers, this smaller dia will actually help with the reduction.

Actually they aren't that expensive to begin with, not sure what website I saw before but the price looked ridiculous... maybe I glanced at the wrong thing by accident.

 

[Grizzlypeg]

If you need bearings for the non drive rollers, skateboard bearings are really cheap and can handle a lot of weight. If you were around here, I'd give you some used ones.

 

[mactroneng]

If you need bearings for the non drive rollers, skateboard bearings are really cheap and can handle a lot of weight. If you were around here, I'd give you some used ones.

My initial thought was actually roller skate bearings.

 

[Grizzlypeg]

My initial thought was actually roller skate bearings.

In most cases, the same thing, if you are talking about inline skates.

 

[mactroneng]

In most cases, the same thing, if you are talking about inline skates.

After a quick bit a research, both look to be the same. Gonna hit a Value Village and see what they have (assuming it's cheaper... VV prices have been going up more for the past little while)