Help with Motor Torque requirements for homemade tumbler

[sak]

Hi all,

I recently built a tumbler and I realized that my motor was too small given my setup.  I'm using 6" PVC barrels (resting on 1/2" steel axles) that weigh about 10 lbs each (w/rocks).  My tumbler is designed to support up to (2) barrels at a time.  My maximum loads (assuming I'm running both barrels) would be 20 lbs.

My design is typical (motor shaft pulley w/belt that connects to axle that rotates barrels).

I just found a gear reduction motor.  Can you guys tell me if it's got enough torque for my setup?  (FYI, I was initially planning on using a continuous duty motor without a gearbox, but I found this & thought this might be more efficient)

The motor w/gear reduction specs are as follows:

Speed -  38.4 RPM
Voltage -  115 VAC 60 Hz
Amperage -  0.24 Amps
Power  - 25 Watts
Torque - 40 in.lbs.
Gear Ratio  - 44.3:1
Rotation  - Reversible
Duty -  Continuous
Shaft  - 1/2" diameter
Mount  - 5 holes on front of gear case
Size  - 5" x 3-1/4" x 5-1/2"
Weight - 17 lbs.


Thanks for all your input.

Sak...

[pauls]

That size tumbler usually uses somewhere about a quarter HP motor.
1 HP is around 754 Watts, so 25 Watts I reckon is way too tiny.

[sak]

Jan 23, 2014 2:49:31 GMT -5 pauls said:

That size tumbler usually uses somewhere about a quarter HP motor.
1 HP is around 754 Watts, so 25 Watts I reckon is way too tiny.

Hi Paul's,
Thanks for your input. I was also thinking it might be small but I thought it work because of the gear reduction (I figured I'd get more torque with the gear reduction).

So much for that idea. I guess I'll be sticking with my original plan (larger motor w/o the gear reduction).

Thanks again.

Sak

[sak]

Jan 23, 2014 2:49:31 GMT -5 pauls said:

That size tumbler usually uses somewhere about a quarter HP motor.
1 HP is around 754 Watts, so 25 Watts I reckon is way too tiny.

Hi Paul's,
Thanks for your input. I was also thinking it might be small but I thought it work because of the gear reduction (I figured I'd get more torque with the gear reduction).

So much for that idea. I guess I'll be sticking with my original plan (larger motor w/o the gear reduction).

Thanks again.

Sak

[jamesp]

I agree with Pauls. Most gear boxes are worm drives and load the motor up a bit. And may break down. A rare spur gear gearbox is fine.
Nothing is more reliable and (99%) efficient as a good ole belt drive. I have a 1/8 HP 1000 RPM motor that turns a 40 pound drum at about 20 RPM.
Been running for 3 years non stop.

I usually put a 6 inch pipe O-ring on the posi traction pulleys on the right side ends of the shaft. I removed the rubber hoses.
the PVC barrel runs direct to steel. 1/8 HP

This is a 2 speed tumbler. The large barrel in the back ground turns fast for rough grind.
The three small barrels are turning slow for finish and polish.1/3 HP

[sak]

Jan 24, 2014 9:05:02 GMT -5 jamesp said:

This is a 2 speed tumbler. The large barrel in the back ground turns fast for rough grind.
The three small barrels are turning slow for finish and polish.1/3 HP

Hi Jamesp,

Thanks for your input. This isn't the first time you've given me some brilliant ideas.

Regarding your 2 speed tumbler... I never thought about doing a 2 speed setup. Based on your feedback I'm thinking of changing my design to incorporate 2 speeds.

I'm assuming your getting better results with that (as opposed to 1 speed).

So, here's my questions;

1) Are all your barrels (large & small) 6" diameter?

2) Have you determined that running at your "fast" rpm that your rough grind stage gets completed quicker?

3) What benefits did you notice when running @ your "slow" speed for finish/polish?

4)What is your "large" barrel "fast" rpm, and what is your "small" barrels "slow" rpms?

Thanks again.
Sak

[jamesp]

1 Have 6 and 8
2 yes, a lot faster. but only good for agates.Rose quartz and obsidian sometimes gets little cracks at fast speed.
The only thing i do on the fast shafts are agates,wood, jasper in coarse grind.
3 Do all 220,600 and polish and obsidian and rose quartz on the slow speed. And use 6 inch barrels only.
The fast speed just does not polish well.
4 fast is 50 RPM for 6 inch 38 RPM for 8 inch
slow is 24 RPM for 6 inch 18 RPM for 8 inch

Hope it helps.

[sak]

Jan 24, 2014 16:38:24 GMT -5 jamesp said:

4 fast is 50 RPM for 6 inch 38 RPM for 8 inch
slow is 24 RPM for 6 inch 18 RPM for 8 inch

Hope it helps.

Hi Jamesp,

Thanks for helping me. So, I just got my larger motor & I need to plan for my pulley sizes. My barrels are 6" and my original plan was to shoot for approx 50 rpms.

It's clear to me now that I should shoot for 25 rpms instead. I could also include a secondary smaller pulley on my axle that rotates the barrel to give me a higher rpm (I'm thinking like 35rpm) if I need it.

Sak.

[jamesp]

Here is the reductions

1750 RPM x3/22x1.5/7.5x3/6=24.5

3" motor pulley,22" tumbler shaft pulley,1.5" tumbler shaft,7.5" tumbler barrel,3"fast tumbler shaft pulley,6"slow tumbler shaft pulley

I used 1.5 inch shafts cause they were cheap from junkyard and they could hold a bunch of weight for future bigger barrels if wanted.

[quartz]

I use a 2" motor pulley and a 12" shaft pulley on a 1/2" shaft, gives 27 R.P.M. on a 6" barrel.

[sak]

Jamesp & quartz,

Thanks for your input. Although i haven't started tumbling as of yet I'm really enjoying this preliminary hobby of building a custom tumbler.

Thanks to all your posts, I just discovered the concept of steel recycling yards. I just picked up a perfect continuous duty motor for $10. Now I'm annoyed that I actually paid full price for precision steel rods

Sak.

[jamesp]

If you are going to build it consider Quartz design. The 1/2 inch shafts are way cheaper and require smaller pulleys and bearings.
I used giant shafts for future barrels that may be very heavy.
It is way over built for 6 and 8 inch barrels. And i tumble a very hard coral material on the 50 RPM shafts that takes a long time to tumble.

[jamesp]

Jan 24, 2014 23:20:22 GMT -5 quartz said:

I use a 2" motor pulley and a 12" shaft pulley on a 1/2" shaft, gives 27 R.P.M. on a 6" barrel.[/quote


If you are going to build it consider Quartz design. The 1/2 inch shafts are way cheaper and require smaller pulleys and bearings.
I used giant shafts for future barrels that may be very heavy.
It is way over built for 6 and 8 inch barrels. And i tumble a very hard coral material on the 50 RPM shafts that takes a long time to tumble.
For general tumbling 27 RPM is perfect. Jamesp