Rock Tumbler DIY -reduce RPM

[FAKKY]

Wife wans a rock tumbler (larger).

I have one of these I dont use much.

https://www.harborfreight.com/power-...fer-61557.html

Half inch arbor.
3450 RPM

I need to drop that down to around 30 rpm.

How do I work out the pulley sizes Im likely to need.

Similar to this setup.

[FAKKY]

Damn.
According to this website 1:100 ratio.

Meaning a 1" pulley small to a 100" pulley large.

Ratio 1 : 100

Surely thats not right.

https://www.blocklayer.com/pulley-belt.aspx

[samkost]

I am not a certified electrician
How about a rheostat?
https://www.harborfreight.com/router...xoCb9IQAvD_BwE

[FAKKY]

samkost - thats frigin interesting - just generally

I *think* the issue is the calculator only shows what the final shaft speed will spin at. Its not the final rotation speed of the actual container.

So its like a double reduction.

Gotta work out how to calculate that.

[truckster]

If we say your barrel is 6" in diameter and the drive rod is 3/4", that gives you a ratio of 8:1. So to reduce your 3450 RPM to 30 RPM you need a 14:1 ratio on your pulleys. If your drive pulley (the one on the motor) is 1.5" in diameter, you'll need a 21" pulley on the driven end to achieve 30 RPM.

If you increase the size of the barrel, the size of the driven pulley decreases proportionally. So unless you're planning on a relatively large barrel for the tumbler, your motor might just be too fast for the application. A controller would allow you to dial down the speed, but make sure it's rated for the wattage of your motor.

[cornerstone]

Couldn't you run the motors small pulley to a larger pulley on a shaft that has another smaller pulley on the other end? Then a belt that drives a third large pulley on a separate shaft that drives the tumbler? (To act as a gear reduction)

Will someone smarter than me please explain what Im trying to say

This picture is what I mean.

Or.... You could buy her a rock tumbler instead of giving her old stuff you don't use anymore. I'm kidding. I do this stuff all the time.

[Warrens69GMC]

How big of rocks? You could get a swamp cooler motor and a 55 gallon drum cheap enough....

[mongocanfly]

Just get a 1750rpm motor and itd solve half your problem...then reduce

[FAKKY]

Originally Posted by truckster

If we say your barrel is 6" in diameter and the drive rod is 3/4", that gives you a ratio of 8:1. So to reduce your 3450 RPM to 30 RPM you need a 14:1 ratio on your pulleys. If your drive pulley (the one on the motor) is 1.5" in diameter, you'll need a 21" pulley on the driven end to achieve 30 RPM.

If you increase the size of the barrel, the size of the driven pulley decreases proportionally. So unless you're planning on a relatively large barrel for the tumbler, your motor might just be too fast for the application. A controller would allow you to dial down the speed, but make sure it's rated for the wattage of your motor.

Thankyou !! Good stuff.

[FAKKY]

Originally Posted by cornerstone

Couldn't you run the motors small pulley to a larger pulley on a shaft that has another smaller pulley on the other end? Then a belt that drives a third large pulley on a separate shaft that drives the tumbler? (To act as a gear reduction)

Will someone smarter than me please explain what Im trying to say

This picture is what I mean.

Or.... You could buy her a rock tumbler instead of giving her old stuff you don't use anymore. I'm kidding. I do this stuff all the time.

Yeah - I started going down the gear reduction route with multiple.
Then I realized I dont know how to to do the most basic setup ..... so I stopped.

[FAKKY]

Originally Posted by Warrens69GMC

How big of rocks? You could get a swamp cooler motor and a 55 gallon drum cheap enough....

Npt sure ..... we have petrified wood anywher from the size of a dime all the way up to 20lbs.

Think the larger stuff we will just cut and polish.

[FAKKY]

Originally Posted by mongocanfly

Just get a 1750rpm motor and itd solve half your problem...then reduce

ha ha mongo.
You think just like me.

https://tampa.craigslist.org/pnl/mat...965955841.html

[GOPAPA]

[QUOTE=FAKKY;8585172]ha ha mongo.
You think just like me.




Fakky ,,others have given you good advice to what you ask,,and I have nothing to add except a story ,,(hope you don't mind ) it happens to do with rock polishing

Years ago I was a sawyer in a little sawmill and on week ends a millright

The mill was built up on piling where logs came up a slip to me at the headrig,,as I cut the logs in cants the sawdust /bark ect would fall down into a conveyor that took it out to the Wig Wan where it burnt up

So on one Saturday as I was working millright ,one of the millrights was working on the conveyor where the motor was at ,,,and he welded a big steel truck wheel onto the end of the shaft that came from the motor and run the conveyor chains ...

This how he got the stones he put in there shined ,,he used what ever compound you use to polish them with and the conveyor ran 2 -8 hour shifts day and night ,,

By any chance are
you a sawyer with a sawmill to do the same as the guy I knew..

[mongocanfly]

in post 12..still to much....https://tampa.craigslist.org/pnl/mat...965955841.html

[mongocanfly]

and for the rheostat in post 3 to work youd need a dc motor..not ac

here s a thought....you could use your wifes front load washer and dryer...!!!!!!

[GOPAPA]

Originally Posted by mongocanfly

and for the rheostat in post 3 to work youd need a dc motor..not ac

here s a thought....you could use your wifes front load washer and dryer...!!!!!!

Good one Mongocanfly ,, he probably does not have a sawmill to use to turn a tub ,,and the dryer would be handy ,,noisy but handy

[FAKKY]

Thanks Mongo/Gopa.

Here's some cross sectional with a tile saw.