Tumbler - low budget winter project

Dusty Eagle · Dec 28, 2008

I was thinking about making a tumbler, but trying to keep the project low budget, similar to the ones mentioned before in other message boards.

http://metaldetectingforum.com/showthread.php?t=14194&highlight=tumbler

I say low budget but my wife sometimes compares me to Tim Allen/Tim Taylor on Tool Time.

, but for my tumbler, I already have several components. I have 4" Sch40 PVC pipe, and had a 4" threaded plug left over from other plumping projects. I figured I could use a toilet tank bolt with rubber washer if needed, for the cap and have an assortment of other bolts, bushings and hardware in my shop. I've been looking for some type of motor though, even from the local hardware stores, until I came across one that I had found in my shop today. It's from a 50 year old garage door opener. I check for continuity and it seemed to be ok so I plugged it in. Dang if it didn't work! :yes:

My question is this. What is the speed, RPM that coin/rock tumblers need to run at to be effective for coin polishing?

The motor runs at 1800 rpm with a 1/2" shaft. it currently has 1" V-belt pulley on it. I have some other pulleys recovered from the garage door opening as well. I need to try and find the speed required, so I can see if I can step down the motor, or if possible, run it through a potentiometer switch to make it variable speed. Any suggestions?

Dusty Eagle

tony48 · Dec 29, 2008

I never did finish that project. I found another motor to use instead of the drill. I am now using a salvaged electric motor from a blower on an old fireplace. Maybe I will finish that project up when it is really cold out.

I don't know about a good speed for a tumbler, but it is WAY below 1800 RPM's.

One thing you should do is put something on the inside of the tumbler tank to break up coins form staying on the outside because of centrifical force. On the link if you read the posts, there are some good ideas. If you look inside your dryer, you will notice 3 things sticking out from the sides to break up the clothes from sliding.

Dusty Eagle · Dec 29, 2008

rpm's

I agree too, that the rpms of the motor are too fast, but when it was hooked up for the garage door, it ran through a series of pulleys which I also still have. The motor has a 1" diameter pulley on the 1/2" shaft. I believe the 1" pulley was driving a 4" diameter pulley, which is directly connecte to a 11" diameter pulley. The 11" pulley was then connected to a 9" diameter pullley... I think...
So, any mathematicians? What's the rpm of the 9" pulley? :?:

At least that's how I THINK it was hooked up.

Oh, and I was planning on either using 3 lengths of a 1/2" pvc pipe, cut in half the long way to make a half round or some plastic angle set on the edges, but I would have to buy some somewhere. But I might try a strip of door seal I found in my shop. It has plastic fins on a strip about 1 1/2" wide and would just glue the three peices of what ever I use to the inside surface of the pipe.

Dusty Eagle

ICE · Dec 29, 2008

Try finding a grill rotisser motor it would work. Might have to put rubber on the inside of the pipe or the coins might just slide instead of tumbling. I was thinking of making one and drew one up. For rollers you could use a two pieces of 1 inch PVC pipe with all thread run threw them with washers on the inside this would allow them to roll eaiser Here a quick pic I just drew up I don't have autocad here at home. Make sure the washers are a tiny bit smaller than the pipe. Ice

Dusty Eagle · Dec 29, 2008

my calculations

If my calculations are correct, the 9" pulley would be turning at 100 RPM.
:roll:

Dusty Eagle

kendallkirk · Dec 31, 2008

Dusty Eagle said:
I agree too, that the rpms of the motor are too fast, but when it was hooked up for the garage door, it ran through a series of pulleys which I also still have. The motor has a 1" diameter pulley on the 1/2" shaft. I believe the 1" pulley was driving a 4" diameter pulley, which is directly connecte to a 11" diameter pulley. The 11" pulley was then connected to a 9" diameter pullley... I think...
So, any mathematicians? What's the rpm of the 9" pulley?

The 4" and 11" (direct-connected) pulleys would be turning at 1800*(1/4) = 450 rpm. The 9" pulley would be turning at 450*(11/9) = 550 rpm.

If you swapped the order so that 1" drives 11", which is direct connected to the 4" that drives the 9"... then the 11" and 4" (direct-connected) pulleys would spin at 1800*(1/11) = 163 rpm and the 9" pulley would spin at 163*(4/9) = 72 rpm.

tony48 · Jan 1, 2009

kendallkirk said:
The 4" and 11" (direct-connected) pulleys would be turning at 1800*(1/4) = 450 rpm. The 9" pulley would be turning at 450*(11/9) = 550 rpm.

If you swapped the order so that 1" drives 11", which is direct connected to the 4" that drives the 9"... then the 11" and 4" (direct-connected) pulleys would spin at 1800*(1/11) = 163 rpm and the 9" pulley would spin at 163*(4/9) = 72 rpm.

Good math! It hurts my brain reading that!

Dusty Eagle · Jan 1, 2009

but he's right..

but he's right..except for one thing.. under magnifying glass, I have found the motor to actually have 1750 rpm's not 1800. :cool:

Is 70 RPM still too fast for a tumbler? Not to mention that my tumbler may have to have it's own personal stand.. which I may add, I just might happen to have. I have a radial arm saw that has seen better days, and I just might adapt the stand that it sits on to mount the motor, pulleys, drive belts, tumbler container and maybe a few safety guards. It's starting to sound like I may have the only +$200 plus coin tumbler on a $20 budget! :lol:

Dusty Eagle

kendallkirk · Jan 1, 2009

Windshield wiper motor

Another idea...if you have one laying around...is to use a windshield wiper motor to direct drive the tumbler. I have used them many times on random applications because they are cheap (junkyards are full of them), capable of high torque applications, easy to vary the speed (simply change the voltage supply), and rated at a high duty cycle (you can run them continuously for long periods of time).

Main 2 difficulties to overcome are (1) the relatively high current requirement (can't use any old dinky AC/DC transformer, I have used larger transformers from printers in the past) and (2) coupling your shaft to them can take some creativity.

kendallkirk · Jan 1, 2009

Dusty Eagle said:
Is 70 RPM still too fast for a tumbler?

Wikipedia says 20 to 38 rpm for what it's worth.

ICE · Jan 1, 2009

Rotisserie motor would do great I got one at a yard sale for $3.00. Look for someone throwing out old grill after Christmas may find one for nothing. Ice

Tumbler - low budget winter project

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