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Thread: Pebble Tumbler !
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6th Aug 2022, 11:56 PM #1
Pebble Tumbler !
Hi Guys,
I've found a lovely 24 volt DC electric motor complete with a Hall effect speed feedback sensor. It originally came out of a scrapped colour printer and was part of the print head drive. Its a pity that I didn't keep the gear or belt that it drove. I've measured the motor speed at 24 volts and it rattles along at 12K rpm taking just 0.7 amps off load.
05-08-2022-001.JPG 05-08-2022-003.JPG 05-08-2022-002.jpg
The overall length is 60 mm and its 32 mm diameter. You can see the Hall sensor on the right just under the edge of the magnetic disc. The pink and blue wires are paired and were originally fitted in the white terminal/connector strip. The other four wires are connected to the Hall sensor chip.Best Regards:
Baron J.
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7th Aug 2022, 12:09 AM #2
Roller shafts !
Hi Guys,
After having a search around in the bits and pieces that I have in the workshop, I've found two rollers that I think will be suitable for this project.
06-08-2022=001.jpg 06-08-2022=002.JPG 06-08-2022=003.JPG
Both these have 6 mm diameter shafts and are 223 mm long across the rubber. One is 13 mm diameter and the other is 12 mm diameter. One of them has a drive flat on the end of the shaft. Again both these were salvaged from scrap printers. Originally they would have had plastic bearings supporting the shafts at one time, non of which I still have.Best Regards:
Baron J.
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7th Aug 2022, 01:46 AM #3Most Valued Member
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Hi BJ, I think for a pebble tumbler 12K RPM might be a little bit too fast, 12 rpm might be a bit closer to what's required, I think!!!!
But nice score on the bits, I've scored quite a few shafts, stepper motors, and plastic gears out of all sorts of copiers, printers etc.
KrynTo grow old is mandatory, growing up is optional.
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7th Aug 2022, 03:08 AM #4China
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I agree with Kryn
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7th Aug 2022, 05:21 AM #5
Hi Guys, thank you for your comments, they are appreciated.
Yes I agree that 12K rpm would be a bit too fast, but I am sure that between gearing it down and speed control I can get a reasonable speed, anyway slowing the motor down by gearing and reducing the voltage across it hopefully would reduce any heating particularly since the motor is totally enclosed and doesn't have a fan.
Now you’ve mentioned stepper motors, I hadn't thought about using a stepper motor, I have a lot of those kicking about.
While testing the motor using a variable voltage PSU I was surprised to discover that it runs at a mere 2 volts, no load of course.
Now I need to find a suitable canister to use as a drum !Best Regards:
Baron J.
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7th Aug 2022, 02:25 PM #6Most Valued Member
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An emty paint can and lid, should do the trick, or IF you can find one, a container with a screw on lid. I don't think a plastic one will survive very long, depending on the size pebbles you want to smooth of in it.
https://www.amazon.com/National-Geog.../dp/B01LQCIL88
Depending on the size required you could make one from a piece of poly pipe. You'll probably need to put some thin foam inside it to keep the nose down. Don't want to upset the neighbours.
I used to use a concrete mixer to do tumbling of cut and punched parts, but that was in an industrial area.
KrynTo grow old is mandatory, growing up is optional.
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7th Aug 2022, 04:34 PM #7Golden Member
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I considered using stepper drives but I don't think they are rated for continuous running?
I think any container will just about do, steel, plastic, glass jar etc. use a piece of rubber or silicone sheet cut to the I.D circumference and length, roll it up and put it inside, it'll unravel to line the walls protecting the drum material and reducing noise
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7th Aug 2022, 06:17 PM #8
Hi Kryn, Ned, Guys,
Kryn, thank you for that link ! I hadn't seen that one though when you look at my drawing you will see that its very similar in style.
Ned, thank you for the plastic pipe idea ! I have several feet of 100 mm white PVC plastic fall pipe that I can press into service as a canister. The picture in Kryn's link with a rod and knob through the centre of the canister to secure the ends is a quick and easy method of holding it together.
My drawing:
Pebble Tumbler-01.png
This picture is basically the end view. The motor is the green circle at the bottom with the belt and large pulley in purple. The light blue bit represents the 100 mm canister. I have a sheet of 15 mm thick plastic that I propose to make the end frames from. I might simply be able to drill 6 mm diameter holes to support the rollers, though I do have suitable ball races that I can use. I propose to use a timber base and fasten the end support frames with screws through the bottom coming up from underneath. I think that a simple "U" shaped clamp can be used to secure the motor and would allow some adjustment for tightening the belt.
I've a lot more work to do finding the rest of the bits.Best Regards:
Baron J.
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7th Aug 2022, 06:19 PM #9Most Valued Member
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I had to google what a pebble tumbler was!
Simon
Sent from a galaxy far far awayGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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7th Aug 2022, 06:22 PM #10
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7th Aug 2022, 09:05 PM #11
New drawing !
Hi Guys,
I have redone the drawing with some corrected dimensions !
I got the motor diameter wrong, its 40 mm with a 10 mm diameter gear on the shaft.
Pebble Tumbler-02.png
I've also moved the motor a little to the left to allow belt adjustment.Best Regards:
Baron J.
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7th Aug 2022, 09:29 PM #12Golden Member
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Here’s a pic of my rifle brass tumbler, and a new drum I’m making from heavy wall HDPE pipe, diameter is 250mm with a clear polycarbonate lid, I’ll drill and tap for M8 studs and M8 thumb screws.
F9EF4A65-AD74-4B4D-94E5-E065EC7240B4.jpgC7A0133B-D06E-46B6-85F8-991F84913629.jpgE4E91721-4AAF-476E-874D-5A1E91BFE0D1.jpg
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7th Aug 2022, 11:13 PM #13
Hi Ned,
Thank you for the pictures ! It looks very substantial. Are those 38 calibre cases ? What is the material that you are using to clean the brass ? One of the web sites mentioned using silicon carbide and water, but that was for gemstones. I thought that a sand and water solution was what was used.
Unfortunately Granddaughter is away on holiday, so I can't ask her what they use at school.
When I start to make the container for mine I will post pictures of it. At the moment I'm cutting two end frames out of Nylon 66 sheet plastic as per the drawing. I also have some Nylon 60 bar that I can make the end caps out of and the large pulley. Somewhere in my bits and pieces I have some salvaged flat rubber belts, I hope that one is a suitable size.Best Regards:
Baron J.
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8th Aug 2022, 12:07 AM #14Golden Member
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Hi,
Those are 30-06 cases and I'm using a commercial corn cob media, next time I'll buy a bag of walnut husk used in sand blasters (cheap)
Garnet media might be good for your application? as long as it's higher on the hardness scale than the rocks your granddaughter will be tumbling, although it might be easy to find/purchase purpose made silicon carbide media online?
I actually purchased that heavy wall HDPE from a guy who tumbles gemstones, he had about a dozen drums that would all run continuously for weeks!
I had a bit of a chat with him and he said he uses silicon carbide but he has one issue with using that with rocks/gemstone with patterns through them, the softer mineral areas will erode at a different rate to the harder minerals.
Probably not an issue to a kid just having some fun polishing rocks,
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9th Aug 2022, 05:28 PM #15Most Valued Member
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John/Ned,
I knew a bloke many years ago that did competition pistol shooting and he used to tumble his shell cases before reloading them, he used rice in the tumbler.
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