My Granddaughter is now 8 years old, during walks she has always collected pretty stones.
So, I thought about getting her a stone polisher, was a bit shocked at the price, talking £80 for a cheap one, £115 for a good one, but they go up to thousands!
So, I've created a very simple stone polisher of my own design. It's still very much a work in progress.
Stone Polishing is long term, there are usually 4 levels of grit from coarse through to polish. The stones need to be tumbled at approximately 1 turn per second for a complete week for each stage.
So far I have done 1 week of coarse and am currently on day 3 of stage 2, so early stages.
Been no problems so far.....
Basic design:
Photo of final result.
4 off standard Skate Board 608ZZ, I get these from EBay at 10 off for £2.32.
1 off Flextec FRC365SA DC motor, I bought these off EBay some time back:
- Flextec motor
- FRC365SA,Dc Motor,41V,17000RMP,air compressor
- 3-12v NOMINAL 12v
- No Load: 25500 RPM, 0.40 Amp
- Max Efficiency 20930 RPM, 1.83 Amp, Torque 5.36 mN.m 54.6 g.cm 11.7 Watt
- Stall Torque 29.9 mN.m 305 g.cm 8.4 Amp
Motor is directly soldered to a Maplin mains PSU:
Small gear is mounted to motor using 2 off M2 nuts and grub screws. I also had to create flats on motor spindle.
Rollers are printed and threaded internally.
Rollers are coated with Ooogoo rubber, mould printed.
For Oogoo, see here:
I use 1 part Cornflour to 1 part Silicon and I colour it with printer ink to any colour I choose.
In this case rollers are covered with Magenta Oogoo.
Drum is sealed with a layer of red Oogoo inside both caps.
Drum centre is covered in a layer of Oogoo, then covered in a layer of red electricians tape.
Whole base is sealed with red Oogoo.
It's LOUD, gears make a noise, plus exposed gears could be a safety hazzard, so I added a cover over the gears, that made the gears quieter, but still too loud. Originally I ran it without grit or water, imagine stones tumbling once per second!
So, I built a sound box. Simple ply wood, glued together with PVA glue, then used carpet tiles (lying around) to carpet the plywood box on inside AND outside:
See photo of tumbler, it is mounted to base of ply carpeted box, this box goes over like a hood. Granddaughters name signifies side with cable exit.
More photos:
It's running now in bedroom directly upstairs from where I am sitting, I can just hear it rumbling in the background.
After 1 week of coarse tumbling, stones were nicely rounded, it is working as expected so far.
But time will tell.....
Motor died during last day of 1st week, I hoped this was a bad motor, so switched it for a new one.
After 5 days of second week, motor gave out. They seem to still work but have no power.
So, this time I took both motors apart, suspected brushes were worn out.
Brushes look fine, everything looks fine!
I dressed the armature (where the brushes rub) very carefully with a fine needle file.
Put it all back together, back to fully working.
Coarse week complete, medium week complete, fine next, then polish.
Stones looking really good, these are stones collected by my Granddaughter, not specifically stones normally tumbled, dying to see how they end up.
Maybe I'll try drilling some of them.
