[mxtras]

So my current thinking is to use a single, vertical shaft in the center of a cone shaped bowl. The bowl could be built from steel sheet, welded and then coated with urethane or a spray in bed liner.

This shaft could have one eccentric at the base and one at the top of the cone to create a wobble in the tub. Each eccentric or counterweight could be adjustable - possibly on-the-fly if I can figure out how to accomplish that but on-the-fly adjustment is not necessarily a requirement.

I am also thinking about 3/8"-3/4" of total amplitude with variable speed. If I can adjust the speed and the amplitude, I could create the motion needed for each batch of parts. I like having flexibility - especially when I don't really know what the heck I am doing. I have even come up with a way to move the upper eccentric/weight up or down on the center shaft to alter the rocking action.

It also looks like this equipment supply market is a bit thinly populated (small, full feature equipment under $1500).

Thoughts?

Scott

[Stepper Monkey]

I have three pretty generic cheapo units that came with fixed weights, but quickly found the need to modify them by making adjustable weights for them
(a big cap screw tapped into the hub at 90 degrees to the shaft, two stainless nuts to run up and down the shaft and lock together). I also found adding cooling fans to the ends of the shafts very useful as they can get pretty hot after a few hours run time.

I can't see that an on-the-fly adjustable weight is necessary, but adjustable weights and speeds are definitely useful. Actually, most fine control seems to be best done by just adjusting the weight of the load, or just water level if its running wet. Between all those variables you can control amplitude and frequency which is nice to find the sweet spot for any material.

[Harryman]

I would suggest that if you want to make a concentric vibratory tumbler to buy the bowl. A metal one would be loud and I don't think you have much luck with any coating staying on. Between the abrasive media wear and it hammering away at the bowl, it'd be toast.

Figure on experimenting with frequency (shaft rpm) and amplitude (weight and offset) and design that in. The amount of parts, media and fluid you run will all effect the results as well.

A tub tumbler made with a plastic barrel or other container would be the easiest if you want to go from scratch.

[Stepper Monkey]

What he said. If you aren't going to modify an existing unit, at least buy a standard replacement bowl for an expensive commercial unit and build the rest from there. They are readily and cheaply available from all manufacturers as they are standard wear items.

I think a metal bowl would be a relatively bad idea as well. The commercial units (that type anyway) don't use them either, probably for good reason, which may only be the horrible noise or maybe more, I don't know. In any case no coating would stand up for long at all, that is a guarantee!

[Unabiker]

Sorry to be a bit late to the party.
I agree with the others that you would probably be ahead of the game going with a pre-existing plastic based tub instead of a metal one with a liner. Any sort of goo that you could spray in place will most likely come off too easily or leave marks on the stuff your de-burring. I went with the recycled plastic barrel, mainly due to the fact that they are nice and thick, and I can buy them localy for $5 each. You may want to take a look at a 5 gallon bucket.
Regardless of the tub used, you will want to make adequate accomodations for a drainage system. I started off using 1/2" hose with barb fittings on mine, and that pretty much sucked. It would clog easily with either media or the goo produced by shaking. I'm currently using a bathtub drain setup with good results.
I'm not sure how usefull on-the-fly adjustment of the weights would be. Once I got it pretty close, I left it alone. I haven't messed with the weights in over a year. I do all the adjustment on my machine via speed control, media load and juicing frequency.
Another thing I would reccomend to consider during the design phase would be some sort of sound proofing. I like my shop a lot better after the last shaker upgrade and big sound resisitant box.
Keep us posted.