How about a 12 volt DC motor with a sliding setscrew counterweight so that you can adjust the amount of vibration... The counterweight will slide on a shaft, the further away the counterweight from the center of the motor shaft the more the vibration. The motor would need to be mounted solidly to the bottom of the hopper. The motor shaft would have the counterweight. A drywasher motor works on the same principal but uses air to rotate the motor and the counterweight creates the vibration.
It's a good motor but expensive and there are a few things you'll have to do.
Such as add a variable speed switch that won't damage the motor.
That needs to be a pulse-width modulated switch.
Jay here is a link to what Doc mention above but in a 12 volt version of the vibrator. What I offered in my first post this Vibco does the same thing but for a whole lot more $$$. Yeah they are expensive but they are built to the spec's not to wear out. Whatever direction you go it all needs to be sealed bearings due to the dirt and elements of outdoors.
The good ones are way too expensive for me. There's a place call Apache Reclamation in south Phoenix that might have a motor I can use. I'm gonna try there first and see what I can find.
so I found a 12 volt fan motor at the junk yard for $10. Hooked it up and tested some gravel. I got a few issues but nothing major. I have to tweek the angles and get the sluice level from side to side and I should do pretty good.
Jay did you make counterweight adjustable? Kinda curious how that blower motor is going to hold up due to the constant vibration. Is the motor shaft supported with ball or needle bearings or bushings?
I started small with the counterbalance and have added weight to where it is now. I should put a variable speed so it's not so loud when there is no dirt.
looks good JB EXCEPT for the fact that a person needs to use a sssssssssssshhhooooovel! I hate to use that word on the net but its the truth! its got me sweating just thinking about it! nice job!