DIY jobo base (work in progress, input welcome)

[Colin Graham]

This is a rock-tumbler style motor base I've been tinkering around with for the past few months. Getting the motor and driver sized right was a little tricky for an electronic illiterate like me, but this last version seems to work well with a 12v DC car seat motor and a 10A speed controller board. (More details through the link on the video page.)



The motor had a right angle lead screw attached to it that I wanted to drive the drum shaft. The drive was a weird mix of helical and worm, even the lead screw itself was a strange size, so I ended up hacking off the whole transfer case and using a chain drive. You can see the vestigial worm drive shaft sticking out past the chain sprocket.

Anyway, not sure how much the frequent reversing of the motor will hurt the driver or motor itself over time, but it's working well so far. Now that I have the drive ratio, torque, dB, and a nice broad range of available speeds worked out, I might try a programmable version of this to automate it a bit more. The motor specs list a 25A stall current, but only draws about 1.5A no load. I haven't hooked a multimeter up to it to check the current draw during the switch reversal (mine's MIA), but I'm only using it in the 30 RPM range at light loads. Those higher speeds in the video test were mostly to test the stability of the drum on the rollers. The thing can really fly, almost 120 RPM with a liter of solution at full speed! But I only dared to go halfway on this clip.

Anyway, it would be great if any of the electronically-inclined folks here could point out any potential problems with my setup or suggest a good compliment of motor controller/logic board for this motor. Also, how bad do you think I'm stressing the components switching directions so often?

Thanks in advance for any input.

[David Karp]

I know nothing about electricity and motors, but your creation seems awesome.

[Richard Wasserman]

I unfortunately can't help with any of your questions, but I will be following this with great interest. Looks very nicely done!

[koh303]

Cool project.

Watch your fingers on that exposed drive chain and gears.

Reversing is good for your film, consider adding that into your automation.

[Jordan]

I've been waiting for people to start making these. Please continue and I would happily purchase one as I'm sure many others would as well. Well done.

[koh303]

I've been waiting for people to start making these. Please continue and I would happily purchase one as I'm sure many others would as well. Well done.

Not to detract from this very nice work, Beseller unicolor motorized bases have been around for decades and sell for next to noting.

[Colin Graham]

Thanks for the comments.

Koh303, that's funny, but I guess you're right. It does look a bit menacing with the whirling chain. I've stalled this by actually sticking my finger into the chain drive at the sprocket. It doesn't even pinch, so it's harmless. About the reversing, that's pretty much the point of this project. It's already got a manual rocker switch that allows for changing directions, as the video clip demonstrates. The next step is replacing the manual controller board with a motor driver that will handle the stall current, then I can automate the reversing cycles so I don't have to flip the switch manually. Actually, that's about the only thing I want to program, it's nice to be able to control the speed in real time.

This is the driver I think I need. But they're fairly pricy compared to what I've got into this, and coupled with an arduino is total overkill for what I want this to do. It would be perfect if I could manually vary the rotation speed with one potentiometer, the manually vary a motor-reversing delay cycle with another, but not sure if such a thing exists.

[Jordan]

The Beseller motor bases work indeed, but honestly they aren't great and especially with larger drums. They're slow and fairly unsteady. This is much much nicer and has speed adjustments.

[Colin Graham]

I agree with both sides about the Beseler motor bases. They're certainly adequate, but there were absolutely none to be found anywhere when I first started on this project. On the other hand they do seem loud and rather limited, and the videos I've seen of them in action inspired me to just make my own instead of waiting for one to pop up for sale.

This was inexpensive and easy to make. The only reason I'm in this over $40 is I tried several different motors, drive components and boards. The only reason it took more than a few hours to make is because I enjoy tinkering with DIY stuff. In fact I just replaced the chain and sprockets with a timing belt and pulleys, so now it's nice and quiet. But for now, I'm not going to try to automate the reverse cycles, it's just not worth the added complexity or extra expense. It's no hardship to just flip the rocker switch as needed. It's a pretty nice break from sitting in the dark shuffling film in trays.

[Drew Wiley]

It's kinda late in the game for any advice that I have. Ideally you want a gearmotor that translates the energy into a much lower RPM with higher torque, so you
could potentially drive bigger drum and solution volumes without bogging down. High RPM's are not really desirable in photographic processes. Lowering the speed electronically to 30 RPM helps, but its better to select a gearmotor and control which brackets the right correct mix/max working speed. I realize this is a fun project for you, and you should be commended for it. But if you want to do something more serious, get ahold of a Grainger catalog where you can peruse all kinds of combinations (their website is a poor substitute). Having reversibility is a nice feature, but not essential. But it needs to do this gently, not suddenly. A true linear rocking feature is more useful, esp when working with minimum solution volumes. I've always considered real Jobos motors to be underpowered and too fast. Allegedly the new ones have a bit more clout. Just make sure everything is moisture and corrosion resistant.