Suggest a place that can make some developing tubes

[Oren Grad]

By the way, out of curiosity, can anyone let me know the approx. diameter of the opening of one of the developing cylinders in a 3006 and/or 3010 (3010 should be larger).

A little tricky to measure, as the well narrows a bit a few millimeters down and it's difficult to get a ruler inside. Waving a ruler around just now and squinting at it sideways I'd estimate about 58mm inner diameter at the narrowing in the 3006 and about 66mm in the 3010. Of course that also doesn't allow for the barreling. Anyway, hope that's useful.

[Drew Wiley]

Ditto. Just get some short sections of dirt cheap ABS drainage pipe. But one thing others haven't mentioned is that you need to scrub them well before use, including the caps.
ABS manufacture involves mould release compounds containing sulfur, which will affect developers.

[Michael R]

Thanks, Oren. Those are good enough - I was just trying to get some rough numbers.

I didn’t know the cylinders/wells in the Expert drums were barrel-shaped, but I guess that makes sense. Looks like I’m partially re-inventing the wheel in this one, but it is interesting nonetheless.

Thanks again.

[Michael R]

Resurrecting this thread with some more questions about the Expert drums - working principles. Looking for people’s thoughts.

I’ve just acquired a 3010 drum. Putting some bits and pieces of info together (including minimum solution volumes), it seems like what is supposed to happen - assuming the drum is horizontal the entire time on a Jobo machine - is the solution collects in the lid in the empty space next to the cylinders/wells. As each cylinder rotates into the lowest position radially, it fills at least partially with solution, and then empties as it rotates upward again. How full each cylinder gets as it rotates into the lowest position would depend on the total solution volume, and possibly the rotation speed. There should always be some small amount of solution in each cylinder due to the slight barrel shape, but presumably the rest would always empty as the cylinder rotates upward from the lowest position.

Does this seem correct?

It is difficult to visualize what different solution volumes would look like (ie is the cylinder opening fully or partially submerged when it is in the lowest position? etc)

I am puzzled by the YouTube video posted by CatLABS of an Expert drum (3006) made of clear plastic (lid is black), demonstrating how it works. In that demo, it appears a significant volume of solution remains in most of the cylinders even as they rotate upward and around. How does that happen? And if that is what ends up happening, the development dynamics could be quite different than what I described above.

The reason I’m venturing down this hold is that I’m still trying to figure out if I can cobble together a small volume, manual contraption that essentially duplicates the way the Expert drum works in principle. We know the Expert drums on a Jobo machine are capable of producing excellent uniformity - probably the best. So I’m trying to figure out what actually goes on.