I use a unicolor motor base with a Jobo drum and have had no trouble with Xtol 1:1 or Pyrocat. I don't think the unicolor motor base is too fast. I've seen posts claiming that using a dimmer switch (or any other SCR based speed controller) could damage the motor of the rotary base. I have never tried it, so I don't know. You might want to do a forum seach for that.
I don't think you'd want to fool around with a POT in the AC line. Dimmers (and presumably motor speed controllers) use SCRs that change the effective duty cycle of the AC sine wave by opening the circuit at a particular angle in the waveshape as determined by the dimmer setting. The benefit is that they don't need to dissipate much heat themselves. A POT would simply divide the energy between the motor and the POT so the POT would get hot.
Originally Posted by walter23
Dimmers work great for incandescent lights, but I'm not sure they're very good for some types of motors. Having said that, I use a light dimmer on my Dremmel drill and it works just spiffy. If the motor doesn't get real hot, then it's probably ok.
I've been using the MLCS router speed controller with absolutely no problem. The unit was designed to be used with single speed routers. The idea was to make them variable speed. It worked, but there was a considerable loss in torque as you reduced the speed. This made the router pretty much useless for working any kind of hardwood. However, the thing works great on my motor base. Nothing gets hot, and the base can be slowed to a crawl and still has enough torque to turn a 3005 drum.
Originally Posted by Dave Krueger
I strongly recommend getting the speed controller
Interesting about slowing down a drum roller. I have a Beseler roller- the kind that has a button for auto reverse rolling (I don't use that).
I wonder if slowing down a constantly rolling drum makes much difference- It seems like whether you are doing 20 rpms or 40 rpms, the film is, either way, getting more fresh developer on the surface than it can exhaust, so, it seems it wouldn't make a lot of difference. Maybe I am missing something.
I've occasionally wondered if my Beseler roller was maybe turning too fast, but have to much other testing I need to do before I test whether a reduction in rpms would make much difference.
I usually use a pretty dilute developer when rolling, anyway, which I guess offsets any contrast increase in the faster rpms...
I agree Jeff. I use a Beseler motor base (non-reversing, so I lift and reverse the drum regularly, and probably unnecessarily). I doubt if it makes much difference exactly what the rotation speed is. Just regard it as continuous agitation and don't worry about it.
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Actually, if you read a lot of the literature, the recommendation for many developers is to use the slowest setting when using a Jobo processor. I believe the slowest setting is considerably slower than the standard rotation on a beseler or a Unicolor base. There is a difference. I especially saw it when using the 3005 drum. I tried PMK and Rollo developers prior to switching to Pyrocat. The PMK, in my opinion is unusable for drum processing. At higher rotation speeds its even worse. Oxidation is a big problem, and contrast really starts to jump up. Rollo, although designed for drum processing performs much better at slower rotations.
Originally Posted by Konical
I suppose you could modify the developer dilution to control the activity, but then you increase the oxidation effect. Some people are using two developer pours to overcome this. But its much simpler to use slower rotations.
The statement that you should regard it as continuous agitation and don't worry about it is bad advice. Rotation speed has considerable effect on contrast and developer life during the process.
Jobo itselfs recommend slower speed (@30rpm max or the slowest speed on CPA's) by using the 3000series Expert drums and higher speed (@75rpm) when using 2500series drums. The last one to avoid streaking and bromidedrag.
Release, the best you can do...
Just for the heck of it, I took the light dimmer that I use with my dremmel drill and tried it on my Unicolor motot base and it really didn't work well. There was a very narrow range of adjustment where it would slow down. A little higher and it was almost full speed. A little lower and it would stop. And that was with the empty drum sitting on it.
Originally Posted by don sigl
The router speed controller is probably a much better idea if you want to slow the speed down. I have a little metal lathe that uses a speed controller that pulses the current to the motor. While it makes for an odd pulsating sound, it manages to keep the torque high at even very low speeds.
In any case, for the most part I've been pretty satisfied with the speed of the Uniroller base as is. I will run into uniformity problems if I load up the drum with too many sheets, though. It's possible that's a speed related problem, so I may do some speed experimentation in the future.
Through trial and error, I've found that I get best results using the slowest speed for B&W (Rodinal, Pyrocat-HD, FX-2, D-76), and the highest speed for E6. This seems to be the same for all film sizes (35mm to 12x16") in 2500 and 2800 series tanks.
Originally Posted by hka
-- Ole Tjugen, Luddite Elitist
For past three years I have been using Color drum for my 8X10 developing with unicolor base. It uses small amount of chemicals( 275cc) pro sheet. What I did I replaced motor with a DC one hooked up Model Train controller to it I have reverse and down to 1 RPM. I develop with Pyro-HD. Negatives are excellent. Just another way to skin a cat.I forgot to say I glued small dimples to space sheet of film from the drum wall. 5 rows of 4 dimples.
Hope this helps
Last edited by Buster6X6; 12-06-2006 at 10:07 AM. Click to view previous post history.
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