DIY drum rolling machine

[Dirk Rösler]

Hi, has anyone built their own Jobo drum rotating machine?

Would it be difficult to have a motor with variable speed control and adjustable reversal interval that somehow connects to the drum, by means of the magnet or some sort of "claw"?

Does not sound too difficult and perhaps parts and components can be salvaged from elsewhere. I am not an electronics person, but can do basics, soldering etc.

Regards

Dirk

[Drew Wiley]

Could easily be done, but why? There are plenty of used machines around fairly cheap, and a new DevTec for about a hundred bucks will develop prints every bit as
well as a Jobo. Things get complicated only if you want to make prints bigger than
20X24. The RPM of the Jobo is too high for some applications and the motor itself
is underpowered. You could make drums out of ABS drainage pipe and caps, but some finesse would be required constructing an efficient light trap which will still
allow you to introduce chemicals evenly. I've been down this road, and now have a
significantly modified 30X40 drum processor which will do most things well and
cost effectively, but not as conveniently as a fully automated roller-transport machine. If you like projects like this, have fun at it, but there will probably be some serious speed-bumps redesigning things which others have already spent a lot of time figuring out.

[Dirk Rösler]

Why, because I want simplicity and flexibility. And I don't have space for the bulk of the whole processor not do I need the temperature control, just something that turns the drums on a roller base. Also I want to rotate long drums that do not fit in a Jobo machine. I have the Jobo drums, so no need to re-invent those.

I have done some dev of Acros in Xtol rotating at very slow speed by hand, and the results are great, so I would like the machine to rotate at any speed I want.

For example one could salvage a hand mixer/blender/juicer, which already has speed settings and is powerful, just need to make it stepless and perhaps some gears, plus of course the reversal part.

[Drew Wiley]

Dirk - you would need a small gearmotor adaptable to a speed control, and a way
to keep all this watertight. Two parallel stainless steel shafts can be used, with the
gearbox mounted to only one of them, and the other turning on its own when the
drum rotates. A bi-directional switch is a possible option. Then you need eccentric
friction rollers on the shafts to get some random motion. This idea works quite well
for serious needs but starts getting expensive when you factor in all the parts. A far
less expensive (and less reliable) option can be copied from Dev Tec. The drum floats in a tempered waterbath. A simple friction ring is placed around the outside
circumference of the drum and rotated by a small waterproof motor with a projecting friction shaft. A simple rheostat can be used on this kind of motor for
speed control. Of course, you can simply rotate your drums by hand back and forth
on the bed of a darkroom sink too, without any fancy equipment. But an actual
Dev Tec processor takes up only about two square feet and will probably cost next
to nothing used. You might also be able to find an old motorized Unicolor roller base only.

[Dirk Rösler]

Thanks. I am using the Unicolor base already, but it is problematic with the Expert drums. For hand rolling I have castors on a wood board. No need to be watertight or anything, it should just drive the drum. Don't think I need to randomise more than what the Unicolor or castors are already doing.

I don't have access to DevTec stuff.

[IanMazursky]

Dirk,

Thats a really neat concept!
Im looking into the same thing myself for my 3063 jobo drum.
I just need to figure out how to make a motor auto reverse. Im thinking of scrapping parts from my Wing Lynch model 4 since its in pieces anyway.

Good luck!

[Nathan Potter]

Just adapt the pervasive unicolor roller base for rolling a custom drum. It'll reverse also as well as turn in one direction continuously. I've seen them for sale for a few tens of dollars.

Nate Potter, PEI, Canada

[Alan Rabe]

You might wnat to try http://www.myhurst.com/hurstmfg/index.jsp
for small high torque motors

[BradS]

I made one with my sons' legos once....but then they wanted their legos back so, I picked up a used Unicolor motor base.

[Dirk Rösler]

Thanks for the link. I was thinking of Lego too, to try...

Actually, I think I may try a cheap used electric drill. It is certainly high torque, and has speed and reverse witches built in. Just need to remove from the housing and change the control switches to some sort of knobs.

[Photo Dave]

What RPM should the developing drum rotate? And why and how often does it reverse?
I used to build fly rods and used a "Drying Motor" when applying the finish to the thread wraps-
http://www.customtackle.com/cgi-bin/cts/ctstore.cgi?page=drying.html
But... for the price of a motor why not pick up a used Unicolor roller on the auction block??
Dave

[Drew Wiley]

Dirk - an electric drill is way, way too fast for processing. One of the most wierd things I ever did is to remove the drive device from a small processor, hook up a
high RPM rheostat, then sync this with an automotive timing light and a focus device. (I had a friend over who had gotten a little looped and wanted to see something funny.) We then placed an ant on the drive shaft. As the ant walked back
and forth on the shaft I kept slowly raising the RPM. You could see a big projected
silhouette of the ant in two directions on the opposite wall. The detail was amazing.
First the ant was hanging on with all six legs, then five, then four ...finally the speed
was jacked clear up to 20,000 RPM - about the speed of a Dremel tool. The ant was
desperately hanging on with one leg, then simply flew off somewhere. We found the
ant on the floor walking around in tight little circles!

[Dirk Rösler]

As I said several times already, I am aware of the Unicolor bases, I have several of them already and I want something else.

Obviously a drill would not drive the thing 1:1, it would have to be geared or belt-driven to get a smooth and slower rotation. But a drill has good torque at all speeds and a cheapo used low wattage drill can be had for $10.

I think the Jobos run at around 50rpm, so I'd want something like 20-60rpm, either variable speed or some fixed settings like a blender. Slow - Med - Fast.

Ideally the reversal interval can be set manually as one desires either by a mechanical switch or a timer. But with a slow RPM and a big drum like the 3005 the timer needs adjustment other you will not get a full rotation.

Any idea what kind of components would be needed?

[Turner Reich]

I have a clock motor, 12 volts DC, that's sitting in the shop, I was thinking about making a fine focusing mechanism for the enlarger so I don't have to stretch my are out so far. It is reversible and could be used for a drum turner if properly geared, it has a good size gear on the shaft and could be connected with a timing belt to another gear. It would be a fun project.

[Drew Wiley]

Dirk - a small hobby gearmotor should not cost any more than a drill plus a reduction device. What needs to be calculated is the rate of speed in which the
developer flows over the film, which is dependent upon the circumference of the
drum. You ideally want things slower than the lowest speed on a Jobo machine.
For example, if I was to develop sheet film in a drum intended for one sheet of 8x10
paper, I'd want it to take about six or eight seconds to get around. A bigger drum
holding several sheets should take longer. Otherwise things can get frothy or in the
case of Pyro developers, excess oxidation. Cheap drill have variable speed switches
which tend to be erratic at the lowest speeds, and then you'd have to use pulley
ratios to slow things down. Gearmotors are made for all kinds of things. You should
be able to find something cheap on the web or in an appropriate catalog.

[Dirk Rösler]

Yes, you are right. I think I should go to a modelling shop and look for motors and gears. I will do that next week.

I think low speeds can be a problem with the Expert drums but we can worry about that when we get there.

[Donald Miller]

A DC gear motor is definitely the way to go. DC motor rpm is directly related to voltage input. In addition a DC motor does not decrease torgue as voltage is reduced. That is not true of an AC gearmotor. Thus if you reduce voltage to an AC gearmotor it will lead to overheating and premature motor failure.

There are several ways to convert AC current to DC current. SCR circuits are one way. One can also build a circuit incorporating SCR (Silicon Control Rectifier) design with voltage transformation for the gross reduction (should that be needed) along with a rheostat to allow finer adjustments.

Radio Shack at one time had a AC to DC transformer that would also work provided the motor load was not beyond it's design load capabilities. A transformer/current converter device would eliminate the need for a SCR circuit.

Clock motors are of insufficient load design characteristics for what you want to do. Waaaay toooo undersized.

DC gear motors are also reversible by reversing the polarity of the voltage to the rotor and stator of the motor. This reversibility would require either a solid state or mechanical timer/switching device.

There are available sources for all needed componants. A Google search will locate those if you decide to build up a device for yourself.

[Greg Blank]

Here's a snap shot of what Jobo uses in the CPP2.


.

DC gear motors are also reversible by reversing the polarity of the voltage to the rotor and stator of the motor. This reversibility would require either a solid state or mechanical timer/switching device.

There are available sources for all needed componants. A Google search will locate those if you decide to build up a device for yourself.

[SMBooth]

Try a rotisserie motor you fit to a BBQ.

[Richard Wheat]

I was fortunate enough to find this unit 2nd hand some time ago. :)

It's a home made drum roller and I use it for all my 120 and 4x5 developing. The timer-controller reverses the motor in a set sequence, it rotates for longer in one direction than the other.

HTH,
Richard.

[Dirk Rösler]

Richard, interesting! Can you post a more detailed photo of the motor unit showing the gear and connection to the axle?

Thanks for everyone's input so far.

[PenGun]

Try a rotisserie motor you fit to a BBQ.

Yup I've built a few slow turn devices from these.

[Richard Wheat]

Here are a couple of more detailed shots.

The motor/gearbox combination is made by Parvalux of England. The motor rotates at 1400 rpm and the gearbox brings it down to 42 rpm.

It's set to rotate about 11 seconds in one direction and 6 in the other.

HTH,
Richard.

[Dirk Rösler]

Thanks a lot. This RS box with the two control knobs, do you have any ID on that?

[Richard Wheat]

Dirk,

Yes, the RS device is this (although probably an older version)
http://pk01.rs-online.com/mobile/search/searchBrowseAction.html?method=getProduct&R=0349917

HTH,
Richard.

[Dirk Rösler]

Many thanks! Here is the 110V equivalent:

http://pk01.rs-online.com/mobile/search/searchBrowseAction.html?method=getProduct&R=0347810

[chardl]

Interesting. how about an electric stand fan's motor? Is it too fast even if set to slowest speed?

[Dirk Rösler]

I suppose you'd have to gear it. Depends on the fan, the motor may be fairly weak. The fan blades are light and balanced, not much power needed to spin them.

[Richard Wheat]

If I was making one from scratch I think I would try a drill speed controller with an old electric drill, plus a relay, such as the one mentioned, to reverse the direction.

Coupling the drill to a set of rollers would be straight forward using the chuck.

Just a thought,
Richard.