Motorised Dish Rockers

Discussion in 'Darkroom Equipment' started by youngrichard, Feb 16, 2011.

  1. youngrichard

    youngrichard Member

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    Have a look at this video, and don't forget to turn the sound on, before or after reading on. The video is very amateur but I am learning.

    http://www.youtube.com/watch?v=eJB6QMmmTe9

    I have been meaning to share this idea since I retired 3 years ago and discovered forums. I have never seen such a device mentioned, though for all I know everyone has one. It has been a godsend to me over the last 30 years. The idea is of course not new; there are electric drum processors for colour, and the Paterson orbital motor driven processors; and before that there were rotating and tilting devices to mix blood samples and stop them coagulating in my previous life as a doctor.
    One day in the early eighties I spotted in a surplus store catalogue an advert for geared electric motors, 30 revolutions per minute. A little experimentation with my developing trays suggested this was an OK if not ideal speed for rocking my trays. Keeping it cheap and simple, as I was not sure it would work, I fabricated the devices you see in the video (apologies, video editing not on my CV yet). Melamine covered chipboard held together by screw blocks. A crank attached to the motor spindle, and a 45 rpm record offset by the crank. A little bit of grease where the record runs in the groove of the plastic railing - I thought it would cut through but it never has. The motor runs on 110 volts, hence the transfromer, as UK voltage is 230 volts. A bonus for me is that the box lifts the dishes to chest level; no stooping to see what is going on in the dish.
    I do not use a stop bath, and have found 1 minute in dev and 1 in fix at 20 C quite enough for RC which is all I use routinely, so the Isgus mechanical timer set to its 60 second maximum is perfect; if I want longer I wind it up again.
    I do a lot of run -of-the-mill photography, so printing a 36 frame roll of 35 mm is regular fare, and made much easier by exposing six 5x7 inch sheets, and then developing and fixing them together in 12 x 10 dishes ;if the agitation is being done for you, this leaves hands free to make sure the prints don't bunch and stick together. You can also sip your coffee, take the neg strip out of the enalrger, change the record, whatever. In the video you see me in daylight placing six I made earlier in water; this is purely for illustration as I thought it would make clearer how the sheets slide over one another. For big enlargements in a 20 x 16 dish I normally process one sheet at a time and still use only 2 litres of dev or fix, and help things along with a bit of side to side rocking by hand as well as the motorised back to front rocking. Saves on chemicals and easier to pour out afterwards.
    Only problem for you is finding a powerful geared or stepped motor giving 30 revs per minute; don't know where I am going to find them when these pack up.
    Having said that I have been meaning to share this idea, I did in fact send a video to Nova Darkrooms about 15 years ago; the gist of the reply was that I was 20 years too late!
     
  2. resummerfield

    resummerfield Subscriber

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    Very nice! This would make an ideal agitation unit for large format film development, using that tray that holds the film sheet—I think it's called a slosher tray.
     
  3. GRHazelton

    GRHazelton Subscriber

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    I like it. I'll have to look around for a slow speed motor from Edmund Scientific or some such. One concern - you have highly conductive solutions sloshing around above 230v and 120v wiring. Do you have any splash shield over the motors?
     
  4. jnanian

    jnanian Advertiser Advertiser

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    hi youngrichard

    i was the printer for a portrait photographer who was trained in the 20s/30s ..
    and in the darkroom i used we had tray rockers. they were galvanized metal of some sort and ran on a slow motor. it had 3 platforms and they ran continuously all day long
    ( until i unplugged it ) it made quite a racket and was was a great set-up ..

    i wish i could remember more details about it, other than it was a motor, and a cam that ran over 3 metal platforms. i miss all that automation !

    unfortunately ( for me and her ) one of the rockers broke and stopped
    so it was back to hand-work soon after.

    i wish someone made something like this still !

    john
     
  5. outwest

    outwest Subscriber

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    Barbecue rotisserie motors work well for this.
     
  6. Rick A

    Rick A Subscriber

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    Gear reduction motors and a shelf that pivots at the ends. It doesn't require a long rocking motion,1/8inch rise and fall is all it takes to agitate trays. The main thing would be timing the motion so there isn't a huge sloshing action.
     
  7. tim k

    tim k Member

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    Good idea!!
     
  8. michaelbsc

    michaelbsc Member

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    The rotisserie motor is an excellent idea.

    another possibility is Hurst gear motors. They pop up on evilBay regularly. You have be specific about the speed since they are available in about 20 configurations. And don't pay too much. Occasionally you'll see some go for almost list price in a bidding war. Others sell for a dollar.
     
  9. Perry Way

    Perry Way Member

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    This is a very good idea! (but I am almost totally rotary processing now except for roll films which I have an old habit of inversion agitation, even though I could process them rotary as well.)
     
  10. youngrichard

    youngrichard Member

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    Did anyone ever make one of these? I know there are many alternatives, but something like this gives you time to put the kettle on, change the radio station, whatever.. I couldn't live without it, and dread the day when I have to find a replacement motor!
    Richard
     
  11. Nige

    Nige Subscriber

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    I've got an old electric can opener somewhere that I thought would make a good base for a tray rocker... it seemed to have a low enough RPM speed and I imagine, decent torque ( hey it opens steel cans) so should be able to lift the end of a tray up and down a bit. My thought was to have an elliptical roller under the tray to lift it up and down, but have never gotten around to trying to make it.
     
  12. Smudger

    Smudger Member

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    Well done, YoungRichard- I'll have to pluck up the bandwidth to watch the video (dial-up) , but I had a similar moment of clarity after I diss-assembled an otherwise dead VCR.(That's Video Cassette Recorder,to the technically advanced). The mechanism which propelled the tape in and out of the machine has a nice little 12v motor and all the gearing to give a lovely gentle to-and fro motion to a dish or tank.
    I think I will hook it out and see what happens..