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Thread: DIY 8x10 (or larger) Enlarger Chassis

  1. #41

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    Re: DIY 8x10 (or larger) Enlarger Chassis

    Sounds like a very ambitious project. Are you a good enough "machinist" type of do-it-yourselfer to make this stable/strong enough? My biggest concern is how stable the enlarger head and printing base are relative to each other and will your design actually give you the stability you will need.

    My 8 x x10 enlarger is an old 8 x 10 Kodak 2D camera with a cold light head pushed up against the ground glass. I found the cold light head (a 10 x 10 Durst) somewhere for a couple of hundred bucks. It sits on the counter in my darkroom on a simple horizontal track I built and project it onto the wall. I haven't made prints larger than 16 x 20 before, but no reason I can't make them as large as you are wanting to do.

    Your project seems pretty complicated for something you might not use very often. But, it also sounds like it could be a lot of fun building it.

  2. #42

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    Re: DIY 8x10 (or larger) Enlarger Chassis

    Update-

    I've made a lot of progress on the arduino code for the control unit, it's almost done I think. If you want to check out the code, you can test it out using this simulator here:

    https://wokwi.com/arduino/projects/302878866181980685


    I'm not a very experienced coder, so there's probably ways it could have been done more simply, but it works, and that's what matters for me. The controls are as follows:

    the keypad is for inputting numbers. 1-9 are as they seem, * is exit, # is the enter key, B is a period for decimal numbers, and C is a / for fractions.

    red, blue, and green buttons: input color values for RGB between 0 and 255

    black button: input print exposure time via base exposures, stop size, and stop number. these are input by pressing the black button, typing in the base exposure on the keypad, pressing #, inputting the stop size as a fraction using / and then entering it with #, and finally typing in the stop number you are exposing at, the pressing # one final time. Then you press:

    Yellow Button: EXPOSE. this button just prints !EXPOSE! in the serial window for now, the actual LED head will be connected to the arduino via an xlr cable and a DMX 512 encoder and decoder. DMX512 is a lighting control standard used for stage lighting, and works well for this design, because by using it for control, the same controller can control any LED head wired with a DMX512 decoder. I haven't simulated the encoder, since it isn't available in the simulator, but its just a little pcb with 4 inputs and 3 outputs which gets wired to digital output pins on the arduino.

    Orange button: this is for f-stop test strip mode. after pressing it, you input the print info the same as with the black button, but this time it outputs a exposure time for every stop value. which you print by sequentially hitting the expose button.

    there are two switches wired in as well, one is for manual mode where you input a time as you would on any other enlarger, that part isn't coded yet, but won't take long I think. The other switch is for switching to CMY values, but I won't be able to code that until I build the light source and can compare its light output to a dichroic head.

    You'll also notice one or two white bars underneath the print time on the display. these tell you if the data has been input properly, and only when both are showing will it be able to print. If there's only one you probably need to hit the enter (#) button one more time.

  3. #43
    ic-racer's Avatar
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    Re: DIY 8x10 (or larger) Enlarger Chassis

    There is no standard, but some heads use (CC = log d x 100). So 10cc = 0.1 log d or 1/3 stop, 15cc = 1/2 stop, etc.

  4. #44

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    Re: DIY 8x10 (or larger) Enlarger Chassis

    I've made some changes to the enlarger chassis design. I was inspired by seeing the heiland enlarger which was announced yesterday to make all the movements of my enlarger motorized, like they have done. My first thought was to motorize the pulleys in the first design, but after some thought I've opted for a system which uses lead screws. There are three lead screws which will run the length of the enlarger, and on each there will be a carriage which one of the stages will be mounted to. by turning a motor one direction the stage will move up, and by turning it the other direction the stage will move down. This new design will require more electronics and coding, but mechanically will be much less complex.

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  5. #45
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    Re: DIY 8x10 (or larger) Enlarger Chassis

    In case you have not seen, the Durst L1840 also uses that style of drive to move the head up and down. In the case of Durst, the 240V AC motor control circuit pulses and senses the back emf to determine the motor speed, and keeps it constant. Otherwise going down will be faster than going up.
    I suspect that in your case (now 30 years later than the Durst motor control circuit) a brushless motor can easily be controlled to give constant up and down speeds. Another thing the Durst control circuit does is to power the motor even when it is stationary to 'lock' it in position. The motor is always humming.

    Click image for larger version. 

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  6. #46
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    Re: DIY 8x10 (or larger) Enlarger Chassis

    Also, from an engineering standpoint I'll point out that the twisting torque from the weight of the head, centered around the drive point pictured above, is countered by a pair of ball bearings that ride against a track at the back of the hollow tube on which the up/down carriage rides. Durst CLS2000 head is 24Kg (53lb) per the manual with its center of gravity almost 1/2 meter out from the lift point.
    Even though your LED head will be lighter, it will need to be far out from the column if you want big enlargements.

    Also, in case you have not seen, the Omega 8x10 does have a forward slanted column like their 4x5 enlargers. This would give a shorter lever arm of the head on the lift mechanism for the same maximum print size.

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  7. #47
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    Re: DIY 8x10 (or larger) Enlarger Chassis

    Thanks for the heads up on the new Heiland, I did not know, and here is a link. Personally, as I near retirement, I'd be able to afford a new enlarger if my Durst ever breaks. So the demise of Durst Pro USA is not such a bad thing any more.
    https://www.facebook.com/PhotoKlassi...5399669230275/

  8. #48

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    Re: DIY 8x10 (or larger) Enlarger Chassis

    I was aware durst had made some similar mechanisms, but I hadn't been able to take a close look at them, so thanks for those images! is that an oiling port on the side?

    Click image for larger version. 

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    This is my design for the rollers which will support the cantilevered weight of the stages to keep strain off the threaded rod. I'm also using a 3/4 inch lead screw, which I'm fairly certain will be strong enough, I'm not sure what the diameter of that durst one is, but it doesn't look like 3/4 to me

    The heiland enlarger does look amazing, I'm guessing it will have a hefty price to match though. A friend of mine heard a rumor that it will be $24,000, which seems too high to me, but all the Heiland prices seem a bit high to me.

  9. #49
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    Re: DIY 8x10 (or larger) Enlarger Chassis

    More pictures of the drive. These are from 2008 and I have not had it apart since then. As I recall the drive shaft is off to the side toward the front, and the track with two straddling rollers is on the same side toward the rear, so it is not a symmetric assembly.
    The oil hole aligns with a hole in the housing for easy access when it is all together.
    I think the worm drive is about 2cm in diameter.
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  10. #50
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    Re: DIY 8x10 (or larger) Enlarger Chassis

    Of course the more distance between your rollers, the better support. This Saltzman is probably overkill for a LED head but probably set the standard for enlarger stability at the expense of size and weight.

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