Durst Enlarger Elevation Crank

[gnd2]

Enlarger is a Durst Pro I bought used several years ago. The height adjustment crank was broken when I bought it. Not a big deal, the head can be raised and lowered by hand and otherwise works great, and I got a good deal on it. But every once in a while I get the urge to see about fixing it.



Gear A is turned by the crank and turns gear B. Gear C looks like it should engage the linear gear in the column, but it spins freely from gear B and can move in and out:



What I just discovered tonight is there appears to be a cotter pin that is supposed to lock C in place with B, but has been sheered off:



Wondering if anyone is familiar with these and can shed some light, maybe share pics? Thinking of heading to the hardware store to see if I can replace the pin and get this thing working.

[mpirie]

To shear off a rolled steel cotter pin would have taken a lot of force, so i'd guess at it having been a plastic pin.

If you can't find the right size of cotter pin, try a threaded screw of the right diameter and length and cut to size.

Hold it in place with JB Weld or epoxy adhesive.

Mike

[Renato Tonelli]

Mike has offered the solution in the post above.
I would only add that, after using epoxy (the two-part type), you let it set a good 48 hours.

I have had this enlarger since the early (?) 1980's; it is in constant use.

[Tin Can]

Find the root cause of the failure first

It may be somewhere else in the gear train.

Get an actual roll pin, epoxy makes a future repair far more difficult.

Consider talking to actual experts, including http://www.glennview.com/durst.htm

[gnd2]

Ya, sheering the pin off seems extraordinary, but it's the best guess I have at this point for how it's supposed to go together and how it could have gotten in it's current state.

I don't think I want to epoxy anything. Would rather avoid permanent alterations at this point.

Who knows what happened to it before I acquired it. I've looked but can't see anything else wrong that could have caused the pin to sheer if that is indeed what happened. At this point I'm happy to try a simple fix and see what happens.

If someone that has one in working order wouldn't mind taking a picture I'd appreciate it. Looks like the whole mechanism should easily pop out with the removal of 4 screws. Otherwise I'll see if glenview can offer anything.

[Eric Woodbury]

Cotter pins are soft to allow them to break instead of breaking something worse. What is gear B made of? (What's dirt and what's enlarger bits?) Is that a fiber based product? And why the spiral around the outside? Do this control something else? It looks as though something is still in the 'cotter pin hole'. Are the gears all of the same material? How are the other gears attached?

Since there is a slot in gear B that appears on both sides of the shaft, then something was meant to go through and engage the gear. Could be a cotter pin or shear pin. Perhaps the two gears are held together by something on the crank side and a pressure washer.

Regardless, however the gear was mounted and driven, there was once more material around that slot that is all worn. I would suggest that someone worked it hard, drove it to the stops all the time, or cranked it without releasing the brake. This wore the slot and eventually broke. I'd take out whatever is in the hole and replace. Figure how to keep all the gears in proper alignment. If the gear is steel, you could have it filled by brazing and re-slotted. Or you could fill with epoxy. Just don't drive it to the stops.

best of luck

[gnd2]

Cotter pins are soft to allow them to break instead of breaking something worse.

Makes sense.

What is gear B made of? (What's dirt and what's enlarger bits?) Is that a fiber based product?

I believe the gears are made of nylon. The junk on it is just dust, the gear material itself is very smooth.

And why the spiral around the outside? Do this control something else?

I don't know. I had the same thought, but I don't see anything it could control and don't have any other pieces that go with it so maybe it's just reinforcement.

It looks as though something is still in the 'cotter pin hole'.

Yes, it looks like the remnant of the sheared pin is still in there.

Are the gears all of the same material?

Yes.

How are the other gears attached?

Gears A and C are both attached to their shafts by cotter pins. I should have mentioned that gear B moves freely on the shaft, A and C are both firmly attached to their shafts.

Since there is a slot in gear B that appears on both sides of the shaft, then something was meant to go through and engage the gear. Could be a cotter pin or shear pin. Perhaps the two gears are held together by something on the crank side and a pressure washer.

There is a bushing screwed to the metal plate that the shaft for gears B and C goes through. It doesn't allow the shaft to pull out on the gear side, and when the hole in the shaft is lined up with the slots in gear B everything seems to sit where it appears it should. Which is what leads me to believe that their should be a pin there which would stop all the undesired movement and hold the gears in alignment.

Regardless, however the gear was mounted and driven, there was once more material around that slot that is all worn. I would suggest that someone worked it hard, drove it to the stops all the time, or cranked it without releasing the brake. This wore the slot and eventually broke. I'd take out whatever is in the hole and replace. Figure how to keep all the gears in proper alignment. If the gear is steel, you could have it filled by brazing and re-slotted. Or you could fill with epoxy. Just don't drive it to the stops.

best of luck

Makes sense. Thanks for your thoughts.

[Renato Tonelli]

The gears in my Durst Pro are held in place by metal cotter pins:

[gnd2]

Thank you for taking the time to post up the pictures. I'm convinced now that replacing the pin should get this working again. I'll try to get to the hardware store Saturday and see if they can fix me up.

[gnd2]

Thanks for all the help! I got the new pin in, everything is back together and working perfectly.