Micrometer Control of Bellows

PaulFurman · Post by **PaulFurman** » Wed Dec 02, 2009 11:28 am

click image for wider view of the rig

This is a temporary clamped version of a salvaged micrometer dial set up to push back the front standard on a PB-4 bellows. It's screwed onto the black L-bracket which is clamped. The angled, coarse threaded piece is just being used as a spacer but it should work alright when mounted properly without that gap needing to be filled. It gives 9mm of movement which would be good for a stack of 900 frames with 10 micron steps at very high magnification. Or more reasonably, a comfortable turn with the finger of 100 microns should be good for 10x stacks 90 deep, or 4 of those comfortable turns for 4x work giving stacks 25 deep.
(corrected from 1 micron to 10 microns)

It is kind of a hassle to 'rewind', taking 50 full twists for the full length but not too bad considering the alternative is a huge focus block mounted under the bellows.

It does get in the way for some configurations, being on the front. That's the biggest problem. I'll need to have an extension tube on the front for short lenses so no minimal bellows extension work and I won't be able to tilt the goniometer back to peek under a mounted specimen. That's already a problem. There is no reasonable way to get it to push the bottom rail distance adjustment on the bellows. That would require extending the wood base and a sliding mount sturdy enough to reach up to the back of the bellows. Well, it could work if I mounted to the bottom of back brace and used some sort of adjustable length extension rod below to push against the stationary base of the bellows.

Like an idiot, I first tried attaching to the back to adjust the rear standard, which would be much nicer but that does not work!

PaulFurman · Post by **PaulFurman** » Wed Dec 02, 2009 10:23 pm

Yep, it works. Thanks all for tips to make this stuff work.

ChrisR · Post by **ChrisR** » Thu Dec 03, 2009 2:35 am

Presumably with that Olympus you can use its helicoid, or do you find it moves about too much?
You can stack using the rear standard, that's what elf does with his rig. You have to move the rear one a lot, which can be a help, or not!

I did consider using a "Depth micrometer" mounted on a rear standard, pushing the front one. With those you have interchangeable rods and 25mm or so of travel. You could achieve the same with your wimwom, and bits of studding held end to end with nuts...

I expect you find you have top half-tighten the standard's slide-clamp to stop it wobbling about while you push it? A big elastic band helps to take up the slack

lauriek · Post by **lauriek** » Thu Dec 03, 2009 4:24 am

I did wonder about disassembling a bellows and re-mounting both the front and rear standards onto individual micrometer stages which in turn would be mounted on a study base. But I never got round to it and went down the vertical rig/microscope stage route instead.

PaulFurman · Post by **PaulFurman** » Thu Dec 03, 2009 9:10 am

ChrisR wrote:Presumably with that Olympus you can use its helicoid, or do you find it moves about too much?

Ah, well as you can see I've got it mounted with tape. That should be handy for field work without bellows, just tubes.

You can stack using the rear standard, that's what elf does with his rig. You have to move the rear one a lot, which can be a help, or not!

Yes the rear standard gives extremely fine depth control with just the bellows knob but also considerable magnification change so the background has to be enlarged a lot.

I did consider using a "Depth micrometer" mounted on a rear standard, pushing the front one. With those you have interchangeable rods and 25mm or so of travel. You could achieve the same with your wimwom, and bits of studding held end to end with nuts...

One idea is a long rod with an adjustable stop of the type used in a door swing hydraulic piston with a tab with a hole large enough that at an angle, the rod jams at any point.

I expect you find you have to half-tighten the standard's slide-clamp to stop it wobbling about while you push it? A big elastic band helps to take up the slack

Doesn't seem to be a problem.

DaveW · Post by **DaveW** » Thu Dec 03, 2009 9:14 am

Considering the bellows have lower focusing slide bars could you not mount the device to push the lower slide bar end standard forward instead of working the other way around and pushing the bellows standard back, therefore altering the magnification?

Sorry it's a bit schematic, and ideally the bottom focusing rail block should also be able to slide along the angle bracket and be locked in an appropriate position too.

DaveW

PaulFurman · Post by **PaulFurman** » Thu Dec 03, 2009 9:17 am

lauriek wrote:...and went down the vertical rig/microscope stage route instead.

With horizontal, it's always a big challenge figuring out how to mount the subject. I do like being able to have an out of focus background of my choosing but the mounting can be very difficult.

PaulFurman · Post by **PaulFurman** » Thu Dec 03, 2009 9:22 am

DaveW wrote:...ideally the bottom focusing rail block should also be able to slide along the angle bracket and be locked in an appropriate position too.

Right. You'd need to be able to reposition the thing over a long range and it would need to be quite sturdy: mine is raised up a couple inches from the platform and my platform doesn't even extend back that far.