Reviving a Cycloptic Basket Case

[jgestar]

I dearly miss the B&L StereoZoom that used to sit on my desk at work. My search for a cost effective replacement took me to eBay. The fuzzy photos weren't promising (Photo 1) and the Cycloptic was listed as "for parts", but I felt the eyepieces alone were worth the sales price. I anticipated the rebuild would be an educational project, or at worst a source of scrap parts. At purchase, I knew the left focus knob was broken, the mirror was corroded, the glass stage and one eye cup were missing, and the instrument was decorated with old university inventory tags. After delivery, I found the right focus knob was now broken, the magni-changer drum was oddly sticky, and both prisms were dislodged. However, the objective and eyepieces looked usable.

After disassembly, one end of the magni-changer drum was scored through the black anodized layer from lack of lubrication (apparently a common issue). As a result, one magni-changer knob had been broken (did I mention the university inventory tags?). Fortunately, the broken fragment was still in the knob (Photo 2). The focus shaft and bearings were fully functional, as were the microscope frame, focus rails, and the lenses. The remains of the focus knobs were unusable. The instrument had a few decades of dirt and grime and the lubricants were oxidized and sticky. There's hours of entertainment here!

The first step was to repair the magni-changer. I decided to splint both knobs with metal rings and epoxy (I found a similar repair mentioned here). The knob fragment was aligned with tape (photo 3), super-glued, and clamped for the night. Two 3/4" OD aluminum rings were cut and trimmed, then super-glued into position. The space between the knob stem and the aluminum ring was filled with 5-min epoxy. After curing, the epoxy was trimmed and sanded flat. The rest of the magni-changer was cleaned, lightly greased, and reassembled with the repaired knobs (photo 4). So far, so good.

The weird focusing knobs were the second repair. Because the original knobs were so brittle and broken, I turned knob shafts from brass rod and knob bodies from an amber polymer (photo 5). The knob bodies were reamed and the brass shafts were pressed in, with epoxy to ensure permanence. The knobs were shaped, polished, and the brass shafts were trimmed to length. Finally the knobs were faced and polished. The new knobs were installed onto the original focusing shaft and assembled into the focusing rail. The revived focusing mechanism works as expected, including the focus tension adjustment.

The next repair is re-gluing the prisms. I don't expect this to be easy. Previous forum posts mentioned that American Optical repairmen used a prism alignment jig. Could anyone that has seen the jig post a photo/drawing/napkin sketch? I don't want to reinvent the wheel if I can avoid it. Any jig or alignment process details would be appreciated.

More to follow...


Tom

Photo 1 - Very unappealing eBay photo.

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Photo 2 - Broken Cycloptic parts

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Photo 3 - Repair details of Cycloptic magnechanger knobs

Magni-Changer-Knob-Repairs.jpg (87.57 KiB) Viewed 2130 times

Photo 4 - AO Cycloptic with repaired Magnechanger and new focus knobs

Project-so-far.jpg (43.12 KiB) Viewed 2130 times

Photo 5 - Construction highlights of new Cycloptic focus knobs

New-Focus-Knob-construction.jpg (75.51 KiB) Viewed 2130 times

[BramHuntingNematodes]

Love those knobs!

[apochronaut]

That's the very rare El Diablo model.

[Scarodactyl]

Cycloptics are fun, and you've done great so far! I suspect you've left the hardest bit for last though.

[dtsh]

Nice save of the magni-changer knobs and nice fabrication of the focuser knobs.
In my opinion, the 59M Cycloptic is probably the best model for it's adaptability to various mounts.
I still have a few parts left if you have need of a magni-changer(M) or head in which the prism on one side has become detatched.

[apochronaut]

Although the roof prisms can be and were originally cemented to the prism housing sideplates using an alignment jig, it probably seldom happens that they magically align, given the various locations along the optical path where slight misalignment can occur. The final alignment is done at the eyepiece tubes where solder is used to fix the alignment of the tubes in the correct position. A workaround for that is to utilize a slight xy movement of the prism carrying side plates . To do this, purchase longer screws for the sideplates with round heads plus flat washers, instead of using the original countersunk flush head screws. Reaming out the mounting holes to a larger diameter allows for enough xy movement to align and then lock everything down. Removal of the original slignment pins is necessary in order to effect that workaround.

[PeteM]

For the initial alignment, I've used gage blocks. Under $50 sets are available and most any friend with a fairly complete metal shop should have an old set they might lend out. Been a while since I repaired a few of these, but recollection:

1) Using one good (cemented) prism, find gage blocks that just fit the corners of their carriers. Two blocks.

2) Use the same pair of gage blocks as a jig to located the loose prism.

3) Back then, I made a circle of rag cotton paper as spacers and cyanoacrylate glue to do the cementing. Glass and metal surfaces need to be scrupulously clean. Cures quickly and can be undone with acetone if a mistake is made. Perhaps not the ideal glue, but those scopes have held up for a few years. E6000 glue might be a more flexible glue, but I haven't tried it in this application. It (and rubber cement) seem to work OK for DIC prisms.

Then, the final tweaks as described by Phil.

FWIW, I've seen Cycloptics that had the factory reglue the prisms -- and then those prisms loose again. It was one of the few faults of an otherwise excellent stereo microscope. Happily, some prisms with a bit of glass flaked off from the corners from rattling around may still provide a full field image. Blackening the cracked bits can improve contrast.