Grabhole 80mm OD lever QR clamp for anamorphic projection lenses

This clamp is an improved development of my original Grabhole QR adapter.

what.

With the rise of cheap 80mm OD rings that many people use on their sphericals anyway, I figured it would be smart to design a scope-to-lens connection based on them.

To keep the QR character alive, I decided against a form of rotational locking (like before) as that didn't yield secure connections over time, or when handled incorrectly (read as: "overturn when in a hurry on location"). I am aware a lever has some industrial feel, and not the cool sort of industrial but the generic plumbing kind. Yet, a lever is fast and anyone handling them incorrectly should probably not be close to expensive gear to begin with.

 Have a look on the ease and security of operation::

note.

This clamp must not be used solo. It won't hold your scope and isn't meant to either. It's meant to give another solid, secure-enough and easily switchable point of contact in your rigging. You need some sort of front support (sure, a rear support works, but respecting physics takes us further), my very own Grabhole 70mm front support beam for Anamorphics are in part designed for this very scenario.

use.

It's dead simple - you have an 80mm OD ring on all of your sphericals and just push your supported scope onto this clamp. Lock the lever and be done. As you can imagine, switching a spherical (open lever, push scope away, switch lens, push back, lock lever) is not only fast but also quite easy to be done alone and, except for switching the spherical, with one hand.

Because the scope sits flush against the 80mm OD ring, it will in most scenarios be as close to the spherical as possible, only leaving the thickness of the OD rings between front of the spherical and rear of the scope. If you have an exceptionally “deep” taking lens, this distance will always add onto it, not really a chance I can build around that.

80mm OD rings.

For my point of view, these are (or at least were) on a rise and got cheaper and cheaper. Simmod in the US and Precisious from France hooked us up with the first affordable solutions, but now my absolute favorite stepper ring company in Germany started to sell these at dumping prices at 7,99€. They're called vhbw (example OD ring), and quality-wise I can't find a single difference to the other two; arguably though, the prints are less slick.

scopes.

My time of having an elaborate number of scopes in my shelf are over, so far I have made three different lens adapters that, lucky enough, do fit a much larger number of scopes (little fun fact - many share similar flange thickness or thread sizes). Here a little overview of lenses I do know of:

• 53mm fits
  • Iscomorphot 16/2 (might need a small jab of electrical tape)
  • ISCO Ultra Start (should fit, might also need a little piece of tape)
• M50x.75
  • Kowa Anamorphic 16H and 8Z (not B&H!)
  • Sankor AnamoPrime (remove large golden skirt)
  • Sankor CompactCinemascope (remove large golden skirt)
• M68x.75
  • Schneider Cinelux
  • Sankor New Anamorphic Type-5e
  • Carl Zeiss Anamorphot 2x 63

If desperately needed I can add more lens adapters for different scopes. For that to work though, I need proper measurements of everything around the attachment-area, if there's a thread to be used an accurate measurement with proper pitch (e.g. from a thread gauge) are necessary. Only name-dropping scopes won't cut it, I may have some measurements for a Kowa B&H somewhere but that's about it. I only work in metric and won't likely be able to give you a fast turn-around time; I won't release STEP files either.

BOM - what you need.

• 4-7x M3 nut
• 3x M3 countersunk screw, 7mm
• 1x M3 screw, ~22mm
• 1x M3 nut and screw (not countersunk), 15mm, if you want to use the 53mm lens adapter
• 80mm OD rings for your sphericals
• a suitable font support

I am aware the lengths of the screws are not ideal. The short ones are down to the design, and the long one depends on what kind of tension you want; there is a chance you will need to shorten them e.g. with pliers, a Dremel or some saw. Therefore, I don't recommend getting stainless steel ones. The 7mm ones I bought in correct length in stainless steel, however you can also get longer ones and shorten them as well.

For the M3 nuts, you only really need four, but having three extra ones are more comfortable to adjust the position as depending on your scope you won't be able to add them later.

assembly.

It's quite simple but hard for me to explain, so I do count on your cleverness. Please refer to the attached coloured screenshot for part-names.

• insert M3 nuts into the lens adapter, if you go with only three always leave one space out
• the 53mm lens adapters need to be attached now, yet I recommend installing the scope at this point either way (helps with aligning the lever to a favorable position)
• scopes using the 53mm adapter need to be flush with the base and not stick out
• screw the main clamp to the lens adapter with three 7mm M3 screws
  • there are more nuts than screws so you can adjust the position of the lever in a few more steps
• inserts one M3 nut into the bolt and push it into the lever
• push your long screw through the halfbolt and main clamp, screw it into the bolt sitting (which is already sitting inside the lever)
  • depending on how much tension you want or need, you might have to shorten the screw; it's a bit fiddly to figure out, but you only do this once.
• make sure you can close the lever with an 80mm OD ring inside, and that it grabs properly; adjust if needed
• to make adjusting the screw easier, I placed an additional M3 nut between the screw head and the halfbolt, I will recommend the same to you
• the rear cap is optional and just there to securely store your scope when not in use; no, I won't release a version w/o logo, haha :)

Congratulations, you are done.

printing advice.

I do recommend to use a less brittle, more springy material for the main clamp; PETG is good, ideally no PLA. The rest can be of any (non-flexible) material you like.

For lens adapters with threads, a layer height of 0.24/0.25mm makes a lot of sense because of their pitch. Everything else is a bit to taste, as fine or coarse as you like.

The main clamp is also ideally printed with more outer walls than infill, just so the moving “wings” are nice and springy.

All parts are already oriented as they should be printed. For the main clamp as well as the bolt, you might likely need support; the clamp gets away with some thick support roof which is easy to remove and the bold with anything (it might print well enough without as well, but because walls tend to get thin I would still just keep that in mind).

You don't want any elephant's foot on the lever and the bolt, so printing them on a raft is not the worst idea in general.