90mm Focusing Cam for Top RF Crown Graphic

pandino

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I love using my Graphic handheld with RF, but I only have a cam for my 135mm lens. I'm forced to use the groundglass with my 90mm and it's really dim.

I'd like to make a cam myself, but don't have the dimensions.

Does anybody have one that they can lay on a flatbed scanner next to a ruler and post a scan?

My particular lens is the Optar 90mm f/6.8, although I would think any cam designed for FL's within a few mm's should be close enough because of the DOF with this lens.

Thanks!
 

df cardwell

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Call MPEX right now !

Midwest is the only place to find them. I agree, the DOF will make it easier to use a cam.
 
OP
OP

pandino

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I've seen them sell on eBay for $40 which is a bit high for something I can make in about fifteen minutes. You'd think they were sterling silver! I just need a scan of one and I'm in business!


I checked MPEX's website, but couldn't find any cams. I really miss their old website. Maybe I'll give Jim a call and see if they have them in stock what they're asking for them.

I'd still prefer a scan if someone could please spare the time.
 

df cardwell

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CALL THEM, Jim will tell you exactly what he has.

(There isn't a website big enough for all the stuff they have.)

WARNING: It is just possible making a cam is more difficult than it seems to be.
 

BrianShaw

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They mention the cams in their ad in the latest edition of VC. $29 if I recall correctly. When you call, please ask if there is a diffference between Crown and Super cams and let us know. Thanks!
 

Dave Parker

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There has been extensive talks about making cams over on graflex.org, I think you will find that it is a bit harder than you imagine, but you might look through their archives for any information you can come up with.

R.
 

bart Nadeau

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There is a difference. The ones for the Crown are subtantially smaller. Over on Graflex.com they have lists of the cams by number for each camera.
 

RichSBV

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The cams for the top rangefinder Pacemaker series cameras and the Super Graphics are completely different and not interchangable...

I have been trying to attach a pic of the 90mm cam for the TRF Pacemaker here and have had no luck at all...

So, if you'd like it, send me your e-mail address and I'll send it to you directly.

Making the cam is not all that difficult if you have the right materials and patience. The key is that two diemnsions of all cams are always the same. That's the lenght and the height at infinity. With these two dimensions from another known good cam, you can make a new one.

With buying used cams, be careful and test them fully. Last year I bought a 210mm cam from midwest. It turned out to be a re-ground cam and about 1mm short of reaching infinity...
 
OP
OP

pandino

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Rich,
Thank you, thank you, thank you!!!! I'll PM you my email addy. How'd that Super Speed work out for you?

I've read Graflex.org on this issue some time ago and if I remember right, the suggestion was to make one and whittle away at it iteratively until it focuses correctly. Insane waste of time.

If I have a scan of a known working cam (with a reference scale) I can easily make one that will work very, very close to the original. The key is to replicate the slope at each point along the curve.
 

jacobus

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"WARNING: It is just possible making a cam is more difficult than it seems to be."

DF Cardwell is right. Mechanically it's rather simple to make one's own cams, at least the rough cutting-out part of it. But to get the slope correct by filing and grinding ( and hammering the two "legs" if one has removed too much material) is time-consuming with all the intermediate testing involved.
I made 4 cams ( for lenses from 120 - 210mm). Instead of also making one for my 90mm lens ( a cam with a tricky curve) I made my own focusing scale that's fixed next to the rails by double-tape.
 

RichSBV

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Making a cam can be easy or difficult. It depends primarily on what material you use and your technique.

I have made cams out of thin brass stock that was cut with scissors. Worked fine. Heavier stuff is filed. Worked fine. A dremel helps a lot.

The big trick is having a known good cam. Three sides of all cams are identical! Use the old cam as a template and scribe/mark your material using that cam. Mark the two sides and bottom. These are always the same. If you put your cam into the camer and have it focused on infinity, then mark on the cam where the arm sits on the slope, you have the infinity height. This is also always the same and the starting point for the slope on the new cam. All you need from there if the rest of the slope. If you print the pic of a cam at 1:1 size of a knbown good cam, you can easily come close enough to thew new slope, especialy for a wide lens. I did a cam for a 210mm from an undimensioned pic and it works great...

Super cams, being larger, are a bit easier to work with though...

Chris, I e-mailed that pic in case you don't get it. If you need a dimensioned pic along side another can, I can provide that too but I've have to find my package of cams and scan it. It's around here someplace...

This time I may have the attachment?
 

Attachments

  • Cam 90mm P15.JPG
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