Possible to manufacture a Horseman 970 Rangefinder Cam?

[ivan35mm]

great progress!

i’m not sure how your handing the cams, but if you wanna speed up the process / fix the whole batch, i really can’t recommend a vertical belt sander enough.

$60 harbor freight one

i got one of these years ago, and it’s worth its weight in gold.

 

[loccdor]

Part of my testing of the cam with film was confounded by having a Horseman 6x9 back which consistently back-focuses (by about 6 inches at 3-5 meters). I finally narrowed it down by trying a 6x7 back which is focusing nearly perfectly with the cam. That was causing the difference between results observed on the ground glass vs. film.

It seems to be down to film flatness - the film is bowing toward the camera in the center on the 6x9 back by about a half millimeter, and that's enough to cause observable back-focus at shallow depth of field, which occurs most strongly in the center of the frame vs the edges. I did some shimming of the pressure plate to make it press the film very tightly but it didn't solve the problem.

Well, at least I have one good back now, and can remember to adjust focus slightly on the other when I use it, I'll have to tape a note to it so I remember. It's okay, I prefer the squarer aspect ratio and more shots per roll.

 

[abruzzi]

Part of my testing of the cam with film was confounded by having a Horseman 6x9 back which consistently back-focuses (by about 6 inches at 3-5 meters).

what generation back do you have? I have a bunch of the common black ones, and one of the older silver ones. I don't often shoot wide open, but I have on occasion on a tripod using ground glass, and I haven't encountered any issues with any of my black ones. (I've never used the silver one, so I can't comment on that one.)

 

[loccdor]

what generation back do you have? I have a bunch of the common black ones, and one of the older silver ones. I don't often shoot wide open, but I have on occasion on a tripod using ground glass, and I haven't encountered any issues with any of my black ones. (I've never used the silver one, so I can't comment on that one.)

The black back is the one with the problem in my case. The silver 6x7 back is focusing correctly. It surprises me too, because the black seems more strongly built, and also less corroded.

 

[abruzzi]

odd. The black backs were well made, and well enough that Horseman not only made them with the Horseman logo, but they also OEM'd them for Sinar and Arca-Swiss, so I'd expect if they are good enough quality for those two Swiss companies (or in A-S's case, formerly Swiss) they are good. I wonder what threw your back off?

 

[loccdor]

odd. The black backs were well made, and well enough that Horseman not only made them with the Horseman logo, but they also OEM'd them for Sinar and Arca-Swiss, so I'd expect if they are good enough quality for those two Swiss companies (or in A-S's case, formerly Swiss) they are good. I wonder what threw your back off?

Beats me - included with the camera I bought from Japan. I briefly thought there might be some slight incompatibility between the black and silver cameras and backs, but that seems too outlandish to be right. I don't see any signs of denting on the black back.

 

[srardnec]

Cool. At $35 for 60 of them you could get 60 of each size and throw the entire Japanese used camera shop economy into recession. They ask like $60 plus $50 shipping each these days. I’d ask for one but I already have the whole set (except the fast 105.) I bought mine before the prices got crazy. Amazingly it felt overpriced buying them for $30 plus $10 shipping back then.

I bought in january a 105mm cam for 380¥, in american dollars, currency converter tells it is 2,38$
On Yahoo Japan ((you may need a VPN in Japanese, to display the page):

希少品 HORSEMAN PRO 105mm カム #P755 - Yahoo!オークション

□商品詳細 この度は数あるオークションの中からご覧頂き、誠にありがとうございます。 最後までお読みいただきますようお願い申し上げます。 ★大特価★ ★限定一品のみ★ ★希少品★ ★HORSEMAN PRO 105mm カム★ ‐付属する商品 （写真に写っているもののみの場合、写真に

auctions.yahoo.co.jp

in screenshot:

also bought a Horseman release cable for 10,34 $:

by now most Horseman cams on Yahoo and Mercari sell between 1000¥ and 3000¥. For instance on Yahoo right now:

Five years ago I bought a set of four cams for 8000¥ ~50$

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but for non Topcor/Horseman lenses, DIY is required. For this, focusing glass, a focusing target, a cheap distance laser meter to take several measurements, then trace the ƒ.

 

[grat]

Out of curiosity, how much pressure is on these cams? Could they actually be printed out of something like ASA (ABS relative) on a 3D printer and hold up?

 

[loccdor]

Out of curiosity, how much pressure is on these cams? Could they actually be printed out of something like ASA (ABS relative) on a 3D printer and hold up?

The pressure did not seem to be a problem when I tried mine cut out of a plastic filter case. But I don't know if you can make the curve accurate enough with 3d printed plastic compared to laser-cut steel. It really does need accuracy tolerances less than 0.1mm for best results.

 

[srardnec]

Out of curiosity, how much pressure is on these cams? Could they actually be printed out of something like ASA (ABS relative) on a 3D printer and hold up?

see in action:

 

[grat]

The pressure did not seem to be a problem when I tried mine cut out of a plastic filter case. But I don't know if you can make the curve accurate enough with 3d printed plastic compared to laser-cut steel. It really does need accuracy tolerances less than 0.1mm for best results.

That's not impossible for modern consumer level 3D printers. Bambu Lab claims the accuracy of their H2 printers when combined with their "Vision Encoder" plate produces accuracy down to 0.05mm. At that point, the shrinkage / melting rate of the plastic becomes more important, and would definitely take some tuning. By default, +/- of 0.2mm seems to be pretty standard.

It would be incredibly tricky, and like your cut case, probably not accurate enough to justify the work required.

 

[abruzzi]

My worry with 3D printed cams is the act of focusing drags the follower across the focusing surface. How much focusing would be needed to wear down the surface so it is no longer accurate?

 

[JEC1]

Hey @ivan35mm , I gave up on making a 150mm cam through sanding plastic. I don't think I can get it accurate enough and the material doesn't seem like it will hold its shape for long. I was trying to make a DXF file for sendcutsend.com in Inkscape for this image, to make with steel, but I don't know the program and I'm struggling. Would you be able to make the DXF for me if you have time? The dimensions of the image are 40mm x 18.29mm. The cam is 1mm thick if it matters. Thank you again for the help.

View attachment 418732

Hi there, I am UK based and have just bought a 150mm Super Topcor that unfortunately came without a cam. I wonder if you would mind sending me a copy of your DXF file so i can get one made up this side of the pond please ? Many thanks in advance.