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Speed graphic cam.

 
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mark fewtrell



Joined: 10 May 2019
Posts: 9

PostPosted: Sat May 11, 2019 9:36 am    Post subject: Speed graphic cam. Reply with quote

Thanks for having me here. I am a new owner of Speed graphic in the UK. When i bought the camera the rangefinder was stuck. The steel bearings in the tube between lower lower plunger and internal plunger were solid. I released these with alcohol and lighter fluid. To release the lower plunger had to remove small cap on end of tube. The small cap now seems not to want on stay on the plunger tube. Any suggestions?

The second point is i wanted to get a cam for a 90mm lens i havent yet bought. I have one for 127mm lens and the lens. Has anyone the spec for a 90mm cam and the lens it fits? I understand the cam was specific but its a place to start.
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45PSS



Joined: 28 Sep 2001
Posts: 3757
Location: Mid Peninsula, Ca.

PostPosted: Sat May 11, 2019 6:05 pm    Post subject: Reply with quote

1. Download the Top RF service manual here:
http://www.southbristolviews.com/pics/Graphic/manual-pdf/servicemanual.pdf

The best service on the tube is to remove it from the body, pour all the balls and spacers into a container, flush the tube and balls and spacers with Naphtha, not lighter fluid, or 90% Isopropyl Alcohol then reassemble dry. A very light coating of extra fine powdered graphite can be applied to the balls and spacers but it must be just detectable. Oils, grease in trace mounts will cause the balls and spacers to jam.
There should be 42 to 45 balls and spacers in the tube.

The plastic cap on the Pacemakers was prone to popping off, secure it with a drop of glue (removable) or RTV sealant.

2. This is the cam list for the Pacemaker Graphics:
https://graflex.org/speed-graphic/top-rangefinder-cams.html

A lens is rarely its marked focal length. They can be a few tenths of a millimeter to a few millimeters either side of the marked focal length. The first 5 cams in the list are for 90mm lens.
The greater the focal length difference between the cam and the lens the greater the focus error at closer distances. A .5mm difference will be off at 3 to 5 feet / .9 to 1.5 meters while a difference of 5 or 6 mm will be off at 10 to 15 feet / 3 to 4.5 meters.
Measuring from the aperture blades to the ground glass with the lens focused at infinity will give you an idea of the lens actual focal length as standard 90mm lens were not retrofocus (flange to film plane distancel shorter than lens focal length) design.
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mark fewtrell



Joined: 10 May 2019
Posts: 9

PostPosted: Sun May 12, 2019 8:16 am    Post subject: Reply with quote

Ive essentially achieved the first point in the reply. Was thinking of silicon will give it a try.

The cams list you mention doesnt have spec/measurements. Ive seen bristols super graphic software and printed out for 127mm cam. I notice the speed graphic cam for 127mm i have is 1 inch long and the super 1.5. Curiously the maximum height seems proportional. Am i barking up wrong tree in thinking the cams are proportional to each other and that a 90mm cam for the speed graphic could be derived from the super? It would at least be a starting point for making a 90mm cam for speed graphic. i might add as yet not bought 90mm lens. Ta.
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45PSS



Joined: 28 Sep 2001
Posts: 3757
Location: Mid Peninsula, Ca.

PostPosted: Sun May 12, 2019 5:54 pm    Post subject: Reply with quote

I made this post after using three bodies and two lens with factory matched cams for the measurements:
https://graflex.org/helpboard/viewtopic.php?t=4653

A Crown or Speed will be more difficult to do as the Graphic rangefinder is made into the body and not separable from it as the Super is. As far as I know there is no scale correlation between the Pacemaker cam and the Super cam.

https://graflex.org/technical-information.html
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