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Replacement Cam for 4x5 Crown Available?

 
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semihemi



Joined: 25 Oct 2003
Posts: 85
Location: Boston, MA

PostPosted: Fri Aug 24, 2007 4:30 am    Post subject: Replacement Cam for 4x5 Crown Available? Reply with quote

I recently received a Crown Graphic that looks nice cosmetically. It has a clean coated 127mm Ektar. When I went out to make some test shots I noticed the darn thing has no RF cam! Are cams available? I did not have any luck on eBay. Any suggestions are welcome.

Thanks,
Semi
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RichS



Joined: 18 Oct 2001
Posts: 1468
Location: South of Rochester, NY

PostPosted: Fri Aug 24, 2007 5:30 am    Post subject: Reply with quote

Go to: http://www.mpex.com/

to get their phone number. Call them and ask for Jim. Talk to no one else! He should be able to help you.
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C. Henry



Joined: 13 Dec 2005
Posts: 360
Location: North East Georgia, USA

PostPosted: Fri Aug 24, 2007 1:06 pm    Post subject: Reply with quote

Semihemi;

I seem to recall a post by bertsaunders with instructions & dimensions for making rangefinder cams. I did not succeed in finding it, but you might contact him about it.

C. Henry
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RichS



Joined: 18 Oct 2001
Posts: 1468
Location: South of Rochester, NY

PostPosted: Fri Aug 24, 2007 2:09 pm    Post subject: Reply with quote

There was this recent post by 45PSS:
http://graflex.org/helpboard/viewtopic.php?t=4653

about Super cams. I don't remember anything about Pacemaker cams, could be wrong though? Charles does say the same procedure can be used for them and it should obviously work. Still, for a single cam it would be simpler to buy one if it could be found.
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C. Henry



Joined: 13 Dec 2005
Posts: 360
Location: North East Georgia, USA

PostPosted: Fri Aug 24, 2007 4:26 pm    Post subject: Reply with quote

Rich;

Thanks, that is the post I mentioned above. My apologies to Charles (45PSS)
for crediting Bert Saunders on Charles' work.

Semihemi;
I've been told that the top rangefinder is the same on the Speeds, Crowns, and Super Speeds. Unless I've been misinformed the instructions in the post by 45PSS and cited by RichS will work with your camera.

C. Henry
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45PSS



Joined: 28 Sep 2001
Posts: 4081
Location: Mid Peninsula, Ca.

PostPosted: Fri Aug 24, 2007 9:23 pm    Post subject: Reply with quote

Cams are larger for Super Speeds than for Top RF Pacemakers. The "Procedure" I used to figure out how to make a Super cam will work to figure a Top RF cam. One still needs a Top RF Pacemaker with a factory matched lens and cam to get started.
Set up a target at 100 ft. and with known cam/lens combo on camera, put camera on a tripod and loupe focus on the target. Remove camera from tripod, use a straight edge and scribe cam at the 100 ft. point (next to the cam follower arm of the rangefinder). Replace camera on tripod, move target to 50 ft. , loup focus target on gg, lock focus, remove camera and scribe cam at 50 ft. point. continue for 25 ft., 15 ft., 10 ft., 8 ft., 6 ft., until you run out of cam.
Next position cam at the 100 ft scribe mark. Be sure that scribe mark on cam is on the same side of the follower arm that it was when you scribed it. Measure the distance from the lowest point on the cam follower arm to the cam base or the rail that the base sits on with a caliper. Do the same for all the other distances. Record the measurements in a table.
Now put the cam at infinity and mark then run the focusing out until the travel limit of the bed actuator is reached and mark the cam again. Measure the distance of travel for the cam and record. Now measure the distance that the bed actuator travels from infinity to the closest focusing position.
Divide the cam movement measurement by the bed actuator measurement to get the cam movement factor.
Set camera up on a tripod. Set any lens you want to make a cam for to infinity with rails locked at RF infinity which is rails fully in then foward 1/8 inch (.125). Using painters masking tape or simular run a piece down the actuator side of the camera bed. Using a square, mark the infinity position of the lens. Set up test target at 100 feet. Loupe focus the target and mark the position on the tape on the bed. Continue for all distances previously calculated until the actuator travel is reached.
Measure, with a caliper, the distance from infinity that the lens moved to focus on each of the calculated distances.
Start with a blank cam stock cut to be .437 inch at the infinity point. mark the infinity point of the cam blank with it in the camera. Using a square, straight edge, and caliper mutiply the lens movement fron infinity to 100 feet by the cam movement factor, measure that distance to the left of the infinity mark on the new cam and scribe the 100 foot line then scribe the calculated 100 foot cam height at the 100 foot point. Continue for each calculated distance until the length of the cam has been reached.
Scribe a curved line from the infinity point thru the marked cam heights and file or grind away any material that is above the top of the curved line.
Test and use your new cam. How accurate you are with the lens wide open is dependant on how careful you did all the measurements and cuting of the cam.
This is the "procedure".

If a method of moving the cam follower arm and measureing that distance from a no cam position then the cam heights could be found for any distance by focusing the RF on a target at the desired distances.
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semihemi



Joined: 25 Oct 2003
Posts: 85
Location: Boston, MA

PostPosted: Sun Aug 26, 2007 4:52 am    Post subject: Reply with quote

Did not mean to imply it has a top RF. It is a side RF. Sorry about that.

John

C. Henry wrote:
Rich;

Thanks, that is the post I mentioned above. My apologies to Charles (45PSS)
for crediting Bert Saunders on Charles' work.

Semihemi;
I've been told that the top rangefinder is the same on the Speeds, Crowns, and Super Speeds. Unless I've been misinformed the instructions in the post by 45PSS and cited by RichS will work with your camera.

C. Henry
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RichS



Joined: 18 Oct 2001
Posts: 1468
Location: South of Rochester, NY

PostPosted: Sun Aug 26, 2007 5:00 am    Post subject: Reply with quote

Ummm, then it also doesn't have a cam...

Search the forums for adjusting the kalarts RF and you'll find all the info you could need...
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45PSS



Joined: 28 Sep 2001
Posts: 4081
Location: Mid Peninsula, Ca.

PostPosted: Sun Aug 26, 2007 5:31 am    Post subject: Reply with quote

http://www.graflex.org/speed-graphic/kalart-adjustment.html
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semihemi



Joined: 25 Oct 2003
Posts: 85
Location: Boston, MA

PostPosted: Sun Aug 26, 2007 5:16 pm    Post subject: Reply with quote

Hmmm... to paraphrase, perhaps we are two Graphickers separated by a common language! Perhaps cam is not the right term. The part in question is the the large (approx. 6-inch) long metal arm that translates the motion of the front standard to the shaft that activates the moving RF patch. It can be seen most easily when the front door is open but the standard has not yet been pulled out for action. It is close against the inside wall of the camera on the RF side.

Does this clarify (or further confuse??!!)?

J


RichS wrote:
Ummm, then it also doesn't have a cam...

Search the forums for adjusting the kalarts RF and you'll find all the info you could need...
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C. Henry



Joined: 13 Dec 2005
Posts: 360
Location: North East Georgia, USA

PostPosted: Sun Aug 26, 2007 6:31 pm    Post subject: Reply with quote

John;

I think that part is called a rangefinder lever, an actuating lever or the rangefinder actuating lever.

I suggest that you try either the www.mpex.com that was suggested by RichS or
Fred Lustig
4790 Caughlin Pkwy., #433
Reno, NV 89509
(775) 746-0111
or both of them.

You will have to adjust the rangefinder after this part is installed so it might be worthwhile to have Fred Lustig install it for you and adjust the rangefinder unless you are handy at that sort of work.

C. Henry

PS. Looking at some of the rangefinder literature I see the part referred to as the "actuating arm".

C. Henry
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Rick from OZ



Joined: 05 Jul 2006
Posts: 40
Location: near Melbourne, Australia

PostPosted: Tue Oct 16, 2007 9:06 am    Post subject: Top rangefinder cams Reply with quote

All,

Just to add to the confusion, there is a link to top rangefinder cams which originally came from Bert located at http://graphics.thehills.id.au/Bert's_Top_Rangefinder_cams_for_Graphic_Cameras.jpg
Why add this ?
Well it might explain the confusion between Charles and Bert.
And with Charles' tutorial, anyone needing a top rangefinder cam should be all set ... see: http://graflex.org/helpboard/viewtopic.php?t=4653&highlight

Enjoy !

Rick


Last edited by Rick from OZ on Thu Apr 25, 2013 7:04 am; edited 5 times in total
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bertsaunders



Joined: 20 May 2001
Posts: 577
Location: Bakersfield California

PostPosted: Tue Oct 16, 2007 6:03 pm    Post subject: top RF cam fabrication Reply with quote

My post on top RF cam fabrication was referenced above....For reference.......it was posted on Sun Aug-06-2006 under Accessories Help......RF CAM DIMENSIONS AND ADJUSTMENT
I offered drawings and photos of a dozen or more cams, and someone??? on the board was sent copies of all of them.....he was going to make up a block of drawings with info he allready had! Good thing I sent the drawings when I did, as shortly after they were sent, a computer crash wiped my hard disk clean!
Have a nice day.........Bert
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