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John_shriver
Tinkerer
Username: John_shriver
Post Number: 7
Registered: 12-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 12, 2007 - 07:34 pm: | 
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I bought a nice 4x5 Rochester Optical Company Pony Premo No. 4 outfit on eBay, and I'm getting it into working shape. The shutter is working, but the times other than 1/100 are running slow. I've taken off the timing piston to carefully clean the sliding surfaces, and I note that there's a plug of wood inside the lower part. This makes the exhaust hole a lot smaller. Is this original, part of how they calibrated the shutter? Or is it someone trying to make up for the piston getting to be loose-fitting?
Wonderful little camera, so light, so nicely made. I've got 5 4x5 film sheaths so far, need to score a few more.
I expect dandy results, the Rapid Rectilinear lens is a fine design. |
Dgillette4
Tinkerer
Username: Dgillette4
Post Number: 2
Registered: 04-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 18, 2007 - 11:49 am: |
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HI John: I have worked on many compound and premo,s and the slow timing is set by the bleed down of air. I have never had to plug anything into the piston bore, clean everything. Does that wood plug look like it can be removed? That's the first thing I would look at other than cleaning. The high speed on most piston shutters uses a spring for that speed, the piston is for the slow speeds...Don |
John_shriver
Tinkerer
Username: John_shriver
Post Number: 9
Registered: 12-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 20, 2007 - 06:46 pm: |
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Well, the plug in the inner piston was really some sort of rubber compound. Clearly not original. Once I removed it the shutter was ridiculously fast, pretty much 1/100 at any speed.
So I cut an oversized block of closed-cell foam, and stuffed it in. Now the shutter runs fast, but not ridiculously so. The 1 second speed is flaky, but the others are stable, and I've got a chart.
Perhaps someone replaced the inner sleeve with another one that had a much larger hole in the bottom? It can't just be that the fit between the inner and outer sleeve has gotten a bit loose.
I suppose if I lubed the piston it would be a lot slower, but not consistent. I know it's supposed to run dry. |
John_shriver
Tinkerer
Username: John_shriver
Post Number: 10
Registered: 12-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 20, 2007 - 06:47 pm: |
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The hole in the bottom of the sleeve is about 2mm in size. Seems rather large. |
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