View Full Version : Renovating a Mentor 5x7 SLR
Steven Tribe
10-Feb-2011, 16:15
This has been stored around the house for some time (years).
Sold as a "Zeiss-Ikon" from a former member state of the East Block. It even had a big Zeiss-Ikon badge in front (modernisation?) - whilst the round Goltz & Breutmann "Mentor" plate had fallen off the side long ago. Left in storage for a long time because the Focal plane shutter needed attention. Taken out of storage, stimulated by Ash's series with the Goerz Ango/Anschulz and a realisation that this could be quite a fun camera which could hold quite large lenses - if I gave up the idea of fixing the shutter.
Similar cameras were made by Graflex, Dallmeyer and a few other UK makers.
The good thing about the camera is that the huge viewing hood is as new - otherwise I wouldn't bother to renovate it. The bellows show absolutely no wear at all. It has a revolving back and the framing of the ground glass changes from 5x7 to 7x5 (if you follow my reasoning!) by three thin metal strips that move in and out under the GG. It has a full set of plate holders. The lens board size is such that I am not restricted to small Dagors and G-Clarons in shutter.
What I intend to do is:
- Clean up the leatherette (perhaps replace it all) and make a new side piece on the right-hand side which is full of holes from the Shutter controls.
- Replace the mirror on the flap.
- Adjust the vertical brass bars which move the front standard. One of these wobbles a bit.
- Replace the metal strips which connect the wooden frame of the front standard to the brass bars. These were made of very soft aluminium which have not lasted too well.
- Refinish the interior. At present there is a lot of added black gloss paint.
- Adjustment. Shimming the mirror and/or ground glass.
- Etc.
Warning! Progress will be comparitively slow.
Jim Graves
10-Feb-2011, 22:57
Warning! Progress will be comparitively slow.
Apparently you're not familiar with my projects ... in which the progress is 'glacial' ... which is my wife's reasonably accurate description.
Am looking forward to following it.
Good luck to you! I've got about half a dozen Mentors still to fix - my pace rather slowed down once I had rebuilt my first fully usable modernized (Linhof back) Mentor.
How's the progress Steven?
Steven Tribe
27-Feb-2011, 13:21
A quiet week - but I have checked everything through again.
I'm starting with the right-hand side. This where all the "clockwork" sat. It is made like a lens board, with a central mahogany square and two edges with the grain in the opposite direction. The covering plate (covered with leatherette) is full of holes for focal plane adjustment. This plate is thinner than three ply so I will remove a layer when making a new cover with a single "mirror lifting" lever slot. I have new grained leatherette available and will copy the original simple tooling marks. I hope to post the photo series at the end of the week.
Steven Tribe
3-Mar-2011, 05:08
I have removed the right-hand side plate (?). To my surprise, this is a composite construction - mostly aluminium but with a considerable amount of quality cardboard in the areas that didn't cover the focal plane mechanism. Aluminium was an expensive material back then - but I guess the cardboard is an attempt at weight reduction. This side panel will be given up and a replacement made with just a single slot for the mirror release. Position of the fixing screws will be moved slightly so I will be screwing into virgin mahogany.
The mechanism is in good condition - it is the torsion loss in the rollers which make it useless.
Chauncey Walden
3-Mar-2011, 08:10
I was tempted by one while in Bulgaria but was put off by the need for special film holders which it didn't have. I saw spurious Zeiss-Ikon badges on all manner of cameras, including a 19th century tailboard, on the shelves with all the gold plated, lizard skinned, Russian Luftwaffe Leicas.
Position of the fixing screws will be moved slightly so I will be screwing into virgin mahogany.
I use wood cement on the screw holes to avoid moving positions.
The mechanism is in good condition - it is the torsion loss in the rollers which make it useless.
The steel spring coil inside a brass roller is a rather unlucky design in electrochemical terms - it takes only mildly damp storage to corrode the spring. But it should not be that hard to make a replacement spring from piano wire.
Sevo
Good luck! Looks like you're making some progress
Steven Tribe
3-Mar-2011, 16:18
I'll take a close look at the rollers to see whether they are capable of being dismantled!
Well it looks pretty impossible. The brass rollers have inserted end caps. No threads or retaining screws. Looks like soldered or pressure fit.
On the only Mentor I've had to disassemble to that level, the roller came apart on its own - but that probably won't happen if the spring is broken or the joint (no trace of solder on mine, probably glued or milled down) has come stuck.
Steven Tribe
4-Mar-2011, 06:41
Success!
The end bushes are press fitted and are removeable. In one end, a wood screw into the hole was enough to pull out the bush. On the other, a small hole drilled near the tube end gave enough working area to apply pressure.
The spring is in generally pretty good condition. The friction/release problem is because of distortion of the spring in a few places so it rubs aginst the inner side of the tube. The fixing point for the spring is a thin channel in the bush - which can be seen in the close-up photo. The position is exactly where there is a notch in the tube end.
Doesn't look like a spring type which is readily available!
Doesn't look like a spring type which is readily available!
It is steel piano wire - available in assorted strengths from every piano shop.
Steven Tribe
5-Mar-2011, 03:47
"Every piano shop" - Sevo, Denmark is not quite the centre of European music culture as Germany is (was?)!
Ok, they do exist - but I can see that coiling (at constant pressure) is going to be a trial and error activity so that the end coil diameter and closeness of coils will work properly. There are about 200 coils in the spring - giving a length of 4 meters! This is a very big Steinway!
For general amusement, I thought I would attach a photo of the existing curtains. As you can see, I am not the first to have made repairs. The last gent used his wife's textile measuring tapes as curtain tapes! Readily available, cheap and easy to select the right lengths!
There are companies making nothing but springs, which even do single items. Some of those listed in http://www.industrystock.de/html/Schraubenfedern/product-result-de-36458-0.html would doubtlessly make the right spring on demand - the (very) hard part will be to arrive at the right specifications from the beater spring in the camera.
Personally I simply wound a spring from softened piano wire (thinner than original, as that was what I had at hand) and hardened/tempered it (to 750°C inside a small pottery oven) afterwards - right now the camera is one and a half stops slow, so I'll have to try a bit less tempering and/or a thicker wire the next time.
Winding a new spring shouldn't be that hard to do, since you have the original damaged spring,
you'll need to measure the wire diameter to buy the similar sized music wire and the
ID of the spring to size the rod ( mandrel ) that you'll need to wind the wire around
to make the spring.
The mandrel will need to be under sized to compensate for the spring's uncoiling after being wound,
I've never bothered to calculate what the uncoiling is, I just do short length test winds to get as
close as possible with different rods since stainless music wire is inexpensive in 1/4 lb coils
( .025 dia wire - 233 feet is about $20 USD ) from McMaster, I know you're in Denmark,
there may be similar industrial supply places close to you.
I've made replacement springs for the rail locks of my 2D the same way.
Great thread, I've been tempted to dismantle the lower roller of my Series D to see what
is in there, your Mentor is probably very similar.
The mandrel will need to be under sized to compensate for the spring's uncoiling after being wound,
... and you have to dimension it so that the uncoiled spring just about fits inside the roller, or you'll have to insert it under tension.
... and you have to dimension it so that the uncoiled spring just about fits inside the roller, or you'll have to insert it under tension.
Yes, that too :D
If the wire size, and mandrel size is close or spot on then the OD
should be very close in size to the OEM spring. I'm sure there's
a little wiggle room in the roller when it was made.
Another tidbit is I've used miniature brass tube as the mandrel and as a shim
if the rod is a bit too undersized for the final spring.
Steven Tribe
5-Mar-2011, 12:32
Thanks for the tips.
Now that I have come this far, I might as well continue!
In order to help others with roller spring fp shutters I have made a schematic diagram and calculated how much wire I need!
Steven Tribe
5-Mar-2011, 16:17
Well piano wire is readily available in the appropriate thickness and lengths on-line. A few years ago I could have contacted my cousin who was the premier harpsichord builder in the UK but he has sadly gone.
Steven, sad about your cousin. In all honesty I think a great number of independent music stores have closed this past decade as well - if he were around he'd be moaning at the increasing difficulty to find stuff.
Steven Tribe
6-Mar-2011, 01:49
Mark was a very "back to the original design/materials" kind of person. So it wouldn't surprise me if he had used bronze wire instead of steel - and drawn it himself!
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