@peterm1
It's obviously impossible to be definitive without handling the camera involved. But my suspicion is that, instead of servicing your IIIa correctly, its curtains were dragging a bit and a previous owner increased the tension on their spindles. This will get a shutter functioning after a fashion, although, once the additional friction from congealed lubricants and/or old, stiffened curtains have been added to the equation, the impact of these things on the rate of curtain acceleration tends to negate the likelihood of having a 1/1000, or even perhaps a 1/500 speed, that is actually decently uniform across the gate.
I have to disclose that I have very little experience with the pre-IIIc models. I'm not familiar with their curtain braking system. But a good friend does own a lovely IIIa he acquired at a Melbourne collectors society auction a few years ago for a keen price. When I cast an eye over it for him I fully expected it to not be usable at all, however a white card slipped behind the film rails to improve contrast revealed that it was still delivering consistent looking exposure across the gate even at 1/1000 (which really surprised me). So I ran a quick film through it, and loved it. I get where you are coming from, and I would really not mind a IIIa myself, as a spectacle wearer I prefer the focusing and framing eyepieces a bit further apart than later Barnacks.
Apropos your comments about the IIIc, however yes these do employ an actual friction brake shoe for the first curtain. It's cam operated via a lever underneath the bottom of the shutter crate and is adjustable via a rotatable eccentric that bears on the actuating cam. This does an effective job of stopping the curtain quietly, and the escapement reset system will mechanically brake the second curtain via a pin on a gear meshed to the second curtain spindle.
A well adjusted IIIc–IIIg shutter should be very quiet. When I say "well adjusted", by this I mean an example which has good, soft, supple curtains that will spool easily around their pulleys and rollers so that excess resistance is not a running problem, and a mechanism that is clean and lubricated. These points are both essential for at least a couple of reasons. One: they facilitate accurate high speeds consistent across one's negatives. Two: obtaining optimum shutter efficiency will occur with a minimum of tension applied to each curtain take up shaft. A really good IIIc or later can run beautifully with as little as one and a half full turns of spring tension on the second curtain adjuster (from the braked position of the released curtain at the rewind side of the gate). A first curtain must have enough power to trip the second curtain latch (the first curtain has to all the work in a classic focal plane shutter, a second curtain only has to run itself across the gate unless an escapement speed is set in which case it will first run the gear train off). So the first curtain may need four or so turns of the adjusting worm screw. The point is an actually sorted Barnack needs a minimum of tension to run at its best. But many today will be found over tensioned.
In recent years I've possibly sent more film through my own IIIf red dial than any other camera in my collection. It works really well, and I love the results from the screw lenses. Having serviced that one years ago I know from much experience how quiet, smooth and delightful they can be. Earlier this year I did an indoor concert with it and was pretty pleased with the results. I can fire off frames rapidly simply by sliding my right index finger along the outside of the wind knob. Try this with an over tensioned shutter and you'll either strip the outer skin from your finger by roll's end or just plain won't be able to fully tension the shutter at all.
I've read some good things about the repair service at both Photo Co and Twin City in recent years. If you feel like another III series would be a welcome addition to your fleet of cameras I'd suggest chatting with either of them as to their feelings about tending to a clean prospect for you. I'll be back in Adelaide briefly in January (not my favourite time of year, there I have to say) for my mom's 80th and I do try to stop by Photo Co and the market. No doubt I will have my IIIf on me. If you would like to actually get a feel for what a correctly adjusted IIIf is like to wind and to fire, I'm happy to grab a coffee.
Cheers,
Brett
Back Road by Neal Wellons, on Flickr
