I recently made a new curtain for a 3x4 RB Auto. I've installed it and set the speeds and all seems to be working correctly except...

When I wind to the 1/8" or the 3/8" from the open position, the slits fall as they should. However, if I trip the shutter at 1/8" and then just wind back to it from 3/8", the slit lands a little lower. If I fire it again and do the same, it drops lower still. After 3 or 4 times the slit lands below the top roller. If I wind it down to O, and then wind back to 1/8 it goes back to its proper spot.

I thought I packed the rollers enough to take out slack, but does it just need more?
Do I just need to reposition the curtain? Is there something I'm missing (probably!)
Thanks for any advice and wisdom.

The packing procedure is set the tension to its highest setting then wind to the smallest aperture then run down to closed after open 10 times.

The lower edge of any aperture should be at least 1/4 inch above the guide roller at the top of the image opening when winding to that aperture. The upper edge of the aperture should be 1/4 inch below the bottom guide roller at the bottom of the image opening at the completion of the curtain running with the mirror in the up position. The curtain should drop another 1/8 inch when the mirror is returned to the viewing position.

The only things I can think of that will prevent these conditions from being correct is the aperture spacing on the new curtain are incorrect or the top curtain roller was set before the curtain was packed.

It must be that, I know I didn't set the tension at 6, AND, I attached it to the top before I finished that process. I made the new shutter based on the old one and I confirmed that they match exactly, both in spacing and in length.

I can see I'm almost there, so I'll reset the curtain now that it has been properly packed. It's all becoming more clear to me.

Thanks so much for the information, I do appreciate it. I'll report back on how it goes.

On curtains I've replaced I attached the curtain to the rollers as the original was, set the top of the O aperture close to the bottom edge of the top roller, pack the curtain, then reset the top roller as needed to align the apertures positions when wound and run down.

That's a good reference point.

I spent a rather frustrating afternoon with it, repositioning the curtain several times, looks like it ended up pretty much where it was when I started. I ran through them at the highest tension at least 15 times. It's strange, each opening lands where it should, if I wind through all of them they stay put, but if I just trip the 1/8", and then wind back to it and trip it again, it drops. it's like it's slipping somewhere, but if I then run it down and back up it goes back to where it should be.

I'm going to sit and think on this a little.

As long as the edges of the aperture remain 1/4 inch above the top image box guide roller or 1/4 inch below the lower image box roller when wound to or after release there will be no light leak.

The factory original curtain was .007 inch thick when new.

That's the problem; the 1/8" opening doesn't stay above the top roller.

It's not slipping; I don't think it just drops too much when the mirror is brought back down. Looking at another camera, I see that some movement is just part of the mechanism, but in this case, it's going too far.

Something else I notice. I matched the length of the curtain I removed, and there is a lot of material above the open position, enough for the curtain to travel 3 full clicks past the "O" setting. On the camera that I'm comparing it to, which is essentially identical, the curtain travels one click and can then travel no more; beyond that, it's cemented to itself and the top roller.

What would be the effect of too much material on the roll be, a fatter diameter in other words? Wouldn't that increase the spacing between the slits?

I have seen 6 complete turns of curtain on the top roller cemented to itself at closed after open.
Reset the top roller so that the curtain is 1 roller gear tooth higher than it is currently.

The curtain isn't attached to the top roller at this point. Will I need to remove the mirror shaft to reset the top roller?

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The curtain isn't attached to the top roller at this point

That may be the cause of the problem. Pliobond contact cement https://www.ebay.com/itm/152489399143?epid=1800924761&hash=item2381139367:g:VoQAAOSwbk9gcQPa
applied to the curtain then attached to the roller can be removed several weeks later if needed. Apply to 1 1/12 inches of curtain or 1 turn on the roller.

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Will I need to remove the mirror shaft to reset the top roller?

Depends, did you remove it initially or just the taper pin holding the H lever to the shaft? Its best to remove the wind plate.

Thanks. I had cemented the curtain to the roller, but I removed it again so I could adjust.

It's getting clearer to me, I think I'm getting there!

Appreciate the insights as always.

Just a follow-up to report that I worked it out and I now have the shutter working properly and running very nicely. Thanks for the help. That's one Graflex back to life.