Going barrel end shake

[PeterS]

Everything runs smoothly with the train wheel bridge in place but as soon as I tighten the barrel bridge and I test the operation by turning the centre wheel, when it comes to a stop the centre wheels turns back a little, I guess 15-20 degrees (regardless of which way I turn the centre wheel)
I’m guessing that this could be due to the bridge being too tight but I don’t know how to test the end shake on a going barrel. This is a very small movement and grabbing the barrel arbor with tweezers doesn’t work (side shake is good). But wouldn’t it just stop instead of going back on itself?

This is an old 1940s scrap movment. The main plate, barrel bridge, the going barrel all look fine under magnification and I don’t overly tighten the screws.

[Nucejoe]

Have you check the barrel lid, should fit flush inside the barrel.

[Nucejoe]

To check the barrel endshake, push on one side of the arbor first, it should move as you push on the otherside next.

[PeterS]

9 hours ago, Nucejoe said:

To check the barrel endshake, push on one side of the arbor first, it should move as you push on the otherside next.

I pushed it from the bottom and there was no movement, then I pushed from the top (the threaded hole) and didn’t detect any movement. I don’t quite understand pushing on the opposite sides, that would show the side shake?
The barrel lid looks good.

[watchweasol]

Hi Have you tried fitting the barrel and bridge on their own and testing for shake and freedom  if there is no end shake it will need further investigation as to why.

[PeterS]

28 minutes ago, watchweasol said:

Hi Have you tried fitting the barrel and bridge on their own and testing for shake and freedom  if there is no end shake it will need further investigation as to why.

No, I haven’t tried that, I’ll try it this evening and see what it’s like.

[nickelsilver]

It's easiest to see the shake if you hold the arbor ends between the inside of some tweezers.

In the pic above the cap does look like it's a bit concave, which might be killing the endshake. If you find it has none, you can press down on the barrel perimeter, with the barrel assembled, like you were going to pop the cap off- but hold the edges so it just flexes up. This can bend it up slightly creating shake.

[Nucejoe]

4 minutes ago, nickelsilver said:

It's easiest to see the shake if you hold the arbor ends between the inside of some tweezers.

In the pic above the cap does look like it's a bit concave, which might be killing the endshake. If you find it has none, you can press down on the barrel perimeter, with the barrel assembled, like you were going to pop the cap off- but hold the edges so it just flexes up. This can bend it up slightly creating shake.

 Perfect. 

[PeterS]

Fitting the barrel and the bridge on their own proves that the problem is there. The barrel stops as soon as I stop pushing it. And it’s definitely the non existing end shake. It was a struggle testing it, I ended up with the ratchet wheel screw in the barrel arbor and trying to move it with tweezers. The barrel’s end shake is good but the barrel itself when the bridge is fitted does not move up or down.

The lid looks good I’d say, I would have thought it would be the barrel arbor shoulder that would cause the friction but I’m no expert, I don’t know. Looking at the bridge, it does look a little bent but I don’t know for sure, it could be the shape that makes it look bent. I am tempted to use peg wood and give the pivot hole a little push but I don’t know whether that’s the way to handle it and maybe I would introduce another problem.

[Nucejoe]

I think the problem had existed before,  the previous watch destroyer ha ha had shimmed the bridge with pieces of like aluminum sheet which got washed away as you cleaned. 

Finding/ fixing  the fault comes first, but if to no avail, you may end up shimming the bridge. Is there any sign of gauging on mainplate?

I cut a piece of transparent film off of cigarette boxes are wrappings and test shimming.

[PeterS]

Repairs like these are totally new to me. I wouldn’t know how to shim it. But having no end shake, I would have thought I need to make space, bending/filing etc.?
I’ll check the main plate and take a picture of it when I get home, currently I only have the one I posted in my second post in this thread.

[watchweasol]

Hi   No bending or filing  as once done no recovery path, Get hold of a couple of watch dial washers and put them between the bridge and the front plate and screw the bridge down with the barrel in place, Put the screws  so as they go through the dial washers ,  Once done and screws tightened down recheck for freedom. Hopefully that should work with no butchering and can be altered easily.

[aac58]

I've always heard that a bit of backwards movement once the MS has unwind is a good train wheels healthy sign. Am I wrong?

[nickelsilver]

If the barrel has shake on its arbor, but the arbor is tight between the plate and bridge, should really not have an effect on the running but would make winding harder. The arbor turns when winding, the barrel turns around the arbor during running.

 

Yes, when the watch is assembled, fork and balance out putting a few clicks of wind on the barrel should set the train in motion and the escape wheel should reverse at least a bit and hopefully a turn or few turns. That's an indication the train is free and clean. In the OP it wasn't really clear what was reversing or why (center wheel?), but it's pretty clear there's an issue with the barrel.

[Nucejoe]

Shimming is placing a piece of like thin aluminum foil between mainplate and the bridge to increase the distance between the two. 

Yes turning back as the barrel unwinds fully, indicated the train is so friction free that kenetic energy of the runing train winds the MS back.

[PeterS]

Now I understand! I’ll start with aluminium foil and progress to dial washers if need be.
When the barrel is between the plate and the bridge on their own it’s not hard or difficult to turn it but the fact that it stops turning immediately as soon as I stop giving it a push is an indication that it’s not right and it needs more freedom to run. It runs smoothly when all bridge screws are in just before they ‘bite’ but as soon as I tighten them it’s not as smooth as I think it should be.

*Nickelsilver – everything reverses. It’s usually the centre wheel I give a push when I test it and I used the centre wheel to describe the issue. The barrel reverses a notch (magnifier needed to see it) and the escape wheel spins backwards a lot as you’d expect when the centre wheel turns back 20 – give or take degrees.

[PeterS]

Beautiful! Well, not quite, but now the train runs smoothly. I could have made the shim thinner and work my way up until it’s perfect but this is a scrap movement, I use it to find problems and learn how to deal with them.

I shimmed it in two places just by the screws. The third screw (the furthest away) did not have any effect on the running of the train when screwed down tightly.

Thank you all for your help and input.

 

[Nucejoe]

2 hours ago, PeterS said:

Beautiful! Well, not quite, but now the train runs smoothly. I could have made the shim thinner and work my way up until it’s perfect but this is a scrap movement, I use it to find problems and learn how to deal with them.

I shimmed it in two places just by the screws. The third screw (the furthest away) did not have any effect on the running of the train when screwed down tightly.

Thank you all for your help and input.