Tissot 28.5-21T Bumper Movement (Similar Omega 350?) Powertrain Issue

[gvmcd]

I may have bitten off more than I can chew with this movement, but I'm now determined to figure out what's going on.

I bought this as a non-runner and am trying to fault find, so I've stripped it right down and am building it back up. 

The powertrain seems to be running smoothly from the escapement back up through that left hand side of the train in image attached, the problem starts when I add in wheel 'E'. It becomes stuck at this point, technically I can get things moving pushing the barrel with some pegwood, but the resistance is very very high.

Wheel E itself turns freely when the bridge above (not shown is added). My thought is that there's something not right between the seconds pinion 'C' and the centre pinion of the centre wheel 'A'. Does this sound reasonable, and how can I confirm if this is the case? I believe the seconds pinion is straight and I believe the centre pinion 'tube' is not crushed. They seem to turn OK when pushed round outside the movement.

Should there be lubrication between the seconds pinion and the centre pinion that surrounds it? Although I'd be surprised if that makes the difference given the high resistance I feel.

I attached an illustrated schematic as well, hopefully this makes sense. My assumption is that A and C should turn freely independently of each other but they are somehow binding. 

[rjenkinsgb]

I'd separate A and C (the centre seconds pinion, from the look of it?) and clean them both thoroughly. There should be effectively zero friction between them.

If they are tight, see if C is absolutely straight? It's possible it has been slightly distorted when removing or fitting the seconds hand, at a guess.

Edited August 13, 2024 by rjenkinsgb

[gvmcd]

Thanks, I cleaned already but will try again to try and get this as low friction as possible. I think the seconds pinion is pretty straight, attached high magnification images. Maybe the very end where the seconds hand attaches is a tiny bit off, but minimal if so.

[nevenbekriev]

First try barrel+A only. Then Barrel+A+E. Then Barrel+A+E+C..... When does the resistance appear?

[gvmcd]

11 hours ago, nevenbekriev said:

First try barrel+A only. Then Barrel+A+E. Then Barrel+A+E+C..... When does the resistance appear?

Barrel+A (with bridge 1 installed) is good, Barrel+A+E (with bridge 1 & 2 installed) us good. Barrel+A+E+C (and bridges) is bad, almost completely seizes up. So that indicates as issue with the centre seconds pinion C I think. Just need to work out how to remedy it now.

I also noted this removable piece on bridge 2, does this allow adjustment of some kind?

[nevenbekriev]

Well, this 'adjustable' thing is the elephant in the room... It is DIY thing and may be it's function is to be bearing for the bumper weight. But it probably presses the top of the seconds pinion pivot. So, remove it and try without it. What is the condition of the stone for the seconds pinion? Is there axial free play of the pinion? The pinion itself is OK on the pictures.

[gvmcd]

On 8/14/2024 at 11:59 AM, nevenbekriev said:

Well, this 'adjustable' thing is the elephant in the room... It is DIY thing and may be it's function is to be bearing for the bumper weight. But it probably presses the top of the seconds pinion pivot. So, remove it and try without it. What is the condition of the stone for the seconds pinion? Is there axial free play of the pinion? The pinion itself is OK on the pictures.

I realised afterwards that the removable piece is just the pivot for part of the bumper mechanism which is assembled later, I don't think it affects anything. 

I'm pretty sure now the issue is between A and C directly. Barrel + A is good, but when I add in C and hold C with tweezers while turning the barrel, there is resistance. I need to check the opening at the dial side of C next, I feel like the opening of the tube may not quite be perfect. 

[Nucejoe]

I suppose each wheel turns Ok and  resistance comes when all  wheels are installed, in which case , this points to wrong pinion engaging with adjacent gear teeth, or faulty pinion / gear or wrong order of installation. 

This movement is actually easy to work on, uncommon looks makes it scarey.

 

[oldhippy]

What are the teeth and pivots like on wheel E?

[nevenbekriev]

On 8/16/2024 at 7:04 PM, gvmcd said:

I realised afterwards that the removable piece is just the pivot for part of the bumper mechanism which is assembled later, I don't think it affects anything. 

I'm pretty sure now the issue is between A and C directly. Barrel + A is good, but when I add in C and hold C with tweezers while turning the barrel, there is resistance. I need to check the opening at the dial side of C next, I feel like the opening of the tube may not quite be perfect. 

Sorry, but You don't seem to make reasonable conclusions.

Do You know what is 'axial free play'? Put the small seconds pinion alone with the bridge and see if it turns free. I bet that it doesn't and it hasn't axial free play. Didn't You actually remove the DIY bumper bearing?

[gvmcd]

On 8/17/2024 at 8:23 PM, nevenbekriev said:

Sorry, but You don't seem to make reasonable conclusions.

Do You know what is 'axial free play'? Put the small seconds pinion alone with the bridge and see if it turns free. I bet that it doesn't and it hasn't axial free play. Didn't You actually remove the DIY bumper bearing?

I assumed 'axial free play' to just mean that there is a small amount of clearance in the axial direction between jewel and pinion so that the pinion isn't being clamped.

Yes there is axial free play with just the small seconds pinion and bridges, in fact there is too much, because part A is not there to support as the bottom pivot for C. With A + C + bridges everything turns freely.

Yes I removed the bumper bearing to check that, it makes no difference.

I'm not sure why my conclusion isn't reasonable. In isolation, A does not turn without resistance in C where I think it should. Unless I'm mistaken and there should be friction here.

[nevenbekriev]

12 hours ago, gvmcd said:

 With A + C + bridges everything turns freely.

Ok, but then

12 hours ago, gvmcd said:

 A does not turn without resistance in C where I think it should. Unless I'm mistaken and there should be friction here.

Yes, there must be no friction between C and A. So actually the first claim is not true.

But I still am not sure what exactly happens. There are 2 possibilities here.

1. A turns free, but C in the same time stays still. There is resistance when trying to turn C.

2. A and C turn together free but there is friction that doesn't let C turn without resistance when A  is still.

If 2 is the case, then C would not get out easy from A when disassembling. As You don't say something like this, I believe that actually this is 1. Will You check this? Look at C when turning A (only C and A in movement) and share here if it turns or stays still.

[gvmcd]

11 hours ago, nevenbekriev said:

Ok, but then

Yes, there must be no friction between C and A. So actually the first claim is not true.

But I still am not sure what exactly happens. There are 2 possibilities here.

1. A turns free, but C in the same time stays still. There is resistance when trying to turn C.

2. A and C turn together free but there is friction that doesn't let C turn without resistance when A  is still.

If 2 is the case, then C would not get out easy from A when disassembling. As You don't say something like this, I believe that actually this is 1. Will You check this? Look at C when turning A (only C and A in movement) and share here if it turns or stays still.

From the options above 2 is the case. Disassembling C from A is not difficult, but C does not just fall out of A it must be pushed or pulled axially, there is something resiting the two pieces pulling apart (and also pushing back together). Sorry, I thought I mentioned this part earlier but I did not. 

I managed to get some high mag photos yesterday with the seconds hand end of C in assembled position. I noticed some residue(?) on the underside in the photo,l. Maybe there is some 'gunk' inside A. I am trying to figure out a way to clean the inside (inside diameter there is only ~0.2mm.

[gvmcd]

Oh, also should there be lubrication between A and C, or should this be dry?

[nevenbekriev]

OK, there is a brass bush inside A that serves as bearing for C. A's pivot is made as a tube and the inside diameter is relatively big. Then a brass bush is pressed inside the pivot. To clean the tube, You can use some wire that gets inside but doesn't go thru the bush. I can guess that at some point the seconds pivot has been replaced and the new one has bigger pivot diameter. You can put the pinion tip only from the other side of the bush in order to check if it goes in with resistance or free. Probably the problem will be solved by slightly reaming the bush hole by broach

And yes, oil is applied same as on the other side pivot in the stone

[gvmcd]

On 8/20/2024 at 7:33 PM, nevenbekriev said:

OK, there is a brass bush inside A that serves as bearing for C. A's pivot is made as a tube and the inside diameter is relatively big. Then a brass bush is pressed inside the pivot. To clean the tube, You can use some wire that gets inside but doesn't go thru the bush. I can guess that at some point the seconds pivot has been replaced and the new one has bigger pivot diameter. You can put the pinion tip only from the other side of the bush in order to check if it goes in with resistance or free. Probably the problem will be solved by slightly reaming the bush hole by broach

And yes, oil is applied same as on the other side pivot in the stone

Thank you, I think this is it. I took measurements and it looks like I have a 0.220mm pin trying to get through a 0.205mm hole. I will need to buy some broaches, I'm thinking Bergeon 1896-F will do it.

[gvmcd]

On 8/20/2024 at 7:33 PM, nevenbekriev said:

OK, there is a brass bush inside A that serves as bearing for C. A's pivot is made as a tube and the inside diameter is relatively big. Then a brass bush is pressed inside the pivot. To clean the tube, You can use some wire that gets inside but doesn't go thru the bush. I can guess that at some point the seconds pivot has been replaced and the new one has bigger pivot diameter. You can put the pinion tip only from the other side of the bush in order to check if it goes in with resistance or free. Probably the problem will be solved by slightly reaming the bush hole by broach

And yes, oil is applied same as on the other side pivot in the stone

I managed to get in with the smallest broach from that set to widen the hole out slightly. There was an immediate improvement when I reassembled the gears, much more free running now. 

Movement actually runs now! It runs with about 60 degrees of amplitude, but it runs! I'll need to do a thorough clean and relube, see if I can get it better. Thanks again.