Anyone got experience of the JLC 240?

[Scootle]

Hi all, 

I have been asked to have a look at a JLC 240/3 movement that stops randomly every 4 hours or so. I've cleaned it and the heavy duty wheels under the main bridge are running freely. The third wheel (#210) is held between the base plate and the mezannine style bridge that forms the lower jewels of the balance and pallet fork so rather conveniently I can see immediately that it is this 3rd wheel that is causing the problem. It is touching the beefier intermediate wheel (#203) to the right of it in the picture. The problem is that I can't see that either part is damaged.

Does anyone know if this is a known fault? I did consider that the 3rd wheel could be a replacement part but the parts list suggests not. Both parts are true and not bent. Neither show sign of wear. There's no end shake on the 3rd wheel and only a small amount on the intermediate wheel but that would tend to make the touching worse not better. ( in other words, in the picture, the intermediate wheel will move very slightly to the left tending to push harder on the 3rd wheel as opposed to creating the required gap). The jewel that the 3rd wheel is sat in is absolutely flush with the base plate so I doubt I will be able to lift the 3rd wheel enough by moving it.

I am at a loss - any help or advice would be gratefully received.

Scott

[nickelsilver]

Some more pics would help, are you sure you have the 3rd wheel (and everything else) the right way up? Sometimes you can actually put wheels in upside down and they almost work.

[Scootle]

36 minutes ago, nickelsilver said:

Some more pics would help, are you sure you have the 3rd wheel (and everything else) the right way up? Sometimes you can actually put wheels in upside down and they almost work.

thx for the quick reply. I can be sure they are the same way up as they were when I disassemble it but since it was showing this problem before I got hold of it I will double check the orientation. However, the long pinion on the 3rd wheel would prevent it from being upside down. The intermediate wheel pinion engages with the mainspring barrel so that is definitely correct. I have lots of photos. I always photograph while disassembling. Which would you like? In this one you can see the intermediate wheel and about a quarter of the 3rd wheel resting on it. 

[nevenbekriev]

May be just trueing hte wheels is needed. As stops ones per 4 hours, then the intermediate wheel is not perfectly trued - it makes full revolution for 4 hours. Then, look at the intermediate wheel bearings - they may have weared and the wheel may not stay upright.

[Scootle]

57 minutes ago, nevenbekriev said:

excellent point about the 4 hour revolution - I'll look into that.

 

[oldhippy]

Going by your photo. Looks like something has been rubbing the barrel cap. The teeth on this type of barrel are pron to be rough and poorly finished check them all. Teeth on that wheel also look rough so need checking. What about the pivots, have you burnished them if not do so. Are you sure all the wheel holes are good no rough marks in side. Springs are very powerful in this movement as its an 8 day duration. It must be something big to stop all the power. Check for end shake and freedom of the complete train. Have you checked the mainspring. Fault finding can be time consuming. You might like to start from the beginning again.  

[Scootle]

37 minutes ago, oldhippy said:

Great feedback thanks. Please see below. 

 

 

All,

thank you so much for your input. It's amazing how just talking about these things helps.

Can I just make a schoolboy correction to my own notes so far on this. The wheel causing the problem is the fourth wheel (220) not the third as I have been saying previously. I have no idea why I said 3rd when it is as plain as the nose on my face

Nicklesilver - you will be pleased to hear you hit the jackpot. Who ever had serviced this last time had put the fourth wheel in upside down. Putting it in the right way up gives plenty of clearance from the intermediate wheel and it runs like a dream