Bfg 866

[Legarm]

Hi,

I am repairing  a Watch for a friend with a BFG 866 movement, I have fully serviced the watch and re-assembled. All was fine the balance started straight away and all cogs rotating as they should. I refitted all parts, synchronised the day date function, fitted the hands and the only one to work was the second hand. I am baffled as when the clutch is applied to change the time, all is OK, push the crown in to wind position and the hour & minute run free still.

Help please..............................

[Geo]

Good evening Legarm, you really do seem to have a puzzler here. I had a look on the net to see what sort of movement it is, and I have never seen the likes before. Needless to say I can't offer any help being totally unfamiliar with the calibre, but if anyone clicks on this link it may jog some memories.

http://www.christophlorenz.de/watch/movements/b/baumgartner/baumgartner_866.php?l=en

[Marc]

First port of call would be the cannon pinion.

When the movement is running power is transmitted from the going train to the motion works via the cannon pinion which is a friction fit onto the centre wheel arbor. This is to allow the cannon pinion to slip on the arbor when setting the time.

If the cannon pinion is too loose on the arbor then power won't be transmitted to the motion works and the hands won't move. However, as the seconds hand runs independently of the motion works it will still run.

Tightening a cannon pinion is not too difficult, the main problem being going too far. If you don't have access to specific cannon pinion tightening tools then a common substitute is to gently crush the pinion at the pinch point using nail clippers. If you insert a needle into the pinion first then you can control the amount it closes. 

[Legarm]

First port of call would be the cannon pinion.

When the movement is running power is transmitted from the going train to the motion works via the cannon pinion which is a friction fit onto the centre wheel arbor. This is to allow the cannon pinion to slip on the arbor when setting the time.

If the cannon pinion is too loose on the arbor then power won't be transmitted to the motion works and the hands won't move. However, as the seconds hand runs independently of the motion works it will still run.

Tightening a cannon pinion is not too difficult, the main problem being going too far. If you don't have access to specific cannon pinion tightening tools then a common substitute is to gently crush the pinion at the pinch point using nail clippers. If you insert a needle into the pinion first then you can control the amount it closes. 

 

Thanks Marc, surely if the Canon pinion is crimped to the fixed centre wheel arbor, would this not, just lock the free running indirect drives from the Barrel?

[Geo]

Thanks Marc, surely if the Canon pinion is crimped to the fixed centre wheel arbor, would this not, just lock the free running indirect drives from the Barrel?

I totally agree. This is not a "standard" type of movement with the hands being driven via a friction fit cannon pinion, it uses what appears to be a clutch driven by the barrel. It is this part of the mechanism that needs closer inspection.

[Legarm]

I totally agree. This is not a "standard" type of movement with the hands being driven via a friction fit cannon pinion, it uses what appears to be a clutch driven by the barrel. It is this part of the mechanism that needs closer inspection.

 

right, crimped the Canon Pinion on.... and Nado, Zilch, nothing. 

I agree with you that the clutch drives something, but what> there does not appear to be anything between the Barrell and the minute/hour cog.

Really confused.

[Legarm]

 

It's no good I'm going to strip it right back an check the Barrel set up as there must be something the to drive the cogs, otherwise they would free run.....

The pic shows the base of the Barrel and the two drive plates for the Canon Pinion and the Hour Wheel......

[Legarm]

stripped and cogs just run free, no clutch or spring to arrest wheels to provide drive .... Aaaaarrrgggghhhhhhhhhh

[Marc]

Ahh... I should have had a look at the link before posting.

 

What you have there is not a centre wheel arbor, it's a static centre post fixed to the main plate.

The set up I described in my initial reply describes the "typical" transmission of drive through to the hands.

 

On your set up the centre wheel arbor doesn't come through the main plate at all and the centre wheel isn't even in the centre!! It 's been offset to make room for the indirectly driven seconds hand.

This set up still requires some form of friction clutch between the motion works and the going train or it would not be possible to adjust the hands, and some form of off set or split cannon pinion is used other than the pinion that the minute hand sits on.

I had a look at the parts sheet for this calibre (download from Cousins) to see if I could spot where it is but it's not obvious. A closer look at the pics on the Metatechnical Cabinet page though suggests that the mainspring barrel may be the culprit.

If you look at it closely you can see the biggest diameter of the barrel (the "great wheel" or the "first wheel") drives the offset centre wheel (or "second wheel") pinion in the 10 o'clock position. However, there is another wheel (the second wheel sits in between this and the great wheel) with a pinion on top of and coaxial to the barrel. The wheel meshes with the intermediate wheel in the keyless works, but also looks like it should mesh with the minute hand pinion sitting in the deeper recess around the centre post. The pinion meshes with the hour wheel.

My best guess is that the friction clutch is in this extra wheel and pinion set up on top of the barrel.

The good news is that if it can't be adjusted pretty much all of the necessary parts are in stock at Cousins.

The bad news is that the minute hand pinion that you tightened needs to be a free turning fit on the centre post so you will need to open it up again.

 

My apologies if my initial response lead you astray.

[Legarm]

Hi Marc,

All wheels are present and correct. The only difference I can possibly see from the Metatechnical Cabinet, is that at the 7 o'clock position on the minute drive  wheel it looks like there is a spring or something.

[Legarm]

This is the Barrel......

 

 

The two cogs at the top rotate freely and are supposed to drive the minute and hour hands....

 

[Marc]

That's the fella, I suspect that that is the bit that shouldn't turn so freely.

If you take the barrel cover plate off then with any luck you will find that the wheel and pinion is just riveted in place. If that is the case then a light tap to tighten the rivet just a fraction is all that is needed.

A staking set would help here and by the look of it a conical stake may be the best option to open out the top of the rivet slightly.

[Legarm]

That's the fella, I suspect that that is the bit that shouldn't turn so freely.

If you take the barrel cover plate off then with any luck you will find that the wheel and pinion is just riveted in place. If that is the case then a light tap to tighten the rivet just a fraction is all that is needed.

A staking set would help here and by the look of it a conical stake may be the best option to open out the top of the rivet slightly.

 

Thanks Marc, I wondered if that was the case as when I cleaned the mainspring it looke loose.

I have a staking set coming from the bay so I shall wait for that.

Once again many thanks, I would never have had the confidence to just **BLEEP** it without some other input...... :)

[Legarm]

Found this.....

Rosskopf design / "cannon pinion" tightening

[Geo]

That's an excellent find, I'm sure a lot of us have learned something new!

[Marc]

Thanks Marc, I wondered if that was the case as when I cleaned the mainspring it looke loose.

I have a staking set coming from the bay so I shall wait for that.

Once again many thanks, I would never have had the confidence to just **BLEEP** it without some other input...... :)

Hmm...  I would still be a little cautious of just "twatting" it...

Several light taps whilst testing the result between each tap will enable quite precise adjustment.

The WUS link that you found is excellent, shows exactly what's required.

If it all goes horribly wrong Cousins have barrel covers in stock for £5.95+vat so no tragedy.

Let us know how it goes. 

[Legarm]

Hmm...  I would still be a little cautious of just "twatting" it...

Several light taps whilst testing the result between each tap will enable quite precise adjustment.

The WUS link that you found is excellent, shows exactly what's required.

If it all goes horribly wrong Cousins have barrel covers in stock for £5.95+vat so no tragedy.

Let us know how it goes. 

 

I wasn't really going to "**BLEEP** IT", gently coerce it into place  -_-

 

Cousins do have two covers, so all is not lost...... thanks for all the help.....

[Legarm]

Staking tool arrived.... Let the Twatting begin ......  :o

[Marc]

Did you **BLEEP** it then?

Was there success?

[Legarm]

Did you **BLEEP** it then?

Was there success?

 

Will hopefully be attempting the manoeuvre today..... reading and deciphering the method ....... :unsure:

[Geo]

We wait with baited breath! :-)

[bobm12]

Please, hurry, I can't hold my breath any longer!

[Legarm]

"Twatted" and all serviced and running very nicely at the moment, Waiting to see how it manages with the extra torque at midnight with the day,date change.

I must say though, if anyone takes on one of these movements, there is a fine line between free running and locked. Take care and the stake to use is as the link I put on earlier in this topic.

Thanks for the interest.....  :)

[Marc]

Yeah!!!!!

Well done that man, glad it worked out fine.

You're not wrong about the fine line. My Clarkson spanner of choice when it comes to watches weighs in at about 15 or 20 grams as this gives me plenty of control. Rarely do I need anything much bigger, unless I'm regulating a fake, then I find the 20lbs lump hammer a good option.

 

Any way, nice one :-)

[Legarm]

Yeah!!!!!

Well done that man, glad it worked out fine.

You're not wrong about the fine line. My Clarkson spanner of choice when it comes to watches weighs in at about 15 or 20 grams as this gives me plenty of control. Rarely do I need anything much bigger, unless I'm regulating a fake, then I find the 20lbs lump hammer a good option.

 

Any way, nice one :-)

 

Thanks Marc, you never quite know what your going to get when you crack open unknown brand names...... I had a BFG 800,  dead easy ..... 866... thinking cap on..... anyway, another method learnt.... and my mates watch is running again .... :)

Edited July 10, 2014 by Legarm