Smiths Chronometric speedo

[Marc25]

I quickly had a look but I was nott able to find the info I was looking for on the forum.

My Smiths Chronometric Speedo is not working anymore.
I unmounted it... and well.... It's a wonderful part of clockmaking... that's it

How can I unmount the needle ? What are the most probable problem ?

[bsa-bill]

It's a wonderful part of clockmaking... that's it ;)
Hi  Marc25 - it certainly is,
What are the most probable problem ?
Wel ldon't know where you are located but if in the UK  putting it back or forward an hour twice a year is bit of a bind sorry - quite a bit of sherry still in the system

There are people here that seem to understand the working if I recall, myself I'm happy to post the thing off to Mr Pople  http://www.speedorepairs.co.uk/and let him get on with it although he is or used to be a very busy man so you wont get it back in a hurry.
Ah just read he had some personal problems which might have explained some delays
there is also http://www.chronometricspeedos.co.uk/ also heard good reports

[Triton Thrasher]

The needle pulls straight off the pin it's on.

If the cable socket can be turned, but nothing else happens, follow the train of gears until you get to the tufnol one. It could be stripped.

[Marc25]

Thanks ! 
It's exactly that : when I turn the "cable" at the back of the speedo nothing happens.

[a10 gf]

^^^ Si possible, quelques bonnes images of your findings in the speedo internals ?

[RichardL]

^^^ Si possible, quelques bonnes images of your findings in the speedo internals ?

Franglish?   (Google translator seems to think so.)

[Marc25]

Looks like

I reassembled it. Unfortunatly it's snowing here and I am not able to test it on the road But it looks better with the drill now...
I have cleaned it with gazoline and then put some oil and I realized that a small gear was not working as it should...
Let's hope it was the problem.

I'll put you some pictures 

[bsa-bill]

Surname Rolex by any chance 

[Marc25]

http://i39.servimg.com/u/f39/17/12/21/72/nk7_6010.jpg
http://i39.servimg.com/u/f39/17/12/21/72/nk7_6011.jpg
http://i39.servimg.com/u/f39/17/12/21/72/nk7_6012.jpg
http://i39.servimg.com/u/f39/17/12/21/72/nk7_6013.jpg

[RichardL]

The parts all look pretty good. You could brighten-up the numbers on the wheels and the face with a little mild soapy water and a Qtip (I don't know the name for a French equivalent product for a cotton swab on a stick).

Others may correct me here, but I believe the "1025" indicates the number of revolutions of the cable to achieve a km/minute or 60 km/hr. This does not quite jive with my own MPH speedometer indicating "1440"' but I am assuming the plunger speedo drive ratio or rear tire diameter are different from my swingarm. If I am correct, and you were to use a drill motor like mine that goes to 1500 RPM, the speedo would read about 89 km/hr at that RPM of the drill motor ((1500/1025) x 60 = 88.7). You should be able to replace the 1500 in this arithmetic with the RPM of your own drill to determine if this is the correct logic.

Richard L.

[wilko]

http://www.hells-confetti.com/Technical%20data/Jaeger%20Instruments/Carl%20Cederstrand%20on%20the%20Chronometric%20mechanism.pdf

[RichardL]

When I said that "the parts all look pretty good", take nothing from that implying that I understand chronometrics to the degree described in Wilko's post. I don't. I took mine apart, cleaned and lubricated it and it worked.

Richard L.

[muskrat]

Great link wilko, thanks mate.
I did the same Richard, 30 odd years ago. The number counters are a bit hit and miss, the trip meter never worked, but speed indication is pretty close.
Cheers

[a10 gf]

Thanks for the link, well done by Mr Carl Cederstrand writing that document.

Enjoy your chronometric instruments and muse about their wonderful mechanical complexity. The world will never manufacture their likes again. They have been banished 'in perpetuity' by the twin Gods of Economics and Solid State Electronics

[Marc25]

Thanks for this link !

How should I post the photos ?
^^^ adm edit: see http://www.a7a10.net/forum/index.php?board=15.0