Smith Chronometric Speedometer Sc3305/20 1620 Help

[WasDonkey]

Does anybody know anything about these? My '62 5TA's Speedometer needle has decided to give up the ghost. I've dismantled, the cable/square pin rotates with the wheel moving as it should, and having since stuck a drill bit of equal size into the speedometer, I can tell you the trip/milage goes up...so I've obviously got a problem with just the needle mechanism. 4 questions I guess...

1) does anybody know anything about them and can shed light on the problem?
2) assuming it's probably too complicated for me, does anybody know where/who and/or if they can be restored?
3) failing that, does anybody know where I could pick up a new/old/replica one?

and finally...

4) the numbers "SC3306/20 1620", having done a little research, I've found similar looking speedometers but with different numbers. Now I'm pretty sure I know they won't be compatible, but if anybody could shed light on these I'd be interested to know what they correspond to...

Thanks in advance

 

[Rocky]

I don't think many of us here are "brave" enough to take one apart and try a repair.
Probably your best bet is to locate a repair shop in the UK.
Look through the adverts in the back pages of classic bike mags such as Classic Bike, The Classic Motorcycle and Classic Bike Guide.
Local vintage bike clubs and the internet can also help steer you to a reliable repair shop.

But this is just my take on the situation, so maybe there is somebody here who can help.
Good luck.

 

[grandpaul]

The different part numbers relate to the face markings, drive ratio, mileage indication relative to corresponding driven wheel diameter, etc. There are MANY different combinations.

I have used Joel Levine repair in Georgia with 100% success over 40 meters (3 chronometrics).

 

[harper6t]

I have a good friend who does these up for a living, from memory the 1620 is the number of turns per mile, so any with 1620 would suit your needs. These a too complex for me to understand, so i leave it to him. There are plenty of articles on chronometric speedos on the net, if I remember correctly Kashif had lots of pics and details on his 3TA (twenty one) restoration on this very site.
There are plenty of cheap and nasty repros from India on the market (magnetic movements not the complicated chronometric movement), but they don't look good and I doubt that they would fit the nacelle.
I would recommend too that you find a repairer in the UK, lots of them come up on searching the web.