chronometric speedo

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Myford

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Just reading highdeserts thread about speedo drives, got me thinking, chronometric speedo's are said to be the classy swiss watch of speedo's, has anyone thought about using a smiths chronometric (I assume they're the same size) & maybe swapping the face for the geen dot one?
Terry
 
I think they are really hard to find and if you do find one it'll probably run you a small fortune to purchase. The last one i saw sell went for 700 dollars
 
Blimy I never realised they were that kind of money, that kind of puts an end to that,
Terry
 
Myford said:
has anyone thought about using a smiths chronometric (I assume they're the same size) & maybe swapping the face for the geen dot one?
Click to expand...

It should be possible, as I think the units are basically the same size, but cable rotation and drive ratios could be different?
 
Well the drive gearbox's are the same fit, just different ratios? just need to match the gearbox to the speedo. Didn't the Interpols use chronometric? I wonder if they had green dot faces.
Terry
 
I run Chrono's on my 66 atlas, it's really just a matter of matching up your drive ratio with the gauge. In order to use the gauge cups I suppose you could track down a nacelle style speedo so you can still use the trip-meter. They can get a bit pricey depending on the actually model. My tach ran about 700 but that's because it has the red tell-tale needle (hidden behind the white one in the pic).

chronometric speedo
 
Interpol Chronometrics were the generic late version. No special markings and were used because of their superior accuracy. They do have an odd needle movement but don't flikker like the SSMs.

I think that one difficulty in installing in Commando cups is that the trip set is on the side and not underneath.

I have a Chronometric but installing it on the Commando would be to risk a bent needle at 85mph.

chronometric speedo


UK speedo restorers will usually pay £60 for a complete chronometric in restorable condition and will sell an exchange unit for around the £200 mark, depending on rarity (but most can be converted). It is quite difficult to buy restored units outright now which means finding a donor unit first.
 
IIRC, the Atlas speedo gearbox is 1600 revs/mile and the Commando is 1000 revs/mile. When we first started prototype testing, the speedos didn't match the gearbox, and read 1.6x actual speed. The p/n printed on the face of the instrument has a slash followed by a number which is the revs/mile it's calibrated for.
 
In the 1970's i brought an ex New Zealand Traffic [police] drum brake commando reg 72 but a 71 model and yes it was fitted with a chronometric speedo mounted in the alloy cup. i also have a 1966 650SS which is also an ex cop bike and again it is fitted with a chronometric speedo.
 
Hi i have a Smiths chronmetric speedo and i am looking to swap it for a smiths green dot one.

cheers.
kenny.
 
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