Author Topic: Chronometric trip rebuild  (Read 963 times)

Offline iansoady

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Chronometric trip rebuild
« on: 18.10. 2010 17:08 »
Has anyone attempted this? I've managed to strip it and get it back together (note to self: the second time is easier!). I had to strip the speedo anyway as some previous owner had managed to almost fill it with horrible grease - hence reading up to about 130 mph! I know A10s are fast, but...

Anyway, I perhaps foolishly took the trip apart so that when I squirted contact cleaner around the place the numbers wouldn't come off (as I later discovered they seem to be proof against the cleaner). On reassembly, which isn't exactly an easy matter, as it's full of little springs and spacers, all the drums seem to turn together when the mechanism is spun by an electric drill, ie it starts at 000.0 then reads 111.1, 222.2 etc etc.

I know I should give it to someone who knows what they're doing but I like to try myself. So, any pointers would be useful before I give up.
Ian.
1962 Golden Flash (arrived)
1955 Velo Viper/Venom (departed)
2004 Triumph Tiger 955i (staying)

Offline a10gf

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Re: Chronometric trip rebuild
« Reply #1 on: 18.10. 2010 17:35 »
(I'm no expert on this)... but obviously sounds like the 4 wheels (dials?) are glued\stuck\pressed together (it's only the small tabs that should make the next LH dial\wheel click one notch up pr. revolution. Maybe something is too tight, or residues of the grease ?

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Offline Stu55Flash

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Re: Chronometric trip rebuild
« Reply #2 on: 19.10. 2010 00:08 »
The counters, washers and drivers are probably in the wrong order. See this document for the correct sequence:



If you search the internet for Repairing Jaeger and Smith Speedometers by Anthony Rhodes this gives the best guide. I don't know how to upload it here,

Stu
"Keep a distance from lady "L" drivers in cars. Some are not mechanically minded, are slow to acquire road sense, an are apt to panic..." The Pitman Book of the BSA Twins.
Golden Flash Plunger 1955, Francis Barnett Falcon 67 1954, Ferguson TEA Tractor 1951. Looking for another project!

Offline iansoady

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Re: Chronometric trip rebuild
« Reply #3 on: 19.10. 2010 11:05 »
Thanks both. Mine doesn't look quite like the drawing, although the principle is obviously similar. Ageing eyes and consequent long sight don't help matters!

I'll have a look for the guide you mention Stu.
Ian.
1962 Golden Flash (arrived)
1955 Velo Viper/Venom (departed)
2004 Triumph Tiger 955i (staying)

Offline iansoady

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Re: Chronometric trip rebuild
« Reply #4 on: 19.10. 2010 11:11 »
Stu,

Found the guide (which is excellent, although referring to magnetic instruments rather than chronometric). I think the key lies in this section:

The ?old? style odometers work by friction trying to turn all the odometer wheels and then a restraining clip underneath the wheel prevents motion except at certain times.  The drive gear is keyed to the shaft and there are keyed washers between each of the wheels. The wheels themselves are not keyed and can turn freely.  As the drive gear turns, it turns the shaft.  The shaft turns the washers between the wheels.  By friction, the wheels try to turn, but the clips prevent turning.  The restraining clips underlie two adjacent wheels, so one wheel can disengage the clip under the next wheel to the left.  The left and right edge of each wheel have a thin metal edge with notches.  These notches engage the clips.  On the right side of each wheel the edge has ten notches.  The left side of each wheel has one notch.  When looking at two wheels, as the right wheel turns one entire revolution, it disengages the clip under the left wheel once.  The right wheel moves ahead by one notch, then the clip re-engages and prevents further forward motion until again disengaged.

So I need to look at how the clips are engaging and disengaging.

Fascinating stuff!
Ian.
1962 Golden Flash (arrived)
1955 Velo Viper/Venom (departed)
2004 Triumph Tiger 955i (staying)

Offline iansoady

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Re: Chronometric trip rebuild
« Reply #5 on: 19.10. 2010 14:32 »
Having pulled it to bits again I have found the problem - the little finger leaf springs weren't touching the drums - probably I'd bent them by being ham-fisted when I dismantled the thing. It does seem to be working fine now - at least the tenths drum is going round without moving the next one.

That article is excellent for understanding what should be happening and I commend it to others. It's here.
Ian.
1962 Golden Flash (arrived)
1955 Velo Viper/Venom (departed)
2004 Triumph Tiger 955i (staying)

Offline a10gf

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Re: Chronometric trip rebuild
« Reply #6 on: 19.10. 2010 20:00 »
Good to read you nailed the problem, and thanks for all the xtra info.

A10 GF '53 My A10 website
"Success only gets you a ticket to a much more difficult task"