Chronometric Speedo How should the odometer trip reset work?

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Chronometric Speedo How should the odometer trip reset work?

Post by Group Leader »

My '53 16MS has a Chronometric speedo that seems to work well (up to 35 mph anyway!) and both the odometer and trip count up the miles as I chug around the local lanes :D .

It seems to be missing its knurled knob from the reset shaft (emerging from the rear) which rotates and pulls out a few millimeters apparently against a light spring. Rotating and/or pulling the shaft out does not seem to have any effect on the trip meter. My question is how does/should the reset work? Is mine likely to be U/S or am I just "doing it" wrong?

TIA!

Alan
Speedo2 - Small.JPG
Speedo1 - Small.JPG
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1953 AJS 16MS, 1939 BSA 250 and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:
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thornebt
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Re: Chronometric Speedo How should the odometer trip reset w

Post by thornebt »

I can't remember if you pull it out and twist or push it in and twist but it's one of those two. It's hard enough getting to it and resetting it when it's complete with the knob so I'm sure it will be very tricky with just the spindle. It hasn't got a particularly light action. Cheers. Bruce.
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clive
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Re: Chronometric Speedo How should the odometer trip reset w

Post by clive »

The speedo in the picture is one for a headlight nacelle mounted unit. The fork mounted ones would have a trip reset coming out the side which is much easier to use. To make yours operate you need to buy the brass trip reset knob ( search "smiths trip knob" on eBay ) and split pin it to the hole in the shaft you have showing. To operate it you pull down and rotate at the same time.
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Re: Chronometric Speedo How should the odometer trip reset w

Post by Group Leader »

Thanks very much for the information.

I feel a quick turning exercise on my little Unimat lathe in the offing :-)

Alan
1953 AJS 16MS, 1939 BSA 250 and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:
39speedtwin
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Re: Chronometric Speedo How should the odometer trip reset w

Post by 39speedtwin »

When I make these l make sure that the hole in the knob is a few thou over the diameter of the shaft, this avoids breakage in trying to remove a tight one. Make from 3/8th diameter brass.
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Rob Harknett
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Re: Chronometric Speedo How should the odometer trip reset w

Post by Rob Harknett »

Your speedo head is as has been stated, it is the type that fitted in a headlamp. You should have one with the knob coming out the side. Also other things have been stated. I believe one point has been missed. The type of speedo you have, did not have just a knob it had an extension about 3" long with a knob on the end. This enabled access has it hung down, the knob clear of the speedo head and easy reach with fingertips and turn. Just like the speedo with the knob out the side, was clear of obstacles and easy to reach and turn. So I suggest you fit the extension with the knob on the end. If you just fit a knob it would not be easy to turn it, perhaps even more difficult to turn than just the bare spindle. As the knob will be close to the speedo cable. You do need to get a firm grip on the knob to pull it down and turn it, so go for the extension with the knob on the end.. I had just a knob on one of those speedo's in the headlamp of my 55 G3LS I could not turn it. I got 3" of that coiled curtain wire with a screw eye in one end. The other end I opened up a bit until it pushed tight onto the spindle coming out the speedo. I later found a small plastic screw in knob, just like the speedo knob, to replace the screw in eye. Its now still firmly fitted after about 30 years. Probably have a job to get the extension off the spindle now. So perhaps best to get the real thing fitted with a split pin. Note what Dudley says about getting them off again , this certainly does apply to my curtain wire extension knob bodge.
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Re: Chronometric Speedo How should the odometer trip reset w

Post by Group Leader »

Well that seemed to work although I have to say the "action" is rather hit and miss!

I don't think it's a feature I shall make great use of now I've set it; I just want to keep track of the miles I'm covering without recourse to a bit of mental arithmetic every time!

Anyway, thanks as ever for the advice given.

Alan
1953 AJS 16MS, 1939 BSA 250 and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:
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Re: Chronometric Speedo How should the odometer trip reset w

Post by 39speedtwin »

If as you say it works, but is hit and miss, then probably one of the teeth on the gear has broken off. These gears are only made of thin steel and are fragile. However to replace this it requires removal of both the needle and the face. So best left as it is unless it annoys you.
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Re: Chronometric Speedo How should the odometer trip reset w

Post by Rob Harknett »

Or hit & miss through not maintaining the pull down while turning. This can happen if there's lack of space to manoeuvre.
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