K speedos - just for fun

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K speedos - just for fun

Postby John R » Mon Oct 06, 2014 6:53 pm

It was customary in the 50's for manufacturers to deliberately make speedos read fast but with reasonably accurate odometer. With my '56 KHK it reads very fast. So I started thinking...

The speedo is driven via 1st gear splined to the mainshaft to 1st gear on countershaft. In 52 this was 18 to 29 teeth, in 53 18 to 27 teeth, then 54-up 17 to 27 teeth.

Then the speedo spiral gear fitted to 1st gear on countershaft was 7 starts in 52/53 then 54-up 8 starts.

Then the sprockets were 21/51 in 52/53, then 54 up as different as 22/49 (though other possibles).

Then nominal tyre circumference was 6.68' in 52/53, and down to 6.55' 54-up.

Do the maths and presuming they started with an intentional 10% fast speedo in 52, because the speedo didn't change, by 56 it could be another 7% fast.

The K speedo does look cute though!

I must get out more...
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Re: K speedos - just for fun

Postby hennesse » Mon Oct 06, 2014 7:41 pm

John R wrote:Do the maths...


I tried, and now my head hurts. But you are right - all the gear changes and tyre changes affect the accuracy of the speedometer. Over here in the US, Interstate highways have mile markers, often every 1/10 mile. So theoretically, you could drive a constant 60 mph by your speedometer, and use a stopwatch to measure your time past two mile markers. Multiply 60 x 60, then divide by the number of seconds, and you get your true speed.

Or you could do what Harley did, and just multiply by the imaginary number i...
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Re: K speedos - just for fun

Postby Hammie13 » Mon Oct 06, 2014 9:49 pm

I just go by the buzz in my butt cheeks, butt then I'm no mathsmatician.
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