Hi all
I have a 71 B50T that I am restoring to a everyday usable condition.
Going through the various parts to decide what needs replacing, repairing or simply cleaning, I'm a bit stuck with the speedo.
Is there a way to test it for basic operation.
I thought about simply spinning it up with a drill on the end of the cable but I'm not sure what range of rpm to use or even if it should be spun clockwise.
If it helps, it's marked up as a Smiths SSM-5007/02A 1600
TIA
The 1600 figure is the number of turns per mile. The rpm required to indicate a speed S in mph is therefore given by
RPM = S x 1600 / 60 = S x 26.7
For example, to indicate 30 mph, you would need to spin the input to the speedometer at 800 rpm. From memory, I believe this needs to be CCW.
There's not much to go wrong in a Smiths magnetic speedometer although the spring connected to the needle tends to weaken with age causing the speedometer to indicate a higher speed than it should. However, it's not easy to calibrate the speed of an electric drill to check the accuracy of the speedometer.
What a great reply, thank you