| 1883warren | -- 09-18-2010 @ 7:43 PM |
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We got our '36 tudor running this spring, and I put in the nicest speedo' with the best bezel. But...it read about 20 mph slow, so put in another from my stock. About the same ~ Tried another, and the same. Finally realized that my parts' storage is on the second floor of a tin roof building and it gets HOT up there in summers. Also realized that the magnets in all had gotten weak because of this heat..on and on over the years. So, I made a charger, out of 3/8 steel rod, with a coil of wire, 100 turns on each end, as shown. I used a compass to get a N & S reading, with proper hookup of coils, and polarity of the leads. I used one 12v battery, and a 6v battery in series to get 18 volts. Took the magnet wheel out of the best speedo' and put N to S (opposite) contact from the charger to the magnet, and 'hit it' for 5 seconds. Worked great and now my speedo' reads about 2 mph fast, according to the GPS. Close guess, at that.... Warren
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| 1883warren | -- 09-18-2010 @ 7:47 PM |
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Here is another picture that shows it a little more close up........ Remember; N & S poles of the charger point to OPPOSITE poles on the magnet of the speedo'. Warren
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| 1883warren | -- 09-18-2010 @ 7:51 PM |
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Should have added: The ends of the charger must touch and contact the magnet. The magnet is split from the center, so those 'ends' are N & S poles. Use a compass to find which is which. Warren
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| 40 Coupe | -- 09-20-2010 @ 5:53 AM |
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I assume you checked the speedometer turtle to see if the ratio was correct??
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| 1883warren | -- 09-22-2010 @ 6:52 PM |
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My chassis and drive train is all original... 4.11/1 In any event, a plus 20 mph slow reading would not fall into any speedo' drive category. Did I mention that a friend with a '47 Buick Roadmaster also broght his speedo', which was reading almost as slow as mine. I had to bend the core steel outward a little, to fit and touch on his larger and differently configured speedo' magnet. His now reads a tad fast, but we're hoping that the magnet will loose as time goes on and read on the money. A lot of guesswork with this sort of thing..... Warren
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| supereal | -- 09-23-2010 @ 9:54 AM |
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In addition to the magnet strength, the spacing of the disks and condition of the shaft "bushings" which are often just the pot metal of the case, should be considered, as well as the hair spring that returns the needle.
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