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  1. #1
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    Oct 2014
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    Speed sensor replacement - driveshaft ring

    Ok - next little job to sort is an intermittment fault with the speedo - it just drops to zero!

    Think we have tracked it to magnetic ring on the propshaft. It is a Smith guage. The sensor seems to be fine but the magnetic ring is deformed and the gap varies from by over 4mm - I believe it should be a constant 0.8mm.

    The orignal builer has clearly taken a grinder to it before fitting. My engineer did not like my idea of just bonding the magnets to the prop!!

    WhatsApp Image 2021-01-22 at 12.22.03.jpeg

    I can't seem to get any details of this part or where to find a replacement. Anyone recognise it or any suggestions?

    Thanks

  2. #2
    Join Date
    Jan 2006
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    Chelmsford Essex
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    1,510
    Split collar magnetic pick up

    https://www.ebay.co.uk/itm/Haltech-D...sAAOSwNntgCakl

    Holley do one which is a lot more from USA. Tax and shipping.

    I would use a pick up and pick up the bolts off the prop

    You might get this to work as alternative 50mm shaft 4 pick up. They use these on karts.
    https://www.demon-tweeks.com/alfano-...E&gclsrc=aw.ds
    Last edited by jon1d; 23-01-21 at 11:56 AM.
    Dax 351 Cleveland T5 2.88 PL

  3. #3
    Join Date
    Jan 2006
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    They do a 50mm but does not state the pickups. Its not split collar is only down side.

    https://www.aimshop.com/products/aim...SABEgKtlPD_BwE
    Dax 351 Cleveland T5 2.88 PL

  4. #4
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    There are some 2" (51mm) split shaft collars on eBay at the moment.

    https://www.ebay.co.uk/itm/2-ID-Spli...t/154212597768

    The prop shaft is 50mm and the magnets are easy enough to drill and fit so I have ordered one of these to play with - seems a more Yorkshire approach than the £70 option from Haltech which would also work.

  5. #5
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    That looks a good option . Always look at the most cost effective route. Those split collars look well made.
    Some careful drilling and placing of the magnets.

  6. #6
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    Quote Originally Posted by jon1d View Post
    That looks a good option . Always look at the most cost effective route. Those split collars look well made.
    Some careful drilling and placing of the magnets.
    Arrived. Needed the bolts machining down a bit as they were slightly proud of the ring but simple enough - also easy to drill and fit the magets and now have a stable and working speedometer .

    Great and cost effective solution which now fits as it should.

    Speed Sensor.jpeg

  7. #7
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    Quote Originally Posted by david.mt View Post
    Arrived. Needed the bolts machining down a bit as they were slightly proud of the ring but simple enough - also easy to drill and fit the magets and now have a stable and working speedometer .

    Great and cost effective solution which now fits as it should.

    Speed Sensor.jpeg
    Looks neat and I suppose will prevent the usual problems of magnets flying off the prop. Presumably you used 4 equi-spaced around the ring and araldited into the drilled holes?
    Dek

  8. #8
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    Quote Originally Posted by Dek View Post
    Looks neat and I suppose will prevent the usual problems of magnets flying off the prop. Presumably you used 4 equi-spaced around the ring and araldited into the drilled holes?
    Dek
    Yes bonded in but only 2 magnets in the original. I believe the speedo is based on pulses per mile so should work with any number of magnets. I am hoping that as the original had 2 magnets and the replacement now has 2, the speedo should remain calibrated.

  9. #9
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    Interesting alternative to the "usual" bolts-on-the-diff approach. I wonder how much lateral movement your prop shaft sees? Presumably you have stiff engine & gearbox mounts to limit the movement - that was my first thought, anyway. Other than that, probably more reliable than making sure all the bolt heads face the same way etc?
    My DeDion build diary..
    Hon Sec of the Digidash branch of the Unpopular Kit Car Design club

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