Which fuel tank sender

Discussion in 'Mech Tech' started by Mark Darby, Oct 24, 2019.

  1. My guess/calculation is about 52ohms per metre which would be about 0.16mm wire. Anyone?
     
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  3. Mine still working , been five years... Daily driver..
     
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  4. Measure the old one ;). The original would’ve used metric wire not AWG, obvs.
     
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  5. Kind of obvious when you think about it..... doh!
    Micrometer ordered - need one anyway. Calipers aren't accurate enough at that level I don't think.
     
  6. Micrometers better for such things. Screwfix actually do a not-bad 25mm mike.

    Be interesting to hear how you get on. Should be possible to rewind the things, although would appear that on the ones with the flat board, the windings get closer together to get the right (non-)linearity. There’s the sine of an angle involved somewhere, I think...
     
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  7. I think the trick is once you remove the old wire, not to clean the board. It's easier to follow the old tracks then. I will take a photo and enlarge it as a precaution. I've also got one of those big magnifiers with a light which might help. I've bought that other one so have nothing to lose really. I like trying these things too.
     
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  8. Go for it! Nichrome’s about thruppence a metre on fleaBay.

    Didn’t realise the proper VDOs weren’t really available any more.
     
  9. I've got some 32g but that's way too thick. I'll wait for my micrometer to arrive. I unwound the old one and measured the wire (including all the bits!) and it's about 1.65m long. So if we need a max of 70 ohms for "empty", 42ohm/metre wire would be right by my calculations; that's 0.18mm. Still going to wait.
     
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  10. You also have a bit of adjustment at the gauge
     
  11. I did this on mine - it's 0.1 mm or 42 SWG. But rewinding is not going to be that easy.
     
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  12. Interestingly you have a rectangular former for the wire but the windings are tighter each end. I'm guessing that will be the hardest bit to copy.
     
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  13. Does anyone know if you could use a 0-100 ohm pot in place? Not sure how it would fair in a tank full of petrol but perhaps someone with more common sense than me could answer?
     
  14. No.
     
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  15. My micrometer hasn't arrived yet but my old wire does indeed measure 0.1mm wit the calipers. One of the pieces I unwrapped is 1m long and measures 50.4 ohms. So I need to find 0.1mm 50ohms/m wire.
     
    Last edited: Nov 12, 2019
  16. A bit of digging and this is what I reckon. Both the guy in Sweden on YouTube and the guy on Samba used NiChrome wire. The problem there is the resistance per metre for the same thickness is different to the original wire. I've found a 0.112mm bare constantan (copper nickel) wire that is 50 ohms/m which is spot on compared to original. The NiChrome the other guys used was 0.14mm 70 ohms/m. That's why, as the Swedish guy said, their gauges read empty long before it was.
    This is all my best guess as I'm no expert. Anyone see a hole in this or have I potentially cracked it. Copper nickel may be softer than NiChrome I'd guess.
     
  17. I must be the only bay owner in the country that has an accurate fuel guage. ?
    This takes me back to my younger days when I worked as a die polisher in a copper wire factory. I used to shape a hole in a diamond to a funnel shape to the size of wire required . Hole made to within two thousandths of a millimeter .a good job and we'll paid worked with some good lads also.
     
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  18. I’d think copper nickel would be softer, maybe. The tracks on those see a lot of action with the float bobbing up and down, so would wear more quickly?

    My brain’s packed up for the day, but you could overwind it giving more resistance, and limit the travel with the bendy endstops on the frame? Could also “pad” the resistance value with an external resistance?
     
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  19. I'm planning on smearing epoxy glue over the windings and immediately scraping it off the surface of the wires. May need a tickle with fine wetndry when set. The originals have a coppery tinge so I suspect they're copper nickel. Quite keen to stick to the known windings that work, rather than reinvent the wheel I'd prefer to try and do the original with a bit of added resilience :). It's going to make it more feasible to follow the original wire tracks using the same diameter wire too. What does padding the resistance do?
     
    Last edited: Nov 13, 2019
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