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Technical Traditional-looking self-cancelling indicator idea

Discussion in 'The Hokey Ass Message Board' started by Ned Ludd, Aug 7, 2016.

  1. Let me know what you come up with!

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  2. ghornbostel
    Joined: Jan 3, 2012
    Posts: 131


    The TR3 unit requires a straight open ended column. The unit is connected to a 3/8" id tube that is anchored to the end of the steering column allowing the wheel to turn but not the turn signal unit and thus the self canceling feature. My TR3 has some universal joints in the column to get around the engine and to make it work again I put a offset in the system which gave me the open column again. I don't know if the unit is Lucas but it has worked without fail for the 39 years I've owned the car


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  3. Late to the Party
    Joined: Nov 16, 2015
    Posts: 863

    Late to the Party

    I don't think I need a self-cancelling unit. I put a Grant wheel on my work truck several years back, and the turn signal no longer cancels when I turn right. I've managed to learn to cancel it manually when turning right, and it wasn't a big deal to learn. It seems to me that I could learn to cancel it both directions in my Hot Rod. ;)
  4. Ned Ludd
    Joined: May 15, 2009
    Posts: 3,820

    Ned Ludd

    I looked at it a bit, found a circuit that'll work. The limitation is in the tilt switches: we'd need something damped so the indicators wouldn't self-cancel over every little bump, but with the sensitivity to switch on under the ~0.025G acceleration you'd experience in a leisurely urban turn. That translates to an equivalent tilt of 1.35°. I haven't been able to find a suitable switch off the shelf.

    The circuit will work off switches reading parts of the steering, though, e.g. pitman arm, drag link, ifs centre link, etc. But I'm wondering if a mechanical system using bicycle cables might not be simpler on balance.
  5. Nice piece, but over two hundred bones, so I'll pass
  6. Ned Ludd
    Joined: May 15, 2009
    Posts: 3,820

    Ned Ludd

    I've come back to this after almost two years, and in retrospect I think my first intuition had merit. In fact the motorbike speedometer drive idea has more possibilities than I thought of then, especially if you start playing with short speedometer cables. You can position the switch wherever suits your build and still have self-cancelling.

    Considering both the genuinely useful information @Crazy Steve contributed and some subsequent researches of my own: Firstly, not all drive gearboxes have the central sleeve which rides on the stationary axle. Earlier British ones generally seem not to:
    They are available new and not very expensive. The ones on the brand new Royal Enfields made in India follow this pattern. Note that the central hole can easily be enlarged to clear the steering column. Drive adaptors and divers bracketry will obviously have to be arranged.

    Second, advertised drive ratios need to be approached with care. "2:1" doesn't always mean two rotations of the cable for each rotation of the wheel. Sometimes it does but at other times it means 2000 rotations of the cable for each mile travelled, and there is no way of telling unless you have the unit in your hand and can rotate the various parts. Many UJMs seem to have used a nominal ratio of 2240 rotations per mile, which works out to an actual ratio of around 2.5:1, depending on the tyre size.

    Third, the fact that the cable turns faster than the wheel isn't a problem. All the gearbox is driving in this application is a cam wheel similar to the ones attached to OEM steering column shafts, which mostly have four cams on them. If our new cam wheel turns faster, it merely needs to have fewer cams on it. At an actual 2:1 ratio, a wheel with two cams will produce the same action as the OEM indicator switch. (I can't remember why I thought a slower action might be advantageous before. I can't see it now.)

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