Distance problem with cadence magnet for Edge 500

Daystate
Daystate Posts: 14
edited December 2010 in Workshop
Hello,

The issue that I am having is that the distance between the crank magnet and the sensor is too big so the sensor is not reading the revolutions. I have tried all feasible positions bearing in mind I need to get a reading off the spoke magnet as well.

So basically, all I can think of is shimmimg between the crank magnet and the crank, maybe with some thin layers of hard plastic?

Has anybody else had this issue or can anybody come up with some bright idea's for shimmimg material that will look neat.

Many Thanks.

PS: It's definately a distance thing, as I have checked that the sensor pick's up the magnet when I move it closer.

Comments

  • Gary D
    Gary D Posts: 431
    I had the same issue.
    My solution was to buy a pack of 10 Neodium magnets. Do an internet search. I think they cost about £6. They are about 10mm diameter and about 5mm thick.

    Basically, to start with I stacked 2 of them together (10mm total thickness) and glued them to my crank arm. However, they got knocked off fairly easily so in the end I just put them on the end of the steel pedal spindle and the magnet is so powerful it holds them there.

    It works! :D:D

    Hope it helps.
    Gary.
    Fungus The Muffin MAn wrote:
    Oh and I feel like I've been raped by an Orangutan :shock: And I've got legs like Girders :lol:
  • SBezza
    SBezza Posts: 2,173
    There is an arm that is adjustable for the wheel speed sensor. I have set mine up so the sensor reads the cadence magnet, and then adjust the arm out towards the wheel to read the wheel magnet.
  • Daystate
    Daystate Posts: 14
    Many Thanks for the suggestions, but I cannot have the magnet as far as the end of the crank (pedal spindle end) or the position of the sensor would be hitting the spokes. And due to the odd shape of my frame I can only really mount the sensor vertically and not at a jaunty angle which would get the sensor closer to the crank magnet and I could then use the adjustable arm to get close enough to the magnet on the spokes.

    Basically, the spoke magnet is no problem, it's the fact that where ever I position the sensor it is too far from the crank arm.

    Any other suggestions?
  • SBezza
    SBezza Posts: 2,173
    In that case, pack out the magnet on the crank arm, that is the only other thing I can think of.
  • Twostage
    Twostage Posts: 987
    I think it does come down to putting something between the magnet and the crank to bring it closer to the sensor or the neodymium option. I'd probably go for the neodymium magnets. If you haven't come across them before you will be stunned how powerful they are. I think mine came next day off fleabay.
    Could you upload a picture so we can see the problem ?
  • paul64
    paul64 Posts: 278
    There is an all-metal type of spoke magnet you can get with a stronger magnetic force and this might allow you to have the sensor further away from the spokes and closer to the cadence magnet. Otherwise I'd be trying the previous suggestions.
  • forward_loop
    forward_loop Posts: 314
    What frame is it ?

    Unless the stays are rectangle you should have some flexibility with the angle of the gsc unit, after all its only held on with zip ties. If neither of the rubber mounting pads fit your frame you could perhaps use some oonld inner tube to put somehting together. If they do fit then surely you have movent toward the crank arm, the "slack" being taken by the extending arm.

    have you tried both above and below the stay ?
    Many Thanks for the suggestions, but I cannot have the magnet as far as the end of the crank (pedal spindle end) or the position of the sensor would be hitting the spokes. And due to the odd shape of my frame I can only really mount the sensor vertically and not at a jaunty angle which would get the sensor closer to the crank magnet and I could then use the adjustable arm to get close enough to the magnet on the spokes

    do you mean he sensor or sensor arm ? - If you open the sensor arm up 180 so it points above the unit instead of resting next to it your clearance would improve and be equal or indeed less than the clearance between spoke and stay. Contrary to intuition the sensor arm wont be "dragged" into the wheel :wink:
  • mikeeye
    mikeeye Posts: 162
    I have cadence sensors on two bikes so that I can use my Garmin on either one. In both cases, the crank is too far from the cadence sensor, so I have packed out the magnet using plastic wine-bottle corks, trimmed to size and then glued on with araldite rapid.

    Incidentally, I use neodymium magnets for the wheel sensor, and they're araladited onto a spoke. (Araldite rapid - keep the wheel rotating for 5 mins unit lit hardens)

    The spokes look really neat with the tiny magnets. The cranks look a bit rubbish, but hey, it works.

    ---
    If you still don't know what recursion is, read this sentence.
  • Daystate
    Daystate Posts: 14
    Thanks for all the good ideas :D

    I am going to try a combination of your suggestions. Firstly, I have found that the sensor can sit upside down below the frame (sitting on top was a little unsecure as the frame shape comes to a 'peak' in this area). This then places the cadence alignment of the sensor close to the spindle of the pedal, so I am going to try the magnet option (I have ordered the 10mm wide by 5mm deep type).

    I am assuming that the new magnets will bridge a wider gap than with the garmin supplied magnet? If not I guess I can just stack the magnets until a reading occurs (Ordered a pack of 15 for £3, so should have enough!!!)

    Again, many thanks, hopefully the above will work and the bonus will be to not have an unsightly ziptie around the crank arm :D

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