Strong magnets to raise a barrier.

whyamihere
whyamihere Posts: 7,695
edited March 2008 in Commuting chat
At college, there's a couple of automatic barriers, which are raised when a car rolls over the sensor. However, my bike doesn't have enough metal to set it off. So, I intend to put some very strong magnets on the bike, which should theoretically set off the sensors. However, the big question is, where do I put them?

They need to be as low as possible, to have the best chance of working. The ideal place would be the bottom of the fork legs, but as I'm using a suspension fork (awful roads), the nuts which hold it together are down there, I don't want to be supergluing magnets onto them.

The BB shell is the next obvious choice. Does anyone have any problems with mounting them here, or suggestions of a better place for them?

Thanks.

Comments

  • DavidTQ
    DavidTQ Posts: 943
    What about on the pedals? moving the pedal to 6 o'clock position should get the magnet pretty low.
  • whyamihere
    whyamihere Posts: 7,695
    Problem with the pedals is that I change them regularly. When I'm doing a full day, I use flat pedals and trainers (nowhere to store spare shoes), and when I only have one lesson, I use SPDs.

    I suppose I could fit one to each set though, as I'll be getting two magnets in the pack...
  • redddraggon
    redddraggon Posts: 10,862
    BB mounting should be your best bet. Levi Leipheimer has a special mounting on his Madone to get the bike over the UCI limit of 6.8Kg, so you should be able to do the same with a magnet.
    I like bikes...

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  • Have you done a dry run to make sure the magnets actually trip the sensors, prior to gluing them to your bike? :shock:
    Even if the voices aren't real, they have some very good ideas.
  • Won't you end up with random bits of scrap metal gradually attaching themselves to your bike?
    <a>road</a>
  • Put 'em in your socks!! 8)
  • whyamihere
    whyamihere Posts: 7,695
    Shadowduck wrote:
    Have you done a dry run to make sure the magnets actually trip the sensors, prior to gluing them to your bike? :shock:
    Not yet, I don't have the magnets at the moment. Naturally, I will be checking first...
  • whyamihere
    whyamihere Posts: 7,695
    Won't you end up with random bits of scrap metal gradually attaching themselves to your bike?
    That is a possiblity... Scraping them off once a week or so would take less time than having to wait for a car to raise the gate though (the pedestrian gate next to it is always locked).
  • Gambatte
    Gambatte Posts: 1,453
    powerslide underneath!! :D:D:D
  • Won't you end up with random bits of scrap metal gradually attaching themselves to your bike?

    You never know what you might find though! Small change, jewellery... it could pay for itself in no time :lol:
  • C1234
    C1234 Posts: 26
    Crack open a broken Hard drive. Those magnets are strong, and if you're lucky enough to have a 14Kg steel behemoth like mine, you'll find that the magnet sticks to the frame quite nicely! Job done.
  • C1234 wrote:
    *snip* ... if you're lucky enough to have a 14Kg steel behemoth like mine ... *snip*
    Wouldn't that trip the sensors on its own? :lol:
    Even if the voices aren't real, they have some very good ideas.
  • WyS
    WyS Posts: 254
    as a kid i used to set of the sainsburys barriers by doing a skid in front of it, the 2 bike wheels were placed where the front car wheels would normally be.

    will only work if it is on pressure pads though.

    :D
  • chronyx
    chronyx Posts: 455
    Why would magnets need gluing to a bicycle? :?
    2007 Giant SCR2 - 'BFG'

    Gone but not forgotten!:
    2005 Specialized Hardrock Sport - 'Red Rocket'
  • phil_ss1
    phil_ss1 Posts: 194
    if it was carbon, or aluminium per chance ???? :?
  • chronyx
    chronyx Posts: 455
    Oh yeah.

    A neodymium magnet is what you want, they are bloody powerful.
    2007 Giant SCR2 - 'BFG'

    Gone but not forgotten!:
    2005 Specialized Hardrock Sport - 'Red Rocket'
  • 1217.jpg

    Nd magnets from Supermagnete.de

    I can see you picking up manhole covers with these as you ride over them.
  • Gambatte
    Gambatte Posts: 1,453
    Stick one to the chainstay and be unable to move the crank past it?

    Mind, I guess you wouldn't have to ensure a <5mm gap to the cadence sensor? :lol:
  • chronyx
    chronyx Posts: 455
    h i r 0 wrote:
    1217.jpg

    Nd magnets from Supermagnete.de

    I can see you picking up manhole covers with these as you ride over them.

    :shock: That pic actually looks kinda scary (As well as impressive)
    2007 Giant SCR2 - 'BFG'

    Gone but not forgotten!:
    2005 Specialized Hardrock Sport - 'Red Rocket'
  • whyamihere
    whyamihere Posts: 7,695
    I shall be purchasing this. Should be powerful enough. :D
  • neiltb
    neiltb Posts: 332
    have you asked the college for a button you could press? would be an inexpensive solution all round.

    You are paying for the privelege of attending.
    FCN 12