Strong magnets to raise a barrier.

whyamihere

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.

DavidTQ

What about on the pedals? moving the pedal to 6 o'clock position should get the magnet pretty low.

whyamihere

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

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.

Shadowduck

Have you done a dry run to make sure the magnets actually trip the sensors, prior to gluing them to your bike? :shock:

el_presidente

Won't you end up with random bits of scrap metal gradually attaching themselves to your bike?

neillcp

Put 'em in your socks!! 8)

whyamihere

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

el_presidente wrote:

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

powerslide underneath!!

mediamonkey

el_presidente wrote:

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

C1234

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.

Shadowduck

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?

WyS

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.

chronyx

Why would magnets need gluing to a bicycle? :?

phil_ss1

if it was carbon, or aluminium per chance ???? :?

chronyx

Oh yeah.

A neodymium magnet is what you want, they are bloody powerful.

h i r 0

Nd magnets from Supermagnete.de

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

Gambatte

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?

chronyx

h i r 0 wrote:

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)

whyamihere

I shall be purchasing this. Should be powerful enough.

neiltb

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.