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From: Mark Olson on 8 Jul 2010 19:12
tylernt wrote:
>> Yes, I have heard of the same solution before by other bikers. The
>> other recommended was to drive the rims of the tyres overtop the
>> embedded tripwire loop in the black top. However, I have found that not
>> all signals will work even with that solution.
>
> Correct me if I'm wrong, but if your wheels are aluminum alloy (as I
> understand many tubeless wheels are), I don't believe a magnetic loop
> sensor will pick them up. Where possible I try to position my bike's
> engine block over the loop... seems to work pretty well, and should
> have a lot more metal than even tubed/spoked rims.

The loop sensors used to detect vehicles do not rely on
the presence of magnets or even ferromagnetic materials.
They detect aluminum just fine. They work in much the
same way as a hand held metal detector, which as any
beachcomber of a certain age knows, picked up those damned
aluminum "pop tops" just as well or better than they did
gold coins or diamond rings.

From: tylernt on 8 Jul 2010 20:05
> > Correct me if I'm wrong, but if your wheels are aluminum alloy (as I
>
> The loop sensors used to detect vehicles do not rely on
> the presence of magnets or even ferromagnetic materials.
> They detect aluminum just fine.  

I'll be darned, you're right. Interesting reading:

http://www.humantransport.org/bicycledriving/library/signals/detection.htm

Makes me wonder if putting a magnet on the bottom of your bike is just
a form of placebo...
From: High Plains Thumper on 8 Jul 2010 21:12
tylernt wrote:
>>> Correct me if I'm wrong, but if your wheels are aluminum alloy
>>> (as I
>>
>> The loop sensors used to detect vehicles do not rely on the
>> presence of magnets or even ferromagnetic materials. They detect
>> aluminum just fine.
>
> I'll be darned, you're right. Interesting reading:
>
> http://www.humantransport.org/bicycledriving/library/signals/detection.htm
>
> Makes me wonder if putting a magnet on the bottom of your bike is
> just a form of placebo...

I don't think so. EMI is electromagnetic interference. Radio waves are
a form of electromagnetic waves. If you want to be scientific, pick a
light or two that you know gives problems, try it with and without the
magnet. If it works, keep doing it.

YMMV,

--
HPT
From: Bob Myers on 9 Jul 2010 15:08
tylernt wrote:

> http://www.humantransport.org/bicycledriving/library/signals/detection.htm
>
> Makes me wonder if putting a magnet on the bottom of your bike is just
> a form of placebo...

In general, yes it is, as a static magnetic field would not be expected to
have any effect on most of these systems. If it does anything at all, it
would generally be just through putting more metal into the loop (i.e.,
the fact that said piece of metal is magnetized has nothing to do with
it).

Bob M.


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