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Old May 13th 19, 11:56 AM posted to rec.bicycles.tech
Sir Ridesalot
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Default Wheel/Spoke Magnets

On Monday, May 13, 2019 at 6:47:07 AM UTC-4, John B. Slocomb wrote:
On Mon, 13 May 2019 07:06:48 +0200, Tosspot
wrote:

On 13/05/2019 01:45, John B. Slocomb wrote:
On Sun, 12 May 2019 16:26:11 -0700, "Mark J."
wrote:

On 5/12/2019 6:27 AM, sms wrote:
On 5/12/2019 1:29 AM, Tosspot wrote:
Anyone know of some 'decent' ones.Â* The Sigma supplied ones won't
attract a whore in a crack house.Â* The Bosch type ones always seem to
corrode and fall off, and on top of that are easy to X-Thread.Â* The
Cat-Eye ones don't seem to stay put[1].Â* The Echowell/Yamaha ones seem
pretty decent but are like rocking horse **** this side of the pond..
Any other ideas?

[1] Yes, it is getting OCD!

When I lost the cadence magnet on my crank I used a hard-drive magnet,
i.e. https://www.ebay.com/itm/173209158372 but I got some used ones
from someone I knew at a disk drive company. I heat shrinked it over the
crank. I guess for a wheel magnet you could use some cable ties or some
baling wire and attach one of these to the spokes. The pick-up doesn't
have to be so close to the magnet when you use a disk drive magnet.

If heat shrink is too much trouble, the ?vinyl? stretchy plastic
electrical tape works pretty well also, I've done this for cadence
magnets. The tape may start to peel and degenerate into a sticky mess,
but if caught/redone in time, the mess is quite containable.

Mark J.

I bonded used Hard disk magnets onto the aluminum crank arms of all of
my (4) bicycles as much as 10 years ago using epoxy glue. To date the
magnets are all still attached :-)

As to the original post, I have spoke magnets that I attached to front
wheels both with radial spokes and with crossed spokes that have been
in place for 4 - 5 years.

What is the big problems with attaching magnets to bicycles?


It isn't a problem per se. For some reason there is a *big* gap between
the spokes and the Surly LHT frame, which means at best, standard
magnets are intermittent. The fix is obvious, a small neodymium disc
magnet, but this tends to cause enough of some adverse force to cause
the above problems. In short, the Sigma ones don't cut the mustard,
different ones work ok for a year or two. I want a good magnet, that
stays put, doesn't corrode and I can't fyckup fitting.


I think that you are referring to a cycle meter pickup - spoke magnet
and sensor mounted on the front fork? What I do is mount the magnet
and than mount the sensor with a bit of offset - bent in, one might
say. Works for me :-)

The indomitable Sheldon recommends installing the magnet as near the
hub as possible as it means that the magnet passes the sensor
(transmitter) slower which he feels might make things more accurate.

As an aside, it also means that the magnet is closer to the fork tube
and therefore the sensor is closer to the magnet and requires less
offset. See https://www.youtube.com/watch?v=q-eGGDFeaUM
for an example (I know it is a cabled meter but the position of the
sender is the same as a wireless sensor).

--

Cheers,

John B.


Some wireless magnets NEED to be mounted close to the rim in order to be picked up by the sensor which also needs to be as close to the actual computer unit as possible. I had a wireless computer that had intermittent readings and readings far in excess of my actual speed. Those problems were corrected when the magnet and sensor were moved as far up the wheels and fork as possible. It seems that the distance that the sensor was from the computer was a critical factor with that computer as it was a very short range from the sensor to the unit that worked.

Cheers
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