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Old 01-03-06, 11:38 PM   #1
megaman
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Reducing magnet space on computer

I've got a Sigma computer that requires less than 5mm distance between the pickup and the sensor. I have at this point 20mm distance, so it doesn't register at all. There is just no place on the frame and spokes to get it any closer.

So what do I do? Find some material to build the sensor in closer to the magnet? What kind of material would you use on a heat treated aluminum frame? I prefer to only have to mount it once?

Thanks for any help.
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Old 01-03-06, 11:50 PM   #2
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Why can't you mount the pickup and the magnet closer to the hub where the spokes get close to the hub? That's the typical answer. Do you have a wireless that does not work that far apart?
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Old 01-04-06, 12:15 AM   #3
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If push comes to shove, I have had decent luck with double-sided foam mounting tape. It is usually 1/16" thick and available in hobby shops and office supply shops.
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Old 01-04-06, 12:35 AM   #4
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I had the same problem. I just used electrical tape and wrapped it around many times until it was thick enough. As already suggested, I would've used double sided foam tape if I had it. Much lighter.
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Old 01-04-06, 02:45 AM   #5
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Another vote for two sided mounting tape. I used it to mount the cadence magnet on a crank with a hollow spot on the back.

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Old 01-04-06, 06:47 AM   #6
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I moved my sensor to the disc side of the wheel because my new wheel set has radial lacing on the non-disc side. The spokes are farther away from fork on the rotor side. I made a spacer a little bigger than the footprint of the sensor. In my case, I cut a small piece from the wall of that thick plastic clear tubing (Tygon?) sold at Lowes which I keep on hand. I supplemented the two plastic ties with a few drops of Shoe Goo to make sure nothing moved.

The rotor side actually makes a better installation because you can run the wire up the brake cable. It looks neater (you hardly see it) and it's less prone to catching on branches and stuff because the brake cable keeps the wire behind the fork leg all the way up.

Since the wheel is laced two across on the rotor side, the sensor is closer to the hub now. I thought it might lose sensitivity. It didn't, it registers as low as 1.2 mph.

Al

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Old 01-04-06, 08:14 AM   #7
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Originally Posted by Al.canoe
I moved my sensor to the disc side of the wheel because my new wheel set has radial lacing on the non-disc side.
Out of curiosity, what characteristic of radial spokes prompted you to mount the sensor on the non-radial side of the wheel?
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Old 01-04-06, 09:10 AM   #8
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Originally Posted by supcom
Out of curiosity, what characteristic of radial spokes prompted you to mount the sensor on the non-radial side of the wheel?
My magnet is kinda big, and the holder is obviously designed to be placed at a spoke crossing: there's two grooves and the are angled like the angle of crossing spokes. So I was convinced that just hanging it on one spoke was probably not secure enough.

On the very first ride with the new set-up, I ran into a club member on his ATB training bike. Darned if he didn't have what appeared to be the same magnet attached to one radially laced spoke. He'd had it that way for years. It looked like it could rotate outward and hit the fork, but it hadn't.

I could have done the same, but I didn't really like it. Moving the magnet turned out so neat, that from now on I'm putting it on the rotor side irrespective of the lacing.

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Old 01-04-06, 11:54 AM   #9
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Quote:
Originally Posted by Al.canoe
My magnet is kinda big, and the holder is obviously designed to be placed at a spoke crossing: there's two grooves and the are angled like the angle of crossing spokes. So I was convinced that just hanging it on one spoke was probably not secure enough.

On the very first ride with the new set-up, I ran into a club member on his ATB training bike. Darned if he didn't have what appeared to be the same magnet attached to one radially laced spoke. He'd had it that way for years. It looked like it could rotate outward and hit the fork, but it hadn't.

I could have done the same, but I didn't really like it. Moving the magnet turned out so neat, that from now on I'm putting it on the rotor side irrespective of the lacing.

Al
Thanks for the explanation. BTW, I've used some pretty large magnets on single spokes, radial as well as cross laced, and never had a magnet slip.

Obviously, if your setup works, all power to you. As I said, I was just curious.
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Old 01-04-06, 12:11 PM   #10
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How about sticking another, possibly stronger, magnet to the existing magnet? You can get some very strong permanent magnets in very small sizes. I'm not sure this would work because I don't know if the pickup requires a certain magnetic field strength but it might be worth a shot.

I have these at home and they would stick to the wheel magnet through just about anything.
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Old 01-04-06, 12:33 PM   #11
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Might help to post a photo of your current setup for us to examine. Sometimes it's easier to point things out visually rather than verbally.
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Old 01-04-06, 02:54 PM   #12
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Quote:
Originally Posted by cyccommute
How about sticking another, possibly stronger, magnet to the existing magnet? You can get some very strong permanent magnets in very small sizes. I'm not sure this would work because I don't know if the pickup requires a certain magnetic field strength but it might be worth a shot.

I have these at home and they would stick to the wheel magnet through just about anything.
A stronger magnet would work. Two magnets would be ok as long as you could keep the poles aligned properly. However, the danger is when I passed a steel fence post, I'd collide with it. I have enough trouble peeling myself off of trees!

Just kidding of course.

Al
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Old 01-04-06, 03:19 PM   #13
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...However, the danger is when I passed a steel fence post, I'd collide with it. I have enough trouble peeling myself off of trees! ...
Not to mention going out for a leisurely ride one day and ending up at the North Pole!
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Old 01-04-06, 05:57 PM   #14
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I also have sigma. Are you using wired or wireless? I have used wireless on 2 mtbs and one road bike. I have used wired on both mtbs but not on the road bike. Both MTBs have front shocks. If you can wait a minute, I'll go look and tell you where they are mounted...

...Sorry I took so long. I decided to take some pix. The ones of the mtbs came out ok, the one of the road bike didn't & I not gonna try again, its cold in the garage.

The first is my bike, the sensor is mounted about 4" from the hub. The second is my son's bike & is mounted just below the brakes (the bike is handing from the ceiling by both wheels). The road bike sensor is also mounted just below the brakes.

I hope this helps!
Attached Images
File Type: jpg sensor1.jpg (83.1 KB, 37 views)
File Type: jpg sensor2.jpg (84.8 KB, 32 views)
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Old 01-04-06, 07:53 PM   #15
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Thanks for the advice. Ritehsedad, thanks for the pics. I'm mounting this on a Catrike Road (tadpole trike) on the rear wheel. Why the rear wheel, well there only one place to mount it on the front wheels and that is the steering arms(I don't think I can keep the sensor stable enough there), the only other place to mount it on the front wheels would be impossibly far away. On the rear wheel is where I get the 20mm no matter where I place the sensor(wired) and magnet.
To the posters who recommend using double sided mounting tape, just how long could I expect this setup to last.
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Old 01-04-06, 08:06 PM   #16
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Ha!

I've got your solution!

Sigma has a new magnet called the Power Magnet, "Power magnet is the SIGMA SPORTŪ solution for unusual spokes and distances between the magnet and sensor that are too large Distances of up to 20mm are no longer a problem for the newly developed magnet and it fits all possible types of spokes and diameters."

You can find it at the Sigma Web Site .
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Old 01-04-06, 08:28 PM   #17
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Originally Posted by Ritehsedad
Ha!

I've got your solution!

Sigma has a new magnet called the Power Magnet, "Power magnet is the SIGMA SPORTŪ solution for unusual spokes and distances between the magnet and sensor that are too large Distances of up to 20mm are no longer a problem for the newly developed magnet and it fits all possible types of spokes and diameters."

You can find it at the Sigma Web Site .
That looks like a winner! Thanks. Now I've got to see if my local dealer(who isn't even listed by Sigma) can get me one. Other than him, it looks like my nearest dealer is 200 miles away. That just can't be right, I've got to check that again.
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Old 01-04-06, 08:44 PM   #18
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Boy, is the Sigma web site screwy. I put in my Zip Code and it gives me cities 200 miles away. I put in my town and it gives not found. I key in just WI and it gives me 4 pages worth of dealers in state, including one in town here. Looks like every bike shop in the state sells Sigma stuff.
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Old 01-05-06, 06:02 AM   #19
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Good luck. I think you can actually order directly from Sigma if you need to.
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Old 01-05-06, 09:46 PM   #20
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I'm sure one of the shops in Madison would be a sigma dealer and I know Wheel & Sprocket is.
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