# Foo - Bike Computer Idea

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View Full Version : Bike Computer Idea

Falkon
07-28-07, 09:13 AM
Okay, here's my idea. You know how your bike computer only registers speed with a certain delay, because the magnet has to pass the sensor? I'm thinking about putting on another magnet and changing the wheel size in the computer to make it register faster. It'll also balance the wheel a little more if it matters.

The way the computer calculates the speed is using the circumference, so if I double the value in the computer, it should work, right?

Tude
07-28-07, 09:19 AM
Crikeys! I'm all wrapped up in avoiding potholes and cars versus speed :D

Falkon
07-28-07, 09:26 AM
eh, I use it on group rides, because I've been told more than once that when I start pulling the group that I ramp up the pace. Last time, I dropped part of the group.

Tude
07-28-07, 09:29 AM
eh, I use it on group rides, because I've been told more than once that when I start pulling the group that I ramp up the pace. Last time, I dropped part of the group.

Yeah, for the group rides - the roadie comes out and I find myself analyzing the computer more - specially cadence.

jsharr
07-28-07, 09:32 AM
Okay, here's my idea. You know how your bike computer only registers speed with a certain delay, because the magnet has to pass the sensor? I'm thinking about putting on another magnet and changing the wheel size in the computer to make it register faster. It'll also balance the wheel a little more if it matters.

The way the computer calculates the speed is using the circumference, so if I double the value in the computer, it should work, right?

it seems it would be critical to get the magnets equidistant from each other.

Falkon
07-28-07, 06:46 PM
it seems it would be critical to get the magnets equidistant from each other.

That is not a problem. I can get them directly opposite. I think I was wrong also. I think I would actually half the circumference that was entered into the computer.

jsharr
07-28-07, 08:08 PM
two magnets = double circumference or leave it like it is and just divide the end result from your computer by 2.

markhr
07-28-07, 08:40 PM
Don't, unless I'm mistaken, avocet do that already with their transmitter?

http://www.cambriabike.com/Images/product/avocet_3-prong_transmitter.jpg

Falkon
07-28-07, 11:55 PM
Eh, this is easier. I forgot about the avocet one. their's is a little more unsightly though.

07-29-07, 12:38 AM
My cheap little computer's display has a set update frequency. I dunno how nicer ones work, but I'd be suspicious that the computer might change your displayed speed at exactly the same time intervals regardless of how often it counts a rotation.

tspoon
07-29-07, 03:35 AM
it seems it would be critical to get the magnets equidistant from each other.
Probably not particularly critical. There'll still be two pulses per revolution. Also you'll need to halve the value in the bike computer, not double it.
If anything, having two pulses per revolution will more likely lessen the measuring resolution of the computer, than improve it. In reality though, it's neither here nor there.

dragracer
07-29-07, 03:36 PM
it seems it would be critical to get the magnets equidistant from each other.

I don't think it would really matter would it. It would basically be like two short wheel revolutions. If it were off a bit, one revolution would be bit longer and the other a bit shorter. Would sorta offset each other. For each COMPLETE wheel revolution(two magnet passes) it would be exactly the same(if you had the computer setup correctly) as if you just had one magnet. Wouldn't it? :o

Falkon
07-29-07, 03:59 PM
I can get them exactly apart. I just wonder if it would make the computer faster. I need to go to the shop tomorrow and get another to find out.

Tom Stormcrowe
07-29-07, 04:37 PM
How about a magnet on each spoke and post the picture of what the display reads on a downhill?

Example: 36 spoke wheel = speed X36!

37 MPH*36=1332MPH. I'd love to find out how whether a bike computer could discriminate individual pulses coming that fast!:p:D:beer:

Mr. Gear Jammer
07-29-07, 06:08 PM
Okay, here's my idea. You know how your bike computer only registers speed with a certain delay, because the magnet has to pass the sensor? I'm thinking about putting on another magnet and changing the wheel size in the computer to make it register faster. It'll also balance the wheel a little more if it matters.

The way the computer calculates the speed is using the circumference, so if I double the value in the computer, it should work, right?

I think this is a great idea.

Falkon
07-29-07, 09:25 PM
Okay, instead of adding an extra magnet, I'll buy a \$250 Garmin Edge. Nah, I'll stick with my idea. I need to go to the shop tomorrow to get another magnet for this experiment. It would be great if it registered speed faster.