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Another FlightDeck question(6 posts)

Another FlightDeck questionMrGrim
Jun 21, 2002 11:05 AM
Ok.. I'm almost done with the setup. So far so good!

The only thing is that I don't see proper instructions in the manual on the placement of the magnet/sensor pair. The manual specifies anywhere within 50cm of the computer. 50cm? This constitues the entire length of my fork????

It seems to me that the placement of the magnet is critical for the computer to determine correct speed?

Where on the spokes do I set the magnet... and where on the fork do I place the sensor (obviously near the magnet!).
re: Another FlightDeck questionChen2
Jun 21, 2002 11:50 AM
Does not matter for speed. Any position on a spoke will result in the same speed calculation. I put my magnets on the lighter side of the wheel for balance, but that's not very important either.
re: Another FlightDeck questionDrD
Jun 21, 2002 12:34 PM
It's just counting revolutions, so position doesn't matter (as already indicated) - however, one could argue that the closer to the hub, the longer the residence time in front of the sensor, which might help when you go really really really fast :-)

For wireless, the closer it is to the computer, the better chance of getting a reliable signal - I have mine about half way up the fork, which works out to be 40cm-45cm from the computer, I think (I remember it was a little less than the limit) - make sure you have the proper horizontal and vertical position of the sensor relative to the computer (If I remember correctly, the manual describes it as a cone with a 10cm base (left-right-front-back location of the receiver relative to the sensor) and a 50cm height (vertical distance from the sensor to the receiver)
re: Another FlightDeck questionwolfereeno
Jun 25, 2002 12:50 PM
>> however, one could argue that the closer to the hub, the longer the residence time in front of the sensor, which might help when you go really really really fast <<

This is probably not the case. The faster the magnet moves by the sensor (which is just a coil of wire) the more inductive force. So it would create a sharper, stronger electronic pulse if the magnet was nearest the rim where it moves faster.

Although putting the magnet towards the middle does reduce the rotational mass of the wheel. Plus it's easier to get the magnet close to the spokes as they fan out towards the hub.

Factoring in the wireless signal strength (or running a length of wire) it probably makes the most sense to just put it somewhere in the middle :-)

Question: do you have your sensor facing forwards or backwards? I'd think it would be safer facing forwards in case it got pushed into the spokes. But for some reason the shop put mine on facing backwards.

re: Another FlightDeck questionDrD
Jun 25, 2002 6:11 PM
The sensor for mine is on the front of the fork - the fork is sort of bladed in the back (Kestrel EMS pro), so it was easier to get it to stay in place on the front of the fork. Also - on the occasions when I must drive to a ride, I take off the front wheel and put the bike in the car - if the sensor were on the back of the fork, it would get bumped/moved as I slid the bike into the car.
re: Another FlightDeck questionCrankist
Jun 24, 2002 8:26 AM
50 cm? - probably a misprint. Consider 5mm a maximum gap.
Installing the magnet an inch or 2 from the rim alleviates
sluggish readings at slower speeds. And as a previous response stated, radial magnet/sensor placing is not critical to speed accuracy.