Tandem Cycling - Garmin Cadence sensor

We have a cannondale T1000 and i put a garmin cadence sensor on to switch my 500 between my road bike and tandem. I installed it where i would on a normal bike - so one sensor is at the rear crank and one at the rear wheel.

The issue is the magnet on the crank clips the timing chain. Anyone experience this? have a remedy?

I am thinking of moving the sensor to the right side of the front crank and loosing the speed sensor or getting a shorter profile magnet for the crank but i worry about it still attracting to the metal chain.

thanks

Use a strong neodymium magnet. Stick it to the end of the pedal spindle. See this thread (http://www.bikeforums.net/showthread.php/337744-Installing-cadence-magnet-on-crank-with-hollow-back). For instance: Radio Shack 3/8 inch (http://www.radioshack.com/product/index.jsp?productId=2102642)

I opened up a dead hard drive and got the strong pair of magnets from the swing arm. I had to score and break one in two to fit into the end of my crank arm. (I had one fall out somehow, even though they stick to the steel pedal spindle very well. I used some "goop" type of glue around the edges on the replacement.)

There's a half inch gap between the cadence sensor on my chainstay, and the pedal spindle magnet. It works great, and there's no zip ties on the crank.

You can press the little button on the Garmin cadence sensor, and it'll blink each time the magnet comes by. One color is the cadence sensor, and the other is the wheel sensor. So you can see if the gap is too big to work reliably.

These magnets are very strong. I stuck one of the disk drive magnets to my fridge, and couldn't pry it off with my fingernail. I had to slide it off the edge of the door.

+1 on the rare earth magnet. Been using that approach for a year on our daVinci. You can get a package of these magnetics at Ace Hardware, OSH, etc. (almost any HW store).

+1, I picked up our magnet at LBS
R&J

I cut the magnet out of the Garmin sensor and krazy-glued it to the crank arm - with a piece of inner tube in between the magnet and crank arm to get the spacing just right. Works great, no need to buy another magnet.

Have you had solid results with the sensor? I put a Garmin GSC10 on the L chainstay, and both of us had trouble getting cadence data.

We "solved" the problem with an awesome but insanely expensive solution, so I'm no longer concerned about the issue, but nonetheless I'd like to know how others have fared.

I didn't even glue our magnet, just stuck it to the inside end of the pedal shaft, has worked flawlessly. Sensor is mounted to rear stay in the usual position.
R&J