Tandem Cycling - Cadence computer for tandem
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04-06-04, 11:33 AM
Does anyone have any suggestions for a computer with cadence to use on a tandem, specifically a Burley Duet? I am totally addicted to my cadence computer on my single bike. Speed, distance, etc., are all secondary to me. When training, I watch my heartrate and my cadence.. When just riding, I skip the heart monitor and watch cadence and pay attention to my effort level. If I keep myself pedalling fast and keep my effort stable, I can ride all day and the speed and distance take care of themselves.
So I tried to put a NASHBAR cadence computer I bought for my lady friend's single bike on the tandem. The only way for it to work was to put it on the stoker bar, with a mess of wires and sensors at the same point on the chainstay. I don't like it.
I am thinking of trying to mount the cadence magnet on the chainring of the timing chain at the captain's pedal. The pedal itself is about 2"" from the tube at this point (Side question, what is the big lower horizontal tube called on a tandem?). I might need to shim.
A better solution would be a cadence computer made for tandems, but I bet the distance from the rear chainstay to the captain's handlebar would be too far for the small currents involved.
Bob Van Siclen
04-06-04, 12:43 PM
You have at least three different options...
1. As you suggest, use a standard computer with wired-in cadence and mount the pick-up sensor on the boom tube** and your magnet on the backside of your left timing ring. You can either use a standard magnet or a stronger one to open the sensor in the pick-up or you can move the pick-up sensor head out closer to the magnet by using a small piece of hard rubber. Just zip-tie the pick-up sensor in place.
2. If you have Shimano STI levers that are compatibile with the FlightDeck computer you can use "virtual cadence" which doesn't require a cadence pick-up sensor. It just calculates your RPM based on the bicycle's speed and your pre-programmed chainring and rear cassette cogs.
3. You can buy one of Vetta computers that feature wireless cadence and, again, mount the pick-up on the boom tube. Cateye is also coming out with one this summer that features encoding and boasts some really long transmission distances which will allow stokers to have a wireless computer option other than via fiddling around with the dip switch on a Polar HRM/cyclocomputer transmitter.
Just some quick thoughts.
**Boom Tube is one of the names for the big horizontal tube connecting the two bottom brackets. The others include the original and policitally incorrect "Boob Tube" and geographically correct Bottom Tube.
The Flight Deck has the added advantage of the gear position indicator or "bubbles" that show you what gear you are in, very handy on a Tandem.
Keep those wheels spinning!!!
I've been splicing the wires to get computers to work in the stoker position for longer than I can remember, probably starting with the Avocet 45s before the Avocet Altimeter 50 was released (that's a long time ago). A low wattage soldering iron and thin-wire low-temperature solder and thin speaker wire, all available from Radio Shack, make the job easy. I had two Avocets wired in parallel to one set of sensors on my pre-'98 Cannondale road tandem. With large framesets, single or tandem, I find it is routinely necessary to splice the wires on the computers I use, with the wheels I use, to get them to fit.
The Avocet cadence sensor has a tall base, so all that is necessary to mount it on a tandem is to zip-tie it to the bottom tube, and the magnet goes on the captain's right crank, thereby saving the magnet from contamination by drivetrain lubricant.
I have a stoker who absolutely insists on a computer (that way we can argue about cadence with facts, and she knows I can't reliably be counted on to start the computer when the ride starts), and to mount the Avocet, I (sort of, my stoker stem is virtual), went from the stoker handlebars to the captain seatpost and then down the captain seat tube to the bottom bracket, and then the wires split, going back to mount the cadence sensor as described, with the speedometer wiring spliced to go up the down tube almost all the way to the head tube, and then bridging across to the steerer tube, and then down the left fork blade to mount the speed sensor next to the wheel magnet track.
I've spliced the Flight Deck wiring to get it to fit on the C'dale before there was a wireless kit, but now that there is a wireless kit I'd rather get that.
The Shimano Flight Deck computer system has a number of advantages over other computers. There is a graphic display that shows what chainring and cog you are on, and a forward mount on aerobars keeps your eyes closer to looking down the road, which is much safer than looking down or back.
Virtual cadence is better than actual cadence because it calculates what your cadence would be, based on the gear you are in (you input the chainring and cog sizes during the setup) and road speed. So if you are coasting downhill at 48 mph, you will know exactly how fast you will have to pedal to catch the gear, because a virtual cadence will be displayed even when you are coasting, based on the gear and the road speed.
My ideal stoker computer is a repeater display of the Flight Deck, with all twelve (?) screens accessible by the stoker. I told Bill McCready (Santana CEO) I wanted one, but I guess he hasn't gotten around to that yet.....
05-14-04, 07:01 AM
I bought the Flight Deck. A bit pricey at $100 (LICKBIKE.COM) but I LOVE IT!!! I like the ease of installation, and the fact that it tells me what gears I'm in. I'm a single rider with a new tandem, and I never knew how often I looked down at my gears to check gearing until I got the tandem. The virtual cadence is fun: It works most of the time, and is great fun when going down hills coasting, and seeing cadence rise to 208 RPM. And the shift button on the STI levers is, as we bikey nerds USED to say before it was, "like, OVER, Dad!"...WAY COOL.
Bob Van Siclen
05-18-04, 08:21 PM
I caught this post a little bit late but will still offer a suggestion for others.
I use Specialized wireless computers on my road bikes and the cadence feature is wired. From looking at a couple of tandem frames, you should be able to mount the sensor to the tube that connects both of the bottom brackets together and use the crank arm mounted magnet. This would be the same as mounting on a single bike by placing the sensor on the chainstay and the magnet on the crank arm.
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