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07-16-05, 07:57 AM
Thought I'd pass this along just in case anyone else was looking for a way to use a HAC4 computer on a recumbent.
The HAC4 (besides having tons of useful features) had one feature that I couldn't find on ANY other computer. If you ride the same route, it will show your progress vs. a stored earlier ride, letting you know how many seconds ahead or behind you are. I find this extremely motivating, much better than trying to guess at how you're doing by looking at average speed.
Problem is, the HAC4 is wireless and won't work on most recumbents because of the distance from the wheel to the bars.
To make it work, I hacked the transmitter, turning into a wired unit. While it might seem a little scary to hack into a several hundred dollar computer, it's not as bad as it seems. If you screw up, a replacement transmitter can be purchased for about $35.
1. Cut off the top of the transmitter. I did this by cutting along the seam with a dremel.
2. Remove the circuit board.
3. Drill a small hole in the bottom of the transmitter housing for the new wires.
4. Pass the wires from on old computer magnetic sensor through the hole.
5. Solder the wires on to the circuit board. They just go on either end of the existing magnetic sensor that's mounted on the board.
6. Reassemble the transmitter. Epoxy the case back together. Seal the hole for the wires with silicone caulk.
Now you just need to mount the new magnetic sensor to the front fork, run the wire up to the handle bars and mount the transmitter a few inches below the HAC4's handle bar mount.
It worked perfectly on the first try. With only a few inches between the transmitter and computer, it's probably more reliable than when mounted on most DFs. Cadence is wired, and so presented no problem. The heart rate is wireless, but seems to work at greater distances than the speed sensor, so again presented no problems.
The HAC4 (besides having tons of useful features) had one feature that I couldn't find on ANY other computer. If you ride the same route, it will show your progress vs. a stored earlier ride, letting you know how many seconds ahead or behind you are. I find this extremely motivating, much better than trying to guess at how you're doing by looking at average speed.
Problem is, the HAC4 is wireless and won't work on most recumbents because of the distance from the wheel to the bars.
To make it work, I hacked the transmitter, turning into a wired unit. While it might seem a little scary to hack into a several hundred dollar computer, it's not as bad as it seems. If you screw up, a replacement transmitter can be purchased for about $35.
1. Cut off the top of the transmitter. I did this by cutting along the seam with a dremel.
2. Remove the circuit board.
3. Drill a small hole in the bottom of the transmitter housing for the new wires.
4. Pass the wires from on old computer magnetic sensor through the hole.
5. Solder the wires on to the circuit board. They just go on either end of the existing magnetic sensor that's mounted on the board.
6. Reassemble the transmitter. Epoxy the case back together. Seal the hole for the wires with silicone caulk.
Now you just need to mount the new magnetic sensor to the front fork, run the wire up to the handle bars and mount the transmitter a few inches below the HAC4's handle bar mount.
It worked perfectly on the first try. With only a few inches between the transmitter and computer, it's probably more reliable than when mounted on most DFs. Cadence is wired, and so presented no problem. The heart rate is wireless, but seems to work at greater distances than the speed sensor, so again presented no problems.