R E C U M B E N T C O M P U T E R M O U N T I N G
Recumbents are interesting beasts, because you quickly discover that much of the gear designed for cyclists is not suitable for use on a recumbent. Take your typical cycling jersey, for example. Put your keys and a couple of bannanas in the back pockets, lean back into that seat, and, well, you get the idea.
So it was on Saturday, July 19th, 1995, I found myself with a shiny new Avocet 50 computer (the one with the altimeter) and my recumbent in front of me, wondering how to get the one on to the other. I have underseat steering on my R-20, which puts the handlebars well away from my normal field of view. I considered mounting the computer on the handlebars anyway, but I would have had to turn it sideways and looking at it would have involved looking down at the ground to my right, more or less, which would be inconvenient at best, dangerous at worst.
The obvious place to have the computer was on the boom in front of my seat, just in front of the headset between my legs. However, the strap on the mount wasn't anywhere near large enough to go around my 1.75" boom, and the computer would have been sideways, anyway. I decided to go down to Cambie Cycles, Vancouver's recumbent specialist, and ask their advice on the problem.
Brock, the owner, had seen the computer mount for my R-20 kicking around somewhere at one point, but it seemed to have been lost over the course of time. So he suggested I take a bit of elbow-bend PVC pipe, file a curve into one end so it would sit flush against my boom tube, drill a couple of holes in it to zip-tie it down, and mount the computer on the other half of the bend.
I grabbed my mount and popped out to the nearest plumbing shop and started searching for some pipe. It was after a few minutes here that I realised that handlebars must be 5/8" in diameter, because the shop had only 1/2" and 3/4" joints, and the former was to narrow and the latter too wide! I finally decided on the 3/4" and took it back to Cambie Cycles.
Filing out one opening of the elbow joint with a half-round file worked fine, giving me a very good fit, and it was no problem to use a small drill bit to drill a hole on either side for the zip-tie. Getting the computer mount on the other end was a bigger problem, however. I eventually had to file down the entire outside surface of that end of the joint to reduce the diameter enough to get the mount on. Once I did get it on, however, it was quite secure.
Securing the mount to the frame was another matter. The PVC elbow pipe slid quite easily against the smooth painted surface of the boom. I cut a piece of rubber cut from an old inner tube, roughened it with sandpaper, and placed it between the PVC elbow and the boom, which helped somewhat. A good crank on the zip-tie has locked it down moderately securely, but it still slides about if I push the buttons hard.
I think the next step is to take the zip-tie off and remount the entire assembly with inner tube right around the boom, to minimise slippage. The other option would be to glue the rubber pad to the PVC and to the boom. I'm also going to see if I can't shorten the end that the computer is mounted on to centre the computer a bit more; there is a bit of a tendency to brush one's leg against it occasionally.
However, as it stands the assembly has worked out well. It not being perfectly secure allows me to move it about on rides to find the optimal position for it before I tighten it down better. The display on the 50 is quite large, and easily readable from a riding position without taking my eyes off the road. The only real disadvantage of this position is that a fair amount of arm movement is required to push the buttons; changing settings is slightly faster and easier with the handlebar mount on a traditional bike.
One advantage the recumbent does offer, however, is easier cable mounting. Because my R-20 has only about 60 degrees of front wheel motion (the handlebars under the seat hit the frame at about 30 degrees of turn) I need to leave very little slack at the headset- fork juncture.