I ran across a binary encoder at work, and noted that it has the ability to determine rotation. Like a JO counter, you could back up with this type of counter.

Disks are available that will fit a bike wheel. All that's necessary is a circuit board that powers the encoder and provides a readout. The readout could be mounted to your handlebars.

You can have anywhere from 64 to 2500 counts per revolution. I think 100 is sufficient.

Pricing for the encoder and disk is less than the Veeder-Root counters currently used. Pricing for the circuit board and display remains to be seen.

If there is sufficient interest, I will pursue this design. I plan to build a prototype regardless and put it in the hands of an experienced measurer, but it could be a while before it happens.

Stu, can you post the information and web link, if there is one, for the encoder? I look forward to hearing more about your prototype.

The encoder I found is a surface-mount unit, just a wee thing:

http://www.usdigital.com/products/aedr/

It would have to be mounted to a small board near the wheel hub, and be connected by wire to the display/power unit.

So far I've only found a two-inch disk, which seems a bit small for our needs, but will suffice if I can mount it to the bike wheel.

Weatherproofing will be an issue, as will encoder-disk clearance. This counter will be a semi-permanent installation, unlike the JO counter. It's more akin to Neville's calibrated-rim setup, with the advantage of the machine counting the partial revolutions.

Once again I am forced to abandon a design

The degree of precision required for the encoder (.010 max runout) and lack of a suitable disk means that we won't see this design anytime soon.

Sorry guys.

I wonder if the principle can be applied to a spoke-counting design? I'll have to look into that...

You know, Stu, a possible design would be to take a few of those plastic reflector things that you see stuck to the spokes of Kmart bicycles, partially cover them with black tape, so you has maybe 30 visible reflective spots on a rotating wheel, and then monitor it with a retro-reflective photocell and a counter.

Steve Collins

Stephen,

My knee-jerk reaction is that a reflective device would be too prone to error.

I measure some courses, and many time calibrate, during darker periods when cars have lights on. If I passed in front of one of the newer cars with really bright headlights, I can imagine false readings. Or, sunlight reflecting off of a shiny surface in a concentrated beam.

I, for one, would not trust a reflective unit.

Just my thoughts.

Nor would I.

I believe the encoder's receiver is calibrated to ignore all wavelengths but one, which is emitted by the LED. This would eliminate the problem of false readings, but the main problem, that of finding a suitable encoder wheel, and mounting it to a bicycle so as to have less than .010 inch of lateral runout, remain. Thus the design remains a dead end, albeit one that could be solved with a massive infusion of cash. A couple hundred thou ought to do it.

It could be done using the spokes themselves as the encoder wheel. If the LED were on one side and the photodetector was on the other.....Maybe a piece of tape across every?? spoke to interrupt the link.

That might work at the point where the spokes cross. The encoders I've seen all have a gap for the tone ring that's about 2-3mm wide. A more powerful LED might do the trick, if the receiver were properly shielded from outside light.

One downside to the encoder as opposed to a Jones is its reliance on batteries. The display and processor will take some juice to operate, and their duration is unknown.

It's going to be pretty hard to beat the Jones for size/weight and simplicity. While the encoder is theoretically capable of much greater resolution than a Jones, I'm not sure we need accuracy down to 1/512 of a wheel revolution.

Power should not vbe a problem on a bicycle - recharge using a good old-fashioned dynamo..