I used the Model J-R for a real half marathon measurement yesterday with complete success. I would have liked to have been able to use the detachable tab extender. With its help, I would have been able to slightly simplify my technique in order to eliminate on-site calculation of the predetermined counts for the mile splits. This measurement was a simple fixed finish to start ride, marking the mile splits and start position. What I would like to do is as follows:
1. Calibrate at home normally
2. Remove tab extender and note JR counter reading
3. Run the pre calibration constant calculation on my home computer and calculate the splits based on the noted counter reading
4. Drive 50 miles to the course and ride to the start
5. Engage the tab extender and check the count is still on the noted reading so the calculate splits do need no further arithmetic.
This would method would result in a small saving in on-site calculations compared with the usual situation where I am messily adding in my note book the starting reading to a prepared list of split calculations.
I am frustrated because on my bike the tab is always engaged with the spokes see:
Here the counter has been installed with one washer between the hub inner and the JR model counter. This was needed to make sure that the spokes cleared the black delrin gear. You can see that the tab is engaged with the spokes by several mm, so the removable extender has no useful function.
Also in the picture you can see the thickness of two further washers held in position so that one can judge the effect of adding these two washers to the one that is already installed. It looks as if with these two washers in place and end of the existing tab snipped off through the hole there the extender could be made to work as required. The only problem I can see with this is that the nut on the axle holding the wheel to the fork on this side would then hardly engage the thread on the axle. I think that means I have to dismantle the axle and move the cones for the bearings to give more axle on this side. I have not actually tackled this yet since I am a little reluctant to start messing with my bike axle as I need it to be ready and reliable for another measurement next weekend.
Has anyone tried moving the position of the hub on the axle to overcome this sort of problem?
I know Tom & Pete did their best to accommodate a wide range of bike configurations, and I can't see any obvious modification to suggest which would improve things. Tom has said that he intends to slightly reduce the thickness of black delrin gear for the next batch in order that the gear will clear the spokes for my bike configuration,
The next order will feature a slightly thinner delrin gear. I measured mine at almost 0.29", which is a little more than the 1/4" ordered. I'm going to try for 3/16" next time, increasing the space where you found encroachment. I can't say it will fit them all, but this may help fit a few more.
However, this will not help at all with the tab length problem, so I would still need insert about 3 washers and then undertake an adjustment of the the cone bearings on the axle.