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Friday, January 1, 2010

Mechanical Repairs Still Underway

First up is a wheel relacing, to replace the badly damaged (destroyed, really) wheel currently on CB2. It's a standard wheel build, except that it is using thicker stainless ones donated to me that are for a wheelchair wheel.

It required a bit of creative relacing that may affect wheel strength as a whole, as these spokes are for a 540 rim, where mine is a 507, I think. I had to install them as crossed pairs where normally they'd be parallel pairs, in the typical 2-cross pattern, so that they would not be so long as to poke thru the tube. ;)

It still gives parallel pairs, just not the same ones as the originals--basically works out as if you went backwards for lacing, going *across* the hub instead of out from it. If that makes sense.

The rim and hub were from the previous CB2 rear wheel, which had a bent axle and a slightly bent rim. I fixed the rim with some working of tension on the original spokes and rebending of the rim, and then I used the axle and bearings from the rear wheel of the Magna 26" I just got as a parts bike a few posts back. I used the Shimano 6-speed cassette from the other (Huffy) parts bike, as it has the shifting-ease type edges to teeth and whatnot, where the Falcon 6-speed cassette on the Magna is all flat edges and plain teeth.

I still have to pull the tire/tube/protection strip off the damaged wheel and put it on this one.

While I was at it, I also decided to do something about having to pedal too fast for comfort or to be able to assist the motor, with the motor at full speed, due to the nearly 1:1 pedal to drivetrain system. I swapped out the single-ring crank I had on the front, and installed the 3-ring from the Magna, which gives me the outer large ring that is one and a half full chain links larger than the single (which also gives me the ability to make a properly tensioned chain, instead of one with a lot of sag).

However, this larger ring is leftward just far enough to cause interference with the motor chain. So I have to move the motor chain leftward, too. The only way to do that is to move the receiver rings on the jackshaft leftward, so I pulled the slightly longer BB axle (crankshaft) off the Magna and replaced the one already on CB2's jackshaft with it. That moves the whole receiver ring set leftward about 1 cm or so.

Then I had to take off the motor's drive ring hub, so I can install spacers on the shaft that push it leftward the same amount. I have not yet done this part yet, as I was too worn out by then.

Once that's done, I can reassemble the drivetrain and have spacing that should allow all the chains to clear each other and remain taut, and in line, removing one more problem that has plagued me since the beginning in one fashion or another. I'm apparently terrible at making good chainlines. :-(

Then I have to look into one more problem:

The last time I started doing a chainline test before the chainline modifications, using the motor to drive the chains at a slow speed so I could watch them pass and move, I heard a clicking noise, and whenever I heard it, the motors' gearbox output shaft stopped for an instant.

It is possible that there is something wrong in the gearbox and something is slipping, but I doubt it as there is no sign of it in other noises I would expect to hear from a wear problem like that, and there is no problem at all when there is no load.

However, it does seem possible that the coupler between motor and gearbox could be at fault. It is made so that both the gearbox and the motor have shafts that are slotted all the way thru, in the center, for about 1/4" or deeper. Into these slots fit a steel tab about 1.5" or so long, which fit together to form a + sign. They are cast into a rubber disc, which is itself enclosed in a pair of metal "cups" with a hole in the center just large enough for the shafts to fit thru from each side.

This makes a flexible coupler that can transmit power but isolate vibration and shocks from the motor shaft, but it is possible for this coupler to fail. I have not yet taken off the motor to examine the coupler's current condition, but I suspect I will find enough wear or damage to cause a problem, probably caused by that last disaster which I am repairing. It did not show a problem in the inital tests of the motor with the Curtis, but all I did was some "bench tests" and then some riding around the block slowly.

If the coupler is bad, I do have another one somewhere around here, if I can find it. I might be able to make one, too, as it is a simple construction.

Again, while I am at it, I also intend to add a fourth battery to the system, which for now will be clamped down inside the rightside rear cargo pod, at the front inside corner. Later when I have more time, I will try moving it plus the third (rearmost center area) battery up to the front in that dual-battery case over the top tube just behind the front headstock.

That will give me 48V. I don't need the speed this could give, but it will mean I don't have to use full travel on the throttle pot to get my original full speed (simplifying setting up the new throttle pot and arm lever), and can "lock out" the higher throttle speeds with a physical adjustment or set screw.

It will also give me more range, since I can use higher voltage to lower the current draw from the batteries for the same power output, decreasing the Peukert effect on them, as well as the additional power from simply having one more battery.

One more benefit is that it will allow me to install both 24V chargers on the bike for opportunity charging, each one wired across two of the 4 x 12V series 48V pack.

Yet another benefit is that I will no longer need the laptop adapter wired in series with the CFL/battery hookup just to start them, so I can leave it off if I choose, or leave it on for even brighter lights.

As bright as the taillight already is, I think I will have to wire the laptop adapter only to the headlight, and take it off the taillight.

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