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Sunday, April 12, 2009

...Is Not Absolutely Easy To Wield

After getting home from work this evening, I unbolted the frames from each other and started checking out spacing by putting the motor in various positions to see how well it lines up to possible chainring positions, including flipping the hub/chainring around on it's axle.

Unfortunately all of the easy mounting points, without modifying anything else on the frame, end up with the chainring either badly misaligned with the receiver chainring, or else physically interfering with the frame or the pedal chain.

I even checked for setting it up so that the motor chain would go to the grannyring on the actual rear drivetrain side, as I would only need that ring if trying to pedal up a steep hill (and with the motor I shouldn't need to shift down that low, hopefully), but even that would require either placing the motor to the right of the whole bike frame, essentially mounted just under the seat's right side, or removing part of the Magna's right seat stay.

The best option appears to be to move the pedal chain to the inside of the left drivetrain, replacing the 1/2" chain chainring with another lathed-out rear-cassette chainring to get me a little lower ratio for the pedals than I have now (I went a little too far in the uphill-climbing direction with it, sacrificing the ability to go much more than 15-16MPH without pedalling like crazy on a flat).

Doing that would leave the outer chainring free to line up with the motor's chainring, if I mount it vertically between the stays of the Magna's rear triangle, just behind the throttle setup, with the gearbox directly below the motor. There are other positions it might work in, too, including clamped to the down tube of the Schwinn frame, as simulated in last post's picture of me holding it next to the bike, but doing that would require spreading the stays apart at least another two inches to clear the motor's chainring with chain on it, and also require spreading the ex-fork that bolts to the dropouts at the back of those stays apart by the same amount.

Doing *that* will affect other things, including the chain for the pedals, probably forcing it to go down and under the frame where now it just *barely* does that as it passes by the ex-derailer nee-chain tensioner.

It's too dark tonite to continue, and too late to be using any powertools anyway, so I'll continue working on it a bit tomorrow before I go back to work, hopefully coming up with something before I have to just bolt the bike back together and leave (in which case I'd have to unbolt it and take it apart *again* the next day, to continue this on my days off).

Another thing I need to fix is that in it's reversed orientation, the brakes on the front fork don't grab well. They work fine if I push the bike backwards and engage the brakes--grab and lock! That means I need to put the fork back in it's normal orientation, and make a new steering limiter panel that doesn't depend on the fork's built-in angled design, as the current one does.
Also means I have to flip the marker/signal lights around, as they're mounted to the fork itself.

While I'm at that, I think I'll also change the front part of the remote steering in the manner I'd pondered about before, so that it takes *more* handlebar movement to make *less* actual steering movement, which hopefully will help stabilize the bike at lower speeds. This should be as easy as changing out the current pivot arm, which is just an aluminum handlebar stem, for another handlebar stem that is steel, completely vertical, and can have a flat plate/tab welded to it that has at least two holes for the pivot point on it. One will be where the existing point is, and the other will be farther away from the center of that stem's pivot, by about 3/4" or less, so that I can try out the new steering ratio but can switch right back if I have to for any reason, without having to carry the original stem with me.

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