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Thursday, April 2, 2009

Steering Thoughts

As of Monday March 30th, my "new" bike now has 62 miles on it, and seems to be doing well now. Still gotta get a longer belt for the motor so it and a couple of car batteries can go on there (will add roughly 100 pounds to the bike) and help me out on trips like the one last Thursday in the wind-from-oz. I definitely like this bike much more than any other I've ever had, despite the various little problems it has, and that it is much heavier than any of the others, and will only be moreso once the motor system is on it (because I can't yet buy the battery I actually need to use).

Apparently that hard trip in the wind taught my muscles how to control it's steering a lot better than I could before. The next day after the trip I was so worn out I didn't go out and do anything, but the day after that I rode it to work and it felt...easy, like a regular bike's steering.

Normally, the steering on this one is a bit more difficult because of the slight proportional difference between the handlebar pivoting and the front wheel pivoting, which was originally intended to make it easier to not hit my knees with the bars in a hard turn while pedalling. Even though I reduced the amount of difference greatly, there is still a tiny bit of it, and that makes it harder to steer perfectly straight, because any movement of the handlebars is slightly amplified by the pivot difference, moving the front wheel more than the bars move.

Now that my muscles/nerves/brain/whatever have figured out how to do it, it's a lot easier, but I am actually considering changing it so that it takes *more* handlebar input to turn the front wheel, rather like power steering in a car, just to make it easier to steer at slow speeds. I tend to ride below 12MPH, closer to 10 or 11, most of the time, and the bike is a bit more difficult to balance that way just because of what's called the "pendulum effect", where a taller bike/rider setup would be easier because of that same effect. At faster speeds, the lower bike/rider position is better because it can change states faster and is easier to handle, so in most traffic situations it works out better.

But in balancing, it is natural for me to "wiggle" the bars a lot as I shift my weight around to keep it balanced, especially at slower speeds, and that can give a positive feedback to the balancing problem, causing me to weave around up to several inches or more from a straight path. That's both energy-inefficient *and* unsafe. At first I thought it was still slop in the tie-rod bearings causing it, but it's not--there is still not *zero* slop, but it is close enough for now. Changing the steering so it requires a larger input to change directions will fix the wiggle, or at the least, tone it down quite a bit, because I am pretty sure it's my own overcorrections causing it.

I'm not actually going to change it yet, as I'm still pondering implications of the change, and imagining ways I can change it so it's adjustable easily on the road. At the moment, it is a fixed pivot amount, and cannot be changed at all without physically removing and replacing the pivot arm at one end or the other. Easiest is to change the front pivot arm, as that is just a bike's handlebar stem turned at right-angles. To change it, it just takes undoing the bolt for the pivot point and the stem bolt. If I make a new pivot arm out of a different stem, I can put a plate on it with a slot the pivot bolt can be tightened down into whatever position gives the steering I want at the time. Then it can be readjusted even just very slightly to change the feel of the steering based on handling experiences I have with it as I ride. I'd still have to stop to adjust it, but it could be done with just two wrenches (one for bolt, one for nut) anytime on any trip.

Still pondering, though....

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