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Saturday, November 7, 2009

Chain Reactions, Part 3

After the work done in the last Chain Reactions, Part 2 post, I did 24+ miles yesterday in two trip legs (with a partial recharge at the far end, halfway). No problems with the chain coming off or anything unless I try to push the bike backwards.

Comes off at the motor end every time if I do that, because of the misalignment between motor ring and receiver ring. Have to cut at least 1/8", maybe 3/16" or more off the inner end of the hub to get the ring lined up again, and then use spacer washers between the locknut/retaining washer on the axle end and the hub to keep it from sliding back and forth.

The entire bike is very much quieter, and the motor is also quieter now; not sure why. Only annoying noise now is from the fixed-in-place guide/tensioner wheel on the pedal drive, thinking of replacing this with a guide tube instead, if I can find some of my tough plastic sheet that won't wear away from the rubbing. It might also be quieter as a sprung wheel instead of fixed, because the tension on it changes as the pedal and receiver rings go around, since they're not perfectly centered on their shafts.

Current draw with the 28T ring is higher by an amp or so (for same speeds as 24T), average, but I can also go higher speeds all the time because it's now reliable. :) I can also push the throttle to the max to accelerate, and I actually had the rear tire slip a bit on certain areas of older pavement (where the top layer is gritty and a bit loose, not sticky anymore especially since the weather is cooler now), during the first couple miles of the ride while the batteries were at full charge. That's kind of cool, in that it means I have *plenty* of torque available now, and I just need to get batteries to match the power draw of the motor for really good range at top speed.

I now get 20.0 MPH max speed on a level no head/tail wind, motor only, draws more than 12A (max panel meter reading) solid for a few seconds getting there, then tapers off and sticks around 10-11A to hold there. Pedal some and I can stay at that speed with motor dropping to 4-9A swinging wildly, but it doesn't increase the speed, which seems a little wierd, as I have no limiter on there for that. I still need to mess with the shunt and panel meter on that 30A meter to get it working again.

Seems like with 28T vs 21T, with the same rear ratio at the high end, I ought to get a lot higher speed than 20MPH, since around 18MPH was the max on 21T. Still pondering that one.

Wondering if perhaps the throttle adjustment inside the controller has coincidentally changed (vibration? the pot is not locked down and it does turn easily). I want to open it up and do the mods to up it to 48V capable anyway, so I can test with a fourth UPS battery, for kicks.

Still considering swapping the 3-ring set off the upright bike to this one, just to see what happens; I could then run on the middle ring most of the time instead of the big ring; bit less chain wear from running angled, since commonly I run at largest front ring (farthest right) and somewhere in middle on rear rings. I could also then run on the big front ring for faster speeds, which would have less ring wear on the back and more teeth to put the power into the rear wheel at any one time, rather than using the smaller rear rings to go faster, which leads to much faster ring wear and as I've seen, chain skip. :(

I do think I'm going to end up needing a lot of new chains based on the wear and skip problems now obvious with this heavy bike, or I need to find a way to seal up the chain and rings in a clean, lubed, dust-free enclosure. Road grit can't be helping the problems.

This is where the belt-based CVT in a sealed box would be nice. Still researching how I might be able to build one; lots of ideas but have to work out the mechanics using parts I already have--that's difficult.

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