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Saturday, April 18, 2009

Test Ride Video, Some Fixes Completed

Well, I didn't get a whole lot done today. Somehow I bruised my rightside ribs on Thursday, but didn't feel it until Friday when I got up for work. It got worse all day long; a couple hours in I could barely lift a 35 pound bag of dog food, and after that I couldnt' do it at all--even sliding the 20-pounders hurt, and lifting them was difficult. Sleep took a long time to come after I got home, and I was still sore and tired until midafternoon.

I did do some minor work, mostly fixing the rubbing the motor chain had on the plate above it. Part of it was caused by the sprocket bolted to the motor hub not being perfectly centered, and thus not being able to fully clear the plate without extra shims between the motor and plate. The shims are just some old broken hacksaw blade and utility knife blade (good steel, never throw anything away you might still be able to use!).

Another place the motor chain was rubbing was some bolt-heads I had used to secure the largest sprocket back onto the 3-chainring set, back when I had originally gotten it on one of the junk bikes from the "Bicycyle Bonanza" post early in this blog (2007, I think). I filed the bolt heads a little flatter for better clearance, but one or two are still rubbing a bit and need a hair more filing.

Since the derailer being used as a chain tensioner on the pedal chain was a bit too far leftward for proper lineup, but had no further adjustment range to fix that, I moved it temporarily rightward by adding spacer nuts between it and the bedframe corner bracket being used as a hanger for it. Since the bracket has long slots it's screwed thru to the main mounting plate, I can adjust the whole plate farther rightward, but at the moment it's butted up against the motor already, so I need to cut away some of that edge of the bracket so it can move farther rightward. Not much, perhaps 1/4" at most--just enough to let the derailer fully align with both pedal drivetrain chainrings. I also need to use slightly different spacers on the two bolt-points for the derailer, so that it does not sit at an angle, or else slightly increase the hole size for the axle-hole point, which will do the same thing.

The biggest problem with this tensioner is that unless it really is lined up exactly perfect, then the chain tends to catch on the front chainring's tooth tips instead of engaging them, when I'm backing the bike up or when the motor speed exceeds the pedal speed (or I hesitate even for an instant during pedalling without the same hesitation in throttle control, a common thing so far in the 3 days I've been getting used to how it works and handles.

If I make the tension-based motor throttle, it will fix this problem because it will in theory never go faster than the pedals, or run when I'm not pedalling. Any hesitation in pedalling will stop the motor, too. This I'm still working on the design for.

If I add a freewheel for the pedals so they can't be driven by the motor, that will fix it too. This is difficult at best, with the limited parts I have to use for it (and no means to readily make a square-taper freewheel holder that would hold two freewheels plus chainrings on the freewheels), as it means I must make the pedal chain go not directly to the receiver chainring, but rather first to a freewheeled ring on a separate axle, then have another chain from a secondary sprocket on that axle go to the receiver chainring. More weight, more complication, etc.

Ideally I'll have both freewheels and tension-controlled throttle, but they each will take time and resources to make, so I have to do just one at a time. I think the throttle really needs to be first, as it will have more effect than the other on my whole riding style with the motor, including removing the distraction of a hand-operated throttle completely.

After I finished what I could of the work today, I took it out for another test ride, finding that while the chain problem is less than it was before the spacers, it is still a pretty bad problem, requiring perhaps a dozen stops to put the chain back on the pedal chainrings after it was jolted off by bumps or by my hesitations or other pausing without throttling down fast enough at the same time.

A helpful camera-wielding bike rider captured this video as I was testing it out today:

There will be more videos of today's tests as I receive them, on a separate new post.

This one includes part of a 22.3MPH test run on a paved canal path that's long and fairly straight, with no other bike or foot traffic.

I might have acheived faster speeds if I had fully-charged batteries, but I was still doing the rundown test, with around an hour of runtime so far, with about ten miles on them. By the end of this trip, I had another 5 miles or so, and about 30 minutes (lots of stops to fix that chain, unfortunately slowing me down, as it actually took at least 45 minutes to do the test ride, even though only 2/3 of that was spent riding).

If I finish readjusting the front chainring set's derailer (on the wheel drivetrain) for the 2-chainring set that replaced the 3-ring set, I will be able to shift onto the larger ring and the motor could drive the bike faster than the approximately 15MPH that it can currently do by itself with no pedalling, but I'm not sure it's really necessary. I can't use the motor faster than 20MPH on the roads anyway, whether I'm pedalling or not, so trying to go faster with it (to keep up with traffic, for instance) is not a good idea, regardless of how much more that would make motorists happy (if I could keep up with them so they didn't have to go around me).

Going faster has safety issues as well, since it makes it very much harder to stop quickly, since the bike's brake system was originally designed to stop a lightweight 25-30 pound bike and it's rider, not a 120-pound (dry weight with just motor/batteries/bike!) behemoth cargo bike plus 150-pound rider, plus any cargo I might carry (theoretically another 100 pounds max, 20-30 pounds typical). Even more once I redesign the cargo pod mountings so they are very stiffly mounted to the frame, such that the loading is not all on the rear triangle of the bike, and the batteries are in separate boxes forward under the seat. Less if I get some smaller batteries (like 17Ah) to use for short-range stuff, saving the U1s for the long trips I make roughly every two to three weeks nowadays, and for trips I will be hauling a trailer full of heavy stuff.

Even after I install the rear brakes and flip the front fork around to fix the front brake issues, it's still going to be harder to stop than a typical bike, with just these rim brakes. I may put two sets of rear brakes on, one on the seat stays, and one on the chainstays, to give me more frictional area to stop with. If I had any, I might install disc brakes. I've considered trying to design some from recycled materials, as an additional system to the rim brakes, but it's more complicated than it seems at first. :-)

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