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Sunday, September 9, 2007

More pictures, some explanations

First up is the bike that will be converted, once I have a working design. It's a 2005 Columbia 26" Comfort Bike, with an aluminum frame. I like that the frame is strong and light, but being aluminum I can't weld anything to it (even if I find or build a steel-welder, as I don't know if I could make an aluminum-welding rig, and I really doubt I'll find one of those in someone's junkpile).

The baskets are from previous bikes--the front ones are actually rear baskets with minor modifications to fit on the front, because there never seems to be enough cargo space. Can't carry much of a load up there without seriously affecting steering, but it works for all the light but bulky groceries, like various products that come as essentially bags of air with a little product inside, ramen, powdered milk, and the like. Liquids up front are a huge no-no, as the side-to-side sloshing will quickly resonate and cause steering loss and a crash. :-( Those baskets will be replaced with panniers of some type once the motor implementation is finished, very likely a variant of these cool mop buckets from Jake Von Slatt, which are a pretty cool idea. I like the way this man thinks. You should look at the rest of his sites, too, when you're done reading this one. There are some interesting projects at his main pages, and his Steampunk Workshop is interesting and inspiring.

This is the drivetrain frame, with wheel and chain, but missing the actual pedal shaft and sprocket (which were separated for modification at the time). It's pretty grungy and rusty, plus it's bent up at the rear wheel axle mounting point, which is why the bike it came from was originally scrapped (I hit a huge pothole that was invisible in the dark, somehow only with the rear wheel as I turned a corner, and the rear wheel was yanked right out of the frame, and the frame hit the ground. Like usual, I was lucky only to get scrapes). But it will work well enough for testing purposes.

I'll find a different organ donor for the real version, likely from a thrift store or yard sale--$5 to $15 for a bike is not uncommon, if you look for them--they're not rideable due usually to rotted rubber and plastic, but that doesn't matter for this purpose, as long as the frame is not rusty or bent (in back). I simply hacksawed this part of the frame off the rest of the poor Murray Biotech, and hammered the bent parts back in shape as best I could.

This is the way the pedal levers and pedal sprockets looked before I started, with the pedals themselves simply unscrewed from them with a crescent wrench. It's still on the frame here.

This is after I used a carbide cutting wheel with my handy Black&Decker circular saw to cut the pedal levers off the pedal shaft, so that I will have a place to connect the motor's output gear to. I still have to file the motor side flat and level, I couldn't hold the circular saw steady enough to cut it perfectly, and I don't have a table saw or other large tools like that (and haven't built a table mount and mitre for the handheld one yet, either, though I probably will before I do the rideable version). I will need to make a way to weld a connecting piece between the non-sprocket end of the shaft and the motor's output gear. A spot weld would be fine for tests. Full weld would be needed for rideable version, assuming the design even works.

This is the actual motor to be used, in several views. You can see the output gear, which is a pretty hard steel (it didn't scratch much when I was scraping crud off of it with a utility blade, for instance). That gear will fit nicely inside a 1" star-type socket from a socket wrench, with the teeth moving just a bit against the socket's inside star-points. It's even better on a 15/16" socket, but because this gear has 9 teeth, and the sockets have an even number instead, I can't actually make it fit. I'd need to file down at least one tooth, and possible several, or do the same thing inside the socket, and that's tedious and difficult with hand tools, or even with my Dremel. Whichever socket I end up going with would be what gets welded to the pedal shaft above. Then when I bolt the motor down to the frame, it would be held into the socket on the sprocket, and I can turn it on and take off like a rocket. Or something.

There are bolts already intended to hold the gear assembly to whatever mating object would be driven by it, formerly the LTD's window crank, but now whatever I build for the motor mount. I'm still scrounging for parts on that, but I've got some good aluminum L-brackets, over 1/8" thick, and hard enough that I can't bend them by hand. Those, along with a few other odds and ends like a long pipe clamp I found in an old toolbox, will probably work for the motor mount, after suitable drilling of holes for mounting bolts and such. The motor feels a bit heavy, but shouldn't be an issue since I am mounting it close to and parallel to the frame--there should not be much cantilever force to yank it out of alignment even with some significant bumps and potholes.

Attached to the motor is part of the harness that includes the window up/down switch. It's spring return, and already designed to handle the current from the motor, as well as significant usage cycles, so it will certainly work for the purpose of a test deadmanswitch, until I build the actual throttle and PWM circuit for the system. Right now, I'm testing using just a 12V gelcell battery directly connected to the motor (via the switch/harness), since none of this is running for more than a minute or two at a time. Efficiency is irrelevant for these tests--I just need to see if it physically works and drives it with enough power to move me and the bike. If it doesn't do that with direct battery power, it will never do it any other practical way, either. :-)

I might be able to use higher voltages, like two cells in series for 24V, but this motor was intended for 12v use, intermittent short-period loads (rolling up a window). I am not sure what would happen at double that voltage, and sustained periods driving a heavier load than a window crank. I'll not test it unless it doesn't work the other way.

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