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Wednesday, November 11, 2009

Realigning The Motor Chain

The motor chain coming off, especially under heavy load, is a serious problem. It means I can't trust it to accelerate without problems, especially in situations like traffic when I really really need to trust it.

So I decided yesterday to fix it; couldn't post till today because I didn't finish until shortly before I had to go to work, and just didn't have time or energy once I got home. So here are the details of that.

First, a daylight pic of the new chainring setup from last post.

About the only serious problem I have found with it is that under acceleration, the frame on the left front is pulled together by the motor chain, and the frame on the rear right is pulled together by the main shiftable drivetrain to the wheel, so the whole bike "curves" a tiny tiny bit to the left, pushing out the middle section to the right, causing the crank arm that I can't cut off to scrape the point you see just above it in the pic. If I were to accelerate really hard, I imagine it might actually strike it.

So I used a C-clamp to tighten down across that bolt to bend the tab behind it out about 3/32" so it should now clear no matter what.

On to the motor alignment. In order to align the sprockets front to back, the motor hub needs to slide in about 1/4" further, and then I need a spacer of the same approximate depth to put between the nut/washer that holds the hub to the motor gearbox output shaft and the end of the hub, to keep it from drifting around on the shaft. It's very tight, but these are some serious loads, as I have found. ;-)

I figure that since I have no washers that will fit, the best way to get a spacer is to use the piece I'm going to cut off. That means I can't simply lathe it off in layers, like I normally might have.

Instead, I used the lathe to make a light notch, then used a hacksaw held in the resulting notch, moved slowly back and forth, to cut narrowly but all the way thru.

Took about 20-30 minutes and wore the blade out pretty well (this hub is very hard metal).

My main worry was that the blade would catch in the notch, if I didn't keep it straight, but that turned out to not be a problem.

As I didn't run the lathe fast, it was easy to hold the blade against it, but still with my body out of the line of fire should something go wrong. ;-)

It worked even easier and better than I had expected.

The resulting spacer only needed to have the center edge of the cut lathed out a tiny bit to remove the "flange" created by the cut, and the same on the hub.

I re-greased the hub's core and the axle, slid it on, put the spacer on and the key pin back in, tightened it down, and voila--it lines right up now. :-)

A test ride around the block, surging the acceleration and turning, hitting bumps, etc, didn't throw it off, so I should be good for a while, until the next weak point of this bike shows itself.

Eventually I'll find enough of those and their solutions to warrant building the next version from scratch, but at the rate I'm accumulating parts for it, it might be a while.

I'll definitely need disc brakes front and rear (preferably dual disc on the front), even if I have regen braking. If something goes wrong feeding the torque back into the motor for regen, I still need a way to stop, especially with a heavy cargo load. So for that, I will need new hubs that have disc brake holes, along with brake handles, calipers, etc., since I have no parts at all for disc brakes right now, and haven't got the right parts to build them from scratch in any way I've thought about so far.

If I go with one version of the regen drivetrain I'm considering, I will probably not be able to fit disc brake in the rear, unless I cleverly use the sprocket itself as the disc rotor, assuming I can find calipers that will go around the chain, or mount the calipers on the leading edge of the rotor, so they are on the "clear" side of it.

For a new version of the bike, I'd also need more square-taper BBs, shafts, bearings, etc, as well as 3-ring cranksets for them in various sizes, preferably with a bolt-on spider type so I can change the rings easily for customization.

Would like to have more 70s and 80s 10-speed or touring type bike frames, as the cromoly tubing they use is very light but still strong, and would be good to make this bike from.

Ideally, I'd be making a tadpole trike rather than bike, but that would also require the air-ride suspension parts to do it the way I really want to. Either way, I do need a good rear shock design that does not interfere with cargo pods on the sides being on the sprung part of the bike.

More wishing later. ;-)


  1. Get you a dremel tool with the little cutoff wheels. Mount it on the lathe when you want to cut something like that off. It works well and the cutting disks are cheaper than good lathe bits! I've even used a 90% air grinder on mine.... makes short work of hardened steel stuff.
    Also I have to ask, since you have a lathe, why don't you make all your own bb stuff? you can easily cast aluminum disks from scrap to make the bearing retainers from and then use whatever size axle in them you want. That's what I did for my tadpole trike when I added a motor through the rear bb. I got what I wanted that way instead of having to figure out how to use some odd stuff to do it. Metal casting blank forms from aluminum to use on your lathe is very easy to do and a pretty quick way to get needed parts too.

  2. I have a dremel with those wheels, but in this case the hacksaw was much simpler than dealing with two things rotating in different speeds/etc (i'm not all that coordinated).

    I didn't have to wear out lathe bits doing it, just a cheap hacksaw blade. (I might've even gotten this one out of something I found in trash, IIRC). Just used the lathe bit to make the score line to guide the blade.

    The only problem with casting things to use for these purposes is I would also need to thread them, and I don't have the tools needed to do that. I have a few SAE dies and taps, but they're all small. It's about $50 plus shipping to get a tap *or* die (not both!) for the 24TPI BB sized threads (also used for freewheels). Money I don't have to spend.

    If I had all the gears for the lathe, I could turn threads on it, but I don't. I'm not coordinated enough to manually move the tool platform at the rate needed to cut the threads by hand.

    I'm probably still going to do some casting and whatnot eventually, but for the moment I have not enough parts that I need to do this, that I can't more easily make out of other things.

    For my "nice" version of this bike (or trike) to be made once I figure out enough of the problems with this design and fixes for them, I will certainly be learning casting to make all the odd bits I want for it. :) I've been saving up old harddisks for their aluminum bodies partly for this reason.

    I might pester you with questions about the casting process once I get that far. ;-)

  3. No problem, "pester" away. We are going to have to teach you how to make gears on that lathe too I see. It can be done if they are not too big.

  4. Do by chance know where to buy those 24 tpi dies that will work with a freewheel? I would like to get one myself. It would save me a lot of time on some of the stuff I build.

  5. Gears...I could use teh ability to make custom gears. Could I make helical-tooth ones? I think that would be too complex for this lathe, and my skills and coordination. :( I ask because they are quieter than regular ones, which means less energy being wasted as noise and vibration and heat.

    The 1-3/8 x 24 tpi [1.375 x 24 tpi] dies can be had from VictorNet
    and I thought McMaster-Carr had them, but I don't see the 24 tpi, they only go up to 12?

    I forgot what other places I found them (besides bike parts dealers, who only sell to bike shops, so you would have to have your local bike shop order them for you).


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