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Old 11-16-10, 06:25 PM   #1
mrchip
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Cranks spin forward without catching and chain not moving

I have an Autobike that I have ridden for about 18 years with no problems. It has helped me recover mobility after knee replacement, and am now riding it back and forth to work - the high school where I teach. This last week I began having a problem with my cranks and the local bike shop says They cannot fix or get the parts for it. I am looking for an autobike I can use for parts, or someone who can tell me where to go to get parts.

The crank spin forward and won't catch. The chain is not moving. This is intermittent. I go about a couple of miles toward school and then all of a sudden, I can pedal like crazy, but not get any thing to the sprocket. I walk the rest of the way to school, lock the bike up and do my job. Come out after school and ride like normal a mile or two and then it happens again.

How about it? Anyone help this old (61) Vet out? Anybody got any ideas?
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Old 11-16-10, 06:33 PM   #2
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OK first question what's an Autobike ?

and, what is the drive-train made up of?
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Old 11-16-10, 06:37 PM   #3
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Your bike has "front freewheel" meaning the ratchet mechanism that allows coasting is in the cranks as opposed to the normal location in the rear hub. In all probability corrosion has gotten to the mechanism and the little spring-loaded pawls aren't springing out and engaging. It's also possibly simply dried grease or dirt, so repair may be possible.

If you're lucky a decent mechanic can save/fix it with a clean and lube, though if the rust is severe, it'll call for replacement parts which may not be readily available.

If you cannot repair or replace the front freewheel mechanism, things get complicated and expensive and the bike may not justify the cost involved.
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Old 11-16-10, 06:45 PM   #4
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OK first question what's an Autobike ?

and, what is the drive-train made up of?
Here's something:
http://www.disraeligears.co.uk/Site/...railleurs.html

A lot like the classic LandRider
http://www.landriderbikes.com/
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Old 11-16-10, 06:47 PM   #5
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Apparently they made autoshifting style bicycles. A google turned up a few oddball looking examples. Without a picture we don't know which you have.

Either way I'd say that FB hit the nail on the head. It either had a front mounted freewheel which needs attention or something in the crank arm system let go so the chain rings are no longer connected to the pedal cranks.

If it turns out to be really messy with lots of special parts that you can't get anymore then you may need to join the rest of us and get used to shifting. It really isn't that bad. And if you commute over level or near level ground you likely will only use one gear anyway.

But I concur with the "take it to the local bike shop" suggestion. From the description of your problem I'd say that you're not all that mechanically inclined or you would have used different terms and provided more details on where the issue is actually located in terms of breaking it down into subsystems.
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Old 11-16-10, 06:58 PM   #6
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The Autobike was indeed a self-shifting bike with weights on the rear spokes that moved outward under centrifugal force to operate the shift mechanism. It was sold via "infomercials" and is generally reguarded as a very poor quality bike. The OP's 18 years of service from one is astounding. Most died very quickly.

I agree that getting it repaired is going to be difficult if a simple infusion of oil into the freewheeling mechanism doesn't solve the problem.
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Old 11-16-10, 07:14 PM   #7
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Given that it's intermittent, I'm now leaning toward the possibility that it's just dried lube, or dirt, meaning there's hope.

If you feel up to it, try wicking some oil into a gap between the crank and chainring units while back pedaling, and see if it gets any better. You'll know you're on the right track if the freewheel ratchet sound changes. BTW- this will make a bit of a mess, so do it outdoors, or on a plastic dropcloth.

Otherwise try a different bike shop. The first one gave up too quickly, and you may be the victim of some bike shop elitism, or a mechanic who hasn't been around long enough. A decent mechanic should be able to open, clean and service the front freewheel mechanism and breathe some fresh life into it. That assumes that it is repairable, which it may not be. If you want to keep this going, and have a knowledgeable, willing mechanic, put an inquiry out through Craig's List, looking for another bike from which to cannibalize parts. They sold hundreds of thousands of these, so I'm sure there are plenty still sitting around and gathering dust in garages all over the country.
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Old 11-16-10, 09:22 PM   #8
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I'm kind of suprised by the devotion I see with Autobike riders, my sister is one of them. When she or one of her cult mates trashes one of their rides they come to me for repairs. A clean and lube solves most problems most of the time. We have a couple of parts bikes we got cheap on CL, you can usually find them on CL in the $20-$50 range(I've also seen a few the sellers wanted $400+ for) It's hard to beleive how important not shifting is to some folks.
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Old 11-16-10, 09:34 PM   #9
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A lighter, simpler, more-reliable singlespeed would make more sense to me. Or, an IGH. Oh, well.
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Old 11-17-10, 12:58 AM   #10
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May I recommend a piece of fine Victorian British Engineering,
the Sturmey Archer 3 speed internal gear hub.
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Old 11-17-10, 03:08 PM   #11
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An Autobike is one that has a set of a kind of sliding weight on the back tire spokes. The faster the tire spins the further out the weight slide by centripital force which then, somehow being engaged to the shifting derailer, shifts the chain from sprocket to sprocket. Therefore, automatically shifting the bike through 5 or 6 gears. Other than this mechanism the bike appears to be a normal 5 or 6 speed mountain bike with out the normal shift levers up front.
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Old 11-17-10, 03:40 PM   #12
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.......Other than this mechanism the bike appears to be a normal 5 or 6 speed mountain bike with out the normal shift levers up front.
Yes and no, with theNo being key. Autobikes use a Shimano front freewheel system, making shifting possible while coasting. That's a key difference from a typical mtn bike since that's where the OP's problem is.
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Old 11-17-10, 04:43 PM   #13
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The faster the tire spins the further out the weight slide by centripital force which then, somehow being engaged to the shifting derailer,
Yeah, that's really the correct descriptive term but I wrote "certrifugal force" since that's how most people think of it, even though it's technically incorrect. Physics major or engineer?
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Old 11-17-10, 05:07 PM   #14
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Yeah, that's really the correct descriptive term but I wrote "certrifugal force" since that's how most people think of it, even though it's technically incorrect. Physics major or engineer?
Don't substitute one wrong term for another.

Centripital force is the real force exerted by the springs pushing the weights inward and resisting their inertial tendency to move outward when the wheel spins.

Centrifugal force is the equal and opposite of Centripital force. It's a semantic convenience to descride what's felt or seen as a force, but is simply the inertial tendency of a rotating body to move in a straight line, ie. fly off tangentially. From another frame of reference, centrifugal force is what the weights exert on the springs compressing them. It's analogous to the force that pushes you back into the seat when a car accelerates.
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