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Old 09-29-13, 07:33 PM   #1
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e-assist on older bikes (60's-90's), what bikes to design around?

Assuming that i'm wanting to make either a stout e-assist or even a system capable of just coasting at the desired speed...

Assuming i'm hoping to homebrew as much as possible due to issues of expense primarily... (may or may not even be a proper hub motor, trying to figure out where I can save money... the high crime areas I have to park in I expect this to all be stolen at some point so don't really want to dump $1000 on it :-/ )

Assuming i'm not terribly concerned about weight. (except my own, I can drop 20lbs more easy than the bike can for the money, by just cycling more :P ) A steel frame is strong and repairable anywhere, even if it wont look pretty afterwards. Reliability and long life matter more.

Assuming I need a decent amount of cargo (like 50lbs of college books, plus potentially a long range 40mi of battery assist pack... plus my large heavy frame pushing probably 280lbs right now until I get that down though some of that is muscle and not going anywhere... so really going for bike strength here more than lightness)

What kind of bike features, specifications, and similar would I want to be designing my system around? The bike isn't picked yet, the potentials for e-assist engineering are going to drive the bike. For instance I read somewhere that i'd want a 36 spoke wheel if I ever plan to use a hub motor - because all hub motors are 36 spoke wheels. So an older bike would need that, or have to be converted to that. I'd like to try to adapt a front disc brake from a newer department store mountain bike parts bike if possible without excessive reengineering in the future due to weight, speed, downhill coasting concerns - not sure how well normal calipers stop from 20mph with extra weight. Factoids like that is what i'm looking for to keep in mind at this early early before even pre-alpha stage of the process as I research possible directions for this future project.
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Old 09-30-13, 02:17 PM   #2
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A mid 90's steel frame mountain bike would work the best. Probably want one with rack mounts, eh?

Good V-brakes with good pads work fine. Why do you think disk brakes would be better? If your heart is set on that you can always buy a new fork for $50 and add front disk brakes to that. I ride a 500lb (GVW) tandem around on V brakes and it works fine (20 - 40mph), as long as I'm not riding down the side of a mountain.

Yeah, hub motors are typically 36 hole, but that is a requirement for a rim, not for the bike.
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Old 09-30-13, 06:30 PM   #3
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Yes, older steel mountain bike frame is one of the best options. Aftermarket rigid triple tree fork kit with good thick steel down tubes with a disk brake caliper mount and either steel or good thick heavy aluminum top and bottom triple plates is often a good choice for a good strong front fork that allows a good disk brake on the front which is sufficient if combined with a V-brake on the rear rim with high end quality pads (good quality pads make a huge difference with V-brakes).

Such an aftermarket good strong rigid triple tree fork kit is also a good way to take the load of a front hub-motor as well, one of my most recent builds was done just that way. I put a hub built and wound for low end torque in the rear wheel and another build and wound for speed in the front and set it up with an electric relay system to switch between the two motors running off a single controller so I had a low and high gear by changing between the motors which is controlled by a set of micro contact switches when I shift the pedal gearing between the two gears accomplished via a single front derailer with an old 52/40 double chainwheel road crank up front and a single speed heavy duty BMX bomb proof freewheel on the rear with a single idler on a spring loaded arm pusing up on the center of the bottom of the chain look for a chain tensioner.

Works like a charm and that aftermarket rigid triple tree fork is good and strong and takes the front motor load really well.

Last edited by turbo1889; 09-30-13 at 06:51 PM.
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