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  1. #1
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    What is a good donor bike for an electric bike project?

    ...and a couple of related questions...

    I have read through a number of threads on this site. I have found this question touched on in a few places but I would like to create a central place for this info.

    I live in China and often need to tote things around with my bike, as much as 100 pounds of fruit and vegetables, oil, etc. I often need to carry someone also - not at the same time as totting the veggies.

    I have two needs. For longer trips without so many stops I am looking for pedal assist. For about 60% of my traveling I am looking for the motor to do most, if not all of the work so that I can concentrate on the dangerous idiots around me that are not paying attention to me at all.

    I had a beach bike that i was riding before. I found that the upright position was very comfortable. Can I add the beach bike handlebars to another kind of bike?

    Most of the bikes or bike kits that I have looked at say that maximum weight is 300+ pounds. I find this strange because 500 pounds can be considered to be 300+ pounds It is likely that I will have at least 350 pounds on it sometimes, if not 400 pounds...plus the weight of the bike, motor, batteries etc. Is some kind of rear suspension (shock absorber) recommended?

    Are there types of bikes that are usually designed for more weight? I don't have the money to have a custom frame made but if you think it is necessary I would save up for it. What is the part of the bike that determines the weight capacity? The frame? the wheels/tires? It seems to me that the wheels/tires are the weak link in the system.

    I have read that putting the motor on the front wheel can be dangerous because the hub/bicycle connection was not designed for torque. Is this significant? Can this be eliminated by finding a new hub? Are there any other problems with putting a motor on the front?

    It seems that belt or chain driven motors are cheaper than hubs? They also have the advantage of allowing you to hook them up to a set of gears, possibly allowing me to use a less powerful and less expensive motor - more energy frugal. Any comments on this?

    Do I need to have a motor mount welded to the frame of my bicycle to be able to mount a gear or belt driven motor?

    I have seen a few production ebikes with a motor on the front axle and on the back. What advantage does this have? - maybe can use cheaper motors because both are lower power?

    Will hub gear boxes designed for bicycles withstand the torque of a 500-700 watt electric motor?

    How much of the stopping of a bicycle is done by the front wheel? The rear wheel? I ask this because I want to put a disk brake on one of the wheels of my ebike and want to know which one will provide the most benefit.

    What is the safest maximum speed of a bicycle?

    Sorry for the hodgepodge of questions...not all are strictly related to ebikes but all have an impact on my decision making.

  2. #2
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    Hmm, bikes and e-bikes are great for some things, but if I were interested in toting those kinds of loads economically, without alot of exertion, and at faster than a snails pace, I'd consider a moped, scooter or small motorcycle. Why not go that route?

  3. #3
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    If you have been using a particular bike sucessfully for your intended load, why not convert that frame? The idea that a hub motor is unsafe in the front wheel mainly applies to aluminum forks, they can't handle the rotational torque of higher power motors. If yours is steel, then there should be no problem. It is true that a motor driving the chain would benefit much from the ability to use different gear ratios, even more with the huge load you're talking about. Many of the motors typically used for ebikes struggle to get the weight of the rider alone up to speed easily, so I'm not sure any would be able to handle the task without plenty of pedaling.

    As far as wether or not an internally geared hub could handle the extra power - I'm curious about that too, but doubtfull.

  4. #4
    put our Heads Together cerewa's Avatar
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    How much of the stopping of a bicycle is done by the front wheel? The rear wheel? I ask this because I want to put a disk brake on one of the wheels of my ebike and want to know which one will provide the most benefit.
    On dry pavement, a regular bike (or motorcycle) will have almost all of its weight shift to the front wheel if you stop as fast as you can, meaning the rear brake becomes useless. If you put 100 pounds of cargo over the rear wheel and ride on wet pavement, the rear brake will be about as important as the front brake. Overall, the front brake is more important. You need a fork and wheel (hub) made for a disc brake in order to add a front disc brake.
    Some awesome folks who are working to give Haitians the ability to manage their safety and their lives:
    Haiti Partners

  5. #5
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    mopeds, motorcycles, etc are not allow within city limits of most Chinese cities. I have seen people using ebikes to move refrigerators, chairs, twin beds, long ladders, etc I have considered just buying one of the many chinese electric bikes but I feel that the brakes are really inadequate.
    Last edited by pengyou; 06-26-07 at 11:05 AM.

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