Re: Mini-engine positioning on bicycle ?

Discussion in 'Road Cycling' started by [email protected], May 6, 2006.

  1. In article <>, Werehatrack <[email protected]> wrote:

    > On 5 May 2006 01:39:40 -0700, "Chalo" <[email protected]> wrote:
    > >The central problem of power assist is the same as that of human power:
    > >it is in short supply. Variable gearing helps make the most of a small
    > >amount of available power, and when all else is equal, it is preferable
    > >to a single ratio.
    > >
    > >...the only argument for a single gear ratio that seems to apply
    > >to a gas motor is that of mechanical simplicity.


    Werehatrack wrote:
    > Simplicity, weight and cost, actually, but I didn't mention weight and
    > cost in the original post because the subject of a motor/gearbox power
    > unit wasn't what had been posited. The OP had advocated using a, IC
    > motor driving a der system. I've seen this tried several times; it
    > self-destructs in short order.

    Ok, apart from the 'self destruct', what geometries have you seen ?

    The 1 hp often advertised, seems absurd. As stated the engine power
    should be half of an athelete's; so that you can get athelete's performance
    from a relaxed pace. Then also the drive-train forces don't exceed

    > Electric drive through a der can be
    > done, but as you correctly pointed out, it's a poor plan. Electric
    > motors work best when they run at rated load and speed, and having the
    > der available would put the motor speed and loading out of the control
    > of the engineer and into the hands of the rider; range and motor life
    > reduction due to the rider's attempts to max out the motor's
    > capability would, as you posit, surely result.

    If electric motors have restricted speed range, all the more reason for

    > I still hold that if a motorcycle is the desired result, then that's
    > what should be built; common bicycles are designed for human power,
    > and adapt poorly to having engines added. Power augmentation from a
    > battery and electric motor is more easily retrofitted, and far cleaner
    > as well. Its sole current disadvantage is lack of support in
    > infrastrucure; there's almost never a place to recharge at your
    > destination, so range is severely limited. Gas engines, although
    > nearly unlimited in range, have more adaptation problems, and with the
    > ones presently available, are high in pollution.
    > --

    The question was NOT about pollution. Read the subject again ;-) ,
    how to mount the engine to:
    * use the existing pedal gearing,
    * achieve gearing down from the motor,
    * achieve 'disengaging' of motor.

    Thanks for info .

    == Chris Glur.

  2. In rec.bicycles.misc [email protected] wrote:
    >> --

    > The question was NOT about pollution. Read the subject again ;-) ,
    > how to mount the engine to:
    > * use the existing pedal gearing,
    > * achieve gearing down from the motor,
    > * achieve 'disengaging' of motor.

    What's required is a rather specialized transmission. To the
    best of my knowledge nobody makes one.

    One would start by moving the freewheel to the chainring,
    so the pedals could stop while the chain keeps moving. This
    I believe has been done but is not common. Next, one has to
    add an extra sprocket to the chainring, driven by the engine
    at human cadence, necessitating a large speed reduction from
    the engine. Finally, some sort of freewheel or clutch is required
    'tween engine and human power train, so that a pedaling human does
    not have to spin the engine power train. Lastly, the engine is
    apt to need a clutch to permit engine starting and idling.

    When all is said and done there will be many pounds of drivetrain,
    a tiny engine and a substantial loss of the "civility" that makes
    bicycles acceptable in environments where motor vehicles are not.

    I don't mean to discourage you, but I've pondered the same problem
    and find it highly satisfactory to ride both motorcycles and
    bicycles in different environments.

    If you do a Google search on "power assist" in combination with bicycle-
    related keywords you'll likely turn up what you're looking for. I've not
    found anything simpler than keeping a motorcycle in the garage.

    Good luck,

    bob prohaska