Does a 4 Stroke Frame Mount Engine Cause Resistance When Pedaling?

Discussion in 'General Questions' started by Wayneburg, Jun 27, 2008.

  1. Wayneburg

    Wayneburg New Member

    I didn't know if I should post this in the 4 stroke forum or the Frame Mount forum, so I decided to post here just to be safe.

    I'm interested in a 4 stroke engine that is frame mounted, but I want to know if there will be any resistance on the pedals when the engine is not running? Just so you know I'm interested in using the bicycle's gears together with the engine for increased efficiency and speed. My thinking is, I could use a lower powered engine to do the same amount of work that a higher powered engine without gears would.

  2. JemmaUK

    JemmaUK Guest

    Re the resistance question:

    If the engine has a manual clutch then so long as the clutch properly disengages you should have no extra drag from the engine set up. A centrifugal one will cause an amount of drag because its always partially engaged.

    Re: multispeed transmission.

    With a geared system you will get more performance out of a given engine - this is basically because you'll effectively have more than powerband for a given motor.
    In a 5 speed transmission for example the ratio for first would be high - which would mean you get alot of torque for starting off but the top speed would be correspondingly low - as you work up the gears to top you may (certainly in car applications) have a ratio as low as 1:1.5 or something similar which means a high road-speed but low available torque (hence that horrible juddering when you try and start off in 3rd gear).
    Theoretically you could get a 1.6hp 32cc engine that is good for 30+mph as a single speed to get a much higher top speed with a geared system and appropriate ratios - but at the cost (in higher gears) of being able to deal with hills etc.

    Jemma xx
  3. HoughMade

    HoughMade Guest

    It depends on what gearbox you have. To my knowledge, there are no manual clutches available for the fram mount 4 strokes, only centrifugal.

    The Grubee gearbox comes standard with a freewheel 11 tooth sprocket and the drive sprocket may be disengaged from the gearbox- there is little resistance when pedaling normally, no more than a 2 stroke where you are moving the chain itself while pedaling, but nothing more.

    the JL Hoot gearbox does not have a freewheel (I believe, someone please correct me if I am wrong) and cannot be disenaged. When pedaling you turn the gears in the gearbox, not the engine, of course, because with the engine not turning, the clutch is not engaged. there is more resistance, but I have the Grubee and have never ridden the Hoot, so I cannot compare the feel, only the mchanics.