Pre Build Questions

Discussion in 'Frame Mounted Engines' started by edrock, Sep 9, 2008.

  1. edrock

    edrock New Member

    I am starting the pre-build process, figuring out what i want to build, what is possible, best practices, so on.

    My first question has to do with the drive train. I have looked at many of the bikes on here, and see that the majority of them have 2 chains. One chain for
    the motor that propels the rear wheel, and the other standard bicycle chain. Although I want the bike I build to be both pedal and motor powered, is there a way to use only 1 chain that can be used for both? I have seen some of the bikes on hear, using a gearing system..with a rear derailleur. I do not want/need more than one gear in the rear. Is there a system for engaging the drive/disengaging the drive from the front sprocket(that the pedal is connected too)? I would understand the need for 2 sprockets in the front, one that is able to disengage from the crank when the motor is on, and one that is fixed to the crank when using the pedals for power.

    Any help, definition, terms that could push me in the right direction would be appreciated

    Though I understand the frustration in users not searching before posting, since I'm new to the terminology/concepts with this type of bicycle setup, I sometimes face questions in which knowing more about this type of bicycle setup would help me in figuring out what terminology would help me find results in the search feature.

    Thank you.

  2. HoughMade

    HoughMade Guest

  3. edrock

    edrock New Member

    I did see this system, and it looks more like the direction i would like to go in. I would rather not deal with the rear derailleur or gears. Im assuming this system would work with a single speed gear in the rear? If so, this looks like the solution for me.

    Thank you for the quick reply!
  4. mralaska

    mralaska Member

    At the risk of expounding on a topic of which I have no personal experience, the sickbikeparts jackshaft is on my want list but it would seem a tragic waste of its greatest gift to use it without gears. If you mount it without gears, I might recommend start budgeting for the addition of a Nuvinci hub which is another term you will see bandied about that seems to be a sweet transmission that works from within the rear hub. I can almost bet money that you have reconsidered your position on gears by the time you get the motor broken in.
  5. Ghost0

    Ghost0 Guest

    I could not agree more, there is very little advantage to the system without the gears. Not only would you not have variable gears to pedal but you would also not be able to alter the gearing of the engine which the 2 stroke so desperately needs. As mentioned the NuVinci is a great alternative to a derailleur or mechanical internal hub. But it is expensive.
  6. edrock

    edrock New Member

    After spending a good part of the day reading more and more, I might as well include some gear options, as it seems to make a lot of difference. I stumbled across Clotho's felt build and fell in all sorts of love. This is almost exactly what I was imagining my build to be like.

    Gearing is something I would like to pursue, however I would like it to be a in hub option. I know there are several options for internal geared hubs (thanks to sheldon brown for the list), however has anyone used any of them? All the reading I could find was either external gearing or NuVinci. The only thing that kinda ruins NuVinci for me, is having to cut/re-thread the spokes (or find perfectly sized ones)/ and rebuild the rear wheel. Will I burn/wear out an internal mechanical hub any differently than an external mechanical gearset would wear out? I also read that even though NuVinci is supposed to be a friction"less" drive, I read that you still need to back off the throttle when shifting. Is that true, still true, and i would guess a mechanical internal hub would need the same attention.

    When looking at the advantages of the jackshift system, i do see the benefits of gearing, however I think (unless i am not understanding the other mount/drive train systems available) having only "one" chain that connects to the rear, having the other side of the rear hub to put disc brakes on, and having to only worry about one side of the bike catching you clothing is a pretty big advantage. Aesthetically there is quite a bit of advantage, and too me, less is more. (image of Clotho's bike)

    Thank you for the replies, this is really helping me out.
    Last edited: Sep 9, 2008
  7. edrock

    edrock New Member

    Another quick question about the jackshift system. I read in one clotho's posts that he would ride his bike motor "on" to the park. Once he arrived, he would take the chain off the drive(from the motor) and ride around pedal powered.

    Is this step necessary, I understand there is a freewheel in the front, but is there no way to lock out the chain drive from the moto, so that you could just pedal around?

    This an important feature for me, as when im riding with family/friends that do not have motor driven cycles, i would like to be able to pedal along with them.. though i know they are going to have somewhat of an easier time, due to less weight on their bike.

    thank you
  8. Ghost0

    Ghost0 Guest

    By removing the chain that runs from the jackshaft to the chainring it eliminates a little drag and noise associated with turning the jackshaft and chains but is not at all necessary. Just pull the clutch in and pedal just like a normal bike. Most people have commented that the jackshaft actually makes pedaling the bike easier because the amount of mass that needs to be pedalled decreases and the bike will freewheel. With the stock set up the other chain and sprocket are always turning which adds a lot of drag to the system so you can't coast very well.
  9. edrock

    edrock New Member

    Sweet. that was my main concern with the jackshaft system. There is a very very very very good chance that I will be going with that upfront. Now to descide if I want to go with a NuVinci hub, or an alternative mechanical internal 7 or 8 speed SRAM/Shimano hub.
  10. Ghost0

    Ghost0 Guest

    I would like to make a suggestion though. We recommend that you install the motor in the stock configuration and run it that way through break in. The advantages are that, especially if you are new to motorized bicycling, you can get all of your systems functioning correctly and weed out any potential problems concentrating specifically on the engine, the only drawback is a little extra work. Since the front freewheel system is the method of starting the engine we have found that trying to start a new motor over and over puts added stress on the unit and may cause it to fail prematurely.
  11. QuadManiac

    QuadManiac Member

    Another option is to get the motor with the recently available pull start and centrifugal clutch. The centriugal clutch has a one-way bearing (equivalent to a free-wheel) so you can still start the motor using the pedals and it still has the stock clutch too. It does make it wider (6 7/8") but i mounted my engine a little higher (with the SPB shift kit) and filed just a bit from the Sick supplied wider cranks and voila, works like a charm.

    Had it together for about a week now, have 30 miles on it (with the 6 speed rear derailleur gearing driven by the SBP jackshaft) and it is sweet! Starts cold with the choke within 2 or 3 pulls on the pull start or just one good push on the pedals... with the low gear, acceleration from a stop with the centrifugal clutch is immediate even on hills and the cent clutch seems to engage very quickly without slipping much at all. It pulls hills with ease in low and in the top gear I'm seein 29 mph even with lower breakin RPM's. I only use the standard clutch while using the pull starter, to pedal w/o engine or to back the bike up.

    BTW, i originally started with an Autobike Classic which has the rear derailleur controlled by rear wheel speed, esentially a simple automatic transmission. This was fun, but after riding it a bit i realized that the shift points and seperation were not very appropriate for an engine driven bike. ALways seemed to be in the wrong gear at the wrong RPM even after adjusting the system to try to optimize... so I went back to a regular thumb shifter controlled derailleur and am extremely happy now; and plan on changing to a twist grip shifter soon.

    After minor adjustments this has turned out to be exactly what I was hoping for.

    Good luck in your build!
    Last edited: Sep 12, 2008