Mechanical sustainability with large engines?

Discussion in 'General Questions' started by af6rf, Sep 6, 2008.

  1. af6rf

    af6rf New Member

    So I was all set to go for a chain-drive kit with the GX-50, and I talked to a mechanic friend of mine who rained on my parade. The concerns he raised are:

    1) putting a 50cc engine on a system designed for a relatively weak human powerplant would lead to unacceptable wear on bike components, especially frame, forks and (obviously) brakes.

    2) Lots of hills where we live, and without a variable-speed transmission even a well-made engine is going to have a tough time doing steep grades without putting a ton of wear on drive-train components and the engine itself.

    He bet me dinner that I'd have trouble finding people who had put a lot of miles on a system such as what I've described without constantly making repairs. So let's hear it...!
    Last edited: Sep 6, 2008

  2. s_beaudry

    s_beaudry Member

    You should base your judgement off more then one opinion....

    I am sure more then a few will chime in here with several thousand miles on thier MB's.
  3. af6rf

    af6rf New Member

    <You should base your judgement off more then one opinion.>

    Well yes. That is why I am here.
  4. kerf

    kerf Guest

    You don't mention which system you're considering. I'm running a Staton chain drive and your friend is wrong, the system is plenty robust after 1500 miles. From what I understand of the GXH50, it has plenty of torque for hills.
  5. af6rf

    af6rf New Member

    I'm not familiar with that particular type of chain-drive system, but I'm not sure it matters in this case. The question is what sort of effect the forces exerted by the engine would have on the bike, especially since a rear-mounted engine would produce a very large upwardly-directed force on the rear fork. Any chain-drive system is going to produce force in this manner, no?

    I'm not questioning whether the engine is capable of generating the force, there's no question the GXH50 is a pretty mighty powerplant for the application. What I'm asking is how much stress pulling steep grades, without the benefit of a VST, is going to put on the drive-train.
  6. kerf

    kerf Guest

    The bicycle I'm riding is on it's third engine, second drive unit, close to 2500 miles. Your friend is wrong, motorize one if you want to, while you think about it, I'll be riding.
  7. Happy Valley

    Happy Valley Active Member

    I think it's fair question. I recented stated in another thread:

    My thinking is based on the grind of road wear, at more constant sustained speeds afforded by powered assist. I don't think engine torque is a big issue because the engines that are sized to be feasibly mounted at all don't generate that much torque in comparison to human power.

    To illustrate, I had a conversation with a pretty sharp young mechanic at a local bike shop a while ago. We were talking about internal rear hubs and I asked him what he tthought of the NuVinci. He said "not much".

    I wondered if he thought they wouldn't be rugged enough or something and said I knew guys who put them on MBs and they seemed to have no issues handling the torque. He replied torque wasn't the issue as a human rider was able to able to generate far more apllied torque on the pedal strokes than any small engine ever could. (He rides competitively and his stated dislike of the Nuvinci was weight and power loss.)

    When I thought about it I think he's right about that. However I think road wear from more constant sustained speeds and vibration are other matters. I ride more with a motorized bike so that naturally means more maintenance.
    Last edited: Sep 6, 2008
  8. af6rf

    af6rf New Member

    Wow, you have to swap an engine every 800 miles? That's like what, five tanks fulls of fuel? Thanks, kerf! In your own peculiarly hostile way, you've answered my question.
  9. kerf

    kerf Guest

    I didn't swap because I had to, all other engines are still on the road. I swapped in search of horse power, running 4.2 at this time. In quiet mode top end is 40, in loud mode top end is pushing 50. First time I've been called "peculiarly hostile" for giving someone what they ask for, takes all kinds I guess.
  10. Mountainman

    Mountainman Active Member

    Where the rubber meets the road on a MB

    some thoughts from a former bicycle shop owner

    I am nearing the 15 hundred mile riding time on my MB
    even though I know it's a good idea - due to extra vibration
    I didn't use Lock-Tight on nuts and bolts when doing my assembly
    NOT ONE THING HAS CAME LOOSE ON MY MB - to date anyway

    I did break one spoke just a while back - I guess that's more than loose
    cause -- I am not sure
    I honestly do - hear about some broken spoke problems here on site
    I have made an opinion in regards to spokes breaking --
    I am leaning towards believing
    that spokes today are not made as good as when I owned a bicycle shop
    back then 1070-73 few spokes were breaking on newer bikes sold than today
    at least that's the way I remember it --- long time ago

    but -- in regards to drive units that are attached directly to spokes
    this would have some extra wearing effect -- note - to keep an eye on

    frame - again - should be checked occasionally for cracks - welded points
    some here on site take about drilling into frame for certain mounting
    that if done wrong -- could weaken a frame

    here's a fact -- most of us know
    give a wild boy a bicycle -- he can tear it up in no time
    broken frame, broken spokes, worn out tires from skidding, bent handlebars ect.

    how we treat our EQUIPMENT

    we could go on and on here -- BOTTOM LINE
    small motor bikes have been ridden -- since way back when

    if we buy a quality bicycle and engine - drivetrain ect
    we should reasonably expect -
    many carefree miles with some maintenance required

    if you buy one -- Ride That Thing - Mountainman
    Last edited: Sep 7, 2008
  11. HoughMade

    HoughMade Guest

    I am running a Honda GXH50. Once it was all set up, ran like a champ. I blew it apart for paint, but road it a lot looking kind of rat rod (see sig pic).

    The Honda engine is much smoother than the Chinese 2 strokes, a lot less vibration, and many with those engines have put thousands of miles on.

    That being said, these contraptions do require more frequent maintenance than a non-motorized bike or a scooter. If gas and go is what you want- forget this. This is for people who don't mind lavishing some care on their mounts, or, like me, absolutely love wrenching. You can't use cheap parts or be haphazard and expect anything to stay together. For instance, I put high quality, heavy duty wheels on (11 ga spokes), but even knowing the wheel supplier is a quality operation (Husky), I repacked the wheel bearings myself for certitude. The same goes for the bearing on the fork/headset bearings and the crank bearings. You get the idea.

    I have no idea why a fork or frame with a larger 4 stroke would wear down. What you will see is more frequent wheel bearing and brake maintenance. No big deal. The original motorcycles were bicycles with engines (pre-WWI). Even then, some were running in excess of 1000ccs (yes, I said one-thousand).
    Last edited by a moderator: Sep 7, 2008
  12. Mountainman

    Mountainman Active Member

    There it is from HoughMade ----- 1,000cc MBs -- those were VERY COOL !

    it's all in understanding the limits of our equipment

    I would love to have a MB (bicycle) with all kinds of hp
    knowing what we are working with - much
    being gentle when we have to - can rip with a slight touch
    I have been thinking about a true beast of a MB a lot lately

    I know that I could keep this beast up and running - much respect
    but - I will also guarantee you
    my son - would tear this thing apart - in no time !!!!

    At many times - it's all do to - the rider..

    While repairing equipment for the City -- saw this a lot
    poor operators = torn up machinery...

    Happy Riding from - Mountainman
  13. Drunkskunk

    Drunkskunk Member

    I know its a slightly diffrent animal, but I run an electric bike at upto 4 horsepower. Its a hub motor, so no gears. After several thousand miles, the only major wear was to the rear tire. I was running too small and too cheap a tire back there. Oh, and some spoke breakage from cheap spokes and too much power. No problems now running 14 guage DT swiss spokes and a good rear tire.

    There's no problem adding the extra power, if you do so responsibly.
  14. duivendyk

    duivendyk Guest

    A lot of people have opinions about things they know little about,usually negative ones,rather like the NIH syndrome.The NV hub is on the heavy side,other internally geared hubs are not all that light either.I suppose he likes deraileurs.Severe vibration in frame mounted bikes with light frames is a cause for concern in my opinion, but these sweeping blanket condemnations are stupid,it all depends on the system inplementation.
  15. loquin

    loquin Active Member

    Also, keep this in mind - the small engines are able to produce more horsepower than a human can maintain. However, humans can GREATLY exceed the torque that one of these motors can produce. A motor's torque is smooth, whereas a human's is pulsed. If a 200 pound rider is standing up while peddling, his entire weight is supported by first one, then the other peddle, which works out to (assuming a 7 inch radius on the peddles) about 116 foot-pounds. A Honda GX35 motor provides about 1.4 lbf·ft at 5,500 rpm, and geared through one of Staton's 18.75:1 gearboxes, outputs about 26.25 foot-pounds from the gearbox.

    And, there is ZERO net 'upwards force' on the rear fork. This is because any force caused by the motor 'pulling upwards' is exactly balanced by the down-rods from the motor to the rear axle.

    BTW. The GX50 has about 50% more torque than the CX35, so, the 26 foot pounds would be raised to about 40 foot-pounds. And, that's still much less than a human can produce.
    Last edited: Sep 7, 2008
  16. Alaskavan

    Alaskavan Guest

    I'm not sure I understand the question. Things wear out comensurate to the amount and style of use. You could put a motor on a bike and have it last forever (don't ride it). You can totally destroy a bike without a motor in short order (ride like me). I have over 3,000 miles on my trike. The brake pads are pretty worn, and I think I have a bearing starting to go. Oh well.
  17. duivendyk

    duivendyk Guest

    Gradual deterioration is one thing,catastrophic failure in the wrong place (an intersection for instance) quite another,greater speed means that the performance of bearings increases in importance (regular lubrication,but the forces can actually be lower as Loquin has pointed out.Brake performance is certainly more critical,esp the front brake!,more mass and more speed and a high CG and therefore more weight transfer to the front.Practice emergency braking!.
  18. graucho

    graucho Active Member

    Well lets see....LOL
    9,556 threads, 103,270 Posts, and 1,623 Active Members can prove your mechanic friend wrong. :cool:
  19. i agree is all about how you take care of things check things often dont ride as fast as you can down bumpy roads just basic maintance and my g>> watch for cars otherwise your bike may not need to last just my 2cents too many peeps gettin hurt these days
  20. SirJakesus

    SirJakesus Guest

    I agree with most of you guys. It all depends on your system and how you ride it. If you're nice to the bike it'll wear as a normal bike would just faster since you're traveling much greater distances than when pedaling. Weight increase on most systems isn't considerable and is well within most bicycles designed load. It can definitely be done reliably as long as it's made well and not abused.