shaft driven drivetrain (internal hub) - dynamicbicycles

Discussion in 'Cycling Equipment' started by jasong, Aug 30, 2005.

  1. jasong

    jasong New Member

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    You guys seen this?

    Special BB/crankset with no chainrings coupled to a shaft drive, coupled to an internal geared hub. Great idea.

    http://www.dynamicbicycles.com/
     
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  2. artmichalek

    artmichalek New Member

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    Pierce was building these over 100 years ago. If they weren't so terribly heavy and inefficient, we'd all be riding them by now.
     
  3. jasong

    jasong New Member

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    Are you saying that this model is inefficient and heavy, or previous? Because they're listing weights around 28lbs and efficiency at 99%, irregardless of gear selection and cleanliness of drivetrain.

    Which seems to contradict a bit the efficiency specs that have been available for internally geared hubs. They've not been at 1%, especially in every gear ratio. That would also assume no loss in the shaft.

     
  4. cydewaze

    cydewaze New Member

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    It's funny how many "new" ideas are actually recycled old ideas.

    One that comes to mind is the refrigerators with the freezers on the bottom. when I bought my new fridge last fall, the salesman tried to talk me into one of the "new" freezer-on-the-bottom models, and told me how it was the newest and greatest thing, and how eventually all refrigerators would be like that some day.

    So I told him about the old freezer-on-the-bottom model my parents had back in the 70's, and how the top-freezer models were billed as the latest and greatest. I even remember the TV ads with the kid jumping and trying to reach the ice cream, but it was too high.

    I wish we recycled everything as consistently as we recycle ideas.
     
  5. AussieRob

    AussieRob New Member

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    Actually they are not saying it weights 28lbs:

    "Our mountain and hybrid/road bikes weigh approximately 31-33 lbs...."

    http://www.dynamicbicycles.com/chainless/technology.php

    I asume you have to send the bike back to the factory if there is an issue. My mechanic has 20 years experience, but I doubt he has ever worked on one of these before. If a car transmission needs work, why wouldn't this?

    I think I'll stick with chorus.
     
  6. jasong

    jasong New Member

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    You're right, I had remembered the low number they said for "traditional recreational bikes".

    I wish bikes were as maintenance free as reliable cars. Many cars require nothing more than an oil change for 100,000 miles. That's 20 years of heavy riding for most people. And they're infinitely more intricate devices.

    I don't believe there is anything complicated in their design that any bike mechanic wouldn't be able to diagnose. The complexity is in the Nexus hub which is Shimano's issue.

     
  7. jasong

    jasong New Member

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    I don't think this is really a recycled old idea, unless one would say any innovation in cycling really is a recycled old idea since the chain driven bike is a hundred years old. Or a 30 speed drivetrain a few years ago a recycled old idea, or even a few years earlier ago 27 speeds.

    The gear range (and the number of steps in that range, and the efficiency) that they are sporting [with internally geared hubs] has only been possibly in the last 2 years or so. The Rohloff 14 speed hub, SRAM's, and now Shimano's 8 speed (which is supposed to be very efficient in all gears) have not been available that long.

    What other shaft driven multi-geared bikes are you familiar with?

     
  8. artmichalek

    artmichalek New Member

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    Diagnosis isn't the problem. It's getting replacement parts. And I'm not sure about the efficiency numbers they give. On one page they say 99%, and on another they say 95%. For one thing they neglect to mention that you have to backpedal internally geared hubs in order to shift them. They also claim that "Chain-Derailleur" bikes have "sharp spokes".
     
  9. jasong

    jasong New Member

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  10. jasong

    jasong New Member

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    Definitely agreed - proprietary systems might make the bike unusable in a few years if the company doesn't succeed and the bike has a problem. At least the internal gear hub is an off the shelf product.

    Yes, everything I've read about the internal gear hub says that chain drivetrain efficiencies can't be emulated except for a small subset of the total gears. Coupling that with the shaft definitely makes their claim sound incredulous.

     
  11. garage sale GT

    garage sale GT New Member

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    I used to want one of those bikes but decided to upgrade my mountain frame instead.

    The site claims the unit is tested to 1,000 inch pounds. Big deal. It may be stronger than that, of course. Maybe they did not test it to failure. However...if your bike has a six inch crank you can generate 1000 inch pounds just by standing on the pedal with one leg, if you weigh more than 166 pounds.

    Just imagine if a reasonably fit cyclist fitted the thing with toeclips or spd's. you could exceed the rated torque several times over. If you are powering up a hill and the shaft fails, injury is virtually guaranteed.

    P.S. I don't think you have to backpedal a Shimano internal gear hub to shift. I have used several older 3 speeds and a late model 4-speed Nexus, and you just have to ease up on the power momentarily (i.e. pedal very lightly for a second), and you feel it go into the new gear.
     
  12. garage sale GT

    garage sale GT New Member

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    I was in a bike shop today and there was a muddy, knobby tired, shaft drive bike on the repair stand. I did not take note of the brand but it looked like the ones currently on the web, they all look the same to me...from the same factory in Taiwan perhaps?

    Apparently, someone in or around Naperville, IL is trying one out. I just wonder what they weigh.

    The website for one of the companies said their machine was tested to 1000 in*lb of torque, which is very little as I pointed out; however, maybe the company that runs the particular site I saw just doesn't want to stick their neck out.
     
  13. wilmar13

    wilmar13 New Member

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    I saw one in a duty free store in the São Paulo airport a few months back. Looked it over quick and while my intial impression was "wow that is innovative", after 20 seconds more evaluation I decided it was clearly positioned towards the same demographic as the "auto-shift-bike".

    Yeah 1000 in*lb is not much force at all but again it is being marketed to people who will only ride it once around their housing development and then let it collect dust.
     
  14. Retro Grouch

    Retro Grouch New Member

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    I call bullshit!

    99% efficiency with two sets of bevel gears? I don't think so. How'd they measure that? It's going to take more than somebody just saying it's so to convince me.
     
  15. threaded

    threaded New Member

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    I'd be charitable and say they meant 99% of theoretical maximum efficiency, and forgot to print two words. So that'd be 97%*97%*99%=93 and a bit.
     
  16. fauxpas

    fauxpas New Member

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    Of shaft drive motorbikes, they lose power with changes of direction in the drive train and make the bike rise and fall with variations in power. Also, they there is a twisting of the chasis.

    I'd like to see an 18 speed gearbox attached to the bike version though...

    The animatic only shows a single speed...

    http://www.dynamicbicycles.com/Animation/dynamicpopup.html
     
  17. Ignore Me

    Ignore Me New Member

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