Belt Drives - the future?

Discussion in 'UK and Europe' started by Mark T, Feb 1, 2008.

  1. Tom Sherman

    Tom Sherman Guest

    Michael Press wrote:
    > In article <fo0o66$d66$3@registered.motzarella.org>,
    > Tom Sherman <sunsetss0003@REMOVETHISyahoo.com> wrote:
    >
    >> carlfogel@comcast.net aka Carl Fogel wrote:
    >>> ...
    >>> The relative size of the rear sprockets reminds us that bicycles gear
    >>> up, while engine-powered vehicles gear down--even at low RPM, an
    >>> engine turns an order of magnitude faster than legs.
    >>> ...

    >> Mr. Fogel should be aware that large marine diesel engines operate in
    >> very much the same RPM range as a hominid cyclist.

    >
    > What? Each cylinder fires 1 to 1.5 Hz?
    >

    Go here: <http://www.hyundai-engine.com/engine/engine.asp?aa=a2>.

    Click on "Marine Engine" from the top menu, use the "Products" tab on
    the left, and choose "Two Stroke Engine". For example the S80MC6 has an
    operating range of 59 to 76 RPM, which is not unlike what many a cyclist
    would pedal.

    --
    Tom Sherman - Holstein-Friesland Bovinia
    "And never forget, life ultimately makes failures of all people."
    - A. Derleth
     


  2. Nigel Cliffe

    Nigel Cliffe Guest

    Simon Brooke wrote:
    >> 4) How long will it last? Will it wear out from friction?

    >
    > In car engine applications, typically 50,000 miles at average about
    > 3,500 rpm, or something like 262 million rotations of the whole
    > chain. Or, put it differently, the lifetime of several bicycles.
    > Belts outlast chains in camshaft applications by a factor of about
    > two - and those are chains which are running in an oil-bath, which
    > ours aren't.


    Getting off topic for u.r.c,
    Car cam chains, totally enclosed within engine oil system, last
    indefinitely.
    My BMW has cam chains, its done 110,000 miles and they don't have a service
    replacement date/time/mileage. Most of my neighbours have cars with
    cambelts with replacement schedules between 30,000 and 60,000 miles. (A
    Ducati motorcycle's engine cambelts seem to need replacing weekly; I think
    its really 7500 miles, but it felt like weekly when I owned one. But Ducati
    value systems are a law unto themselves)






    --
    Nigel Cliffe,
    Webmaster at http://www.2mm.org.uk/
     
  3. Rob Morley

    Rob Morley Guest

    In article <fo422u$jh$1@news.albasani.net>, Nigel Cliffe
    me@invalid.invalid says...
    > Simon Brooke wrote:
    > >> 4) How long will it last? Will it wear out from friction?

    > >
    > > In car engine applications, typically 50,000 miles at average about
    > > 3,500 rpm, or something like 262 million rotations of the whole
    > > chain. Or, put it differently, the lifetime of several bicycles.
    > > Belts outlast chains in camshaft applications by a factor of about
    > > two - and those are chains which are running in an oil-bath, which
    > > ours aren't.

    >
    > Getting off topic for u.r.c,


    Not really - it's just a good example of why a fully enclosed oil-bath
    chain transmission is a good idea for bicycles. I don't know why nobody
    makes them for derailleur bikes - modern materials like carbon fibre and
    PTFE would make it quite feasible.

    > Car cam chains, totally enclosed within engine oil system, last
    > indefinitely.
    > My BMW has cam chains, its done 110,000 miles and they don't have a service
    > replacement date/time/mileage. Most of my neighbours have cars with
    > cambelts with replacement schedules between 30,000 and 60,000 miles. (A
    > Ducati motorcycle's engine cambelts seem to need replacing weekly; I think
    > its really 7500 miles, but it felt like weekly when I owned one. But Ducati
    > value systems are a law unto themselves)
    >

    ITYM Ducati /valve/ systems. :)
     
  4. Peter Clinch

    Peter Clinch Guest

    Simon Brooke wrote:

    > A Rohloff has as wide a range of gears as a typical 27 speed mountain bike
    > setup. You want more than that?


    No, but I would like to be able to tune different steps between the
    ratios easily and relatively cheaply. Only way to do that with a
    Rohloff is multiply /everything/ by a constant.

    Pete.
    --
    Peter Clinch Medical Physics IT Officer
    Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
    Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
    net p.j.clinch@dundee.ac.uk http://www.dundee.ac.uk/~pjclinch/
     
  5. Paul Rudin

    Paul Rudin Guest

    Peter Clinch <p.j.clinch@dundee.ac.uk> writes:

    > Simon Brooke wrote:
    >
    >> A Rohloff has as wide a range of gears as a typical 27 speed mountain bike
    >> setup. You want more than that?

    >
    > No, but I would like to be able to tune different steps between the
    > ratios easily and relatively cheaply. Only way to do that with a
    > Rohloff is multiply /everything/ by a constant.


    If you have a chain tensioner then you can use a regular set of chain
    rings and a front mech with a speedhub.

    You can also use a mountain drive or speed drive
    <http://www.schlumpf.ch/antriebe_engl.htm> although that starts to get
    expensive on top of a speedhub.
     
  6. Peter Clinch

    Peter Clinch Guest

    Paul Rudin wrote:

    > If you have a chain tensioner then you can use a regular set of chain
    > rings and a front mech with a speedhub.


    On the one hand, yes, but on the other you're throwing away some of what
    you've paid a lot of money for, and more to the point given the topic of
    this thread, won't work with one of them noo fangled drive-belt thangs...

    > You can also use a mountain drive or speed drive
    > <http://www.schlumpf.ch/antriebe_engl.htm> although that starts to get
    > expensive on top of a speedhub.


    That won't help do what I wanted though, which is reduce the gear range
    a little by making them closer together.

    Pete.
    --
    Peter Clinch Medical Physics IT Officer
    Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
    Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
    net p.j.clinch@dundee.ac.uk http://www.dundee.ac.uk/~pjclinch/
     
  7. CJ

    CJ Guest

    On 1 Feb, 12:53, Mark T
    <pleasegivegenerously@warmail*turn_up_the_heat_to_reply*.com.invalid>
    wrote:
    > <www.bikebiz.com/news/29367/Carbon-belt-drives-are-standardised>
    >
    > Now that there's a new standard out there, does anything stand in their
    > way?


    I've downloaded all the technical data available from Gates and
    searched it for efficiency. The best I can find is a claim that it can
    be as high as 98%, accompanied by a good-looking but ultimately
    useless plot of efficiency against ... er, they don't say what! I can
    only guess it's plotted against transmitted power, as that's all that
    makes sense.

    In this graph the synchronous (carbon) belt efficiency rises rapidly
    from zero to flat-line at 97.8%. This curve is always reassuringly
    higher than that given for a comparable V-belt, which slowly heaves
    it's way up to 94% then declines. Efficiency of any drive drops off
    dramatically at low levels of transmitted power, since all involve
    some irreducible friction, so it takes a certain amount of power to
    turn the drive even when there is no output at all.

    Unfortunately they don't also give a curve, however vague, for chain.
    However we know that the efficiency of chain drives also holds up very
    well at low power levels.
    The design problem for bicycle transmissions, that chain deals with so
    well, is that the average human engine has a miserably low power
    output but can nevertheless apply an inconveniently high torque when
    stalled. I think it's proven that carbon belt can handle the torque
    and that its friction is low enough not to be a problem for an athlete
    in a mountain-bike race. The question remains unanswered as to whether
    it's low enough not to absorb an uncomfortable proportion of the
    average rider's much smaller power output.

    I expect that the niche for this drive will be the kind of city
    cyclist who wants to keep clean on a naked-looking bike, i.e. no bulky
    chaincase, who is also young and strong enough not to be bothered if
    their cool, uncluttered machine is a bit harder to pedal. I expect
    these bikes will be designed with an elevated chainstay, to facilitate
    belt fitting.

    I'm also curious about what sort of mountain-bike races these drives
    were tested in. The situation of a stone dropping onto the chain or
    belt, staying there and being carried back into mesh with the rear
    sprocket, seem simultaneously more likely and more damaging in the
    case of a wide, flat and rubbery belt wrapping around a similarly wide
    alloy sprocket, rather than the narrow plates of hardened steel of an
    interpenetrating chain and sprocket.
     
  8. BikerAlex

    BikerAlex New Member

    Joined:
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    Just wanted to throw it out there that recently I put a belt drive on my bike. It can be retrofitted to an existing bike. Veer makes a split belt that is spliced and riveted to fit around any frame. I'm psyched on it. Thought y'all would appreciate another option. veercycle.com has more info.
     
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