Belt Drives - the future?

[Tom Sherman]

Michael Press wrote:
> In article <[email protected]>,
> Tom Sherman <[email protected]> wrote:
>
>> [email protected] 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

 

[Nigel Cliffe]

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/

 

[Rob Morley]

In article <[email protected]>, Nigel Cliffe
[email protected]lid 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.

 

[Peter Clinch]

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 [email protected] http://www.dundee.ac.uk/~pjclinch/

 

[Paul Rudin]

Peter Clinch <[email protected]> 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.

 

[Peter Clinch]

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 [email protected] http://www.dundee.ac.uk/~pjclinch/

 

[CJ]

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.

 

[BikerAlex]

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.