Belt Drives - the future?

On Fri, 01 Feb 2008 14:17:44 +0000, Peter Clinch wrote:

dabac wrote:

I wonder how the bike (marketing) industry would cope with a
CVT-equipped bike? With no longer being able to use the number of gears
to separate categories, what would they do instead?

Google NuVinci, it's been released in the fairly recent past and
according to all the reviews I've seen thus far works very well indeed.
the current Gotcha is the hub weighs about 4 Kg, which is a lot in bike
terms. But it's version 1, I imagine it will improve.

Personally, I'd love CVT, just as soon as the costs and weights come
down (previous implementations have been rather inefficient AIUI, but
from what i read the NuVinci has got at least most of that sorted).

Well, it's about 8 lbs and there's a suspicious absence of efficiecy
figures on their website, which typically for lubricated CVT drives is in
the range of 80-90%. Roller chains (can) do much better.

Dave Larrington said the following on 01/02/2008 13:42:

o Can't be retrofitted to an existing bike (or can it?)

Not unless you take a hacksaw to your chainstay. Orange basically did
this, then cut'n'shut the join.

--
Paul Boyd
http://www.paul-boyd.co.uk/

Nigel Cliffe said the following on 01/02/2008 13:23:
I can see how it may work well off-road.

I'm not so sure - what happens when a great big splot of mud or a stone
lands on the belt? Where does it go when it reaches the pulleys?

--
Paul Boyd
http://www.paul-boyd.co.uk/

On Fri, 1 Feb 2008 13:42:17 -0000, Dave Larrington wrote:

In ,
Mark T pleasegivegenerously@warmail*turn_up_the_heat_to_ reply*.com.invalid
tweaked the Babbage-Engine to tell us:
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?

o Can't be retrofitted to an existing bike (or can it?)

Oooo, yes.

That'd have to be a design challenge; either a separable belt, a detachable
chainstay, or a frame made to be disposable if the belt should fail.

I bet Shimano goes for #3.

Mark T 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?

Some questions that come to mind:

1) Has it been independently tested to see if efficiency really is as high
as with a conventional chain - and at high torque? Or do we just have the
designer's word for it?

2) Could the belt ever slip?

3) How critical is belt tension? Will the usual methods of tensioning be
adequate?

4) How long will it last? Will it wear out from friction?

5) What kind of sprockets will be needed, and what chainsets and hubs will
they fit?

6) How much will the chain and sprockets cost?

~PB

In article ,
says...
On Fri, 1 Feb 2008 13:42:17 -0000, Dave Larrington wrote:

In ,
Mark T pleasegivegenerously@warmail*turn_up_the_heat_to_ reply*.com.invalid
tweaked the Babbage-Engine to tell us:
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?

o Can't be retrofitted to an existing bike (or can it?)

Oooo, yes.

That'd have to be a design challenge; either a separable belt, a detachable
chainstay, or a frame made to be disposable if the belt should fail.

I bet Shimano goes for #3.

Or:
http://mos.bikeradar.com/images/news...day/Cannodale-
conceptedit-798-99.jpg
--
Cheers,
Mark

Paul Boyd usenet.is.worse@plusnet wrote:

Nigel Cliffe said the following on 01/02/2008 13:23:
I can see how it may work well off-road.

I'm not so sure - what happens when a great big splot of mud or a stone
lands on the belt? Where does it go when it reaches the pulleys?

mmm yes, think just water on the fan belt in a car.

roger
--
www.rogermerriman.com

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?

needs to be a fair bit cheaper to make or make faster bikes? hopefully
both. being simple and easy maintain probably will not sell at least
well.

the problem is the chain is attually very good.

roger
--
www.rogermerriman.com

bugbear wrote:

dabac wrote:

o hub gears only ..
You need to consider that snowmobiles, certain cars and various other
vehicles have been using belt drives for years under the catchy phrase
of CVT (continously variable transmissions).

IIRC such transmissions have losses that aren't
acceptable on a HPV.

BugBear

on a about town bike, i'd be quite happy to take some losses for some
conviences

roger
--
www.rogermerriman.com

On Feb 1, 4:26 pm, "Pete Biggs"
p...@pomegranateremovehighlyimpracticalfruitbiggs .tc wrote:
Mark T 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?

Some questions that come to mind:


2) Could the belt ever slip?
It looks like a toothed belt to me so no, it will never slip. (Much as
the cambelt on a car never slips - at least, if it does you've got a
very expensive problem to sort out)


3) How critical is belt tension? Will the usual methods of tensioning be
adequate?
Probably not very although efficiency might vary a lot if it's not
quite right. On something like a Brompton where you have to have a
chain tensioner then the tension should always be right.

At 95% of the efficiency of a chain, and no maintenance or oil at all
I'd be very interested in this on something like the Brompton which is
a "get me about" bike. At 99% efficiency I'd want this on the
Brompton. Not sure about my other bikes - would be nice on the
windcheetah but the width might be an issue and there would have to be
some sort of different gearing.

Tim.