CVT interest

"Dave Larrington" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

In article <[email hidden]>, Jonathan Kaplan

() said:

There used to be a bicycle called the Yankee Bike that was eventually
bought
by Nordic Track before they eliminated it. The claim to fame of this bike
was a single rear rim band brake and a front crank that continuosly
varied
in and out to change the gear ratios.

There was a pully/chain tensioner in the rear with a single cog. All the
"gears" were done by the movement within the crank. Several stems/teeth
would move in and move out to change the diameter of the crank.

Sounds not dissimilar to the Deal Drive which almost, but not quite,
made it to production in the early 1980's.

The weakness of this system is manifold. For one thing the SMALLEST ratio is
dependent on the number of teeth on the front chainwheel at it's lowest
compression. This in turn limits the largest expansion because when the
chain starts pulling straight between the teeth quadrants it rapidly
increases the frictional drag of the chain through the ring.

The sum effect is that the system is continuously variable between two
pretty narrow ratios.

Quoted message said:

This has been an exiting project, and it seems like there is
interest not only in the cycling community, but in the automotive
industry as well - at least among those who don't think they are smart
enough to "know" that a design such as this can't exist.

Excellent. I recommend mortgaging your house and cashing in your kids'
college savings accounts.

In article <[email hidden]>,

Quoted message said:

Quoted message said:

I'm sure you can succeed where so many others have
failed, in part because you have already demonstrated
your keen judgement and razor sharp business acumen
by asking anonymous guys on the 'net for advice.

First of all, I'm not asking for advice, I am using the group to get an
assesment about the market in which this device would try to sell.

Quoted message said:

From all of the responces it is obvious that there is serious

scepticism, if not down right jadedness amoung people. I am not
developing an opposed cone design or a hydrostatic transmission, both
of these designs have serious problems with efficiency that renders
them useless in this application. To clear up the idea of how this
would opperate, it would be a manual transmition, which is to say the
rider at any point could change the gearing to any ratio that they
wish. If you want to stand up and really crank you just shift up. The
differance being that you never get stuck in a possition where the
right gear is right in between the two you have. Thanks for all of the
input. This has been an exiting project,

That last sentence was certainly accurate.

Quoted message said:

and it seems like there is
interest not only in the cycling community, but in the automotive
industry as well - at least among those who don't think they are smart
enough to "know" that a design such as this can't exist.

Tim

If the design exists, then you will need to convince someone before they
will buy it.

For efficiency, you are keeping the roller chain, right? And to "change
the gearing to any ratio" means that you are using a variable size
sprocket so as to avoid gearing with discrete steps.

At least one of those have been marketed, but sank like a stone.
Perhaps you have overcome some of the problems, and if so, I would
certainly be interested in learning more about the technical aspects.
Can you share any information? Patents?

--
Ted Bennett

In article
<[email hidden]>,

Quoted message said:

Quoted message said:

I'm sure you can succeed where so many others have
failed, in part because you have already demonstrated
your keen judgement and razor sharp business acumen
by asking anonymous guys on the 'net for advice.

First of all, I'm not asking for advice, I am using the group to get an
assesment about the market in which this device would try to sell.

Quoted message said:

From all of the responces it is obvious that there is serious

scepticism, if not down right jadedness amoung people. I am not
developing an opposed cone design or a hydrostatic transmission, both
of these designs have serious problems with efficiency that renders
them useless in this application. To clear up the idea of how this
would opperate, it would be a manual transmition, which is to say the
rider at any point could change the gearing to any ratio that they
wish. If you want to stand up and really crank you just shift up. The
differance being that you never get stuck in a possition where the
right gear is right in between the two you have. Thanks for all of the
input. This has been an exiting project, and it seems like there is
interest not only in the cycling community, but in the automotive
industry as well - at least among those who don't think they are smart
enough to "know" that a design such as this can't exist.

Bicyclists do not need a CVT. How about 5% jumps in gears
from 1:2 to 5:1? 48 gears if my arithmetic is accurate.

--
Michael Press

in message <[email hidden]>, Tom

Kunich (') said:

"Simon Brooke" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

in message <[email hidden]>, Ryan

And an opposed-cone system is a variant of belt drive. I just wish I
could find some efficiency figures for it, but thus far I can't.

It's my guess that the SIZE of an opposed cone belt drive is simply out
of scale.

Opposed cone systems as used in motor scooters are very small indeed. The
'dernies' used to pace velodrome cyclists use them, so they can clearly
transfer the power to pull a cyclist up to race speed. Size isn't
inherently a problem. The potential problems are ability to transfer
sufficient torque with reasonable belt life, and overall efficiency.

Jobst's objections with regard to the step-up ratio are an irrelevance,
since the step-up can be handled in the final drive chain. His
objections with regard to torque transfer are not an irrelevance and may
genuinely be a killer for the idea, since, as he rightly points out,
motor scooter engines rev two orders of magnitude higher than racing
cyclists. But I'd still like to see figures rather than assertions.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; ... exposing the violence incoherent in the system...

in message <[email hidden]>, Tom

Kunich (') said:

Tim, the market really isn't there but you can assume it is. You can
also assume whatever you like about writers such as Jobst Brandt who is
a rather famous cyclist and not particularly unknown mechanical
engineer who worked for various places such as the Porche racing team
and a long stent at Hewlitt-Packard.

If someone came up with a CVT design which was as efficient as a
derailleur, which was no heavier than a derailleur, and which was
reasonably reliable, and which the UCI didn't immediately ban, racing
cyclists would buy it in droves. While all of those things are
significant engineering challenges, nothing that's been said so far
proves that they're impossible.

I'd also point out that while the derailleur system is highly reliable
under road racing conditions, it's much less reliable under mountain
bike conditions, and mountain bike racers might well tolerate a small
efficiency deficit if it was compensated by a significant increase in
reliability. A broken or bent derailleur on a mountain bike is usually a
lost race.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

'graveyards are full of indispensable people'

Quoting Simon Brooke <[email hidden]>:

Quoted message said:

I'd also point out that while the derailleur system is highly reliable
under road racing conditions, it's much less reliable under mountain
bike conditions, and mountain bike racers might well tolerate a small
efficiency deficit if it was compensated by a significant increase in
reliability.

All the ones buying Rohloffs seem to, anyway.
--
OPTIONS=name:Kirsty,menustyle:C,female,lit_corridor,standout,time,showexp,hilit
e_pet,catname:Akane,dogname:Ryoga,fruit:okonomiyaki,pickup_types:"!$?=/,scores:
5 top/2 around,color,boulder:0,autoquiver,autodig,disclose:yiyayvygyc,pickup_bu
rden:burdened,!cmdassist,msg_window:reversed,!sparkle,horsename:Rumiko,showrace

Per Simon Brooke:

Quoted message said:

and mountain bike racers might well tolerate a small
efficiency deficit if it was compensated by a significant increase in
reliability.

For whatever it's worth, an MTB racer that checked out my Rohloff-equipped FS
said that the extra two pounds would cost him races.
--
PeteCresswell

Simon Brooke said:

If someone came up with a CVT design which was as efficient as a
derailleur, which was no heavier than a derailleur, and which was
reasonably reliable, and which the UCI didn't immediately ban, racing
cyclists would buy it in droves.

Your list? I think you left out "and tossed in a free pony."

Carl Fogel said:

Quoted message said:

Quoted message said:

> I can't imagine how you can design a CVT for bicycling, because
> torque is much higher than that of a small car, there being a
> trade-off between rotational speed and torque. Humans operate at
> about 50 to 100 rpm, 20 times slower than a motor vehicle engine.
> Beyond that, most vehicle transmissions are step-down gears that
> reduce rpm rather than a step-up transmission as on a bicycle
> which runs as much as 1:5 ratio. Beside that, mechanical CVT's
> work on friction, making this even more difficult.

http://www.sheldonbrown.com/brandt/continuous.html

Quoted message said:

Quoted message said:

Quoted message said:

I agree that a good bicycle CVT will probably not happen in our
life time. However, I don't agree with your arguments:

Quoted message said:

Quoted message said:

Quoted message said:

1) A 250 lb. rider standing on a 7.5 in. crank arm generates 156
lb-ft of torque. The Audi A4 has a CVT with a V6 engine with 207
lb-ft of torque.

Quoted message said:

Quoted message said:

That is what you estimate but I have seen over 500 lb-ft torque in a
sprint or just standing still on Filbertreet (31.5% grade, much less
riding up it.

Quoted message said:

[snip]

Quoted message said:

I'm not following the torque figures.

Quoted message said:

Assuming an ordinary 6.9 inch (175mm pedal arm), we've got a lever
0.574 feet long.

Thanks for the arithmatic check. I divided the crank length (in feet)
into the pedal force instead of multiplying and that makes a big
difference. My number should have read 175 lb-ft from roughly 300lbf
on the pedal. I'm sure there are stronger thrusts from some riders.

Jobst Brandt

On Tue, 06 Jun 2006 11:17:10 +0100, Simon Brooke
<[email hidden]> wrote:

[snip]

Quoted message said:

Jobst's objections with regard to the step-up ratio are an irrelevance,
since the step-up can be handled in the final drive chain.

[snip]

Dear Simon,

It may be worth pointing out that normal-transmission motorcycles tend
to reverse the final chain-drive gearing found in the bicycle world.
(I don't know what CVT motorcycles use.)

That is, bicycles tend to run a big front and small rear sprocket, a
53-52-50-42-39-30 front and an 11-32 rear.

Motorcycles tend to run the reverse of that, with a tiny front
countershaft sprocket and a huge rear sprocket.

At 20-25 mph, my touring bike is usually running 53 x 11, while my
ancient trials machine is running 14 x 52 (much higher chain speed).

This sort of difference might complicate adapting motorcycle CVT to
bicycle CVT.

There are other reasons why motorcycles use real transmissions instead
of the bizarre derailleurs found only on bicycles. High RPM engines
and chain speeds require much heavier chains and gears than low RPM
bicycles with low chain speeds.

(When I was 12, I learned to ride on a Honda Trail 90, whose 4-speed
automatic no-clutch transmission sat in a fuzzy no-man's land between
CVT and a normal transmission, with a small lever under one foot peg
to throw the beast's gears into low range, like a jeep or a front 39
tooth derailleur. It was clumsy, but it worked.)

Cheers,

Carl Fogel

On Tue, 06 Jun 2006 08:11:01 -0400, "(PeteCresswell)" <[email hidden]>

Quoted message said:

Per Simon Brooke:

Quoted message said:

and mountain bike racers might well tolerate a small
efficiency deficit if it was compensated by a significant increase in
reliability.

For whatever it's worth, an MTB racer that checked out my Rohloff-equipped FS
said that the extra two pounds would cost him races.

Dear Pete,

It might, but . . .

Plug in MTB, 250 watts, and 5 miles on this calculator:

http://www.kreuzotter.de/english/espeed.htm

Make the imaginary rider do 15 miles--5 at 7% climb, 5 at 7% descent,
and 5 at level.

Then add 2 pounds to his bike and do it again.

default +2
weight lbs
5 miles 7% grade 37:02.2 37:30.0
5 miles 0% grade 15:27.8 15:27.8
5 miles -7% grade 8:52.5 8:51.0
------- --------- ------- -------
15 miles loop 61:22.5 61:48.8

Less than 30 seconds per hour, probably important to a racer, probably
an invisible 0.7% difference to anyone else

How often do we hear an MTB racer moaning that he needed to lose two
pounds to win a race?

Cheers,

Carl Fogel

Simon Brooke said:

in message <[email hidden]>, Tom

Kunich (') said:

"Simon Brooke" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

in message <[email hidden]>, Ryan

And an opposed-cone system is a variant of belt drive. I just wish I
could find some efficiency figures for it, but thus far I can't.

It's my guess that the SIZE of an opposed cone belt drive is simply out
of scale.

Opposed cone systems as used in motor scooters are very small indeed. The
'dernies' used to pace velodrome cyclists use them, so they can clearly
transfer the power to pull a cyclist up to race speed. Size isn't
inherently a problem. The potential problems are ability to transfer
sufficient torque with reasonable belt life, and overall efficiency.

Ain't the way it's done Simon. You use a fixed gear that drives one
cone inside of the rear hub. You press in the steel outer cone into the
hub. You then need a friction-ball mechanism to transfer the inner
power to the outer hub and a mechanism that will infinitely move the
balls in and out along the cones.

The problem is STILL that there isn't enough space to make the cones of
sufficient size for balls of sufficient size to maintain frictional
coupling to work with any efficacy.

For the uninformed - originally computers were all mechanical and I was
a computer engineer. Electronics is gooooooooooooood.

Quoted message said:

Jobst's objections with regard to the step-up ratio are an irrelevance,
since the step-up can be handled in the final drive chain. His
objections with regard to torque transfer are not an irrelevance and may
genuinely be a killer for the idea, since, as he rightly points out,
motor scooter engines rev two orders of magnitude higher than racing
cyclists. But I'd still like to see figures rather than assertions.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; ... exposing the violence incoherent in the system...

in message <[email hidden]>, Tom

Kunich (') said:

Simon Brooke said:

in message <[email hidden]>, Tom

Kunich (') said:

"Simon Brooke" <[email hidden]> wrote in message
news:[email hidden]...
> in message <[email hidden]>, Ryan
>
> And an opposed-cone system is a variant of belt drive. I just wish
> I could find some efficiency figures for it, but thus far I can't.

It's my guess that the SIZE of an opposed cone belt drive is simply
out of scale.

Opposed cone systems as used in motor scooters are very small indeed.
The 'dernies' used to pace velodrome cyclists use them, so they can
clearly transfer the power to pull a cyclist up to race speed. Size
isn't inherently a problem. The potential problems are ability to
transfer sufficient torque with reasonable belt life, and overall
efficiency.

Ain't the way it's done Simon. You use a fixed gear that drives one
cone inside of the rear hub. You press in the steel outer cone into the
hub. You then need a friction-ball mechanism to transfer the inner
power to the outer hub and a mechanism that will infinitely move the
balls in and out along the cones.

That's one way of doing it. It isn't the only way of doing it and, as you
so cogently point out, for bicycle applications it isn't the right way
of doing it.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; When your hammer is C++, everything begins to look like a thumb.

in message <[email hidden]>,

(') said:

On Tue, 06 Jun 2006 11:17:10 +0100, Simon Brooke
<[email hidden]> wrote:

[snip]

Quoted message said:

Jobst's objections with regard to the step-up ratio are an irrelevance,
since the step-up can be handled in the final drive chain.

[snip]

It may be worth pointing out that normal-transmission motorcycles tend
to reverse the final chain-drive gearing found in the bicycle world.
(I don't know what CVT motorcycles use.)

[snip]

Quoted message said:

This sort of difference might complicate adapting motorcycle CVT to
bicycle CVT.

Oh, certainly. I wouldn't advocate doing that. I'm merely making the
observation that motorcycle CVT transmits similar (indeed, up to
substantially more) power in a very reasonably sized package. It's true
that it does so at higher RPM with lower torque, and this may mean that
in the bicycle application you can't get enough 'grip' between cone and
belt, or that belt tension sufficient to get enough grip causes too much
loss or premature belt failure.

Whatever you do to change bicycle transmissions in the future will not
come as something 'bolted on' to existing transmission systems, but as a
radical redesign probably of the bottom bracket area. All other things
being equal it would make sense to move delicate transmission components
into the centre of the bike where they do not contribute to unsprung
weight and are relatively protected from accidental damage. Mind you,
that's not an argument about CVT, rather it's one about transmission
design generally.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

The Conservative Party is now dead. The corpse may still be
twitching, but resurrection is not an option - unless Satan
chucks them out of Hell as too objectionable even for him.

Per [email hidden]:

Quoted message said:

Less than 30 seconds per hour, probably important to a racer, probably
an invisible 0.7% difference to anyone else

Definitely invisible to Yours Truly... but I'm about as far toward the other end
of the Barney-Racer spectrum as one can get.

Quoted message said:

How often do we hear an MTB racer moaning that he needed to lose two
pounds to win a race?

My guess is that most serious racers don't have two pounds of non-muscle to
lose.
--
PeteCresswell

On Tue, 06 Jun 2006 18:38:03 -0400, "(PeteCresswell)" <[email hidden]>

Quoted message said:

Per [email hidden]:

Quoted message said:

Less than 30 seconds per hour, probably important to a racer, probably
an invisible 0.7% difference to anyone else

Definitely invisible to Yours Truly... but I'm about as far toward the other end
of the Barney-Racer spectrum as one can get.

Quoted message said:

How often do we hear an MTB racer moaning that he needed to lose two
pounds to win a race?

My guess is that most serious racers don't have two pounds of non-muscle to
lose.

Dear Pete,

If they haven't got 2 pounds of non-muscle to lose, then they're at
less than 2% non-essential body fat, which is unlikely. These sites,
for example estimate body fat for cycling athletes at 5% to 15%, or
7.5 to 22.5 lbs for a 150-lb rider:

http://www.brianmac.demon.co.uk/fatcent.htm

http://www.sport-fitness-advisor.com/bodyfatpercentage.html

This one estimate "essential" fat at 2-4%:

http://www.healthchecksystems.com/bodyfat.htm

(Personally, I take more extensive precautions against a hard winter.)

In any case, the much-maligned extra-2-lb Rohloff (I know you like
yours, so don't misunderstand me) might more than make up for its
Lilliputian obesity by eliminating much of the fuss and trouble in MTB
racing of missed shifts and cross-chaining decisions.

Like you, however, I doubt that MTB racers will shift in the Rohloff's
direction, much less a mythical CVT.

Cheers,

Carl Fogel

Per [email hidden]:

Quoted message said:

(Personally, I take more extensive precautions against a hard winter.)

I've been trying to lose 10 lbs for over fifteen years. Last time I checked,
I'd gained about nine...
--
PeteCresswell

On Tue, 06 Jun 2006 19:22:27 -0400, "(PeteCresswell)" <[email hidden]>

Quoted message said:

Per [email hidden]:

Quoted message said:

(Personally, I take more extensive precautions against a hard winter.)

I've been trying to lose 10 lbs for over fifteen years. Last time I checked,
I'd gained about nine...

Dear Pete,

Your body is merely testifying against predictions of global warming.

Cheers,

Carl Fogel

"Simon Brooke" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

in message <[email hidden]>, Tom

Kunich (') said:

Ain't the way it's done Simon. You use a fixed gear that drives one
cone inside of the rear hub. You press in the steel outer cone into the
hub. You then need a friction-ball mechanism to transfer the inner
power to the outer hub and a mechanism that will infinitely move the
balls in and out along the cones.

That's one way of doing it. It isn't the only way of doing it and, as you
so cogently point out, for bicycle applications it isn't the right way
of doing it.

The problem is that it is the most practical system and it is limited by the
materials possible to use. The main problem is that the torque transmission
necessary is too high for small systems without positive engagement. That
pretty much requires toothed wheels and chains.

We have had 140 years of development of the bicycle and the highest rate of
development was in the early 1900's. I suspect that people who believe
there's a better way have never even BEGUN to look into the patents that
were issued by the tens of thousands on bicycle mechanisms.

We are today riding the finest developments of the finest minds. Hell, even
Jobst has added SOMETHING to bicycling engineering by formalizing wheel
theory.

There is always the possibility that someone will come up with something new
that's a step forward but the chances of that are so small as to be
practically nil.