CVT interest

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

Quoted message said:

Quoted message said:

I am curious about the amount of interest out there in both the
recreation/commuting community and the racing community for a true CVT
a manual gear system that had infinite variability, the same gear range
as a 27 speed system, no loss in efficiency and no weight gain. What
do you think?

Well, since the stated criteria have never been approached, and are
exceptionally unlikely to be met by anything with reasonable
durability and an affordable cost, there's not much point, is there?

Seriously, every CVT thus far introduced has either failed to live up
to the claims made for it, and/or has had a short life expectancy,
and/or has been overly expensive; some combination of the three.

The record in the automotive field is similar. Hondas with a CVT have
a near-zero value at wholesale in this area; not even the least
reputable garage-lot car peddlers will take a chance on them.

Hmmm... not sure about that. here in the UK a number of small cars use CVT,
and work. Honda Jazz (Fit) and Toyota Yaris for example.

I wouldn't put one on a bike though.

Quoted message said:

If someone came to me with a claim that they had such a device, I
would regard the person as a prima facie liar. I might be polite, I
might be courteous, I might listen to the pitch, but my checkbook
would remain out of sight and I would sign nothing.

--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
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Skippy
E&OE

Skippy said:

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

Quoted message said:

Quoted message said:

I am curious about the amount of interest out there in both the
recreation/commuting community and the racing community for a true CVT
a manual gear system that had infinite variability, the same gear range
as a 27 speed system, no loss in efficiency and no weight gain. What
do you think?

Well, since the stated criteria have never been approached, and are
exceptionally unlikely to be met by anything with reasonable
durability and an affordable cost, there's not much point, is there?

Seriously, every CVT thus far introduced has either failed to live up
to the claims made for it, and/or has had a short life expectancy,
and/or has been overly expensive; some combination of the three.

The record in the automotive field is similar. Hondas with a CVT have
a near-zero value at wholesale in this area; not even the least
reputable garage-lot car peddlers will take a chance on them.

Hmmm... not sure about that. here in the UK a number of small cars use CVT,
and work. Honda Jazz (Fit) and Toyota Yaris for example.

I wouldn't put one on a bike though.

One local auto transmission specialist calls them "disposable
transmissions". As of the last time I discussed it with him, his
experience had been that in non-energetic usage, they were good for up
to 120K miles, but not much more...and when they failed, there was no
point in attempting repair, as they were not economically rebuildable
to any acceptable level of reliability. Parts availability and
service tech may have improved, but I don't see a mad rush to replace
the conventional trans with the CVT concept in the mainstream fleets.
I have to think there's more than one reason.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
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Simon Brooke said:

... But continuously variable? Yes, that would be a
win. If it wouldn't, no one would want a 27 speed.

There is a significant percentage of the cycling community that
questions the necessity for 24 or 27, let alone 30; a CVT merely makes
the range selection less easily guaged unless you're going to have a
rather long throw on the control lever or a long rotation on the
gripshift. (And if it had a gripshift, I'd be riding something else
in any event; I can't stand them. But that's just me.)
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

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

Quoted message said:

I am in the process of developing such a device. I was trying to get
an idea of the market interest before I begin funding the prototype, as
I am funding the project with my own money. I did not post that to
begin with because I wanted responces about a desire for the concept,
not a debate about weather or not people think I actually have a design
that works. I will not post a description of the mechanism. Thanks
for your responce.

Tim, unless there's something in it for you I suggest not bothering. That
implies that you can make a CVT cheaper than a derailleur system with no
more losses. I sincerely doubt that you can do that.

Tom

Tim Knodel said:

I am in the process of developing such a device. I was trying to
get an idea of the market interest before I begin funding the
prototype, as I am funding the project with my own money. I did not
post that to begin with because I wanted responses about a desire
for the concept, not a debate about weather or not people think I
actually have a design that works. I will not post a description of
the mechanism. Thanks for your response.

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

Jobst Brandt

in message <[email hidden]>, Tom

Kunich (') said:

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

Quoted message said:

I am in the process of developing such a device. I was trying to get
an idea of the market interest before I begin funding the prototype,
as
I am funding the project with my own money. I did not post that to
begin with because I wanted responces about a desire for the concept,
not a debate about weather or not people think I actually have a
design
that works. I will not post a description of the mechanism. Thanks
for your responce.

Tim, unless there's something in it for you I suggest not bothering.
That implies that you can make a CVT cheaper than a derailleur system
with no more losses. I sincerely doubt that you can do that.

I don't know if he can do it with no more losses, but he can certainly do
it cheaper. CVT is inherently a lot simpler than a derailleur; there
would be many fewer moving parts, and they would not require the same
degree of precision.

Cone on the bottom bracket axle; opposed cone on a drive shaft a few
inches above the bottom bracket; drive belt; cable actuated belt guide;
output sprocket; single freewheel sprocket on the back axle.

The things I don't know are

(i) what the inherent losses of a belt-and-cones CVT are;
(ii) how wide the belt would need to be to transfer the torque without
slipping (and without breaking in a reasonable service life);
(iii) what the maximum practical angle on the cones is.

The length of the cones is obviously limited to the free length of the
bottom bracket axle between the bearings, so the range between the
highest and the lowest available ratios depends on the angle that will
practicably work, and the diameter at the small end that the belt will
effectively run on.

Opposed cone CVTs were developed in DAF cars in the Netherlands, post
war. The cars were low powered and the transmission was simple and
reliable. Subsequently, as the market demanded more powerful cars, there
were problems with the amount of torque the system could transfer - if
too much, the belt would slip on the cones and burn. This is why
opposed-cone CVT is not much used on modern cars - it won't handle the
torque (although modern Honda and Fiat CVTs use steel belts). But CVT is
widely used in low power motor scooters, and the technology is well
understood, light, simple, and quite capable of transferring the amount
of torque a racing cyclist can produce; so it's not in the least
impossible that these will be available for bicycles in the next few
years. What's critical is the efficiency.

In motor scooters, the belt guide is automatically actuated by a simple
mechanical spring driven system. While a CVT does not have to be
automatic, I can see automatic CVT being useful to, for example, time
triallists, who would simply dial in their preferred cadence and go for
it.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/
;; Our modern industrial economy takes a mountain covered with trees,
;; lakes, running streams and transforms it into a mountain of junk,
;; garbage, slime pits, and debris. -- Edward Abbey

Quoted message said:

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

An assessment for bicycles I agree with but spoiled by its lack of
recognition in 2003 when it was written, that CVTs were (and still are)
in reasonably widespread use in cars in Europe and the Far East made by
Ford, Fiat, Nissan and others. They include the BMW Mini which does, I
believe even sell quite well in the USA.
--
Tony

"Anyone who conducts an argument by appealing to authority is not using
his intelligence; he is just using his memory."
- Leonardo da Vinci

Simon Brooke said:

Subsequently, as the market demanded more powerful cars, there
were problems with the amount of torque the system could transfer - if
too much, the belt would slip on the cones and burn. This is why
opposed-cone CVT is not much used on modern cars - it won't handle the
torque (although modern Honda and Fiat CVTs use steel belts). But CVT is
widely used in low power motor scooters, and the technology is well
understood, light, simple, and quite capable of transferring the amount
of torque a racing cyclist can produce;

What's the max torque of a low power motor scooter?

Simon Brooke said:

This is why
opposed-cone CVT is not much used on modern cars - it won't handle the
torque (although modern Honda and Fiat CVTs use steel belts). But CVT is
widely used in low power motor scooters, and the technology is well
understood, light, simple, and quite capable of transferring the amount
of torque a racing cyclist can produce;

Have a read of
http://en.wikipedia.org/wiki/Continuously_variable_transmission and be
surprised at the number of cars with up to 3.5 litre engines
successfully running CVTs as well as tractors, combine harvesters etc.
http://www.tumpline.com/stackyard/news/2005/10/jcb_fastrac.html

--
Tony

"Anyone who conducts an argument by appealing to authority is not using
his intelligence; he is just using his memory."
- Leonardo da Vinci

in message <[email hidden]>, Tony Raven

(') said:

Simon Brooke said:

This is why
opposed-cone CVT is not much used on modern cars - it won't handle the
torque (although modern Honda and Fiat CVTs use steel belts). But CVT
is widely used in low power motor scooters, and the technology is well
understood, light, simple, and quite capable of transferring the
amount of torque a racing cyclist can produce;

Have a read of
http://en.wikipedia.org/wiki/Continuously_variable_transmission and be
surprised at the number of cars with up to 3.5 litre engines
successfully running CVTs as well as tractors, combine harvesters etc.
http://www.tumpline.com/stackyard/news/2005/10/jcb_fastrac.html

Most of the tractors are on variable hydrostatic systems, surely? I've
seen details of a prototype bike with a VHST transmission, but was not
at all persuaded that it was efficient.

I have seen some bloody big opposed cone systems on combine harvesters,
though, and the torque they transfer must be monstrous.

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

;; So, before proceeding with definitive screwing, choose the
;; position most congenital.
-- instructions for fitting bicycle handlebars

In article <[email hidden]>,

Simon Brooke said:

in message <[email hidden]>, Tony Raven

(') said:

Simon Brooke said:

This is why
opposed-cone CVT is not much used on modern cars - it won't handle the
torque (although modern Honda and Fiat CVTs use steel belts). But CVT
is widely used in low power motor scooters, and the technology is well
understood, light, simple, and quite capable of transferring the
amount of torque a racing cyclist can produce;

Have a read of
http://en.wikipedia.org/wiki/Continuously_variable_transmission and be
surprised at the number of cars with up to 3.5 litre engines
successfully running CVTs as well as tractors, combine harvesters etc.
http://www.tumpline.com/stackyard/news/2005/10/jcb_fastrac.html

Most of the tractors are on variable hydrostatic systems, surely? I've
seen details of a prototype bike with a VHST transmission, but was not
at all persuaded that it was efficient.

I have seen some bloody big opposed cone systems on combine harvesters,
though, and the torque they transfer must be monstrous.

Variable hydrostatic transmissions are not at all efficient compared to
gear-, chain-, or probably even viscous-coupled transmissions. But they
get the job done in certain specific circumstances.

Note that even belt drive is inefficient enough to be confined to
specialty commuter bikes and folding bikes, and it's not that bad.

--
Ryan Cousineau [email hidden] http://www.wiredcola.com/
"I don't want kids who are thinking about going into mathematics
to think that they have to take drugs to succeed." -Paul Erdos

in message <[email hidden]>, Ryan

Cousineau (') said:

In article <[email hidden]>,

Simon Brooke said:

in message <[email hidden]>, Tony Raven

(') said:

Simon Brooke wrote:
> This is why
> opposed-cone CVT is not much used on modern cars - it won't handle
> the torque (although modern Honda and Fiat CVTs use steel belts).
> But CVT is widely used in low power motor scooters, and the
> technology is well understood, light, simple, and quite capable of
> transferring the amount of torque a racing cyclist can produce;

Have a read of
http://en.wikipedia.org/wiki/Continuously_variable_transmission and
be surprised at the number of cars with up to 3.5 litre engines
successfully running CVTs as well as tractors, combine harvesters
etc. http://www.tumpline.com/stackyard/news/2005/10/jcb_fastrac.html

Most of the tractors are on variable hydrostatic systems, surely? I've
seen details of a prototype bike with a VHST transmission, but was not
at all persuaded that it was efficient.

I have seen some bloody big opposed cone systems on combine
harvesters, though, and the torque they transfer must be monstrous.

Variable hydrostatic transmissions are not at all efficient compared to
gear-, chain-, or probably even viscous-coupled transmissions. But they
get the job done in certain specific circumstances.

Note that even belt drive is inefficient enough to be confined to
specialty commuter bikes and folding bikes, and it's not that bad.

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.

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

For office use only. Please do not write or type below this line.

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.

--
Dave Larrington - <http://www.legslarry.beerdrinkers.co.uk/>
They came for Eamonn Holmes; I think I'm right in saying that I
applauded.

Simon Brooke said:

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.

Don't worry about efficiency, you can't build such a transmission for
a bicycle for the reasons I gave. Mechanically it would weigh at
least as much as a complete bicycle of the latest kind. High input
torque and a 5:1 step up ratio is prohibitive.

Hydrostatic drive is inefficient but ideal for tractors and
construction equipment, being robust and truly continuous with a swash
plate variable ratio. The motor is located in the wheel and does not
require drive shafts and the like, only a stator against which to
drive. Of course there is electric drive as we have on diesel motor
driven railroad engines and large earth moving machinery, and of
course as piston steam engines of the past, but none of these fits the
definition of a gear box with positive engagement gears, the holy
grail of CVT enthusiasts.

Jobst Brandt

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

Jobst Brandt

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

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.

2) Stepping up speed should be no less efficient than
stepping it down.

3) I agree that current CVT's are less efficient than
conventional bike chain drives. However, because some CVTs
"work on friction" doesn't mean that they are grossly
inefficient. Your tires "work on friction" too but that
type of friction does not soak up energy because there is no
relative sliding motion between the friction surfaces.

The major drawbacks of a bicycle CVT using existing
technology are cost, size, and weight.

Bill Sp? 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.

Quoted message said:

Quoted message said:

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

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:

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.

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:

2) Stepping up speed should be no less efficient than stepping it
down.

"Should" but it isn't.

Quoted message said:

3) I agree that current CVT's are less efficient than conventional
bike chain drives. However, because some CVTs "work on friction"
doesn't mean that they are grossly inefficient.

Engagement and disengagement sliding occurs and that is where losses
are incurred. These are high because the pressure is high enough to
cause metal-to-metal contact in asperities of the surfaces. That is
also where wear occurs.

Quoted message said:

Your tires "work on friction" too but that type of friction does not
soak up energy because there is no relative sliding motion between
the friction surfaces.

Compare contact pressure and you'll find a great difference.

Quoted message said:

The major drawbacks of a bicycle CVT using existing technology are
cost, size, and weight.

Well... isn't that what I said?

Jobst Brandt

Quoted message said:

Bill Sp? 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.

Quoted message said:

Quoted message said:

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

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:

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.

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.

[snip]

Dear Jobst,

I'm not following the torque figures.

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

To generate 500 foot pounds of torque on that short arm, the rider has
to push down with 500/0.574 pounds of force, or about 870 pounds,
doesn't he?

I can put about 200 pounds onto a pedal with my weight, but I rather
doubt that I can pull down an additional 670 pounds with my arms while
bent over the handlebars and standing on one foot.

Am I just goofing up the calculations above?

Or am I missing things completely, and you're talking about chain
tension or something else involved with transmission?

Cheers,

Carl Fogel

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.

Tim

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

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 you DO have a good idea you needn't use it on bicycles since there will
be multiple uses for it in industry.

So by all means carry on if you do have a good idea. We can always lie and
tell everyone how we supported you ever inch of the way.

"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.

The modern bicycle has been improved for well over a hundred years.
Improving on it may not be impossible but significant improvements are.