Continous variable transmission???

I don't know that it would work on a bike, but I love to floor my Saturn
Vue and watch the tach jump up to 5500 rpm and stay there until I am
going as fast as I care to...

The CVT is a significant part of why I bought my Vue. Since I read
about automotive CVT's in Popular Mechanics back in the 70's I always
thought they were neat. Of course there seem to have been issues with
their implementation since they discontinued them.


--
dgregory57

On Sat, 22 Oct 2005 06:51:50 +1000, dgregory57
wrote:

I don't know that it would work on a bike, but I love to floor my Saturn
Vue and watch the tach jump up to 5500 rpm and stay there until I am
going as fast as I care to...

The CVT is a significant part of why I bought my Vue. Since I read
about automotive CVT's in Popular Mechanics back in the 70's I always
thought they were neat. Of course there seem to have been issues with
their implementation since they discontinued them.

DAF couldn't manage to make them sturdy enough to be used with serious
engines, so they became known for bad performance, although it was more
the crappy engines and tiny cramped cars than particularly the fault of
the CVT. Also were mofos to maintain, originally. Plus DAF was just too
small a manufacturer.

Materials science has improved, and now they're extremely useful.


Jasper

Andrew Price wrote:

How do losses through hub gears compare with that?

See http://www.ihpva.org/pubs/HP52.pdf
for results of efficiency tests of several drivetrains,
some with derailleurs and some with internal hub gearing.

Tom Ace

On 21 Oct 2005 16:21:17 -0700, "Tom Ace" wrote:

See http://www.ihpva.org/pubs/HP52.pdf
for results of efficiency tests of several drivetrains,
some with derailleurs and some with internal hub gearing.

Thanks.

Tom Ace Wrote:
Tomek Li wrote:

Over the years I got used to think that such a transmission would be
no more
than another incarnation of perpetuum mobile. But recently I learned
that
some quite serious people got on the task, with interesting results.

http://www.fallbrooktech.com/NuVinci.asp

I have this terrible feeling of Deja Nu.
See http://www.nupace.com/

I don't see much advantage to continuous variability.
If it's at all less efficient or less reliable, why bother.

Reasonably small jumps between gears are available
with either derailleur or internal hub gearing.

Tom Ace

There may be rare niches where the CVT has some advantages.
If a driveshaft bike were used, some CVT designs could used with the
drivetrain direction changes, giving you the option of not having to
suffer a cascading of both inefficiencies on top of one another-the
drive shaft inefficiencies would not be added to those from the CVT.

Anyone noticed that NuPace has a greater overdrive than any Internal
Gear Hub presently on the market (their direct drive is low, and the
Sturmey 8 will have the same range and overdrive as the NuPace when and
if it becomes available). Could be the market is too small for such a
high overdrive for the bigger internal gear hub makers- NuPace may be
situtated to catch such a market and a CVT may fit the bill,
particularly in the small wheeled commuter-folder arena where
efficiency is not necessarily that big of a priority anyway.

BTW- is NuVinci somehow affiliated with NuPace?


--
meb

meb Wrote:
There may be rare niches where the CVT has some advantages.
If a driveshaft bike were used, some CVT designs could used with the
drivetrain direction changes, giving you the option of not having to
suffer a cascading of both inefficiencies on top of one another-the
drive shaft inefficiencies would not be added to those from the CVT.

Anyone noticed that NuPace has a greater overdrive than any Internal
Gear Hub presently on the market (their direct drive is low, and the
Sturmey 8 will have the same range and overdrive as the NuPace when and
if it becomes available). Could be the market is too small for such a
high overdrive for the bigger internal gear hub makers- NuPace may be
situtated to catch such a market and a CVT may fit the bill,
particularly in the small wheeled commuter-folder arena where
efficiency is not necessarily that big of a priority anyway.

BTW- is NuVinci somehow affiliated with NuPace?


The Sturmy Archer 8 speed is already on the market. At least one OEM
that I know of (Cadillac) is using them.
Dan


--
Dan Burkhart

For Gawd sakes man! Don't let Shimano hear you, they'll go and force us
all to buy a complete new groupo again!

- -

Chris Zacho ~ "Your Friendly Neighborhood Wheelman"

"May you have the winds at your back,
And a really low gear for the hills!"

Chris'Z Corner
http://www.geocities.com/czcorner

wrote:
Tomek Li writes:


Over the years I got used to think that such a transmission would be
no more than another incarnation of perpetuum mobile. But recently I
learned that some quite serious people got on the task, with
interesting results.


The links below I copy from uk.rec.cycling:

http://www.fallbrooktech.com/NuVinci.asp
http://www.evworld.com/view.cfm?sect...le&storyid=841
http://www.californiabicycleracing.o...interbike.html


So, what do you think?


NuVinci is nothing new in CVT's. It has been used in places where it
works bes, low torque smooth continuous motion at a large ange of
speeds. I see no way of making it work reliably on a bicycle both
because it is not suited for the high torque (aka low speed) and
maintenance requirement.

You don't see this type of CVT in motor vehicles for good reason.
Expensive sports cars would not be invensting in 7-speed automatic
transmissions if it were so simple to use a CVT.

er, like /these/ "7-speed" cvt's from honda?

http://world.honda.com/news/2002/4020912.html

toyota have them too.


It isn't only bicyclists who beleive more gears will make then arrive
faster at their goal, but 30-speed derailleur gears is more than the
automotive people desire.

No one has shown that all these gears and ready access to constaznt
shifting has the vague benefites alluded to them.

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

Jobst Brandt

Tomek Li Wrote:
Over the years I got used to think that such a transmission would be no
more
than another incarnation of perpetuum mobile. But recently I learned
that
some quite serious people got on the task, with interesting results.

The links below I copy from uk.rec.cycling

See:

http://www.fallbrooktech.com/NuVinci.asp

http://www.evworld.com/view.cfm?sect...le&storyid=841

http://tinyurl.com/cppx3

So, what do you think?

Jobst?

Cheers,

Tomek Li

Not a true CVT as they assert since the blades would span integral
quantities of links, but an interesting approach to hyper selection
ratios:

http://www.andersoncvt.com/

Not sure it gains a lot over a wide ratio deraileur system either other
than some more marketting muscle through a sophisticated solution to a
simple problem.


--
meb

On Wed, 26 Oct 2005 18:51:16 +1000, meb
wrote:
Tomek Li Wrote:

Not a true CVT as they assert since the blades would span integral
quantities of links, but an interesting approach to hyper selection
ratios:
http://www.andersoncvt.com/

It is a true CVT. There is no mechanism that forces the chain links and
the cones into any sort of engagement with the chain. It is, in fact,
pretty close to how automotive CVTs are constructed. The first DAF CVTs
used a belt of some kind on the cones, and torque and power was limited by
the belt. Modern automotive CVTs on the DAF principle use chains like this
one does.

Jasper