Continuously-variable transmission box in Honda MTB

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

Quoted message said:

Did anyone see the latest issue of _Mountain Bike Action_ featuring
Honda's mountain bike and CVT drivetrain? Any comments?

Van
--
Van Bagnol / v b a g n o l at earthlink dot net / c r l at bagnol dot com
...enjoys - Theatre / Windsurfing / Skydiving / Mountain Biking
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It"

looks heavier than a regular drivetrain

Michael

Michael Paul said:

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

Quoted message said:

Did anyone see the latest issue of _Mountain Bike Action_ featuring
Honda's mountain bike and CVT drivetrain? Any comments?

looks heavier than a regular drivetrain

Michael

Downhill rigs looking more and more like motorcross every year.... sure does
look heavy.

A few car manufacturers have made models with CVT boxes over the years, i
think DAF was the first, but they were riddled with problems, related to
belt slippage and the requirement for very frequent maintainance and such
things. I think i read that Audi have made a CVT system which eliminates
belts so maybe things are improving, Even so, i suspect that Honda bike
wouldn't be good for much more than race runs, wouldn't go for long without
maintenance i bet.

Did anyone read about the technicalities of the Honda box? Is it belt/roller
or some sort of expanding sprocket and chain?

--
Mark

On Wed, 12 May 2004 17:08:24 +0100, "Mark \(UK\)"

may have said:

Michael Paul said:

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

Quoted message said:

Did anyone see the latest issue of _Mountain Bike Action_ featuring
Honda's mountain bike and CVT drivetrain? Any comments?

looks heavier than a regular drivetrain

Michael

A few car manufacturers have made models with CVT boxes over the years, i
think DAF was the first, but they were riddled with problems, related to
belt slippage and the requirement for very frequent maintainance and such
things. I think i read that Audi have made a CVT system which eliminates
belts so maybe things are improving,

If Audi's making it, don't expect it to be worth owning. They've had
to go over to a 100,000-mile drivetrain warranty just to get people to
buy their cars in the US, and their resale value on out-of-warranty
units still isn't as high proportionately as most other makes. The
only car that depreciates faster, in my experience, is Daewoo...and
that's because GM took Daewoo off the North American market.

Quoted message said:

Even so, i suspect that Honda bike
wouldn't be good for much more than race runs, wouldn't go for long without
maintenance i bet.

Honda probably figures that there's a market for wierd and unusual
tech. I suspect that they will not sell many.

Quoted message said:

Did anyone read about the technicalities of the Honda box? Is it belt/roller
or some sort of expanding sprocket and chain?

Only the former works in practice; variable-diameter pulleys drive a
heavy belt. Sliding-cone-drive setups have been tried in the lab, and
they always cause some fool at Popular Mechanics to write it up as The
Next Really Great Thing That Will Be In Every Car In A Few Years.
Oddly enough, they never make it to market. CVTs of the belt type are
common in ATVs and LPCs (light personnel carriers; a glorified term
for "golf cart"😉 and are regarded and durable and reliable in most
applications there. I don't know how Honda has adapted the concept to
the relatively low velocities of a bicycle, but apparently they must
have done so.

Here's a picture of the bike:

http://world.honda.com/news/2003/2030203.html

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

Quoted message said:

On Wed, 12 May 2004 17:08:24 +0100, "Mark \(UK\)"

may have said:

Michael Paul said:

"Van Bagnol" <[email hidden]> wrote in message
news:[email hidden]...
> Did anyone see the latest issue of _Mountain Bike Action_ featuring
> Honda's mountain bike and CVT drivetrain? Any comments?
>
looks heavier than a regular drivetrain

Quoted message said:

Even so, i suspect that Honda bike
wouldn't be good for much more than race runs, wouldn't go for long without
maintenance i bet.

Honda probably figures that there's a market for wierd and unusual
tech. I suspect that they will not sell many.

Honda sometimes like to be the Sony of the vehicle market.

Quoted message said:

Quoted message said:

Did anyone read about the technicalities of the Honda box? Is it belt/roller
or some sort of expanding sprocket and chain?

Only the former works in practice; variable-diameter pulleys drive a
heavy belt. Sliding-cone-drive setups have been tried in the lab, and
they always cause some fool at Popular Mechanics to write it up as The
Next Really Great Thing That Will Be In Every Car In A Few Years.
Oddly enough, they never make it to market. CVTs of the belt type are
common in ATVs and LPCs (light personnel carriers; a glorified term
for "golf cart"😉 and are regarded and durable and reliable in most
applications there. I don't know how Honda has adapted the concept to
the relatively low velocities of a bicycle, but apparently they must
have done so.

Last time we had the belt-drive-for-bikes discussion in here, there was a
general consensus that it couldn't be done at all. Not reliably anyway.
--
Mark South
Citizen of the World, Denizen of the Net
<<Tiens! Ce poulet a une grenade!>>

On Wed, 12 May 2004 22:00:02 +0200, "Mark South"

may have said:

Last time we had the belt-drive-for-bikes discussion in here, there was a
general consensus that it couldn't be done at all. Not reliably anyway.

I'd have argued that myself if it wasn't for the fact that it appears
that Honda may have come up with a kluge that at least permits the
bike to move forward. How well it works is, of course unanswered, and
I am skeptical about that subject. Even if they have made it work
reasonably acceptably, though, I don't see it displacing the der
setup anytime soon, since I can't see any way for it to be as
efficient...and the limiting factor in bike performance is the
powerplant, so drivetrain losses just aren't going to be tolerable to
a lot of folks.

The photo of the Honda bicycle shows a unit that bears more than a
passing resemblance to a motorcycle. I doubt that this is mere
coincidence. OTOH, as far as I can see, Honda doesn't have any
marketing channels set up to get this to the places where it might
sell if it really is a worthwhile piece of tech. In my opinion, that
fact is a big hint that this is a showcase item with no mass
production planned. Honda-branded bikes are sold at K-Mart, however
as far as I know those are strictly pasted-on-label units rather than
a product that actually emerged from Honda's plants. A bike with a
CVT would not be a logical thing to market through KMart unless it was
going to be *really* cheap.

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

"Mark South" <[email hidden]> wrote

Quoted message said:

Last time we had the belt-drive-for-bikes discussion in here, there was a
general consensus that it couldn't be done at all. Not reliably anyway.

Belts can be done, but only if you include a Rohloff SpeedHub. And maybe a
Mountain Drive BB.

http://www.rohloff.de
http://www.schlumpf.ch/md_engl.htm

pete

Werehatrack said:

Even if they have made it work
reasonably acceptably, though, I don't see it displacing the der
setup anytime soon, since I can't see any way for it to be as
efficient...and the limiting factor in bike performance is the
powerplant, so drivetrain losses just aren't going to be tolerable to
a lot of folks.

Honda haven't published drivetrain losses for the CVT box, but I imagine it
would operate something like a seamless Sturmey Archer hub. You'd always be
pedalling at the right cadence which is going to help efficiency, the
transmission can be protected from [censored] and dirt, and you're not dragging
the chain through funny angles and idler gears on a derailleur. Might
actually be more efficient. It looks as if there's still a chain doing the
actual drive from the cranks to the back wheel. That said, they're racing it
as a DH bike, so pedalling might not be *that* important.

In article <[email hidden]>,

Mark \(UK\) said:

A few car manufacturers have made models with CVT boxes over the years, i
think DAF was the first, but they were riddled with problems, related to
belt slippage and the requirement for very frequent maintainance and such
things. I think i read that Audi have made a CVT system which eliminates
belts so maybe things are improving, Even so, i suspect that Honda bike
wouldn't be good for much more than race runs, wouldn't go for long without
maintenance i bet.

Did anyone read about the technicalities of the Honda box? Is it belt/roller
or some sort of expanding sprocket and chain?

It appears to be a variable-geometry reciprocating ratchet. It uses no
belts or chains, except for the drive chain from the transmission box to
the rear wheel (as in a single-speed). It does have gears, though.

The basic mechanical transmission is this: Step up pedal gearing to 11:1
or thereabouts; convert circular motion to reciprocating; use the
reciprocating motion to drive a ratchet; ratchet converts motion back to
circular; circular chainring pulls chain; chain turns cog at rear hub.
The variable transmission is in the geometry by which the reciprocating
arm engages the pawls. Gear range is about 3:1, the same as an 11-33
tooth cassette. One key feature is a scalloped or hypocycloid gear that
smooths the reciprocating stroke back into steady circular motion.

Frictional losses are minimized by the liberal use of needle bearings,
and weight is minimized by encasing the tranny in a carbon-fiber shell
with an aluminum "skeleton" for load-bearing. (The entire mech is bathed
in transmission fluid.) The article admits that weight and transmission
efficiency don't match conventional derailleurs, but points out the
advantage of CVT available at all times, even when under load, and that
the mechanism is sealed from the elements, reducing chainsuck. Also the
fixed front-rear cog sizes allow for rear suspension travel without
pedal feedback.

I only thumbed through the article at the magazine stand but that's what
I remember.

Van
--
Van Bagnol / v b a g n o l at earthlink dot net / c r l at bagnol dot com
....enjoys - Theatre / Windsurfing / Skydiving / Mountain Biking
....feels - "Parang lumalakad ako sa loob ng paniginip"
....thinks - "An Error is Not a Mistake ... Unless You Refuse to Correct It"