bike/scooter cvt

[Goofy1]

Here are my questions about the CVT:

Why can't a disconnect clutch be installed between the engine and drive pulley to allow slide and glide riding?

Shouldn't a properly designed CVT start applying power at the torque peak and then transition when the engine is at peak HP, constantly keeping engine RPM in that sweet spot?

[ASV]

almost right
you do want the clutch to open at peak torque
but as the engine is not accelerating you want to stay at peak torque
until the CVT is maxed out
at that point the engine will begin accelerating and HP will be the preferred metric

hope that makes sense

[cRiPpLe_rOoStEr]

Originally Posted by Goofy1

Why can't a disconnect clutch be installed between the engine and drive pulley to allow slide and glide riding?

That could be more useful while starting the engine.

[stiletto2]

Originally Posted by Goofy1

Here are my questions about the CVT:

Why can't a disconnect clutch be installed between the engine and drive pulley to allow slide and glide riding?

Shouldn't a properly designed CVT start applying power at the torque peak and then transition when the engine is at peak HP, constantly keeping engine RPM in that sweet spot?

Actually, I'm not sure where I saw it, but someone was proposing to put a Sprag clutch on the drive wheel of a scooter. If that were done then P&G would not be a problem, but then one would lose the engine braking effect when decelerating... That would mean you would be much more dependent on the brakes to slow you down. Most likely one would be replacing brake pads and possibly brake discs much more often than they would otherwise.

[gil]

Originally Posted by cRiPpLe_rOoStEr

Apart from Harleys and similar models, and also the BMW G 650, I can't remind of any other belt-driven motorcycle.

BTW what are the other things you don't miss about them?

Let me list them, the lack of a fuel gauge ( low fuel lights don't count), the handlebar vibrations, the uncomfortable seat ( coming from a Yamaha V-star 250), the carburetor, shifting gears ( fun but tedious), also the noise ( they are just too loud), just to list a few. I like that I can jump on my scoot and go. It will start right up whether it's cold or hot. Riding a "real" motorcycle is like driving a race car for the daily commute.

Over the years I have realized that every rider has his own idea of what an ideal motorcycle is. Or they haven't really given scooters a chance, maybe not manly enough.


Gil

[cRiPpLe_rOoStEr]

Originally Posted by gil

the lack of a fuel gauge ( low fuel lights don't count)

It also bothers me a lot.

the carburetor

I used to be more favorable to carburettors. Actually still like them because it's easier to perform some emergency makeshift fix, but I recognise an EFI may be better for basically any other aspect.

shifting gears

I'm more concerned about the clutch than the gear-shifting itself. I got quite surprised when I found out about some American companies that make clutch automation kits for nearly every motorcycle.

Riding a "real" motorcycle is like driving a race car for the daily commute.

The way some folks ride them, I won't even argue with you on that matter. Well, most of the people who get them for commutting back here do so in order to save not just on fuel but also the time they don't waste stuck in traffic congestions...

Over the years I have realized that every rider has his own idea of what an ideal motorcycle is.

I'm not even sure about what would be an "ideal" motorcycle for me, but I like the Yamaha Ténéré 250 that is available here in Brazil. I just hope Yamaha fits them with ABS instead of phasing it out in the next year...

Or they haven't really given scooters a chance, maybe not manly enough.

I've already considered getting either a scooter or a regional derivative of the Honda Cub, but since they're more optimized for urban commutting it wouldn't be so suitable for me (considering that I would use a motorcycle mostly for medium to long distance trips, plus there is a lot of pot-holes in our streets and it would be quite costly to replace tyres and rims after falling on them).

[gil]

Originally Posted by cRiPpLe_rOoStEr

I've already considered getting either a scooter or a regional derivative of the Honda Cub, but since they're more optimized for urban commutting it wouldn't be so suitable for me (considering that I would use a motorcycle mostly for medium to long distance trips, plus there is a lot of pot-holes in our streets and it would be quite costly to replace tyres and rims after falling on them).

Looks like we have about the same views on riding. I'm sure that any type of motorcycle is better for the commute in your city. You are right about the possible wheel damage with bad roads. Funny that you mention that, not long ago a member on the PCX forum shared that in Thailand they swap in 13 inch wheels onto their Honda PCX, so that they can fit fatter tires with more side wall, that way it can handle the bad roads. The Honda PCX comes with 14 inch wheels from the factory.

Gil

[cRiPpLe_rOoStEr]

Originally Posted by gil

Looks like we have about the same views on riding.

Possibly.

I'm sure that any type of motorcycle is better for the commute in your city. You are right about the possible wheel damage with bad roads.

Something like this would be nearly perfect.

Funny that you mention that, not long ago a member on the PCX forum shared that in Thailand they swap in 13 inch wheels onto their Honda PCX, so that they can fit fatter tires with more side wall, that way it can handle the bad roads. The Honda PCX comes with 14 inch wheels from the factory.

I also usually prefer a smaller rim and tyres with a higher sidewall.

[ProDigit]

Originally Posted by ASV

I had read the study a number of years ago

a chain starts off with fantastic numbers at lower speeds and power levels
but the friction builds fast as power goes up

with a conventional motorcycle belt you start with crummy numbers
from the needed high pre tension
but it never really gets much worse even if you pour on the power

yeah that's why I prefer a microv belt, with as little as 10 pounds it becomes self locking
and it still has the self leveling friction curve but has far better power consumption at low power levels
this is what makes it a favorite with car designers

This is not really correct.
A chain starts out with little friction, and does increase in friction the higher your speeds go.
But the same is also true for a CVT belt.
It starts out with higher friction, but then it'll switch to where the belt occupies both the driven and driving pulley on the same diameter.
This is where the belt is performing at it's peak efficiency, because it's bending diameter is the largest on both ends.
When you accelerate further the driving pulley's grip will have a larger radius, and the driven pulley will have a smaller radius, at which most of the heat transfer happens in the driven pulley.
And one of the ways you know a chain is more efficient than a belt, is because a chain will always be cooler than a belt.
A chain also rotates slower than a belt, and is longer, but even if not, it just doesn't have the slippage a belt has. And the higher the speed, the higher the forces, the higher the heat dissipation, and the higher the heat, the more the belt will slip (a quality of rubber, unfortunately).


Anyway, it just comes down to a belt has a lower low speed efficiency than a chain, medium or comparable mid speed efficiency, and a MUCH lower, high speed efficiency than a chain.
And the higher the speed, the more a CVT with rubber belt loses out to a chain.

Modern cvts don't have belts, but also are based on chains, or metal belts that have metal parts as belt (not rubber). They not only are more efficient, but more durable as well.
They're also a lot more costly (about 10-15x more costly).