CVT CVT's and Comet drivelines

[Youngbird]

"CVTs and Comet Drivelines"....Huzzah....Huzzah....Huzzah!!!!

 

[DetonatorTuning]

So what would be the official name and description of the forum?

"CVT's and Comet drivelines"

Would it go in the garage or clubhouse?

i'd say that the name is pretty inclusive of what's out there that can or is being used and makes a division between these and all the reduction gear boxes that are out there.

call it whatever you like i guess.

i'd say "the garage"

should we put up a poll for opinions ?

steve

 

[DetonatorTuning]

CBRobots,

my 460 clutch engages at 3,000rpm. i want my CVT to be in the "high range" / 3.15:1 by 8,000rpm.

if i gun it from 8600rpm, will it drop down for transition acell. then move back up to 3.15:1 at the new higher speed and rpm or is this too sophisticated for these little charmers.

thanks,
steve

 

[capturedbyrobots]

CBRobots,

my 460 clutch engages at 3,000rpm. i want my CVT to be in the "high range" / 3.15:1 by 8,000rpm.

if i gun it from 8600rpm, will it drop down for transition acell. then move back up to 3.15:1 at the new higher speed and rpm or is this too sophisticated for these little charmers.

thanks,
steve

Clutch doesn't matter that much with CVTs. Your revs will stay the same if it's tuned right (right in the powerband, with no decrease)
Then once you get to the top of the CVT's ratio changing ability, your revs will continue to go up just like a 1 speed.
If your gearing is too tall, you might have a hard time getting
those extra revs out.

It all has to do with how you tune the variator.
In my experience, you have a bunch of variables to work with,
and each will effect how it runs.

Your gearing has to be right #1. I geared my goped with a 10 inch tire
at 25/72 (with 25H chain and the 3.75:1 reduction in the CVT box)
I am not a math whiz, so I would suggest you figure out whatever gear ratio is standard on MBs, I've heard that 18:1 is about right.

Then, you can tune the variator with various weights.
I've found for a piped 460, 15G should be perfect (take out 1/2 the rollers) (30G standard, 5G each roller)
If you want a multipack of rollers, daywot on Ebay has the 16x13 rollers
in a progressive pack 3G to 15G

But, you will have belt slip without shimming the contra spring with the 460.
Search GPN for posts about that.
I've found that with new CVTs, 3mm shim is pretty good, but once it's broken in, very little shim is needed.
It all depends on how strong the contra spring is, and as we know with china quality, it's all over the place. Some springs I've seen are wimpy, others are very strong.
How much you shim will determine how much slip you'll get, and thus also affecting the rpms you hold steady at.

As well, motor tuning has a big effect as well.
If your motor is not tuned in right, the CVT won't have as much power to work with.

This is why I call it CVT tuning he11.
Once you get it dialed in though, it's a blast to ride.

Go watch some of my vids on youtube.
You can hear how it performs on some CVT ride videos.
Everything I'm doing on my goped could easily be transferred to MBs if you get the gearing and CVT tuning right.

http://www.youtube.com/watch?v=1GxTJMUS4sM

 

[Youngbird]

That brings up a good point. When using the Comet type of variator or TAV2...we need to use a jackshaft for right side drive. What would be good pulley diameters for the final drive....or sprockets for those using a chain for a final? Im thinking something lke a 2 or 2.5:1.

 

[DetonatorTuning]

OK, i watched all the CVT vids and the MB vids.

i'm pretty well convinced on how this works at full throttle. push the throttle down, it revs out and the CVT pulls the ratio up to the limit. that's all good if you have the gearing purposely set to run wide open all the time.

it's OK for take offs too. but i want to cruise in the 8600-10,000rpm range and speed up to max rpm at will.

what i'm asking is, will the CVT drop any ratio as the rpms rise from that point and come back up when it stabilizes, or will it stay in final ratio and the engine has to do it all ?

in my case i'm using the present shifter kit to establish just how much reduction i can use for cruising and topend.

thanks,
steve

 

[Youngbird]

It is infinitely variable....between its lowest and highest ratios. At its lowest it is about 2.8 or 2.9 to 1 and the highest is .90:1 or a 10% overdrive. It will act much like an auto trans w/o the shift points.

 

[DetonatorTuning]

It is infinitely variable....between its lowest and highest ratios. At its lowest it is about 2.8 or 2.9 to 1 and the highest is .90:1 or a 10% overdrive. It will act much like an auto trans w/o the shift points.

CBRobots, is this your opinion about the workings of the PB CVT's too ?

thanks,
steve

 

[Nuttsy]

DT,
The short answer is that the engine will have to do the rest.
What happens from, lets say a dead stop to full speed. Then engine rpms pick up from idle to about 3/4 of max rpm (engines power range) in a few seconds (as clutch engages) from that point on its all CVT. You won't hear much, if any difference in the rpm until the CVT gets to its max ratio. After that the engine is going to drive the rest of the way to WOT/ max rpm.
Well at least that's what my ears hear with my Robin and my CVT. Can't speak for the Comet ones. CBRobots is gave it to you right in his previous post.
Hope this helps. What CVT are you running/planning to run.
WC

 

[Nuttsy]

DT,
CRUD! I just re-read your question and I understand what you're asking. If I'm getting it right... lets say you're cruising along at 25mph. You want to speed up. You twist the throttle to WOT. What happens? Depends on, as CBRobots mentions, many variables.
If the CVT is at its max ratio while you're cruising, then the engine will have to pull the rest. Max is max...period. It's not going to "downshift" to a lower range ratio and then pick back up again. If, however the CVT is "tuned" properly and has some more room to roam, then it will continue to change ratios until it DOES reach its max.
Did that help?
WC