CVT Tranny?

[What's_nitro?]

I actually drew this before I hit "Submit Reply" on my first post but I forgot to attach it.

It's a belt-type CVT. Depending on the size of the belt and what it's constructed of it should handle BL power quite easily.

[lincpimp]

Originally Posted by What's_nitro?

I actually drew this before I hit "Submit Reply" on my first post but I forgot to attach it.

It's a belt-type CVT. Depending on the size of the belt and what it's constructed of it should handle BL power quite easily.

Going by your pic, I assume that the belt would require a spring loaded tensioner, like a serpentine setup on a car has. Unless you vary the effective diamters of the contact surface of both sets of "cones" exactly to allow the belt to retain the ideal tension at all times.

[brushlessboy16]

Originally Posted by lincpimp

Going by your pic, I assume that the belt would require a spring loaded tensioner, like a serpentine setup on a car has. Unless you vary the effective diamters of the contact surface of both sets of "cones" exactly to allow the belt to retain the ideal tension at all times.

they do not need a tensioner, you cent the motor shaft and output shaft's Center-to-center in such a way that the belt would allow the motor to "idle"

* i know this because we run a cvt style centrifigal clutch on my racecar*

centrigal force via ramps inside the primary clutch squeze the cones together, puting force onto the belt. At high rpm, then the cones are as close the belt gets tighter- this tension spreads the cones of the secondary unit, making the effective Pulley diameter of the primary larger then that of the secondary, creating overdrive.



Great concept but your would need to do extensive testing with different ramps, weights and springs to find a good mix

[lincpimp]

Originally Posted by brushlessboy16

they do not need a tensioner, you cent the motor shaft and output shaft's Center-to-center in such a way that the belt would allow the motor to "idle"

* i know this because we run a cvt style centrifigal clutch on my racecar*

centrigal force via ramps inside the primary clutch squeze the cones together, puting force onto the belt. At high rpm, then the cones are as close the belt gets tighter- this tension spreads the cones of the secondary unit, making the effective Pulley diameter of the primary larger then that of the secondary, creating overdrive.



Great concept but your would need to do extensive testing with different ramps, weights and springs to find a good mix

Thats cool, I was not aware that a mechanical method was used to vary the pulley size. I figured that it would be electronically controlled via some sort of electro-hydraulic mechanism.

[brushlessboy16]

Originally Posted by lincpimp

Thats cool, I was not aware that a mechanical method was used to vary the pulley size. I figured that it would be electronically controlled via some sort of electro-hydraulic mechanism.

nope its all centrifugal

as it spins, weighted arms pres against ramps that are attached to the moving cone.

heres a pic of mine

[BrianG]

I knew about the cone/pulley method, but the NuVinci one was new to me.

There's also a toroidal CVT (from howstuffworks.com):



Either way, a design for R/C would have to be a small/light package.

And as someone mentioned, the goal of this is not necessarily to use a smaller motor, but to provide a better spread of ratios, especially in the high-speed projects. Motors can only spin so fast, yet gear them up too high and you have cogging at slower speeds.

And linc, I'll just remove/disable any fan you put in there. Don't think a lack of warranty will scare me.

[brushlessboy16]

Originally Posted by BrianG

I knew about the cone/pulley method, but the NuVinci one was new to me.

There's also a toroidal CVT (from howstuffworks.com):



Either way, a design for R/C would have to be a small/light package.

And as someone mentioned, the goal of this is not necessarily to use a smaller motor, but to provide a better spread of ratios, especially in the high-speed projects. Motors can only spin so fast, yet gear them up too high and you have cogging at slower speeds.

And linc, I'll just remove/disable any fan you put in there. Don't think a lack of warranty will scare me.

wow, that would be fun to mmake, i dont know how you would incorberate it into an RC though

[suicideneil]

We're talking about Vario-matic transmissions right? I saw them used on a build once on Scrapheap challenge (Junkyard wars to you guys):

http://en.wikipedia.org/wiki/Variomatic

The concept was very simple- the two opposing cones changed shape as the rpms increased, causing the drive ratio to alter as the belt shifted shape/posistion between the two cones which spin the belt. Seems the cones were made of a plastic that would deform naturally due to the centrigugal forces at higher rpms. I'd be lying if I said I hadn't though about this concpet for r/c use, just wouldn't really now how to make it a reality...

[Finnster]

Originally Posted by lincpimp

I think that I will try to design and proto this, but will include an electric cooling fan in the core design, so to prevent Brian from using it.

I am surised that you are posting this here Brian, when you have access to the super secret area 51 section of the forum. Surely there is more knowledge in one of the allowed users there than all of us cretins combined?

I would just make it a nitro powed fan and then no one here will want to use it lol. Just think of the huge advantage at the track of a tranny that no one else can/want to use!

Sucks tho if DNF'd a race due to burning out a glow plug in your tranny...

[BrianG]

Originally Posted by Finnster

I would just make it a nitro powed fan and then no one here will want to use it lol...

Yeah, right. No one here has ever converted something from nitro to electric!

[suicideneil]

Thats not entirely true- remember the nitro powered Gorillamaxx conversion?

[brushlessboy16]

Originally Posted by suicideneil

Thats not entirely true- remember the nitro powered Gorillamaxx conversion?

have a link?

the CVT has been used for about 8 years in the FIRST robotic competition

Each transmission weighted about 15 lbs, but one engineer explained ot me why they didnt use it. But you just dont see man CVT's out there..

Ill see if i can dig into them engineers brains

[bruce750i]

My ATV uses a CVT and it has a fan built in so the belt doesn't melt.

[brushlessboy16]

Originally Posted by Andrew32

the CVT has been used for about 8 years in the FIRST robotic competition

Each transmission weighted about 15 lbs, but one engineer explained ot me why they didnt use it. But you just dont see man CVT's out there..

Ill see if i can dig into them engineers brains

Do you do FIRST?!~

Team 87 here