CVT v Conventional Gearboxes

[xpensive]

safeschuck; The general idea behind the conical, or tapered, roller bearing, as pioneered by Timken, was to have:

"The extensions of the raceways and rollers converge at a common point (the apex) on the axis of rotation. As a result, true rolling motion reduces heat generation and wear on the races and rollers."

http://www.timken.com/en-us/products/be ... /TTHD.aspx

As a result, radially movable rollers will also move the converging-point away from the ideal position for rolling, forcing the rollers to slide at some points dramatically increasing power-losses. And on top of that, you have the viscous losses from the lubricant, even if you should happen to be rolling at the sweet-spot.

[safeaschuck]

Mmmm. Gotcha. Never seen those before, very clever!

I'm still convinced that somewhere in Raffs design there is a benefit from what could easily be seen as a flaw...
Those bearing rollers arents actually drivers are they? they are just slave's to an input. They bear a load and they roll with minimum resistance.

Raffs rollers actually exert a driving force when they move position, speeding up or slowing down the surface they are in contact with.
What I was thinking was, if part of the surface of the roller is already at the speed being aimed for, it might act like a kind of viscous clutch for the rest of the roller, easing the speed change. In fact without it, it might require so much force to actually implement the speed change as to make the concept unworkable.

Obviously this is based around the fact that the surfaces of the disc and rollers never actually touch in ideal running conditions (as I believe is the case-Raff?).
They oil is both the lubrication and the traction, so reasonable viscous losses are inevitable with this design.

I'm also guessing that if what I said above is true, trying to change speed too quickly will effectively 'stall' the CVT. If the change in speed is greater than the taper of the rollers and the 'give' of the oil can handle. This situation could be improved by adjusting the taper of the rollers, but would also effect the usable variation in ratio and/or size of the finished product (i.e. longer discs would be needed for the same ratio change if the taper was decreased).

For some reason I have in my head drilling a hole with a 3mm drill bit vs trying to do it with a countersinking bit...

Obviously I am just dreaming all this up, playing devils advocate for what could go wrong, and what could be right about it.
Things like this are why you need a prototype, unless you have some very, very fancy software.

[xpensive]

In a perfect world without contaminants, a roller-bearing should never have any metal-to-metal contact, when the lubricant solidifies momentarily due to high pressure under the squeeze-effect. But on the other hand, that film could be less than a micron thick.

[safeaschuck]

Also perhaps a change in the viscosity of the oil could modify the maximum acceptable speed change (assuming what I was on about above actually holds true).
A thicker oil would allow a quicker speed change, but require more force to change speeds and create more friction.

[Conceptual]

Also perhaps a change in the viscosity of the oil could modify the maximum acceptable speed change (assuming what I was on about above actually holds true).
A thicker oil would allow a quicker speed change, but require more force to change speeds and create more friction.

Now you are getting into the realm of MR fluids for power transfer. It is done, but I think the system is very computer centric.

[xpensive]

Right, it's very interesting with computers and all. However, my humble experience is that eventually, even the most enthusiastic inventors usually realizes there's a reason why transmissions have evolvent-profiled gears rather than plain steel-rollers.
But again, do check things out on www.delphion.com, sky is the limit when it comes to ambitions of the contrary.

[safeaschuck]

Bit expensive for me x, can't even afford a 1 day access pass. I'm not getting paid at the present moment of grace as the bin truck can't make it out in the snow. Ol' Gert almost took out a line of school children yesterday so she's parked up pending the arrival of some salt.

I had a big old post worked out about why gears have been, and for the most part always will be the method of choice but it got a bit deep so I'll leave it and just say that from my little window into that world I saw too many companies heavily invested in producing and using gear cutting, hobbing, broaching and grinding equipment. Too many experienced people designing, making and servicing gearboxes, and too much widespread acceptance, integration and satisfaction with the current method for CVT's to ever really be given a credible shot at overhauling the status quo.
Who wants to gamble right? Even if they are better It'll be a painful transition for the industry in the short term, and perceptions take a generation or two to change.

Good luck though Raff! Holler back :p

[xpensive]

Just click "basic registration", which is for free and will save you a shitload of time exploring dead ends already explored.
Search for "roller transmissions" or "traction transmission"

[mx_tifoso]

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[xpensive]

I wish you the best of luck Terry and envy your optimism greatly!
Regrads, thomas

[xpensive]

Speaking of CVTs in general and Windmills in particular, check this out:

http://v3.espacenet.com/publicationDeta ... cale=se_SE

[mx_tifoso]

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[xpensive]

Terry,
You are right of course, it's a hydrostatic transmission-system with a variable displacement motor, when the Voith principle is hydrodynamic. In the latter, which is another variation of the variable slip-coupling theme, it can only be used for speed-reduction and not increase, while efficieny is directly proportional to the difference in speed.
Terrible in other words.

The hydrostatic principle on the other hand should in theory give you a higher efficiency, but the real challenge comes when you wish to transfer power in the MW-range.