NuVinci CVP hub for bikes and LEV: rollout data

[Reid Welch]

Regarding Fallbrook's first generation continuously variable ratio hub:
It's here, sort of: Seattle Bike Supply now offers the bike hub to retailers in a Blk/Blk laced 26" wheel form,; and by itself in silver.
http://www.seattlebikesupply.com/scripts/fccgi.exe

_________

Developer Fallbrook Technologies' "ATC" site promotes the hub
http://www.atcnuvinci.com/products.php


data sheets and manuals page:
http://www.atcnuvinci.com/support_docs.php

PDF data sheet for the bike hub:
http://www.atcnuvinci.com/docs/ATC_Bike_Datasheet.pdf


PDF for the LEV hub:
http://www.atcnuvinci.com/docs/LEV_Datasheet.pdf


Brand new ATC NuVinci forum
http://www.atcnuvinci.com/support_forum.php

_______________

I've joined the forum (it's quiet at the moment).
I will ask questions.

 

[Lowell]

No mention of how much power it will handle... let us know if you find out more info.

 

[Reid Welch]

Here's a hint about that:
the PDF data sheet mandates a minimum 1:2 ratio between hub cog and chainwheel. To wit: 22/44 (or greater).

I don't suppose they want to see early failures.
This first-gen hub is surely over-built (that's why it relatively heavy).
And I suppose they have engineered this to withstand reasonable guff.

If, for instance, I someday have this hub and were to apply e-drive through the hub, there's no way I'd bust it.

The Unite motor is not all that terrifically torquey on 36V.
I think it would be a fine pairing.

The real question: can it even be done?

The new Currie IZIPS with the Nuvinci do not exploit the Nuvinci for even their modestly-powered e-drive.

I don't know why not--I suppose it's more a matter of keeping it simple
and avoiding custom, added engineering on this fresh product.

However, I suppose the makers have indeed applied e-drive to hubs under test conditions.
Cyclone-type drive would be easy to do.
I just don't favor/have/or want to convert my bike to (imo) relatively unmechanical Cyclone type drive.

The present side motor chain drive is mechanically correct and efficient as any other gear motor and chain drive.
It only lacks for ratio flexibility, to make the most of it's powerband
for better (even greater torque) operation at lower speeds
under the common, transitory loads of wind, grade or acceleration.

A variable transmission is not strictly needed here--though it would be nice;
it would speed the bike and save battery power at the same time.
It would allow drive at high speeds at minimum power wastage
by the simple expedient of dialing in the drive ratio to obtain minimum current draw.

 

[xyster]

http://www.bernsonev.com/izip-fusion-1000-scooter-with-nuvinci-drive-p-752.html
Izip 1000 w/cvt is available now:

http://www.gizmag.com/go/6132/
"The NuVinci CVP is applicable to any product that uses a transmission, including bicycles, light electric vehicles, agricultural equipment, automobiles and utility class wind turbines and an announcement overnight heralds the first use of the new technology by well-known electric-powered vehicle manufacturer Currie Technologies in hybrid electric bicycles and electric scooters which will combine the NuVinci CVP with the Currie Electro-Drive drive system. The first product will be seen before the end of the year and already looks set to give the pedal-electric hybrid bicycle remarkable new capabilities."

 

[TylerDurden]

Bike hub specs from pdf: 130Nm max input

EDIT: I imagine if more than 130Nm were applied, it wouldn't break; but more likely slip... it is a friction drive.

 

[Lowell]

Bah, I make over 130Nm without gears, so I guess I'll be waiting for version 2 or 3.

 

[Toorbough ULL-Zeveigh]

Bike hub specs from pdf: 130Nm max input

EDIT: I imagine if more than 130Nm were applied, it wouldn't break; but more likely slip... it is a friction drive.

That's what worries me. I have roller clutch screwdrivers that once they slipped from trying to drive a wood screw would always slip at that same spot ever after.

 

[Reid Welch]

Bike hub specs from pdf: 130Nm max input

EDIT: I imagine if more than 130Nm were applied, it wouldn't break; but more likely slip... it is a friction drive.

That's what worries me. I have roller clutch screwdrivers that once they slipped from trying to drive a wood screw would always slip at that same spot ever after.

Different principle there. Entirely different.
Interestingly perhaps, I own an example of the world's first application of the roller clutch
--an Edison projector of ca. 1914 with roller clutch take-up reels.

It was for this first home movie projector, that W.K.L. Dickson, a Scotsman who created the machine for Edison,
invented the roller clutch.
Dickson's association with Edison began long before that, though;
in the 1880's, in development of the Edison Kinetoscope.

In other words, Dickson was a prime inventor of the motion picture concept. Yes, his first roller clutches still work.
And sometimes they fail to grab because they are single rollers in gravity-fall.
They are soft steel too, so sometimes they fail to disengage (they stick).

I rather doubt the NuVinci can slip in the manner of a defective roller clutch.
For if it slips all of a sudden---that'd be totally fatal to the mission goal and to a rider's nuts.
Therefore, logic says it can't happen; at least not in massive-slip form.


The NuVinci's friction interface is not metallic, Toor--it's whatever it is in it special lube-carrier that provides the interference fit.
Doubt that secret ingredient is metallic;

more likely it's like...what?

humor: Only Fallbrook and Valvolene and the Patent Office and The Shadow Knows.

 

[Toorbough ULL-Zeveigh]

I've heard of silicone based phase-change(?) fluid used in some automotive clutches which consisted of a series of slotted discs on a concentric shaft in a cylindrical housing that was filled with the fluid. The silicone had a property where if the vanes rotated at a low rpm they could move freely without resistance from the fluid but at high rpm the fluid's viscosity shot up so that the slotted disks acted as though they were physically locked together.

So I could see a substance similar in nature being used in the NuVinci. But every system has limits & can be overpowered if you try hard enuf. I think the problem with the screwdrivers are that the roller clutches were just too small for the job. Which doesn't surprise me since they were made in China & cost only five bucks.

I'm just carrying this baggage around that will make me hold off & wait even though I'm enthusiastic & eager to get a NuVunci regardless. It should do fine on level ground, but I need to see what happens when the system is tested to its limits cranking hard up something like Pikes Peak. Did they design for worst case or did they base their parameters on the kind of riding done by the average. That's the question I need to have answered b4 I possibly break it so that I'm aware of what kind of conditions it's meant for & if I need to avoid certain terrain. With my screwdrivers, were I to get another one, I now know that they are not meant for wood screws & if used for only small machines bolts would probably last forever

 

[Reid Welch]

That drive fluid you describe works on a different principle, of course.
It is termed "rheopectic" when a fluid increases its viscosity in response to churning. That silicone fluid drive is rheopectic-based.

The opposite effect (which can also be engineered into greases, and most generally is so-done) is "thixotropic".

----

I see your concerns, though. We need reports.
Who knows the slip or the drag, the feel and the experience,
until after user reports come in--who knows here whether the hub is strong enough in its grip for ironmen to stomp?

Guessing isn't worth much; not when guesses come from me.

 

[TylerDurden]

Hell's Bells, let's keep guessing, what else are we here for?

What would be a good combination of motor and pedal gearing...

Cyclone style or Randy's stacked freewheels?

I fancy a 750W geared unite for power...

 

[xyster]

Running across a pool filled with a rheopectic-like cornstarch emulsion:

<embed src="http://www.youtube.com/v/f2XQ97XHjVw" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"></embed>

Perhaps NuVinci's hi-tech secret ingredient is corn starch... :lol:

 

[Toorbough ULL-Zeveigh]

Emulsion or colloidal?

One of their engineers probably saw something like that or snowmobiles skimming a lake & the light bulb popped on.

Would it be fair at all to describe the substance as the fluid equivalent of an aramid-fiber composite?

 

[Reid Welch]

Running across a pool filled with a rheopectic-like cornstarch emulsion:

Ha ha, that's hilarious--taking time to get this by dialup
or I would've noted sooner: the pool is filled with a thixotropic, not rheopectic mixture.

How so? Well, at the point where Glasses Guy intentionally sinks himself,
note how it provoked the sinking.

That is purely thixotropic behavior.
Things which liquify when agitated are thixotropic.
Things that thicken, rheopectic.

 

[TylerDurden]

I got kinda the opposite impression...

that he sank himself by remaining still.


Methinks if it were thixotropic, they could casually walk across.

8)

 

[xyster]

FWIW:
http://en.wikipedia.org/wiki/Rheopecty
Rheopecty or rheopexy is the rare property of some non-Newtonian fluids to show a time-dependent change in viscosity; the longer the fluid undergoes shear, the higher its viscosity. Rheopectic fluids, such as some lubricants, thicken or solidify when shaken. The opposite type of behaviour, in which fluids become less viscous the longer they undergo shear, is called thixotropy and is much more common.

Confusion between rheopectic and dilatant fluids

An incorrect example often used to demonstrate rheopecty is cornstarch dissolved in water, which when mixed resemble a very viscous and white fluid. It is a cheap and simple demonstrator, which can be picked up by hand as a near-solid, but flows easily when not under pressure. However cornstarch in water is actually a dilatant fluid, since it does not show the time-dependent change when sheared required to be labelled rheopectic. This is often and easily confused since the terms are rarely used; a true rheopectic fluid would when shaken stay liquid at first, becoming thicker as shaking continued.

The distinctions are all mushy to me...

 

[Miles]

In case anyone missed this....

http://www.fallbrooktech.com/06_tf_FAQ.asp

 

[Reid Welch]

In case anyone missed this....

http://www.fallbrooktech.com/06_tf_FAQ.asp

Yep, I had missed that.

So, the lubricant does not seem to contain microsolids.
I had wondered how it could, without those particles interfering with the general running of ball bearings in the hub.

The principle, then, is based on a sort of rheopectic action, more or less.

And there is no metallic contact between the working surfaces.
The only limit to the device's working life will be the fatigue life of steel under cyclical pressure. And that will be very long indeed, I do think.

Suppose too that the internal power losses will owe in part to the viscosity of the fluid, and then to the deformation-energy losses of the compressed metals--reasonably small losses.

It should roll pretty well indeed--not as freely as a single speed freewheel hub, but pretty freely nonetheless.

general tease question:

Which is the most elastic material? Rubber, or hardened steel?

 

[Toorbough ULL-Zeveigh]

The principle, then, is based on a sort of rheopectic action, more or less

8)

 

[xyster]

The principle, then, is based on a sort of rheopectic action, more or less

I once took some of that stuff for a bad case of diarrhea.

 

[Reid Welch]

http://www.fallbrooktech.com/06_tf_FAQ.asp

"Won't the rolling elements slip at higher torques?"

Most traction drives, including the NuVinciâ„¢ CVP, incorporate mechanisms to dynamically control the contact pressure as torque is increased.

The properties of the traction fluid and the geometric and material properties of the rolling elements and the pressure-control mechanisms are designed to manage internal forces to prohibit slipping.

Therefore, design of a traction drive includes careful selection and testing of the traction fluid.

All traction transmissions have a very small amount of what is called creep that occurs within the fluid under normal conditions.

The amount of creep is generally small enough that precision instrumentation is required to measure it.

 

[Reid Welch]

Here we all tend to be micro-focused on our hobby passion of ebikes.
The best guarantee that this first CVP will be made right and make market,
is to see who has partnered with Fallbrook--who has committed.

http://www.fallbrooktech.com/Partners.asp

There's a great deal of the power transmission world
possibly hinging on this endeavor.

And to think it begins with leisure-class bicycles.

If they, the partner-groups, make good in this field--
this is wherefrom the reality grows upward.

It may be a new day. They sure think so.
And they are a team of savvy brain-powers.

I do not suppose their transmission can slip.

:wink:

 

[TylerDurden]

I was assuming that the unit would slip before a component would break.

Perhaps our field of brainiacs should develop a freewheel held by soft keys that shear before the hub breaks.

My tractor has one that shears each time I hit a stump or rock with the mower-deck.