19 replies to this topic

[manolis]

Hello all.
 
The conventional CVT variator (scooters, ATVs etc) comprises "centrifugal roller drive weights" like:
 

 

 
Despite their name and shape, these rollers, which bear significant loads, cannot help sliding on the ramps they abut on.
Sliding under load creates friction and causes wear.
The current way to reduce friction and wear is the use of low-friction self-lubricated nylon / plastic material.

What if instead of sliding, the rollers were true Rolling-Rollers?

This is what the PatRoR does.

In the following animation, the drive pulley is shown at three different ratios, a long (overdrive), a medium and a low.
Each Rolling-Roller comprises a pair of coaxial rollers (the one is a spool roller in this specific case) rotatably mounted to each other.
The relative rotation of the two rollers of each Rolling-Roller is shown:
 

 
In the following animation the drive pulley is at a low ratio:
 

 
or stereoscopically:
 

 
In the following animation the drive pulley is at a medium ratio:
 

 
In the following animation the drive pulley is at a high ratio (overdrive):
 

 
or stereoscopically:
 

 
Here is exploded a conventional drive pulley for CVTs:
 

 
and here is the same drive pulley modified to PatRoR:
 

 
All it takes for the modification is the replacement of the sliding-roller-weights by Rolling-Rollers, and the machining of a groove on each ramp of the ramp plate (a work that requires neither accuracy nor special tools).


The PatRoR is the substitution of the conventional frictionfull sliding wedge by a frictionless rolling wedge.
 
 
Thoughts?
 
Objections?
 
Thanks
Manolis Pattakos

[Canuck]

Are they any heavier?

[MatsNorway]

I like this one Manolis. This is good stuff. Does not look like that much of a weight gain if any.

[manolis]

Hello.

The PatRoR has nothing to do with weight reduction.

It turns the sliding friction of the conventional rollers into true-pure rolling, eliminating the friction and the wear, enabling a better response, a reliable mechanism etc.


This VVA_roller mechanism:



used in the Honda Civic VVA-roller prototype car:



https://www.youtube....h?v=-zzW8YkReLU

has a similar Rolling-Roller mechanism. And it works just fine (12mm lift at 9,000rpm for a 1,600cc 4-in-line engine).

In a variator the Rolling-Rollers of the PatRoR work, in comparison, “every now and then”.

For more about the VVA_roller: http://www.pattakon....takonRoller.htm

Thanks
Manolis Pattakos

Edited by manolis, 29 January 2016 - 19:01.

[gruntguru]

Looks good as usual Manolis. I wonder if the friction has any benefit (damping)?

[MatsNorway]

Hello.

The PatRoR has nothing to do with weight reduction.

I was in response to Canuck. I thought he talked about the whole unit. But it could also have been just the rollers. As that affects the actuation if nothing else is altered.

[Canuck]

Yes, referring to the weight of the new roller assemblies rather than the entire drive system. Impacts a few things if the mass is meaningfully greater.

[gruntguru]

Eliminating friction would allow a small reduction in mass of the "bobweights".

[manolis]

Hello all.
 
The cheap needle-roller-bearing HK0808A  (8x12x8, 2800Nt (600lb) load rating, 16,000/26,000rpm rev limit, 2gr weight),
 
with a hollowed pin 8x16x5 (4gr weight),
 
can be used as the basis for a typical Rolling-Roller.
 

 
The orange wheels (secured at the sides of the pin) and the dark green wheel (secured at the periphery of the red needle-roller-bearing) define the total weight of the Rolling Roller.
 
The wheels can be made of various materials (from, say, low-friction self-lubricated plastic, as the sliding rollers in the current variators, from steel, from carbon fibers, from material proper for dusty environment, etc).
 
With a pair of seals at the sides of the needle-roller-bearing, the grease cannot leak. The side orange “wheels” do not allow the seals to exit
 
Without a cage, the full complement needle-roller-bearing fits with the significant centrifugal accelerations it undergoes into the variator of a scooter.
 
This way the Rolling Roller can be made cheap, functional, durable and at the desirable weight.
 
 
 
Hello Gruntguru.
 
“I wonder if the friction has any benefit (damping)?”
 
I think the V-belt makes the damping.
 
The only I can see is wear and rough “gearshiftings”.
 
In order the conventional roller weight to start moving from its current eccentricity, outwards or inwards, it requires an initial over push (transition from static to kinetic friction):
 

 
Reasonably the CVT (Continuously Variable Transmission) shifts at steps (and not continuously).
 
With the Rolling-Rollers the transition from a “gear-ratio” to a neighboring “gear-ratio” is sweet / smooth, making the CVT “true continuously” variable.
 
Thanks
Manolis Pattakos

[gruntguru]

I meant damping of the ratio actuation not the driveline. Have you tested a prototype?

[manolis]

Hello Gruntguru.
 
You write:
“Eliminating friction would allow a small reduction in mass of the "bobweights".”
 
A little, maybe.
 
More decisive factor is the diameters of the two “wheels” of the Rolling-Roller and the arrangement (i.e. is the small or the big diameter wheel in the middle).
 
What most scooter riders like is the slight extension of the transmission ratio range at both ends (to have slightly faster accelerations, and to achieve the top speed with the engine not yet in the red).
 
The revenue around aftermarket variators and “weights” shows the problem and the need for solution.
 
“Dr.Pulley” is the most respectable “name” in the scooter forum discussions (the real name of “Dr.Pulley” is Wu Chun-Yi, the inventor of the “trapezoidal bob weights, from Taiwan).
 
The slider-weights of “Dr.Pulley” (the bob weights at right at the two photos in the beginning of this thread) expand slightly the ratio range at both ends. And due to the larger radiuses used at the contact surfaces, the wear rate is lower than in the circular bob weights.
 
Depending on the design of the Rolling-Roller, say like:
 

 
or like:
 

 
and, if necessary, with a different “ramp plate” (the blue part in the animations), the PatRoR can replicate any existing upgrade set (like “Dr.Pulley”, Jcosta,Polini, Malossi etc), keeping the advantages of the Rolling-Roller.
 
 
You also write:
“I meant damping of the ratio actuation not the driveline. Have you tested a prototype?”
 
I think not, because the radial motion of the weights is slow and needs not damping (a full radial displacement, i.e. a full gearshifting from the lowest to the highest transmission ratio, takes seconds for a less than, say, 50mm radial displacement).
 
At the rear – or driven pulley – there is a strong spring, at the front – or driven pulley – there is the variator with the roller weights and the ramps whereon they abut pushing close to each other the two halves of the drive pulley (and the V-belt away from the front pulley rotation axis), which, through the V-belt causes the compression of the spring in the rear pulley.
 
 
The PatRoR is quite fresh and is not yet tested. 
 
Fresh or not, there is already a strong reaction to this simpleminded idea / solution (it eliminates friction and wear, it multiplies the TBO, it offers smoother gearshiftings etc) of a basic problem at a tiny cost.
 
When you have the time, take a look at the now "closed" / blocked thread for the PatRoR at BurgmanUsa forums at http://burgmanusa.co...variators.html 
 
Thanks
Manolis Pattakos

[bigleagueslider]

Definitely an original design approach for adjusting the position of a rubber V-belt CVT sheave. But is minimizing friction in this particular device actually a major concern for the applications where it is used? As long as the friction characteristics in the mechanism are predictable and consistent, is reduced friction alone of much benefit for this application? The typical applications are very cost sensitive, and the added cost of many rolling element bearings would not seem to be acceptable.

[manolis]

Hello BigLeagueSlider

You write:
“Definitely an original design approach for adjusting the position of a rubber V-belt CVT sheave. But is minimizing friction in this particular device actually a major concern for the applications where it is used? As long as the friction characteristics in the mechanism are predictable and consistent, is reduced friction alone of much benefit for this application? The typical applications are very cost sensitive, and the added cost of many rolling element bearings would not seem to be acceptable.”

Minimizing friction in a centrifugal variator of a scooter is important.

The friction causes wear of the sliding rollers.
A uniform / even wear changes the available range of transmission ratios.
An irregular / uneven wear of the sliding roller weights makes the mechanism noisy, rough, vibratory etc. The Vee pulleys suffer. Also the V-belt suffers.



The wear shown in the photo above is extreme, yet the CVT still "works".


The friction causes another problem: it spoils the sweet / smooth gearshifting (i.e. the transition from gear ratio to gear ratio), making the CVT behave like not being step-less.

After a few thousand of miles, the CVT needs replacement of the sliding weights (at urban traffic things are more difficult for the CVT because they are required a lot more gearshiftings).


To take an idea of the cost, a HK0808A needle roller bearing made by INA-Schaeffler has a cost of 1.08$.

With one dollar you take several Chinese HK0808A. The load they bear and the number of rotations they perform inside a CVT variator, make the cheap HK0808A a good selection.

However, the cost of the best quality HK0808A (INA, SKF, NSK, etc) is already quite low, not justifying a cheaper choice.

To have something to compare, an aftermarket set of weights for a Suzuki Burgman 400 has a cost of about 50$.

What I say is that the Rolling-Rollers with an expected duration several times longer than the sliding-rollers, not only solve significant problems of the scooter CVTs, but they can be made substantially cheaper.

Thanks
Manolis Pattakos

Edited by manolis, 02 February 2016 - 10:23.

[MatsNorway]

This is easily my favorite of your designs i believe. It appears it is just as easy to manufacture as the original design, under normal conditions it probably have a better life expectancy, it could be cheaper in the long run? and it it is smoother.

 

Sell it Honda, Yamaha etc. or get royalty deals or whatever it is called if thats possible.

Edited by MatsNorway, 02 February 2016 - 14:46.

[Kelpiecross]

  Manny - I hate to be a wet blanket - but I can't really see that there would be enough advantage in changing over to your system of rollers etc.    - in China/Asia there are countless millions of these little CVT scooters  so clearly they work well enough.    

  But if you could arrange it so that  your roller system could  be sold  as an aftermarket direct swap item - and manufacture and sell the rollers yourself you could make millions of drachmas even if only a tiny fraction of the owners bought your rollers.  . 

 

 (What's a Greek urn - about 30 bob a week.)     (What's a piecost  - about sixpence)   The old ones are the best ones.   

Edited by Kelpiecross, 03 February 2016 - 04:23.

[manolis]

Hello MatsNorway.
 
You write:
“This is easily my favorite of your designs i believe. It appears it is just as easy to manufacture as the original design, under normal conditions it probably have a better life expectancy, it could be cheaper in the long run? and it it is smoother.
Sell it Honda, Yamaha etc. or get royalty deals or whatever it is called if thats possible.”
 
Thank you MatsNorway.
 
Be my guest and try, in behalf of pattakon, to contact the R&D heads of Honda, Yamaha etc for the PatRoR project.
.
We have bad experience in this field.
 
 
 
Hello Kelpiecross:
 
You write:
“Manny - I hate to be a wet blanket - but I can't really see that there would be enough advantage in changing over to your system of rollers etc.    - in China/Asia there are countless millions of these little CVT scooters  so clearly they work well enough.”
 
Your reasoning is not strong.
 
The “countless millions of these little CVT scooters” that work “well enough” are all based on the same basic, and relatively old, design with only minor variations from maker to maker.
 
Instead of thinking the countless millions of scooters today in use, think of the few (say a couple of dozens worldwide) makers of these scooters, or better think of the old design they all are based on.
 
 
On the other hand, as an engineer please point at a disadvantage of the PatRoR Rolling-Roller as compared to the Sliding-Rollers now in use.
 
 
By the way, here is what wrote, a couple of days ago in the MopedArmy forum, the guy (a third party) who made the first PatBox prototype:
 

 
and now he is using it in his Honda Hobbit moped:
 
“Rode the hobbit yesterday,
Love this lever. It's really really fun”
 
Thanks
Manolis Pattakos

[MatsNorway]

So replacement kits for existing bikes? Say Burgmans as you previously mentioned.

[gruntguru]

By the way, here is what wrote, a couple of days ago in the MopedArmy forum, the guy (a third party) who made the first PatBox prototype: . .  
and now he is using it in his Honda Hobbit moped:
 
“Rode the hobbit yesterday,
Love this lever. It's really really fun”
 
Thanks
Manolis Pattakos

 

I wish he would do a video of the bike accelerating - with and without use of the lever.

[manolis]

Hello MatsNorway
 
You write:
“So replacement kits for existing bikes? Say Burgmans as you previously mentioned”
 
This is the reasonable solution to start with.
 
The other way, i.e. to achieve to come in contact with those who decide inside the big makers / companies and then to achieve a reasonable agreement, is a long-term solution.
 
On the other hand, if a CVT is designed around the PatBox and / or the PatRoR and / or the PatEff ideas, thinks can be optimized to the limit, and the extra cost – if any – can be kept minimum.
 
Thanks
Manolis Pattakos

[manolis]

Hello Gruntguru
You write:
“I wish he would do a video of the bike accelerating - with and without use of the lever.”
 
I wish it, too.
 
Till then, here is a quote from MopedArmy Forum that seems to me better than any video:
 
“January 10, 2016, JBOT:
 
Tonight I went to the store.
Coming back I had to gun it uphill to catch the yellow.
The bike just went uphill so fast compared to my other tune I had on it.
It is nice to let the gearing do the work sometimes, and let the revs work other times.”
 
End of quote.
 
 
I hope to achieve soon to have a pair of same scooters, to modify the one and to compare it – on the road, i.e. on real conditions – with the other on:
 
how they go, side by side, from traffic light to traffic light,
 
how fast they complete an overtake,
 
how they go at a steep uphill, and then at a  steeper uphill, and so on until the stock to stall unable to follow,
 
how they go at a long steep downhill (use of the engine as a brake),
 
how much fuel they consume at a highway travel, side by side, etc.
 
Thanks
Manolis Pattakos