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PatBox CVT ( Continuously Variable Transmission )


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#1 manolis

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Posted 04 April 2014 - 16:17

At http://www.pattakon....takonPatBox.htm it is presented the PatBox CVT wherein an auxiliary thin belt rides around the conventional V-belt and around rollers mounted on a lever.
The displacement of the lever varies the transmission ratio:

PatBox1.gif
1 is a drive shaft (the crankshaft in most cases).
2 is a drive pulley comprising two conical halves.
3 is a driven shaft.
4 is a driven pulley comprising two conical halves.
5 is a V-belt.
6 is an auxiliary belt; it surrounds and abuts on the V-belt at the drive pulley side.
7 is a lever comprising free rollers (12, 13) around which the auxiliary belt runs; a restoring spring (not shown) pulls the lever 7 to the left and keeps the auxiliary belt in tension; the linear speed of the inner side of the auxiliary belt 6 equals the linear speed of the external side of the V-belt 5.

 

 

When the lever 7 is free to move, the variator (not shown) controls the transmission ratio conventionally / automatically. The "engine revs vs. vehicle speed" plot can be like:
PatBox2.gif
From p1 to p2 the automatic clutch (not shown) engages.
From p2 to p3 the transmission ratio is constant and short. The revs are not yet adequately high to allow the variator to start reducing the effective diameter of the drive pulley.
From p3 to p4 the variator increase progressively the effective diameter of the drive pulley (as a result, and due to the constant length of the V-belt, the effective diameter of the driven pulley decreases; as another result, the auxiliary belt 6 abuting on the V-belt 5 pulls the free rollers to the left and causes the rotation of the lever 7 for several degrees clockwise). The transmission ratio gets longer and longer (the engine revs remain constant while the vehicle speed increases).
At p4 the transmission ratio is the longest possible (the effective diameter of the drive pulley cannot increase any longer) and remains constant until p5.

 

 

In case the rider, by putting his foot on the end 11 of the lever 7 for instance, blocks properly the clockwise motion of the lever 7, the previous plot can change like:
PatBox3.gif
and the vehicle can accelerate faster (because the engine operates at revs wherein more power is provided).
Until the p9 the transmission operates conventionally (as in the first plot).
From p9 to p10 the driver / rider blocks the upwards motion of the end 11 of the lever 7 (and so the clockwise rotation of the lever 7); in order the variator to increase the effective diameter of the drive pulley, it needs also either to increase the length of the auxiliary belt (which is constant) or to displace to the left, through the auxiliary belt, the free rollers and the lever 7 (which is not allowed by the driver). So the transmission ratio remains constant and short.
From p10 to p11 the driver releases progressively the lever 7 so that the revs of the engine to remain constant while the vehicle speed increases.
From p11 to p12 the driver blocks again the upward motion of the end 11 of the lever 7; the transmission ratio remains constant (like having the second gear in a manual gearbox).
From p12 to p13 the driver releases progressively the lever 7 keeping the revs of the engine constant while the vehicle speed increases.
From p13 to p14 the lever 7 is again blocked (like having the third gear in a manual gearbox).
And so on.
It is characteristic that in all the above steps the driver / rider does not provide energy to the PatBox CVT; he just blocks or releases the lever 7; the energy for the motion of the lever 7 comes from the engine (like having a built-in servo).   

 

 

In the following plot the transmission system operates like a manual gearbox having six distinct gear ratios.
PatBox6.gif
Until the point p27 the transmission operates automatically.
At p27 the driver blocks the lever 7 (and selects this way the first gear); at p28 the driver, by releasing the lever 7 and blocking it again at the point p28, shifts to the second gear; at p30 the driver shifts to the third gear; at p32 the driver shifts to the fourth gear; at p34 the driver shifts to the fifth gear; at p36 the driver shifts to the sixth gear.
It is like shifting gears in a manual gearbox (but without the need of a clutch).

 

In the following plot the driver keeps the lever 7 blocked from the beginning; the engine revs go high; then the driver releases the lever 7 progressively keeping the revs constant.
PatBox7.gif
If the peak power of the engine is provided at the revs corresponding to the point p16, the acceleration of the vehicle is the fastest possible.

 

 

Here is a stereoscopic drawing of the mechanism:

 

PatBox9.jpg
 

 

The rider can either vary, "on the fly", the characteristics of the transmission in order to meet the instant needs for acceleration, quiet operation, fuel efficiency, mileage etc, or the driver can leave alone the CVT to operate normally / automatically.

While the PatBox CVT can provide infinite additional modes of operation, it actually adds no friction; on the contrary, with the additional modes of operation, the overall efficiency (the mileage) can be improved.

 

 

Any thoughts?

 

Thanks

Manolis Pattakos



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#2 manolis

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Posted 07 April 2014 - 16:47

Here is a simple variator (the V-belt section is cross-hatched; the weights - or rollers - are spheres moving along grooves: as the revs increase, the spheres move outwards increasing the effective diameter of the drive pulley):

PatBox10.gif

There are several aftermarket variators for each scooter model.

Question:

Can a scooter with a conventional CVT and with any aftermarket variator be faster or greener than the same scooter modified to PatBox CVT?

Thanks
Manolis Pattakos

#3 Kelpiecross

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Posted 08 April 2014 - 04:56

As ever I may be a little dim - but I don't see how the PatBox actually achieves the variation in pulley size etc. Nor do I understand the function of the "auxiliary thin belt".

The typical Chinese scooter/motorcycle engine (Google "GY6 engine") is of the centrifugal type you describe. There are literally countless millions of these things in China - and they work very well. A clever and practical (and cheap) design which incorporates the engine crankcase, CVT housing and swing arm all in the one unit. It operates in a fully "automatic" manner.
Does the PatBox have an "automatic mode"? (I suspect it would need one). I think the GY6-type CVT could be arranged fairly easily to hold the continuous "gear" range at any point.

My main interest in CVT-type matters is the possibility of a system that achieves (even theoretically) a continuous range of gear ratios strictly by all positively engaged all-teeth-and-gears etc. - something which has never been done in the last 500 years or so - Da Vinci had an attempt but it wasn't a great idea (he should have stuck to painting and sculpting - he was good at that).

Edited by Kelpiecross, 08 April 2014 - 05:58.


#4 manolis

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Posted 08 April 2014 - 13:10

As ever I may be a little dim - but I don't see how the PatBox actually achieves the variation in pulley size etc. Nor do I understand the function of the "auxiliary thin belt".

The typical Chinese scooter/motorcycle engine (Google "GY6 engine") is of the centrifugal type you describe. There are literally countless millions of these things in China - and they work very well. A clever and practical (and cheap) design which incorporates the engine crankcase, CVT housing and swing arm all in the one unit. It operates in a fully "automatic" manner.
Does the PatBox have an "automatic mode"? (I suspect it would need one). I think the GY6-type CVT could be arranged fairly easily to hold the continuous "gear" range at any point.

My main interest in CVT-type matters is the possibility of a system that achieves (even theoretically) a continuous range of gear ratios strictly by all positively engaged all-teeth-and-gears etc. - something which has never been done in the last 500 years or so - Da Vinci had an attempt but it wasn't a great idea (he should have stuck to painting and sculpting - he was good at that).


Hello Kelpiecross and thanks for your questions.

As it is now the conventional CVT in scooters, the rider just opens the throttle.

PatBox2.gif

The revs of the engine (and of the drive pulley which is secured to the crankshaft) start to increase.

Initially the automatic clutch engages (p1 to p2).
The revs and the speed increase.
At the p3 the engine revs are high enough to push the "rollers" of the variator outwards and to cause the spring of the driven pulley to get compressed.
From the p3 to p4 the revs stay, more or less, constant, but the speed increases.
At the p4 the effective diameter of the drive pulley is maximized. From theat point to p5 the transmission ratio is constant (the line p4-p5 passes from the start of the axes).

The ratio of the vehicle speed to the engine revs is the total transmission ratio (shorter at p3, longer at p4).

The conventional CVT provides infinite transmission ratios.
However they are not necessarily the "correct" transmission ratios the rider needs (the integer numbers are infinite, however if you want 1.5Kg of bread, the integers are not good to describe this quantity).

According the above plot, if you go with 80Km/h (take the point p4 as being at (80Km/h, 5000rpm)), the engine revs at 5000rpm. If you have a passenger, the engine at 80Km/h revs at 5000rpm again. If the road is a steep uphill and you try to go with 80Km/h speed, the engine still revs at 5000rpm. If you move on the highway with 80Km/h, the engine still revs with 5000rpm.

This is what the variator does.

Take now the same CVT modified to PatBox.
Suppose that you are moving on the steep uphill and the scooter is fully loaded.
If you block / stop the lever (7) when the transmission ratio is not yet too long, the scooter climbs easily and fast.

How this is realized?
The rider just blocks the lever 7.
The variator of the CVT tries, as usually, to increase the effective diameter of the drive pulley, but it cannot because it has also to pull, through the auxiliary belt and the rollers, the lever 7 clockwise; but the lever 7 is blocked by the rider. This way the transmission ratio remains shorter.

By blocking the lever 7 at various angles, all the area above the line p3-p4-p5 of the plot is accessible.

The CVT offers an infinity of modes. Each mode is the pair: (vehicle speed, engine revs).

The PatBox offers an infinity of infinities of modes: while for each "vehicle speed" the conventional CVT has one only corresponding "engine revs", with the PatBox for each "vehicle speed" there is an infinity of "engine revs" you can correspond.


You write:
"The typical Chinese scooter/motorcycle... operates in a fully "automatic" manner."

This is a solution and a problem.
Fully automatic means that if you need a different transmission ratio than the one selected "automatically" by the CVT, you cannot have it.
Imagine a long ride on the highway with 5000rpm and 50mph (80Km/h). If the engine can provide the necessary power from 4000rpm, why to have the engine operating at 5000rpm? (lighter load, lower mileage, noise, vibrations etc). However the CVT at 80Km/h keeps the engine revving at 5000rpm.
The CVT is a compromize.
The aftermarket variators do not solve the problem. They just shift it to different revs.


You write:
"Does the PatBox have an "automatic mode"? (I suspect it would need one)."

If you release the lever 7, the PatBox operates automatically, as a conventional CVT.
Besides (quote from the www.pattakon.com site):

PatBox1.gif


By blocking or pressing the front end of the blue lever, the rider selects manually a transmission ratio from the infinite available.

By completely releasing the blue lever (the restoring spring of the blue lever, at the back, keeps the auxiliary belt in tension) the rider leaves the transmission to operate automatically.

Strengthening (or weakening) the restoring force that acts on the blue lever (by shifting the anchoring end of the restoring spring of the blue lever, for instance), the characteristic curve of the CVT varies: in order to increase the effective diameter of the drive pulley, the variator has to compress (by means of the V-belt) the spring of the driven pulley as usual, but it has also to displace angularly the lever 7 overcoming a stronger (or weaker) restoring force.

It is like replacing "on the fly" the rollers of the variator by lighter or heavier ones.

In a two-mode version the rider shifts from the "touring" to the "sport" mode by pushing a pin (a button) to anchor a middle point of the blue lever restoring spring: the restoring spring becomes stiffer, a stronger restoring force acts on the blue lever and the variator keeps the revs higher.


That is, the PatBox has a variety of full automatic modes (like, say, an urban, a touring, a sport etc).

That is, with the PatBox you do not lose modes. You get additional modes of operation.


You write:

"I think the GY6-type CVT could be arranged fairly easily to hold the continuous "gear" range at any point."

Sorry.
I don't understand.
What do you mean?

Thanks
Manolis Pattakos

#5 Catalina Park

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Posted 09 April 2014 - 09:08

I like it! I think it would work well. Mind you the last thing I drove with a CVT was a Honda Odyssey (early 80s FL250 buggy and not the minivan)

#6 manolis

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Posted 11 April 2014 - 06:28

Hello.

I think the following (added to the http://www.pattakon....takonPatBox.htm ) are interesting (especially for those driving scooters and for the engineers).

They show a dangerous weakness of the low cost CVT vehicles.



"
Case study: "Overtaking with and without the PatBox"

A rider is cruising with his CVT scooter (and a passenger at the back seat) on a narrow country road at 50mph (80Km/h).
The engine is revving at 5000rpm (wherein it provides its peak torque).
The CVT operates at an intermediate point of the p3-p4 line of the "revs vs. speed" plot:

PatBox2.gif

The rider needs to overtake a long truck in front of him.
All he can do is to completely open the throttle and to wish good luck.
The CVT keeps the revs at 5000rpm and the scooter accelerates, but not as fast as the rider wishes. Every tenth of a second is vital / crucial.

The same rider is cruising with his modified to PatBox CVT scooter (and the same passenger at the back seat) on the same narrow country road at the same 50mph (80Km/h) speed.
The engine is revving at the same 5000rpm (wherein it provides its peak torque).
The CVT operates at the same (as before) intermediate point of the p3-p4 line of the "revs vs speed" plot.
The rider needs to overtake a long truck in front of him.
Instead of wishing good luck, the rider has now the option to use the PatBox lever as he opens completely the throttle valve:

PatBox4.gif

During the overtaking the rider (by means of the lever of the PatBox) keeps the engine operating at, say, 8000rpm wherein it provides its peak power; the time required drops substantially (for several seconds in some cases); the distance required to overtake the truck drops considerably, too.

The PatBox offers several options. The fact that it can minimize the time for an overtaking justifies, alone, its use.
"




Imagine the case you drive a heavy loaded CVT scooter having 70bhp peak power at 8000 rpm (along the line p18-p19).

You are in the point p17 (the speed is 50mph (80Km/h), the engine is revving at 5000rpm) wherein the engine provides only 50 bhp with full throttle.

You need to overtake a truck.

You open widely the throttle.

You necessarily "move" along the p17 to p4 line, with only the 50bhp accelerating the scooter.

Think: You pay for a big motor, you carry a big motor, you "feed" a big motor and the moment you desperately need all the power the engine can provide, the CVT has a different opinion: it leaves useless a good part of the "available" power, losing crucial / vital seconds.

Objections?

Thanks
Manolis Pattakos

#7 manolis

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Posted 15 April 2014 - 15:39

For those who are more familiar with bicycles:

Application of the PatBox on a bicycle.

Replacing the variator by a spring that pushes close to each other the two conical halves of the drive pulley, the PatBox CVT is ready for use in bicycles.

The drive pulley replaces the front sprocket of the bicycle, the driven pulley (with its spring) replaces the rear sprocket of the bicycle and the V-belt replaces the chain.
An auxiliary belt rides around, and abuts on, the V-belt (at the side of the pulley with the stronger spring); the auxiliary belt rides, also, around rollers on a lever.

If the spring of the drive pulley is the strongest, when the lever 7 is released, the PatBox CVT restores at its longest transmission ratio (the two halves of the drive pulley are close to each other).

If the spring of the driven pulley is the strongest, when the lever 7 is released the PatBox CVT restores at its shortest transmission ratio (the two halves of the drive pulley are apart from each other).
This is the preferable arrangement because the bicycle starts with the shortest transmission ratio/ When the lever is released, the system restores at shorter transmission ratios. The lever is located near the pedals.

The rider by displacing the lever varies continuously the transmission ratio.

The rider starts pedalling as usual.
When the rider needs a shorter (or longer) transmission ratio, the rider turns (or releases) the lever 7, the lever 7 rotates for a few degrees and then is secured till the next gearshift.

Objections?

Thanks
Manolis Pattakos

Edited by manolis, 15 April 2014 - 15:41.


#8 Kelpiecross

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Posted 16 April 2014 - 12:39


Might be better if the control lever could be operated by cable from one of the handlebar grips.

#9 munks

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Posted 17 April 2014 - 02:37

Serious bicyclists would concern themselves with aerodynamics and weight. You have a picture of what it might look like on a bike? What do you think this contraption might weigh compared to a set of gears/chain/derailleur?



#10 manolis

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Posted 17 April 2014 - 07:03

Hello Kelpiecross.

 

You are right: "Might be better if the control lever could be operated by cable from one of the handlebar grips.". This is an option.

 

 

Hello munks.

 

You write:

"Serious bicyclists would concern themselves with aerodynamics and weight. You have a picture of what it might look like on a bike? What do you think this contraption might weigh compared to a set of gears/chain/derailleur?"

 

Here is a stereoscopic image of the PatBox CVT arrangement for a bicycle:

 

PatBox_CVT_bicycle_1.gif

 

and here is another stereoscopic image showing the bicycle from another viewpoint:

 

PatBox_CVT_bicycle_2.gif

 

Both pulleys have restoring springs (yellow); the back pulley has the strongest spring, so when the lever is released, the transmission ratio gets shorter.

With the pulley springs, the trapezoidal belt remains in tension and the lever tries to return backwards

 

The pulleys and the belts and the lever are well oversized (their size fit to a 600cc / 40bhp motorcycle rather than in a bicycle).

 

I don't think the weight will be more than the weight of the set of gears/chain/etc.

 

Thanks

Manolis Pattakos


Edited by manolis, 17 April 2014 - 07:04.


#11 Speedman

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Posted 17 April 2014 - 09:37

Hello

 

I am also sure, CVT with a belt is good for scooter oder small motorbikes, but i don't think cvt with belt is not good for bicycles.

 

 

I believe this is the better solution. Nuvinci has less fiction.

 

NuVinci Continuously Variable Transmission

http://en.wikipedia....le_Transmission

 

 

Elektronic cvt for bigger scooter.

http://www.pirmil.in...1_cvtdemo.shtml

 

 

The Conical friction ring transmission is also simple.

http://www.freepaten...EP1855028B1.pdf

 

 

best regards

Speedman


Edited by Speedman, 17 April 2014 - 10:24.


#12 manolis

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Posted 17 April 2014 - 12:58

Hello Speedman.

The electronically controlled CVT's with the metallic V-belt (as Suzuki's and as those used in the automatic cars) are more efficient. However they are also expensive and heavy.

A different, quite interesting, approach is the DN-01 of Honda (hydraulic CVT used in a motorcycle / scooter model) as presented at http://novrizalbinmu...2013/09/hft.pdf I am not sure if it is still in production.


However almost all scooters (say more than 95%) are based on the CVT with the elastic V-belt and the centrifugal variator (governor).

With the centrifugal variator the control is anything but clever.

This is why many scooter owners pay a lot (say from US200$ to US500$) for aftermarket variators in order to get a little more sporty behaviour, or to overtake - a little faster - a truck.
Some scooter owner replace the rollers inside the variator with lighter ones to keep the engine revving at higher revs.
But in all cases the limitations remain.
The problem is not really solved.

It reminds the case with the wild aftermarket camshafts: the engine provides more power at high revs, but at lower revs / lighter loads the engine gets worse.
The solution was the VVA's (Variable Valve Actuation systems, like the Desmodromic VVA at http://www.pattakon....ttakonDesmo.htm wherein you can have a great (or infinite) number of different valve-lift profiles like:

DVVAprog.gif

With the PatBox the rider can modify - on the fly - automatically (or manually) the mode the CVT operates.

The PatBox is for a conventional CVT what a VVA is for an engine.

Actually the PatBox gives the control back to the rider.

Just think how much fuel would be saved if the scooter were operating at the right revs. The required modification is simple and cheap.

The case of the PatBox-CVT-bicycle is strange: without a variator, the rider selects, by the lever, the transmission ratio he likes.

Thanks
Manolis Pattakos

Edited by manolis, 17 April 2014 - 13:02.


#13 desmo

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Posted 17 April 2014 - 14:19

If it can be lighter, cheaper and more mechanically efficient than a conventional Campagnolo, SRAM or Shimano drivetrain then it might make good sense. Bicyclists take those three metrics *very* seriously and the current equipment is very, very good, so that's a tough ask. With the highly developed current systems there are so many ratios easily accessible the CVT part will probably have limited utility or appeal to cyclists.

#14 manolis

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Posted 17 April 2014 - 15:11

If it can be lighter, cheaper and more mechanically efficient than a conventional Campagnolo, SRAM or Shimano drivetrain then it might make good sense. Bicyclists take those three metrics *very* seriously and the current equipment is very, very good, so that's a tough ask. With the highly developed current systems there are so many ratios easily accessible the CVT part will probably have limited utility or appeal to cyclists.


Hello desmo.

In the case of bicycles, the weight and the cost of the PatBox have no reason to be bigger than those of the conventional drive train (like Shimano etc).
I am not sure about the mechanical efficiency.
Does anybody know at what mechanical efficiency the current bicycle-drive-trains operate?


In the case of the scooters, on the other hand, the PatBox offers - for sure - a substantially better fuel efficiency (mileage) because most of the time the conventional V-belt CVT keeps the engine (for the sake of improved performance) at higher revs than necessary (and so at lighter load), i.e. at conditions worsening the fuel efficiency.
And there are millions of scooters on the roads.

Thanks
Manolis Pattakos

#15 Catalina Park

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Posted 18 April 2014 - 00:52

What would be the efficiency losses of a V belt compared to a chain drive on something like the weight of a bicycle? 
I imagine that there would be some extra loss in the belt?



#16 Greg Locock

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Posted 18 April 2014 - 01:03

For our first couple of solar cars we used chain drive, but we did not have a derailleur setup, just a fixed cog. Actually that's not true, the original one had a complex gearbox that somehow did the job without leaving the derailleur in the loop most of the time. That system was abandoned almost immediately once the awesomely useful characteristics of electric motors, and the single operating point required during the race, became apparent.

 

Anyway, for our third car we had to decide whether to follow the herd and go with a wheel motor, which was an engineering effort rather greater than the rest of the car together, or stick with a conventional motor/chain system.

 

So, the lads measured the efficiency of a fixed chain system, and got 98% at low speed, but at high speed the efficiency dropped rapidly.I never saw the numbers, but they were obviously bad enough that the wheel motor project went live.

 

It was a great deal of work, roughly 2 years of all my spare time just managing the design and looking after the mechanical side, I think we probably had 3 electric motor people on it almost full time at the university. But the end result has been almost faultless, it is still equivalent to the front runners, and reliability has been surprisingly good. I just found the drawings in my garage, hence the brainfart.

 

http://www.jhu.edu/n...aug99/bike.html

 

http://www.cyclingpo...efficiency.aspx

 

 

Also note that in a pushbike the apparently rather badly designed derailleur operates under negligible load most of the time, so despite the tortuous chain path the energy absorption  in the chain and bearings is fairly low.

 

You might have guessed I'm a big fan of bicycles, even though the design has scarcely improved in 100 years. Grins



#17 desmo

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Posted 18 April 2014 - 01:43

98% mechanical efficiency is number thrown about for a perfectly tuned chain drive system. Whatever the real world figures, bicycle chain drives are or can certainly be very efficient, so much so that no significant further improvement is possible. And the reason that bicycle design today is remarkably like that of 100 years ago (although no marketer would *ever* admit as much) is that the design was approaching being optimized even then. The French constructeurs of 60-70 years ago had wrung out most of what remained in terms of improvements since. One can in fact ride a bike by one of the better known constructeurs like Herse or Singer built in the early 1950s and the most modern bike built for a similar purpose and there will be little empirical difference in efficiency or performance between the two. The current modern version will or may weigh slightly less and will have more gear ratios (with a weight and complexity penalty, plus a structurally compromised rear wheel to accommodate all the necessary cogs) that are slightly easier to select, but really that's about it. Pure fixed cog track racing bikes still often don't even pretend to be much different than successful decades old designs--they're hardly different at all, even in appearance.

The beauty of a mature developed design is in its near perfection for its purpose; the downside if one wants to view it as such is that there is very little scope for any substantial improvement through further development. The odds that in 100 years time pure bicycles will be significantly functionally better than the best current designs--or even those of 60 years ago--seems to me slight. Of course that won't stop people trying or stop marketers from claiming their innovations are somehow transformative to the extent that you must buy their new "improved" offerings or be left behind.

#18 Greg Locock

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Posted 18 April 2014 - 02:14

Efficiency of V belts varies a lot say 95% new, 90% typical

 

Efficiency of timing belts 95%, and essentially doesn't change until the belt breaks.. 

 

and there is this, haven't read it properly but it has heaps of good stuff in it

 

http://www.michaelse..._efficiency.pdf



#19 manolis

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Posted 18 April 2014 - 08:10

Hello.

Greg Locock thanks for the useful link with the lab-tests for the belts efficiency.

It seems the peak efficiency of the chain is 98%, but as the revs increase it drops substantially.

It also seems (according the lab-tests of Carlisle) that the cogged V-belt has, even at high revs, an average efficiency of 95% (with more than 97% for some designs).


Let’s suppose the chain has a 2% better efficiency than the V-belt.

For a professional bicycler it is an important difference. No doubt. A tenth of second separates the winner from the loser.

But is it for the average bicycle rider?


I think the average bicycler doesn’t really understand what the gearbox is for, neither when it is the perfect moment to shift to a shorter or longer gear ratio.

He/she sees the two levers / selectors on the handlebars as a complication that spoils the fan.

A bicycle having 18 or 21 (or ?) gear ratios reminds the case with the old two-stroke racing motorcycles wherein the torque had a peak at, say, 15,000rpm, and 1,000rpm earlier and later it had nothing. The rider had a lot of work with the gearbox in order to keep the engine at the useful narrow band.

Desmo,
besides the weight, the cost and the efficiency, I would add the “easy of use” (OK not for all, but for, say, the 95% of the bicycle riders).

I hope you agree.

On this field (i.e. on the "driver friendly operation") the PatBox CVT has a good advantage.
A push (a patting) on the lever to move for a few mm and the gearshift finished.
And if the pedaling is still “heavy”, another patting on the lever.


By the way,

while in the case of bicycles the transmission has to be completely replaced to turn to PatBoxCVT,

in a CVT scooter the basics are already there; the efficiency of the V-belt remains as good (or bad) as before the modification; the auxiliary belt and the lever with the rollers just control the transmission in order to keep the engine at the desired revs / load.

Thanks
Manolis Pattakos

Edited by manolis, 18 April 2014 - 08:19.


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#20 Catalina Park

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Posted 18 April 2014 - 08:19

Some riders are always trying to ride in the wrong gear so the efficiency difference wouldn't matter that much anyway!

#21 manolis

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Posted 04 May 2014 - 03:35

At

http://www.pattakon....atBox.htm#PECVT

it is presented the Electronically-controlled version of the PatBox.

PatBoxS1.gif

PatBoxS3.gif


The Suzuki Electronically-controlled Continuously Variable Transmission (SECVT) used in the Suzuki Burgman 650 (and, slightly modified, in the Aprilia Mana 850; it seems Aprilia pays royalties to Suzuki) is regarded as the-state-of-the-art CVT in scooters / bikes
A technical presentation of the SECVT is at http://www.pattakon....atBox/SECVT.pdf

The functionality of the two systems (SECVT and PECVT) is the same.

The simplicity and the cost differ.

Also the loads on the V-belt differ.

Any thoughts ?

Thanks
Manolis Pattakos