Jump to content


Photo
- - - - -

Another Deltic link but a very good one


  • Please log in to reply
84 replies to this topic

#51 bigleagueslider

bigleagueslider
  • Member

  • 1,235 posts
  • Joined: March 11

Posted 03 July 2015 - 04:59

Unfortunately for you, Manolis is not making such representations to a potential manufacturer. He is putting his proposals and supporting arguments to a technical forum and asking for technical criticism.

 

I am sure Manolis is familiar with the "burden of proof" cliché - from the mouths of actual engine manufacturers. Quite pathetic to have it trotted out here!

I am experiencing no "misfortune" from this discussion. I also appreciate the fact that Manolis has an honest intention to solicit criticism when he presents his engine concepts on this forum. The criticism I offer should not be taken personally. It is simply an expression of what I have learned regarding the subject during many years of work experience in the industry. The critique I presented to Manolis was mild compared to what he would experience during a formal design review involving a party like the FAA or NASA.

 

I find your comment "It will only be a truly "technical discussion" when posts like this (mine) and that (yours) disappear." especially unfortunate. Do you not appreciate that any open discussion is a two-way process? i would expect better from you.



Advertisement

#52 gruntguru

gruntguru
  • Member

  • 7,635 posts
  • Joined: January 09

Posted 03 July 2015 - 06:36

I find your comment "It will only be a truly "technical discussion" when posts like this (mine) and that (yours) disappear." especially unfortunate. Do you not appreciate that any open discussion is a two-way process? i would expect better from you.

From what you have suggested of your experience I would assume the difficulties of moving from innovative concept to marketable product would be very obvious to yourself. More to the point, Manolis is an old hand in that space and I would expect you to have the insight to recognise that your input to this "two way process" is obvious to the point of being condescending.



#53 manolis

manolis
  • Member

  • 935 posts
  • Joined: May 03

Posted 06 July 2015 - 16:41

Hello.

The Revetec engine mentioned in previous posts is based on trilobe cams.
For each rotation of the cam, the piston performs three reciprocations.

Using single lobe cams, the engine becomes simpler, more compact and cheaper (more at http://www.pattakon....ttakonGreco.htm )

greco_i1.gif

The following three in line crankless engine:

greco_i3.gif

is perfectly balanced provided the camlobe profile is the appropriate one.
The pistons perform pure sinusoidal motion described as:

Y=Sin(f)*(S/2) + C,

wherein Y is the piston position along the cylinder axis, S is the piston stroke, f is the rotation angle of the cam and C is a constant.

The above three-in-line crankless engine is more vibration free than any conventional reciprocating piston engine no matter what arrangement it uses, no matter how many cylinders it comprises.
The total unbalanced inertia force, inertia torque and inertia moment of the above even-firing engine are all zero.
Comparable with the above three-in-line are only the Wankel rotary engine and the harmonic engine:

I1.jpg

at http://www.pattakon....PE.htm#harmonic


In the “A work of pure genius!” thread of the ultimate-car-page forum at
http://www.ultimatec...read.php?t=2958 you can read three different proofs (one based on geometry, another based on trigonometry and a third based on physics) of the claimed perfect balancing, you can also read the objections recorded and their justification.

Thanks
Manolis Pattakos

#54 bigleagueslider

bigleagueslider
  • Member

  • 1,235 posts
  • Joined: March 11

Posted 07 July 2015 - 03:42

From what you have suggested of your experience I would assume the difficulties of moving from innovative concept to marketable product would be very obvious to yourself. More to the point, Manolis is an old hand in that space and I would expect you to have the insight to recognise that your input to this "two way process" is obvious to the point of being condescending.

Say what? I have stated numerous times that I appreciate the creative aspect of what Manolis proposes with his numerous engine concepts. And he certainly seems to have a fairly good understanding of the fundamental engineering principles involved. But I have yet to see any evidence, or even a coherent explanation, of how he will transition one of his engine concepts into a commercially viable product.

 

It is a cold,hard reality that the only financial value of any invention is primarily its economic worth as a commercial product. Since you don't seem to appreciate this basic fact, how is it "condescending" to point it out?

 

If Manolis  (or gruntguru) were to say here is a fairly comprehensive technical and financial plan to get my engine concept to where it is a marketable product, manufacture it, and then sell enough of them to produce a profit, I'd be first in line to offer my hearty congratulations.



#55 Canuck

Canuck
  • Member

  • 2,384 posts
  • Joined: March 05

Posted 07 July 2015 - 16:00

Why? Is an idea's only value it's ability to be monetized? 



#56 desmo

desmo
  • Tech Forum Host

  • 29,343 posts
  • Joined: January 00

Posted 09 July 2015 - 01:46

No money; no development.



#57 bigleagueslider

bigleagueslider
  • Member

  • 1,235 posts
  • Joined: March 11

Posted 09 July 2015 - 05:01

Why? Is an idea's only value it's ability to be monetized? 

Don't confuse ideas or concepts with inventions.

 

Consider the concepts of indivdual freedom and liberty. To many people in the US these are priceless, and they would not trade them for any amount of money. Yet the founders of the United States that laid out these principles in the US Constitution did not recieve a single penny for their efforts. Or how about Isaac Newton publishing some of the most significant principles of physics in a textbook, but receiving little in the way of financial compensation for his efforts.

 

As for inventions, like the many examples proposed by Manolis, while they may have value to him on an emotional basis, unfortunately the only economic value they have is what someone is willing to pay him to obtain the rights to exploit the invention commercially.



#58 Canuck

Canuck
  • Member

  • 2,384 posts
  • Joined: March 05

Posted 09 July 2015 - 05:23

An invention doesn't require an idea? Regardless, you seem to have misunderstood my statement. I'm asking if the only acceptable value we can assign to any given topic is its economic one? How many light bulbs did Edison try before finally wrestling public credit for the invention of the tungsten filament bulb? We're those multitudinous iterations without value, unworthy of discussion without being dismissed as pointless?

#59 manolis

manolis
  • Member

  • 935 posts
  • Joined: May 03

Posted 10 July 2015 - 06:36

Hello.

Both sides are right.

A technical innovation needs money to develop and to get into the market making profit.
The money needs good / sound technical ideas to be invested on, otherwise the money is lost.


Take the case of Martin Jetpack.
For thirty years Martin, alone, was developing his Jetpack. Away from commercialization and profit. It was a project full of expenses.
Only a few months ago his project was funded with some $24M. A Chinese company is ready to invest another $50M
Unfortunately a month, or so, ago Martin resigned disagreeing with the new orientation of the company which is incompatible to his own dream for a personal Flyer. The biggest asset of Martin Jetpack company is gone.


Take the case of Malloy hoverbike.
A year ago he was trying to gather $80K in order to make his new hoverbike prototype in normal size. Now he is talking with the US Army for a big deal (an escape / survival vehicle for trapped troops).


Take the case of EcoMotors.
The technical idea – OPOC engine - was ready from 15 years ago.
After several years of efforts Peter Hofbauer received the required funds.
Besides the 100 millions (or so) of dollars funded so far, Hofbauer achieved to have as basic investors big names like Bill Gates (the OPOC was presented as an environmental friendly engine).
Besides, the technical magazines around the world publish anything new (or “new”) coming from EcoMotors. Thousands of articles can be found in the Internet.
Unfortunately the original idea was not good enough (there are substantial issues yet to be addressed).
Despite the big money invested, and the big names involved, OPOC’s future remains uncertain.


Take the case of the VCR-i variable compression ratio mechanism / engine of the French mce-5 company.
They were proud for the €100M (some $110M) invested (several of them by public companies).
Their plans were to get in mass production during 2016.
50 engineers were (are?) working full time for the VCR-i.
Unless I am wrong, the last news added to their website are from 2013.
The original idea was not good enough: as happens regularly, it solves a technical problem introducing others, more difficult to be addressed, technical problems / side effects.



Take the Australian Revetec.
Many investors lost their saving investing on Revetec camless engine. For the technically oriented it is OK. For the rest investors the journalists around the world have the blame, because nobody focused on the obvious technical issues of Brad’s design.
I recall Brad proudly spending big money to Cosworth for high-tech cylinder heads (for engines falling apart at 4,000 rpm or earlier; 4,000 is the number of reciprocations per piston per minute).


Take the case of the Wankel Rotary engine.
Half a century ago they were invested, and lost, several billions of dollars (every car maker had an R&D department dedicated to the evolution of the rotary engine; a few of them (Citroen, NSU) bankrupted because of the Wankel rotary.


Money is an important part of the process.
A sound technical idea is more important. At the end, even if it ends up without profit, it leaves a legacy / a reference / a prior art / a basis for the future inventors / engineers.

For instance:
The TCVJ (Thompson) coupling is a constant velocity joint patented by an Australian engineer and presented as the “Holly Grail” of engineering. The money invested to his company was lost. The idea had a small “issue”. The small “issue” proved its Achilles’ heel in practice.
The TCVJ evolved to the PatCVJ (that solves the “issue” of the TCVJ).

TCVJtoPatCVJ.jpg

And the PatCVJ evolved to the PatDAN:

PatDAN_M1.gif

that makes a lot more (for more: http://www.pattakon....takonPatDan.htm )

The problem is simple: to transfer torsional and axial loads by a mechanism that keeps the transmission ratio between the input and output shafts strictly at 1:1.
Either it will be commercialized or not, the PatDAN is a technical solution of a long existing problem.


You can’t imagine how important and useful the objections in a strictly technical discussion may prove.
The engineers, mechanics, scientists (the members of a technical forum like this) look at the new idea from a different than the inventor viewpoint. And their opinion is invaluable for him.
So please do your best posting your strictly technical objections; the more negative, the better.

Thanks
Manolis Pattakos

Advertisement

#60 bigleagueslider

bigleagueslider
  • Member

  • 1,235 posts
  • Joined: March 11

Posted 11 July 2015 - 04:43

Fair enough Manolis. I appreciate that you understand the point I was making about how in order for any invention to be successful, it needs to demonstrate both a technical and economic advantage over existing designs. I have plenty of personal experience in this regard. I have spent a large amount of money on securing half a dozen US patents that I truly felt had commercial value. But I have made far less income from them than I have spent on them.

 

In the future I will limit my responses to technical issues. But I will be objective with my criticisms and will not adopt a negative tone. I understand that inventors consider IP like one of their children, and are usually very sensitive to any criticism of their "baby".



#61 manolis

manolis
  • Member

  • 935 posts
  • Joined: May 03

Posted 13 July 2015 - 07:18

Hello Bigleagueslider and thanks.

Regarding the PatDAN CVJ (constant velocity joint) at post #58,
the three "fingers" of each shaft (cyan and white) may seem long and flexible.
The shafts were designed this way to keep unhide the rest parts (red, blue and yellow forks).

In the following stereoscopic image:

PatDAN_shafts.jpg

the shafts are way more robust (the fingers are bridged by webs). The angle between the two cooperating shafts is 60 degrees (and can be even bigger, if required).

Besides the torsional loads it transmits from the one shaft to the other, this PatDAN CVJ can also transmit heavy thrust (axial) loads; imagine the case it connects the main rotor of a big helicopter with the main shaft.
It uses only three thrust roller bearings (they are disposed between the three yellow forks at the center of the joint). All the rest bearings of the PatDAN joint are simple needle roller bearings.

If anyone is interested, I can further explain.


By the way, compare the above stereoscopic (4D?) animation (post #58) and image with the respective conventional 3D animation and image (all you have to do is to hide the right half of the image or animation).
When things get too complex for an eye, the stereoscopic view (it requires a pair of eyes) is as useful as if a prototype was in front of the viewer.

Thanks
Manolis Pattakos

#62 Kelpiecross

Kelpiecross
  • Member

  • 1,730 posts
  • Joined: October 10

Posted 13 July 2015 - 13:34


As always - amazing 3D - Christ only knows how the mechanism works though. Like a couple of octopuses wrestling.

#63 MatsNorway

MatsNorway
  • Member

  • 2,822 posts
  • Joined: December 09

Posted 13 July 2015 - 13:56

I had the fortune of recieving the device from Manolis as a 3D file.

Sadly it had some modeling unperfections that made it hard to do a FEM on it. (Get either Catia or the Autodesk product design package Manolis ;) )  At least for me not being hired to do it. (i only looked at it during pauses and free time, gimme a couple of hours/days and i could prob fix it up)

 

It is important to remember that there is alot of challenges from that 3D model to a real product.

 

(Going by memory as it is a year ago or so)

 

do you see any bearings/bushings?

How does the yellow senter piece look fully fleshed out in every detail.

How is it locked together when assembled.

Is the design symmetric? because i believe i could not take the other part and use it on the opposite end.

 

Are you going to machine the parts to be round? why? probably better of with billet lumps. Could one simplify the design for production purposes?
 

A fully developed joint would probably look wastly different than the render. Manolis is aware of this. He allready displayed the reasoning for one part being as thin as it is (for showcasing) But the inner parts does not have that spacious luxury.

 

Manolis probably also know that is is a niche product. Its benefit is high angles of attack(?) and a constant speed at those angles (?)

 

The drawbacks are price, probably load transfer capasity for its size, life expectancy(relative), being a unproven part with no historical data, and that it is just a concept.

 

Manolis probably only have the idea. And needs a customer to show interest before he would do full development.

 

In addition surely if it becomes big enough one could start to discuss a solution with gears.

 

Edit: Like this and please. It took me 5min so if it actually does not work. Do not bucher me.

 

Like%20this_zpsobblkuzv.jpg


Edited by MatsNorway, 13 July 2015 - 14:11.


#64 MatsNorway

MatsNorway
  • Member

  • 2,822 posts
  • Joined: December 09

Posted 13 July 2015 - 14:13

It litterally took 5min. The gears are all kept in a solidly mounted housing mounted say.. on the steering hub of the vehicle. Input shaft allows rotation one way. Output shaft takes the other way. To facilitate more angle increase the tranfer gears size.

 

Probably a bunch of challenges there too. i just got the sudden urge to idk.. put ut another options to trow out some ideas for the problem with big angles.++

 

Edit: I understand that everything needs to kinda go around a center on this one but you know. Point is make the joint complicated enough and a geared solution might be an alternative.


Edited by MatsNorway, 13 July 2015 - 14:33.


#65 gruntguru

gruntguru
  • Member

  • 7,635 posts
  • Joined: January 09

Posted 13 July 2015 - 22:23

Mats. At first glance your geared universal looks analagous to a hookes joint which means not constant velocity.



#66 Greg Locock

Greg Locock
  • Member

  • 6,349 posts
  • Joined: March 03

Posted 13 July 2015 - 22:53

The better is the enemy of the good. A traditional double cardan is a fairly good CV joint, with an efficiency of 99.7%. Adding a stabilizing link to the short shaft improves performance slightly at high angles. Thompson's coupling was a further refinement on that, but totally lost my respect when he started spruiking 50% reduction in losses, and then mangling that to imply some huge efficiency gain.

#67 gruntguru

gruntguru
  • Member

  • 7,635 posts
  • Joined: January 09

Posted 14 July 2015 - 04:04

How does it go?

"four fifths of five eighths of **** all"



#68 Kelpiecross

Kelpiecross
  • Member

  • 1,730 posts
  • Joined: October 10

Posted 14 July 2015 - 04:07


Mats - presumably the big gear in the centre can tilt around the smaller gears on the right to give variation in angle in one plane and the big gear on the left can tilt similarly to give variation in the plane at 90 degrees? This would give constant velocity between input and output shafts - but would this arrangement cause a big offset in the alignment of the input/output shafts?

#69 MatsNorway

MatsNorway
  • Member

  • 2,822 posts
  • Joined: December 09

Posted 14 July 2015 - 17:07

Mats - presumably the big gear in the centre can tilt around the smaller gears on the right to give variation in angle in one plane and the big gear on the left can tilt similarly to give variation in the plane at 90 degrees? This would give constant velocity between input and output shafts - but would this arrangement cause a big offset in the alignment of the input/output shafts?

Everything you say is correct as im aware. Not sure if that can be worked around. One idea i had was; If the first small gear gets a internal gearing you can drive a smaller gear (as in further inn)for the output shaft to engage giving clearance against the first small gear allowing tilting on the "same" small gear senter. But i believe it is still offset by the size of the smaller gear (something like that)

 

Ninjaedit: actually i believe it would work. You need to rotate the hub around the senterline of the smaller gear.


Edited by MatsNorway, 15 July 2015 - 15:52.


#70 manolis

manolis
  • Member

  • 935 posts
  • Joined: May 03

Posted 14 July 2015 - 22:03

Hello Mats Norway.

You write:
"How does the yellow senter piece look fully fleshed out in every detail.
How is it locked together when assembled.
Is the design symmetric? because i believe i could not take the other part and use it on the opposite end."

Here are the answers:

PatDAN_M_bearings.jpg

PatDAN_M_bearings_zoom.jpg

PatDAN_M_central_bearings_off.jpg

PatDAN_M_central_bearings.jpg

The two shafts are different. Also, the red yokes (they connect the central triad of yokes with the one shaft) are different in shape than the blue yokes (they connect the central triad of yokes with the other shaft).

For the assembly the last two drawings are explanatory: the red and green central yokes assembled with their thrust roller bearing pass through the side opening of the cyan central yoke; the assembly of the central triad of yokes completes / lockes by inserting the blue part and the left thrust roller bearing through the left hole of the cyan yoke and by tightening the bolt at right; the red and blue yokes of the upper drawing are assembled on the central triad of yokes and then the needle roller bearings are inserted between the central yokes and the red / blue yokes; the assembly completes with the two shafts and the six yellow peripheral pins.


According Thompson Coupling ( http://www.thompsoncouplings.com ) in their CVJ’s the maximum angle between the cooperating shafts is limited to only 15 degrees.

In comparison, this PatDAN CVJ is capable for more than 60 degrees angle between the shafts. If it was limited to, say, only 48 degrees (as the conventional Rzeppa joints used in the front drive shafts of cars) the size of forks / bearings could substantially increase.
On the other hand, the torque load and the axial load split among all yokes of the PatDAN. Even if the roller bearings seem small and the inner yokes seem thin, the load capacity is not small.


Is 60 degrees big enough for a Constant Velocity Joint?

The Technical Review of NTN (Japan, some 20,000 employees) at http://www.ntn.jp/en...R75_en_P016.pdf is titled:

"Fixed Constant Velocity Joint with a Super High Operating angle of 54 degrees"

Compare the efficiency of the PatDAN cvj with that of the NTN Rzeppa cvj at big shaft angles.
The one is totally based on simple needle roller bearings (and on three thrust roller bearings among the central triad of yokes) the other is based on spheres sliding (not rolling) along pairs of deep grooves / tracks.

Quote from http://www.pattakon....takonPatDan.htm :

The PatDan CV joint is based on roller bearings and is rid of loaded sliding surfaces.
In comparison the Rzeppa CV joint is based on heavily-loaded sliding surfaces wherein balls slide.
For the same wide angle between the shafts, the PatDan is by far more efficient than the Rzeppa CV joint (the first runs cold while the second soon overheats).

The PatDan has the qualifications to substitute the Rzeppa CV joints in the automobile drive shafts: true constant velocity joint, way more efficient, greater-steering-angles / smaller-turning-radiuses.

Thanks
Manolis Pattakos

Edited by manolis, 15 July 2015 - 02:00.


#71 bigleagueslider

bigleagueslider
  • Member

  • 1,235 posts
  • Joined: March 11

Posted 15 July 2015 - 04:41

Manolis- Your CV joint concept is definitely interesting. But one significant issue I see with your design is the number of bearings it uses. Looking at the model you provided, it appears that your CV joint requires 24 needle bearings. The typical U-joint only requires 4 needle bearings, and the typical tripod joint only requires 3 needle bearings.

 

How do you justify the cost/benefit of your high-angle design versus existing CV joint designs, that seems to perform adequately?



#72 manolis

manolis
  • Member

  • 935 posts
  • Joined: May 03

Posted 16 July 2015 - 05:21

Hello Bigleagueslider

You write:
”The typical U-joint only requires 4 needle bearings, and the typical tripod joint only requires 3 needle bearings.
How do you justify the cost/benefit of your high-angle design versus existing CV joint designs, that seems to perform adequately?”


The cost depends on the number of the needle roller bearings and on the size of them. When the load splits among several bearings, smaller / cheaper bearings are used.
I.e. the overall cost of the joint is not proportional to the number of roller bearings it comprises.


The U-joint mentioned, is not a constant velocity joint.
The bigger the angle between the cooperation shafts, the bigger the “oscillation” of the transmission ratio above and below the ideal 1:1 during a rotation.
Exactly on this problem / characteristic of the U-joint is based the PatRE rotary engine:

PatRE.gif

(more at http://www.pattakon....takonRotary.htm )


For a constant velocity connection, you need a pair of U-joints (i.e. 8 needle roller bearings) plus a mechanism / casing keeping them properly aligned / oriented (which further increases the number of the required roller bearings).
Even this way, the absence of a unique center in the joint (ideally it should be a specific point of the first shaft and also a specific point of the second shaft) is a big issue. Think what happens when you try to take heavy axial loads.

In the above calculation of the minimum number of roller bearings there are no thrust roller bearings. Can a U-joint operate without surfaces / bearings receiving thrust loads?

The typical U-joint needle roller bearing:

maintance-free-universal-joint-bearings1

maintance-free-universal-joint-bearings3

comprises an integral plastic washer with lubricant grooves and waffle pattern that optimizes lubrication conditions.
This plastic washer receives thrust loads keeping the axes of the two shafts coplanar (otherwise they cannot intersect at the center of the joint).
Similar washers are used in the conventional differentials between the bevel gears and the casing.

Quote from the US6,264,566 patent:

“When the bearing cups are mounted on the associated trunnions, the circular end walls of the bearing cups are disposed adjacent to the axially outer ends of the trunnions and bearings. If the inner surfaces of these end walls directly contact the axially outer end surfaces of the trunnions during operation, friction caused by such direct contact can generate undesirable heat and wear. However, if the inner end surfaces of the bearing cups do not fit snugly against the axially outer end surfaces of the trunnions, relative axial movement between the bearing cups and the trunnions can cause imbalances and result in undesirable noise and vibrations. Thus, to address these situations, it is known to position a thrust washer between the inner end surface of the bearing cup and the axially outer end surface of the trunnion. A typical thrust washer is formed from a relatively low friction, wear resistant material, such as plastic, that can absorb the thrust loads that occur between the end of the trunnion and the bearing cap and take up any looseness therebetween. A typical thrust washer also extends radially outwardly into the annular space between the axially outer ends of the bearings and the end wall of the bearing cup to properly position such bearings relative to the bearing cup during operation.”

End of Quote

If you count the plastic washers as thrust bearings, the overall number of bearings in a true-constant-velocity double U-joint becomes 16, without counting the roller bearings keeping the shafts properly oriented.
In the Thompson CVJ coupling and in the PatCVJ coupling a “pantograph” mechanism is used to make this job requiring six articulated parts (the green, the brown, the two cyan and the two yellow parts at left, with a set of needle and thrust roller bearings) :

PatCVJ.gif

In comparison, the PatDAN (animations and images in previous posts) needs just three thrust roller bearings in total. The rest roller bearings are simple/cheap needle roller bearings rid of end cups, rid of plastic washers and thrust loads.
The geometry of the PatDAN mechanism is what makes the difference keeping the yokes in place, allowing extreme angles between the shafts ( if required ) to be used, providing a strictly 1:1 transmission ratio, allowing heavy torsional and axial loads to pass from the one shaft to the other efficiently and providing a unique center point fixed relative to the one shaft and fixed relative to the other shaft.



A tripod joint is a joint for a specific use (limited angle between the shafts, balls sliding – not rolling, sliding - along pairs of grooves / tracks (friction), absence of a unique center (a useful characteristic for its specific use) etc.
The PatDAN is a quite different mechanism for different applications. Instead of comparing it with a tripod joint, compare it with the Rzeppa joint like the one presented by NTN at http://www.ntn.jp/en...R75_en_P016.pdf
If you put the Rzeppa Joint to transfer a significant amount of torque with the shafts at a significant angle (say 40 degrees), the Rzeppa mechanism will soon overheat and fall apart. If there is interest, I can further explain.

Thanks
Manolis Pattakos

#73 manolis

manolis
  • Member

  • 935 posts
  • Joined: May 03

Posted 17 July 2015 - 03:32

Hello Bigleagueslider.

Let me further explain the split of the load (mentioned in my previous post).


At http://news.pentades...mokinetic-or-cv it is shown the transmission ratio variation of the simple u-joint:

79a4d4220f7db91d3c19a622aa76128d.gif

it is also shown an animated double u-joint at operation:

tumblr_ni5uqbSBtA1u6bmdpo1_r1_500.gif


Follow the load.

On the double u-joint the load passes, through a pair of needle roller bearings, from the first shaft to the first cross; then, through another pair of needle roller bearings, the load passes from the first cross to the intermediate shaft; then, through another pair of needle roller bearings, the load passes from the intermediate shaft to the second cross; finally, through another pair of needle roller bearings, the load passes from the second cross to the second shaft.

It is a serial process / transmission of torsional and axial loads. The “capacity” of each pair of needle roller bearings must be adequate to deal with the complete load (and more; think what happens at big angles).


In the PatDAN CVJ the load from the first shaft splits among three pairs of needle roller bearings; then, through another three pairs of needle roller bearings, it passes to the second shaft.

PatDAN_M_central_bearings_small.jpg


Another issue of the double U-joint is the support of the intermediate shaft in case the orientation of the one shaft relative to the other is variable.


Another worth mentioning issue is the vibration-free quality; the rotation at variable angular velocity of the intermediate shaft of the double U-joint causes vibrations.

Quote from http://www.pattakon....takonPatDan.htm

“The inertia "torsional" vibrations reduce.
Instead of having a single heavy "control" yoke that, with the shafts rotating at constant angular velocity, rotates at variable angular velocity generating an inertia torque and torsional vibrations, the PatDan has three lightweight "control" yokes arranged at 120 degrees from each other.
The smoothness (absence of significant torsional vibrations) of the PatDan is better than the smoothness of the TCVJ and PatCVJ, just like the inertia torque of an even firing six cylinder engine is lower than the inertia torque of an even firing four cylinder engine”

Thanks
Manolis Pattakos

Edited by manolis, 17 July 2015 - 03:44.


#74 bigleagueslider

bigleagueslider
  • Member

  • 1,235 posts
  • Joined: March 11

Posted 17 July 2015 - 03:36

I understand the difference in function between a U-joint and a CV joint. And I appreciate that your CV joint concept provides a greater misalignment angle capability than existing CV joint designs. But is this greater misalignment capability really needed for most commercial applications?

 

Regarding the number of rolling element bearings required, anyone that has ever worked in the auto industry will tell you that when it comes to cost of a mass-produced product, total parts count is what matters most. And dozens of needle bearings, each having a dozen+ rollers, would not be acceptable in terms of cost vs benefit for a production vehicle.



#75 gruntguru

gruntguru
  • Member

  • 7,635 posts
  • Joined: January 09

Posted 17 July 2015 - 05:14

Doesn't that depend on the benefit?



#76 manolis

manolis
  • Member

  • 935 posts
  • Joined: May 03

Posted 17 July 2015 - 05:19

Hello Bigleagueslider.

You write:
“I understand the difference in function between a U-joint and a CV joint. And I appreciate that your CV joint concept provides a greater misalignment angle capability than existing CV joint designs. But is this greater misalignment capability really needed for most commercial applications?”


The 50 degrees angle between the shafts of the typical Rzeppa joint and the 54 degrees of the “champion” TUJ of the Japanese roller-bearing-maker NTN, are not 50 and 54 because bigger angles would not be useful.
They are not bigger because they cannot be bigger (the geometry of the mechanism puts this limitation).


Quote from the technical Review of NTN at http://www.ntn.jp/en...R75_en_P016.pdf (mentioned in previous posts):

“NTN Corporation has succeeded in developing a fixed-type constant velocity joint called TUJ that has the world’s highest maximum operating angle -54 degrees- for automobile drive shafts.
TUJ will allow four-wheel drive and front-wheel drive cars to have a greater steering angle, enabling a very small turning radius.
. . .
Conclusion.
By employing NTN's unique design, we have developed an innovative fixed CVJ featuring a maximum operating angle of 54 degrees while having the performance comparable to that of conventional CVJs (maximum operating angle of 50 degrees). This maximum operating angle (54 degrees) for automotive driveshaft is currently the highest in the automotive industry. The increase of 4 degrees in operating angle means that the minimum turning radius of an average medium-sized FF car can be decreased by approximately 70 cm (13%) or the wheelbase of such class of a car can be enlarged by approximately 40 cm (15%) while maintaining a minimum turning radius. In other words, a medium-sized car can feature a turning radius of a compact car or the passenger space of a larger car allowing designers more flexibility in consideration of layout and design.”

End of quote.

news20060831_1.jpg

See how proudly NTN announces their TUJ Rzeppa joint.
Its only advantage, relative to the prior art, is the plus 4 degrees angle between the shafts.

Do I need to further explain?


Other applications?

Quote from the Internet (Engineers Sydney, June 2009):

“In 2008 Thompson Couplings entered into a commercial agreement with the Boeing Company USA”

Thanks
Manolis Pattakos

#77 gruntguru

gruntguru
  • Member

  • 7,635 posts
  • Joined: January 09

Posted 17 July 2015 - 06:33

Manolis, looking at that image it appears the NTN TUJ joint operates with one or more balls beyond the limits of the outer race when at maximum angle. Is that the case?



#78 manolis

manolis
  • Member

  • 935 posts
  • Joined: May 03

Posted 17 July 2015 - 07:50

Hello Gruntguru.

According the analysis in the NTN Technical Review:

NTN_TUJ.jpg

it appears that for angles above 40 degrees, one ball of the six is supported only by the cage and the inner track.

In the above drawing the ball at the top has left its outer track (groove) for 5 degrees, with the two shafts being at only 50 degrees angle.

With the angle between the shafts at 54 degrees (the TUJ limit) the top ball leaves its outer track for 5+(4/2)=7 degrees.

At extreme shaft angles (say 50 to 54 degrees) and despite the disengagement of one or two balls from their outer tracks, the rest balls / tracks do the job and the joint operates reliably.

Thanks
Manolis Pattakos

#79 bigleagueslider

bigleagueslider
  • Member

  • 1,235 posts
  • Joined: March 11

Posted 19 July 2015 - 02:24

Manolis- Thanks for the marketing materials from NTN. While they provide all sorts of hoopla about the extra 4 degrees of angular travel provided by their latest CV joint design, I did not see any actual proof of why it is necessary for the typical production automobile. I have driven many different FWD automobiles that used conventional CV joints, and I don't recall any of them having an issue with steering capabilities or suspension travel.

 

Also, did you notice that NTN managed to increase the angular travel of their CV joint design without adding additional parts?



Advertisement

#80 Greg Locock

Greg Locock
  • Member

  • 6,349 posts
  • Joined: March 03

Posted 19 July 2015 - 07:34

" I have driven many different FWD automobiles that used conventional CV joints, and I don't recall any of them having an issue with steering capabilities or suspension travel."

 

That's because you've never designed one. Articulation angles are a significant constraint on FWD designs, typically the suspension travel is limited to make sure we don't pop the joints. This has bad implications for ride. Having said that I don't know of a program that has taken the easy option and bought the 4 degree extra joints.



#81 bigleagueslider

bigleagueslider
  • Member

  • 1,235 posts
  • Joined: March 11

Posted 21 July 2015 - 02:37

That's because you've never designed one. Articulation angles are a significant constraint on FWD designs, typically the suspension travel is limited to make sure we don't pop the joints.

Say what? How would the performance of a 2015 Honda Civic, in terms of steering angular capability or front suspension travel, be influenced by whether or not I was involved in the vehicle's design?



#82 gruntguru

gruntguru
  • Member

  • 7,635 posts
  • Joined: January 09

Posted 21 July 2015 - 02:53

Allow me to translate (sorry Greg).

 

There are many FWD vehicles on the road where the steering lock or suspension travel has been limited by available CVJ articulation angle, but subtle enough to be not obvious to the driver. The OEM designers (eg Greg) may be the only person aware of this.



#83 manolis

manolis
  • Member

  • 935 posts
  • Joined: May 03

Posted 21 July 2015 - 04:00

Hello Bigleagueslider.

Regarding the number of parts:


The conventional Rzeppa joint (like that of NTN in previous posts) comprises two shafts, six balls, and a ball cage; i.e. 9 main parts.
They are required special materials and heat treatment.
The machining of the tracks on the shafts is tricky.
The Rzeppa joint is based entirely on heavily loaded sliding surfaces: the load passes through the linear contact of the balls with their tracks. This has nothing to do with the balls in the ball roller bearings (wherein the balls roll along their tracks).
When the shaft axes are not collinear, the balls in the Rzeppa joint have a difficult task to perform: each pair of tracks form some kind of wedge, with the ball sliding between them and keeping them “synchronized”.


In comparison, think of a PatDAN without roller bearings:

PatDan5.gif

the number of parts is 11 in total (the two shafts, the thee red forks, the three blue forks and the three central yellow forks).
Without roller bearings, the mechanism is based on sliding surfaces as the Rzeppa joint.
But in the case of the PatDAN joint, the loads pass through surface contact (and not through linear contact), resulting in substantially reduced local stressing.
With two more parts (11 instead of 9) the bending angle is substantially bigger than the maximum possible bending angle of the Rzeppa’s joint. Besides, the PatDAN fits with transmitting heavy axial loads, too.


PS.

Yesterday it was published by the US-PTO the
NOTICE OF ALLOWANCE AND FEE(S) DUE
for the PatDAN constant velocity joint (it is the continuation-in-part of the original US patent application for the PatCVJ (already granted) and the PatDAN).
The US PatDAN patent is to be granted after the payment of the US480.00$ issue fee.

Thanks
Manolis Pattakos

#84 gruntguru

gruntguru
  • Member

  • 7,635 posts
  • Joined: January 09

Posted 21 July 2015 - 04:50

To be fair a Rzeppa joint articulates with combined sliding and rolling friction - not pure sliding as your post suggests.



#85 manolis

manolis
  • Member

  • 935 posts
  • Joined: May 03

Posted 21 July 2015 - 05:48

Hello Gruntguru.

You are right.
It is combined rolling and sliding.
At high shaft angles, the ball onto, or near, the plane defined by the two shaft axes is mostly rolling along the two tracks it engages, while the ball “90 degrees” away is rolling and sliding as it abuts on the two tracks it engages.
I.e. during a complete rotation of the shaft / tire, each ball passes from sliding/rolling to pure rolling to sliding/rolling and to pure rolling again.

At high angles Rzeppa joint is not efficient (friction). However it fits with FWD (Front Wheel Drive) and 4x4 vehicles because, besides being compact and simple and cheap, most of the time it operates with the two shafts at, or near, a line. And when high bend angles are required (say at a U-turn) the torque loading the Rzeppa joints is low and the speed of the shaft is low, too.

In some 4x4 and in buggys wherein the suspension travel needs to be maximized, the bending angle of the Rzeppa joint is significant most of the time, consuming energy that overheats the joint.

Thanks
Manolis Pattakos