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Driveshaft Angle and Phasing Made Ridiculously Simple


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#1 Magoo

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Posted 28 July 2014 - 10:06

Trying to explain driveshaft angle and phasing can be devilishly difficult, but this video demonstration makes it totally easy and simple.

 

This item has drawn a huge response since it was posted, suggesting that there is more need for good, clear tutorials like this than we may suppose. So if you know of any on automotive topics, please shout out. 

 

 

 

 

Video: Driveshaft Angle and Phasing 

 

 

 

 

qfHBcS.jpg

 

 

 



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#2 gruntguru

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Posted 29 July 2014 - 05:20

Nice video. Particularly liked the credit card flapper as a velocity indicator.

 

Not mentioned but worth adding - constant velocity does not require the input and output shafts to be parallel, only that the operating angle of each joint be the same. Of course if the input and output shafts are not in the same plane, the phasing will need to varied to suit.


Edited by gruntguru, 29 July 2014 - 05:21.


#3 Lee Nicolle

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Posted 29 July 2014 - 09:31

The phasing of modern [last 30 years!!] triple joint tailshafts is a real drama. Many such as Holden Commodore always have a light 'whip' at low speeds under accelaration. Damned annoying. Most others do not do it,,, until everything gets old and tired

This does truly still confuse me. Even just a std tailshaft which all of us take for granted. 

As does universal joints, simple but complex! That and balancing tailshafts, something many places cannot get right. Yet others can be machined off and shortened with no viabration issues. 

Uni joints are not uni joints though. Some cheap ones seem to bind at high speed. Having suffered horrendous vibes at over 150 mph [race car] the brand name unis were replaced with high performance Spicer ones, shaft balanced [hardly needed it so they said]  and no viabrations at all. Tested to about 175mph. In this instance I will reccomend Spicer for balancing whole heartedly.

Interestingly I was told that having the shaft dead straight at ride height is not a good idea. The rollers dont roll in the trunnions and the uni will get roller marks in the cross at a fairly short service life. In my case I just adjusted the nose of the diff down,which helps hook it up at low speed anyway,  not so easy in most cars. This was because the pinion is so low in a 9" diff in comparison to the GM pinion it straightened out the angle. On my vehicle.



#4 sblick

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Posted 29 July 2014 - 20:32

Always been told in NVH that a flat driveshaft is not as good as one with a slight angle. So if you don't want any shaking in the car don't design a flat driveshaft.

#5 Canuck

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Posted 29 July 2014 - 20:57

Your timing could be better. In the middle of a driveshaft redesign as we speak. The vendor's casual "oh yeah, no problem, do it all the time" response has me scared enough to be doing lots of homework.

#6 desmo

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Posted 29 July 2014 - 21:42

All right, 'big bang' traction benefits are misaligned u-joints away!



#7 Greg Locock

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Posted 30 July 2014 - 05:06

One thing to bear in mind is that your diff pitches under acceleration, ruining your carefully thought out angles. You can only truly optimise a driveline for one propshaft torque, managing the compromise is the name of the game. This has led to the popularity of CV joints in RWD propshafts.

 

According to Hookes Joint manufacturers the optimum angle for durability on a rig is 4 degrees, to avoid False Brinelling as it is often called. In a car that is not needed as much because the engine and the diff are moving around a fair bit.

 

Incidentally, if you think driveshaft angles are tricky, wait until you try and lay out a steering column, with typically 3 UJs and massive angles between the shafts.



#8 gruntguru

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Posted 30 July 2014 - 06:45

At least the steering column won't vibrate. :)



#9 bigleagueslider

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Posted 31 July 2014 - 00:54

I love the term "false brinelling". As if the damage done to the race surfaces is not a "true" problem. With needle bearings subject to oscillatory motion, there should be sufficient movement to ensure each roller completes one full rotation. This distributes the wear evenly over the race surfaces. If there is little or no rotation of the rollers, they will create small local depressions in the race surfaces. And when the rollers eventually do pass over these surface depressions, it will produce pitting/spalling of the race.



#10 Magoo

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Posted 31 July 2014 - 02:53

 

 

Incidentally, if you think driveshaft angles are tricky, wait until you try and lay out a steering column, with typically 3 UJs and massive angles between the shafts.

 

About six months ago I drove a street rod with extremely odd steering feel and response. Looked at the steering column arrangement and.... honestly, the things people come up with. 



#11 Lee Nicolle

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Posted 31 July 2014 - 09:12

One thing to bear in mind is that your diff pitches under acceleration, ruining your carefully thought out angles. You can only truly optimise a driveline for one propshaft torque, managing the compromise is the name of the game. This has led to the popularity of CV joints in RWD propshafts.

 

According to Hookes Joint manufacturers the optimum angle for durability on a rig is 4 degrees, to avoid False Brinelling as it is often called. In a car that is not needed as much because the engine and the diff are moving around a fair bit.

 

Incidentally, if you think driveshaft angles are tricky, wait until you try and lay out a steering column, with typically 3 UJs and massive angles between the shafts.

Three unis in a steering shaft is too many. Very few vehicles use that. And really you need a bearing on an intermediate shaft. Or it just flops everywhere .

Having been there and done just that, RH drive car with a Chev engine. The starter is in the way!

Steering column,, uni, short shaft to a second uni,, another short shaft with a carrier [heim joint] then another short shaft to the rack and the third uni. Far from ideal, safe but only just. 

Later I changed the rack to a  stronger one with a better input angle and then only 2 unis. And no more worry about the rack failing. [Which had happened]

If a manufacturer has to use three it is just plain bad design. 



#12 MatsNorway

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Posted 12 August 2014 - 16:13

This might be interesting for you guys.

 

"Through using shifted slot parts of the universal ring the user can also tune the angular speed fluctuations to create chatter which can be desirable in some conditions."

 

http://www.redrc.net...tem/#more-84946



#13 gruntguru

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Posted 12 August 2014 - 21:56

Dirt racer - big bang thinking?


Edited by gruntguru, 13 August 2014 - 05:50.


#14 desmo

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Posted 12 August 2014 - 23:01

See post #6 above.  What, you thought I was joking? So did I.



#15 MatsNorway

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Posted 13 August 2014 - 12:03

:)

 

I think that the shattering stuff is increasing the resistance on the inner wheel making it aid in turning on tight bends.