rontyler
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| posted on 3/2/04 at 01:30 AM |
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CV joint angularity
All,
Been re-thinking my rear subframe... I am seriously considering tossing the factory cradle and lowing the engine/trans. One of the things it would
effect is half-shaft angularity (they are level now). Anybody have opinions on how much angularity I can run before risking disaster?
Thanks.
Regards, Ron Tyler
"Nothing is ever accomplished by a reasonable man."
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kb58
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| posted on 3/2/04 at 01:53 AM |
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I sure would like to know the answer to this myself. I know it depends on the torque transmitted, angles involved, and axle length. I have much the
same issue, but I've already dug a much deeper hole then you.
As far as engine height, I lowered mine until the bottom of the pan was just above the bottom of the car. Also consider that tire OD dictates when
and where all the drivetrain bits become in line. Picking the right size tires might make it all work out.
[Edited on 3/2/04 by kb58]
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rontyler
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| posted on 3/2/04 at 03:12 AM |
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"I know it depends on the torque transmitted, angles involved, and axle length."
Agreed. I'm just looking for a generalization or maybe some experiences.
Regards, Ron Tyler
"Nothing is ever accomplished by a reasonable man."
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suparuss
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| posted on 3/2/04 at 06:31 AM |
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front wheel drive cars seem to cope ok, when you have full lock on the angle is fairly extreme, and in both directions with the car tilting over when
you go so fast you make your tyres screach on every corner like me!  but they might be designed for that in a fronty.
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rontyler
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| posted on 3/2/04 at 06:40 AM |
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"front wheel drive cars seem to cope ok, when you have full lock on the angle is fairly extreme."
Good point. Thanks.
I'm thinking that heat (over an extended period of time) from the increased operating angles may accelerate wear. Anybody agree/disagree???
Regards, Ron Tyler
"Nothing is ever accomplished by a reasonable man."
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sgraber
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| posted on 3/2/04 at 05:24 PM |
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I am running a lowered drivetrain in relationship to the outer cv's. Those FWD cv's will take a huge amount of misaligment while under
load.
Using stock components, with relatively stock engine outputs and considering the type of abuse these components receive during manufacturer testing
(and by moron drivers) I think that several degrees of angularity will be a complete non-issue.
As you are driving, irregularities in the road surface will cause the suspension to move up and down anyways, so you will rarely run with the
cv's at one specific angle.
I can't imagine that you will be putting 50,000 miles on your car. Even if you get 20,000 less miles out of the cv's you will probably
never drive the car far enough to wear them significantly.
Graber
[Edited on 2/3/04 by sgraber]
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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JoelP
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| posted on 3/2/04 at 08:17 PM |
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and even if they only lasted 10k it wouldnt be the end of the world! unless you crashed, then it could be i suppose...
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rontyler
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| posted on 3/2/04 at 08:39 PM |
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Not toooo concerned with wear... I don't want a FAILURE.
Thanks.
Regards, Ron Tyler
"Nothing is ever accomplished by a reasonable man."
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sgraber
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| posted on 3/2/04 at 08:53 PM |
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Well failure is just extremely rapid wear... 
Alright. I see your point. Best to let someone with EXPERIENCE in these matters answer yer question then...
I hear the wind whistling through these empty halls....
Best you just do it, and if it fails, be sure to let us know!
Graber
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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rontyler
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| posted on 3/2/04 at 09:24 PM |
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"Best you just do it, and if it fails, be sure to let us know! "
GREAT idea!
Regards, Ron Tyler
"Nothing is ever accomplished by a reasonable man."
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GTAddict
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| posted on 3/2/04 at 11:25 PM |
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Here's the skinny, numbers all from V.A.W. Hillier's 'Fundamentals of Motor Vehicle Technology', 4th edition.
The Tracta type joint is usually used on heavy-duty agricultural or commercial vehicles. It consists of two forks on the ends of the half-shafts, a
'spherical joint' and a 'spigot joint'. it's unlikely you have these. If you have, they are tough if inefficient, but
can withstand a max angle of 40° off-axis.
The Weiss (Bendix, or Dunlop) CV consists of two claw-like spherical forks, with five ball-bearings in between, four between the forks, and the fifth
in the centre, acting as the pivot between the forks. Max angle, 35°.
Now the common ones: the Rzeppa/Birfield CV joint uses six balls, with a grooved spherical cup on the stub, and a cage on the shaft. It looks like a
big, flexible ballrace, and the cage and balls are protected by the rubber boot and packed with grease. They are usually used on the outer end of
driveshafts, and have a maximum angle of 45° - although not for long as at this angle a lot of heat is produced. However, this angularity means it is
excellent for FWD cars.
The Tripode joint is a strong, efficient design, using three pronged forks, with the shaft carrying three rollers, and the stub having a cup with
shaped channels for the rollers. Again commonly used as an outer FWD, as the maximum (occasional) angle is 45° off-axis.
To take up the variable length of driveshafts, especially for FWD applications, the inner CV is usually a plunge design, and there are variations of
both the Birfield and the Tripode in plunge form, where the stub forms a deep cup with either a six-petal flower-shaped recess for the Birfield
(maximum drive angle of 22°) or three slots for the Tripode (max angle of 25°.
All CV joints should spend the vast majority of their working life with an off-axis angle of less than 10°.
Hope this answers your questions.
Hillier is an absolute treasure trove of simple, and simply explained, automotive engineering, and while some of it simply doesn't apply to
modern cars (e.g. it tells you how a carburettor works) most of it is damned interesting and thoroughly good reference (e.g. it tells you how a
carburettor works...)
Mark.
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kb58
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| posted on 3/2/04 at 11:29 PM |
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Ah, good stuff, thank you very much! I now need to go check some half-shaft angles... and if it's wrong I'm in very big trouble...
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rontyler
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| posted on 3/2/04 at 11:34 PM |
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GT,
Yes! Yes!
Gracias Maximus!!!
Regards, Ron Tyler
"Nothing is ever accomplished by a reasonable man."
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sgraber
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| posted on 3/2/04 at 11:36 PM |
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GTAddict, you are a most useful fellow to have around wouldn't you know?
Thanks,
Graber
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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rontyler
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| posted on 3/2/04 at 11:37 PM |
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GT,
Yes! Yes!
Gracias Maximus!!!
Regards, Ron Tyler
"Nothing is ever accomplished by a reasonable man."
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GTAddict
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| posted on 3/2/04 at 11:42 PM |
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Happy to help, but its all in the books, you know.
Now if you want to know about air-cleaners... I have some first hand knowledge.
Mark.
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TheGecko
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| posted on 4/2/04 at 12:35 AM |
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Mark,
Let me add my thanks for that info. I know you're quoting from the book but it's a book few (if any) of us would have on the shelf (and
Amazon says it's out of print too  ).
Air-cleaners? I notice form your avatar that you wear them as a fashion accessory . Do they actually constitute part of your 'real'
job at AML?
Thanks again,
Dominic
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GTAddict
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| posted on 4/2/04 at 07:52 AM |
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Ah, no. Used to be a project manager at an air-cleaner supplier. That was quite fun - I worked with a variety of cars, from Ford Fiesta to Bentley
Continental.
I now work with electronic systems and multiplexing.
M.
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giel
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| posted on 4/2/04 at 08:28 PM |
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if it is of any help:
in my job designing bus chassis, I learned that the joints of a drive shaft should NOT be aligned straight (0 degrees), to prevent them from
'hammering'at the same contact points all the time, wich will cause early wear.
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