Date: Sat, 4 Dec 2004 09:02:45 -0800
Reply-To: Tom Young <tomyoung1@COMCAST.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Tom Young <tomyoung1@COMCAST.NET>
Subject: Re: Errors in CV Rotation Article at Volkscafe website
Content-Type: text/plain; charset="Windows-1252"
Try this:
Get yourself a cardboard tube from a rool of toilet paper or roll of paper
towels. Mark one end "A" and the other end "B" or one end "C" and the other
end "D". Cut a couple of pieces of fairly stiff wire - like from a coat
hanger - about 4 or 5 inches long. Run the wires completely through the
tube at either end (i.e. right angles to the long axis of the tube) with the
wires more or less in the same plane. This tube and wires setup represents
the axle attached to the inner CV joints.
Now slide your middle two fingers of both hands into the tubes with your
index and pinky fingers outside, resting on the wires, on opposite sides of
the wires. That is, if your index finger of the left hand is between your
body and the wire then the pinkey finger should have the wire between it and
your body, and the right hand index finger will have the wire between itself
any your body while the right pinky will be between the wire and your body.
Your hands and fingers outside the tube represent the outer part of the CV
joint.
Now imagine one hand as the CV joint on the the transmission and the other
hand as the CV joint out at the hub. Slightly turn your "transmission" hand
away from you as if it was driving the wheel and notice the pressure you
feel on the outside fingers from the wire. Go through the various
iterations of "axle" orientation and see how this pressure changes, or
doesn't.
---------------------------------------------------
Tom Young
Lafayette, CA 94549
---------------------------------------------------
----- Original Message -----
From: "John Rodgers" <inua@CHARTER.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, December 04, 2004 8:25 AM
Subject: Errors in CV Rotation Article at Volkscafe website
> I don't want to set off a firestorm here. Just trying to sort out CV
> rotation.
>
> Sam Walters prompted me to have a look for myself at the Volkscafe
article.
>
> I took a look at the article find the article to be really well done.
> Extremely informative. Volkscafe and Ben McCafferty's efforts are most
> appreciated.
>
> However, in the part of the article on the discussion about CV bearing
> rotation I perceive errors. I have double checked it, and I set up a
> model to analyze it, ( axle with bearings marked with arrows indicating
> direction of rotation) and I still came up with the conclusion that
> there are some basic errors in the assumptions. If I am wrong, if I have
> missed something, I hope someone will clarify it for me.
>
> Credits to: http://www.Volkscafe.com and Ben McCafferty
> (for the whole article -
http://volkscafe.com/main.jsp?pa=ip&ip=1150562894 )
>
> * Constant Velocity Joints (CVs): Diagnosis, Maintenance and Replacement*
> By Ben McCafferty
>
> *Quote:*
> "CV's take wear on one face of the ball hubs only (except when you drive
> in reverse), so they can be made to run in the opposite direction to
> extend their life. There are two ways you can accomplish this. Assume
> you’re looking at the back of the van, and the CV's are labeled with
> letters, like this:
>
> /A------B Transmission C------D/
>
> You can move the axles so that the letters now read:
>
> /C------D Transmission A------B (option 1)/ OR
> /D------C Transmission B------A (option 2)/
>
> These two configurations will result in the forces being applied to the
> CVs being reversed. Note, however, that the following configuration will
> NOT reverse the forces applied to the CV joint rotation:
>
> /B------A Transmission D------C/
>
> In other words, if you move the axles to the other side of the van, the
> forces being applied to the CV's will be reversed. If you keep them on
> the same side of the van, they won’t. On a Syncro Vanagon, since the
> outer front CV's are not interchangeable with the inner front CVs, the
> front axles must be rotated according to option 2 above."
>
> *End Quote!*
>
> Given that the goal is to reverse rotation;
>
> it follows
>
> Option 1: Incorrect
> Analysis shows this course of action results in no reversal of
> axle/bearing rotation. It remains in the same direction.
>
> Option: 2: Correct
> Analysis shows this course of action to result in a reversal of
> rotation. Note that the axle shaft assemblies AB and CD were flipped 180
> degrees for this configuration.
>
> Refer again to the diagram:
>
> /A------B Transmission C------D/
>
> Quote:
> "Note, however, that the following configuration *will NOT reverse* the
> forces applied to the CV joint rotation:
>
> /B------A Transmission D------C"
> /
>
> The above statement is incorrect.
>
> The above configuration *will reverse* the direction of rotation of the
> bearings. Note that B-A has the same direction of rotation as B-A in
> Option 2 - which is correct, as does D-C have the same rotation as D-C
> in Option 2 - which is correct, by virtue of the fact that the shafts
> have been flipped 180 degrees.
>
> I believe it is easy to get confused on this "CV Direction of Rotaion"
> issue, and this discussion above is an example of my point.
>
> It is my hope that this has helped to clear the air a bit on the subject.
>
> In summary the following configurations result in reversal of rotation.
>
> Original:
> /A------B Transmission C------D
> /
>
> /Reversal configurations://
> B------A Transmission D------C
> /D------C Transmission B------A
>
> //
>
> Regards,
>
> John Rodgers
> 88 GL Driver
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