Date:         Mon, 27 Jan 2003 09:39:58 -0800
Reply-To:     Tom Young <tomyoung1@ATTBI.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Tom Young <tomyoung1@ATTBI.COM>
Subject:      Re: CV article now available - I'm confused (long)
Comments: To: Ben McCafferty <ben@VOLKSCAFE.COM>
Content-Type: text/plain; charset="iso-8859-1"

I'm confused about the issue of reversing the direction of rotation of the
axles to extend the life of the CV.  In the article it states:
-------------------------------------------------------
"Assume you're looking at the back of the van,
 and the CVs 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 CVs being
 reversed. Note, however, that the following
configuration will NOT reverse 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 ROTATION
WILL BE REVERSED."

(emphasis added)
-------------------------------------------------------

I grabbed the cardboard tube inside a roll of toilet paper and labeled the
left side "C" and the right side "D" and then drew arrows above the letters
pointing away from me:

  ^                   ^
  |                     |
  C                  D

This shows the direction of rotation of the axle on the right side of the
van in the first diagram.

If I move the roll to the left side, as in option 1, it ends up looking
exactly the same:
  ^                   ^
  |                     |
  C                  D

so the statement "In other words, if you move the axles to the other side of
the van, the rotation will be reversed" does not seem to be literally true.

Option 2 orientation, however, results in the arrows pointing toward me
("down" on this page) as:

   D                C
   |                   |
   v                  v

(The D and C should be upside down and backwards, but you get the idea.)

Which *does* reverse the rotation of the axle.

And the last diagram - the orientation of axles on the same sides as they
were, only flipped end-for-end, looks exactly the same as Option 2"

   D                C
   |                   |
   v                  v

which, again, has the direction of the axle's rotation reversed from what it
was.

So it looks to me that if the object of the exercise is to reverse the
*rotation* of the axle then Option 2 should work as should flipping axles
end-for-end.

Thinking that the term "rotation of the axle" wasn't the term the author
really intended to use, I redid my cardboard tube as follows:

  ^
   |
  C                  D
                        |
                       v

which reflects the pressure the joints on the right-hand axle "feel" under
driving load, i.e., the C joint has the torque of the transmission urging it
"forward" while the D joint is overcoming the inertia of the vehicle.

The Option 1 orientation looks like

                      ^
                       |
C                    D
 |
 v
ญญญ
that is, the D joint is now being urged forward while the C joint is
resisting, a change from the original orientation.

But Option 2 looks like

  ^
  |
  D               C
                     |
                     v

resulting in *no* change from the original orientation.

And the final diagram in the article would likewise look like:

 ^
  |
  D               C
                     |
                     v
resulting in *no* change in pressures from the original orientation.

I'm going to assume that the author is correct and that simply flipping the
axles end-for-end on the same side of the transmission as they were
originally is *not* accomplishing anything since I've read this sort of
remark in various places.  However, looking back through the diagrams I've
constructed, that says the *only* orientation that works is Option 1, that
is:

C------D Transmission A------B.

Am I smoking my socks here folks?

---------------------------------------------------------------
Tom Young                       '81 Vanagon
Lafayette, CA 94549         '82 Westfalia
---------------------------------------------------------------
----- Original Message -----
From: "Ben McCafferty" <ben@VOLKSCAFE.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Monday, January 27, 2003 6:44 AM
Subject: CV article now available


> Good morning everyone,
> My first tech article is now available on the Volks Cafe website, covering
> CV joint diagnosis, maintenance and replacement.  From the home page, look
> for it under "New Items", or use this link:
> http://volkscafe.com/articles/cvarticle/cvarticle.html.
>
> It is quite lengthy and detailed, and I'd love any and all feedback.  The
> next article, which covers oil pressure diagnosis and treatment as well as
> OP gauge installation, will be out later this week.