Date: Mon, 27 Jan 2003 10:57:48 -0700
Reply-To: Ben McCafferty <ben@VOLKSCAFE.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Ben McCafferty <ben@VOLKSCAFE.COM>
Subject: Re: CV article now available - I'm confused (long)
In-Reply-To: <002401c2c62b$1cca2b60$7900a8c0@attbi.com>
Content-type: text/plain; charset="ISO-8859-1"
Hi Tom,
Thanks for the clarification, this is exactly the feedback I'm looking for.
You are correct in stating that I didn't intend "rotation of the axle",
rather, "pressure on the faces of the inner and outer ball hubs". In other
words, you're trying to get pressure on the opposite face by moving the
axles around.
That said, I still stand behind my assertions in the diagrams. While your
discussion is close to the mark, it misses one point--where the pressure
gets applied, not just which direction it's being applied from. Try it this
way: hold your hands in front of you with your fingers pointed towards each
other, and interlace your fingertips. Pretend your left hand is an outer
ball hub, and your right hand is an inner ball hub. Assume we're talking
about the inner right rear CV for a moment. As the tranny applies forward
force to the outer hub (your left hand), the inner ball hub (your right
hand) feels that force on the trailing edges. Now flip your hands over (not
easy to do!) and assume that your left hand is the outer hub for the inner
left rear CV. As forward force is applied to it by the tranny, you will
quickly see that the force on the inner ball hub is felt on the opposite
faces, i.e. the other side of your right fingers. The same holds true for
both outer joints. That takes care of the A-B Tranny C-D to D-C Tranny B-A
scenario. The A-B Tranny C-D to C-D Tranny A-B scenario can be proven in
the same manner.
Thanks again for the clarifying comments, I will update the article as soon
as possible.
tx,
bmc :)
Ben McCafferty
ben@volkscafe.com
Volks Cafe
1823 Soquel Avenue
Santa Cruz, CA 95062
831-426-1244
http://www.volkscafe.com
> From: "Tom Young" <tomyoung1@attbi.com>
> Reply-To: "Tom Young" <tomyoung1@attbi.com>
> Date: Mon, 27 Jan 2003 09:39:58 -0800
> To: "Ben McCafferty" <ben@volkscafe.com>, <vanagon@GERRY.VANAGON.COM>
> Subject: Re:CV article now available - I'm confused (long)
>
> 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.
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