Date: Wed, 25 Nov 1998 17:37:45 -0600
Reply-To: Joshua Van Tol <jjvantol@USWEST.NET>
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: Joshua Van Tol <jjvantol@USWEST.NET>
Subject: Re: Bearing load on reverse driven transaxles
In-Reply-To: <2869fcd6.365ba5c6@aol.com>
Content-Type: text/plain; charset="us-ascii"
> jjvantol@USWEST.NET writes:
>
>(Just please remember that this is all quoted out of context)
>
><< Well, actually, with the helical gears that isn't true. There's
>a significant amount of longitudinal loading on those bearings,
>which is why they usually use double tapered roller bearings...>>
>
>The only place a double tapered roller bearing is used in
>the Vanagon gearbox is the pinion shaft. The mainshaft
This is true for most transaxles. I was thinking about the longitudunal
loading imparted by the pinion gears.
>is supported in the front by a ball bearing with an inner
>race designed to accept a very small amount of longitudinal
>load. The halves of the gearsets that are free spinning
>ride on caged needle bearings as well. They do float back
>and forth very slightly when not under load but once the
>slider locks in the torque is transferred axially through the
>main or pinion shafts. If the torque was transmitted
>longitudinally (Man! What a word!) then you'd be blowing
>the gears down the shafts and out the ends of the gearbox.
I agree, axially is probably a better word to use in this context than
longitudinally, although they both mean the same thing, provided you're me,
and you can't remember the right word. :-)
Actually though, reversing the direction you turned the input shaft would
cause the helically cut gears to be forced in the other direction along the
shaft (axially) than if you turned the shaft the right way. You would
normally experience this when overrunning the engine, so some sort of
capacity for this type of use is built into the box. But it mayb the that
there's a thrust bearing for the normal direction, and a simple machined
surface for the other.
>
> <<The helical ring and pinion gears may not work so well in
>reverse, as the load bearing surface would be the opposite side.>>
>
>The Split window Busses up to '67 ran a Beetle transaxle with
>the differential on the opposite side. The pinion head drove the
>coast side of the ring gear due to the reduction gear box design-
>2 spur gears which reverse the direction of axle rotation. If the
>VW engineers where concerned with driving the coast side of
>the ring gear then they would have had 3 gears in the redux
The above comment I made (The helical ring and pinion ...) about helical
gears not working well in reverse meant that turning them backwards might
result in them not working well. Flopping the diff in no way results in any
change that the diff cares about. By backwards I mean turning the input
shaft the wrong way, not flipping the diff.
>boxes. Now, the Type 1s ran a helical cut ring and pinion set
>but not a true Hypoid like the later Busses, Vanagons, and
>Audis. This means that the pinion head intersected the ring
>gear at... say the 3 o'clock position when viewed from the
>side. With a true Hypoid the cut of the ring and pinion is much
>more 'swirled' and the pinion intersects the ring gear more like
>5 o'clock. Frankly, I don't know how that would effect a ring
>gear that was driven on the coast side like the early Bus.
>
> <<May not be a problem, or it may be. I just remember that if
>you run a Corvair transmission backwards, it isn't supposed to
>last long at all. >>
>
>Perhaps that was marketing to sell reverse camshafts and
>so forth?? ;)
Could be, but I'll bet it had to do with lack of thrust bearings in the
"wrong" direction for the gear sets. I'm going to pull out my Bently
Vanagon manual and see what sort of thrust bearings the VW had. Chances
are, if VW didn't use thrust bearings for both sides of the gear, neither
did Chevy.
>
>-Todd Hill
> VolksWerks Transaxles
> Olympia, WA
Joshua Van Tol -- jjvantol@lear.csp.ee.memphis.edu
