Date: Sat, 18 Aug 2007 13:49:31 -0700
Reply-To: Reinhard Vehring <rvehring@YAHOO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Reinhard Vehring <rvehring@YAHOO.COM>
Subject: Re: ride height adjustment? (long post)
In-Reply-To: <000401c7e1c7$9ab2d060$15b2d8d1@dhanson>
Content-Type: text/plain; charset=iso-8859-1
Don,
I see your point. I wonder though if your traction
problems are caused by this. I would think the
suspension would need to be very uneven before you'd
loose traction on a wheel on a straight uphill road.
Maybe if the frame was twisted in an accident or a
broken spring or something like that.
Maybe it's something else? The problem with vanagon
suspensions is that they have so darn little travel.
Classical example is going uphill on a steep sharp
right turn curve. As you go around the turn the right
side of the van get's lifted by the right front wheel,
the left front doesn't climb as fast so the right rear
needs to extend to stay on the ground. Because the
spring constant of vanagon spings is high, extending
the spring causes loss of traction quickly. So the
inner rear wheel starts spinning. This is a pain
especially on paved wet mountain roads. Lifted
vanagons with stiffer springs are even worse in that
respect.
Yes, Moose has the diff lock, but I use it with
caution. Going around a steep curve with the diff lock
engaged is always tricky. If I hit a patch with good
traction I have to disengage quickly to prevent a lot
of stress in the drivetrain. I hate snapped axles in
the wilderness. Disengaging the diff lock is the
tricky part, sometimes it just doesn't want to do that
quickly enough for my taste. Really steep switchbacks
on dirt roads are a massive pain in the butt, even for
the regular Syncros from what I hear (as in rear right
and front left loosing traction).
Have you looked into a limited slip differential?
That maybe a relatively simple upgrade if you want to
maximise traction on the road. As for off-road, I
think we have to accept that a vanagon has its
limitations there. (Now I' expecting a lot of flame
from the syncronauts) To see a true off road
drivetrain and suspension on a similar sized vehicle
google Pinzgauer. Now that thing is cool, but my wife
doesn't let me buy one :-(
Have fun,
Reinhard
--- Don Hanson <dhanson@gorge.net> wrote:
> Hi Reinhard,
> Your post is appreciated. I have a pretty good
> understanding of
> suspensions, having taken my street based race car
> and developed it ,
> learning as I went along.
> I am thinking, though I have no real data to
> support my conjecture other
> than my eyeball and my SOP (seat of the pants)
> feelings, that my van needs
> some adjustment for it's 'static load' as you called
> it.
> As you experienced with your syncro, I think most
> of the weight of my van
> is sitting on two wheels...Now, of course, that is
> on perfectly level
> terrain and only in a static situation..but my SOP
> feeling when driving is
> that sometimes I am losing traction because the van
> is not properly corner
> balanced. At times, when I can reasonably expect to
> keep going, or get
> going, the right rear simply spins, or starts to
> tramp and hop a bit. When
> I am moving uphill without any 'side force' or
> attempting to start backing
> up, on level ground (side to side) it seems like the
> right rear must just be
> 'kissing the ground' rather than taking +/- 50% of
> the load and giving up
> 50% of the motive force.
> On my racecar, I had it all down in my set-up
> book, how many turns of each
> shock adjusted each millimeter of ride height...for
> every set of different
> springs, etc. A VW van? I just want it a bit
> closer, not perfect...
> So, rather than going into all kinds of math for
> spring weights etc, I
> guess I will just start adding some shims here and
> there and see what
> happens..I am guessing some of the imbalance is
> caused by my having an
> inline 4 and a 5sp tranny transplanted into this
> van, with perhaps some
> questionable motor mounts hanging the engine weight
> a bit "off"..
> I take it your syncro doesn't have a locker diff.
> if you got stuck on the
> two wheels?
> Don Hanson
> ----- Original Message -----
> From: "Reinhard Vehring" <rvehring@yahoo.com>
> To: "Don Hanson" <dhanson@GORGE.NET>;
> <vanagon@GERRY.VANAGON.COM>
> Sent: Saturday, August 18, 2007 11:04 AM
> Subject: Re: ride height adjustment? (long post)
>
>
> > Don,
> > interesting question. I had that very problem in
> the
> > extreme at Syncro de Mayo this year, where my van
> was
> > perfectly "unbalanced" with 100 % weight on front
> left
> > and back right wheels and the other two were up in
> the
> > air. I could make it rock back and forth by moving
> in
> > my seat. Anyway, my two cents:
> >
> > The contact force of each tire in a static
> situation
> > is determined by the a couple of components. A)
> > unsprung weight of the suspension parts (wheel,
> > steering knuckle, control arms) this is minor
> compared
> > to the other forces and only becomes more
> important in
> > a dynamic situation. B) spring constant and
> > compression of the coil spring, the most important
> one
> > c) spring forces of other suspension components
> (sway
> > bar torsion to prevent lean, or preloaded shocks
> that
> > have a some compressible gas reservoir) this also
> is
> > usually minor.
> > So it's mostly the spring constant, k, and the
> spring
> > compression. Compression is determined by the
> weight
> > distribution - the center of gravity.
> >
> > I don't know the k for vanagon springs. The guys
> who
> > claim to have designed lift springs must know, but
> > they are not telling (now is your opportunity!)
> But I
> > can try to estimate: It's probably around 500
> N/cm. If
> > this is about right, loading 250 kg of stuff into
> the
> > van ( 4 normal sized guys) would cause an extra
> force
> > of 2450 N (613 N per wheel) causing it to sag
> about 12
> > mm. Now it would really be interesting to know
> some
> > specs on the progressive springs that GoWesty has
> for
> > the Syncro...
> >
> > If I understand you right, you don't want a ride
> > height adjustment, but rather equalize contact
> force
> > (diagonally) to maximize traction. In my humble
> > opinion, unless you want to break a new record on
> a
> > (perfectly flat) race track with you vanagon, that
> > doesn't matter. I guess this is why there is no
> way on
> > a stock vanagon to adjust for that. "Unusual" ways
> of
> > trying this would be:
> > a) Mess with k: Gas bladders in the back that can
> be
> > inflated to different pressure, for example, or
> maybe
> > different preload on gas shocks. (the two easiest
> ways
> > in my opinion)
> > b) Mess with compression: Onesided spacers. Find
> out
> > spring constant, measure diagonal force difference
> > (with driver in place), calculate spacer thickness
> for
> > compensation, machine custom spacer, install,
> measure
> > again.
> > Lot's of work and you can never take a passenger
> in
> > the van or drive on anything else but a perfectly
> > level surface, because it would throw off the
> balance
> > again. If I remember right racecars are balanced
> with
> > the driver in the car and they don't haul around
> > camping equipment :-)
> > By the way, I don't think you can affect front -
> back
> > or left - right contact force balance that way at
> all.
> > That's just a matter of center of gravity. For
> example
> > most Westies sag left. Ride height can be
> corrected,
> > contact force cannot. Even if levelled there is
> more
> > weight on the left side.
> > Have fun,
> > Reinhard
> > 83 "Half-Syncro"-Westy, Moose
> >
> >
> >
> >
> >
> >
> > --- Don Hanson <dhanson@GORGE.NET> wrote:
> >
> > > I know, "Check the Archives"...but my dial-up
> > > connection is so slow that
> > > when I try to get something odd-ball out of the
> List
> > > Archives, it sometimes
> > > takes me all dang morning to not succeed anyhow.
> > > Problem: My 84 2wd van seems a bit 'off' in
> it's
> > > "stance". It is not
> > > exactly 'even' in how it sits. With our
> racecars,
> > > we called it
> > > "Corner-balanced". Ideally, each wheel would
> share
> > > an equal weight, giving
> > > you an equal amount of traction at all four
> tires.
> > > In reality, most cars
> > > are heavier at one end or the other..Examples
> would
> > > be...say,. the Olds
> > > Tornado for a heavy front end weight bias and
> the
> > > Porsche 911 for a heavy
> > > rear/front bias.. You can't do much about the
> F/R
> > > balance, but you can
> > > adjust the side to side/corner to corner balance
> by
>
=== message truncated ===
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