[DeTomaso] need formula for springs needed-- was shocks for ORR

Thu Oct 11 07:24:17 EDT 2007

Jason, I missed some of this thread so I apologize if this is a repeat, but how is your ride around town with the 450/750 combination? How much do you compromise day-to-day driving enjoyment for ORR??

Jason Eaton <jason.eaton at gmail.com> wrote: Nice work Jim. I like your analysis here. I'm pretty sure my springs
are 750lb and 450lb rear, front respectively. Its the setup that Bobby
at Precision Proformance recommended. that extra 50lb may be enough to
keep Dennis's booty off the road :)

On 10/10/07, Mad Dog Antenucci  wrote:
> Fellow Slacker! ;-]>
>
> I think you, Jason and others are all right on with your spring concern
> comments.....all the supporting feedback from mfg's and unlimited drivers is
> forget replacing the shocks and just make an incremental increase to the
> springs to the back end where I had a problem or full compression.  I
> currently am running 400 lb fronts and 700 lb rears.....I may have to
> consider raising the back end up a half inch or so too but hate doing that
> since the car handles so well at every other ORR and at speed be it in
> straights or corners of canyon road I am reluctant to make big changes.
>
> I'm not sure what my speed was at when I hit the first dips but its at the
> end of a long straight...I could  have been 150 but was probably closer to
> 160......so right now I am going with a 750 on rears and adding a poly shaft
> stop on top shock shaft for added protection....if that doesn't work I will
> give up the donuts, macaroons and beer. ;-]>
>
> thanks for your comments.
>
> Dawg
>
> pantdino at aol.com wrote:
>
> Dennis and Jason,
>
> I freely admit that my opinion comes from a total slacker regarding ORR, but
> I wonder if stiffer shocks is the right way to go. My understanding is that
> it is not the shock's job to prevent excessive spring compression-- if that
> is happening, the spring is too soft. The shock's job is to dampen the
> spring's natural tendency to continue to let the car bounce up and down once
> it is disturbed. Indeed, the Brits call them "dampers" because that's what
> they actually do.
>
> At the risk of boring you to tears, I had an Alfa that was "undersprung",
> that is, the springs were too soft.? Despite Konis set on full hard so
> expansion joints rattled my teeth, the car would still "porpoise" when going
> thru depressions at intersections for water to drain away. The car was
> "undersprung and overdamped."? In contrast, my MGB was "oversprung and
> underdamped".? It would also rattle my teeth over expansion joints but never
> porpoised. However, the ride was "bouncy," where you could feel the car
> oscillating up and down more than it should after hitting a bump.? So its
> dampers were not preventing the car from bouncing along in its springs.
>
> What spring rates are you and Jason running??? I have no real world
> experience at this, but if Jason doesn't bottom out at 150mph, that gives
> you an idea of what spring rate is necessary to contain a certain amount of
> kinetic energy. Basically a car encountering a change in road shape is being
> forced to change its course from straight ahead in the vertical plane to a
> different trajectory. Inertia wants to keep it going straight, and the
> springs have to transmit force to prevent it from burrowing into the
> asphalt.?
>
> It seems to me that since Kinetic Energy=1/2 Mass x? (V squared), you could
> get an idea of what spring force would be necessary to keep the same mass
> from bottoming at a different speed.? I'm afraid my physics is too rusty to
> give you the formula, but spring strength is measured in pounds, which is a
> measure of force, mass x acceleration.? The springs have to accelerate the
> car away from the road. If they are not strong enough, they bottom out and
> the whole car becomes unsprung weight. So the spring has to have enough
> strength to not bottom out under this extreme load.?
>
> Again, I don't have the equations for you, but I suspect everything will
> drop out of the them and you'll be left with the velocity squared factor--
> if the car is going twice as fast the springs will have to be 4 times as
> firm to prevent bottoming.?
>
> Meaning you'd be looking at something like:
>
> Jason's spring rate x??? Dennis' speed squared
>
>
> ?????????????????????????? Jason's speed squared??? =? spring rate needed to
> prevent Jason's car from bottoming at Dennis' speed.? If Dennis' car weights
> more or less than Jason's, you would correct by a simple proportion, as the
> M is not squared in the formula.
>
> However, I think this also assumes that the springs in the two cars are the
> same length and will crush the same distance before they bind, etc, etc. But
> it should provide a ballpark estimate, I would think.?
>
> Jack and the other people who really know and don't just make slacker
> guesses like me??
>
>
> Jim Oddie
>
>
> -----Original Message-----
>
>
>
> From: Jason Eaton
> To: Mad Dog Antenucci
> Cc: detomaso at realbig.com
> Sent: Tue, 9 Oct 2007 6:22 pm
> Subject: Re: [DeTomaso] Bigger-Better-Heavy Duty Shocks for Silver State
> WOOPS - No Slacker Content
>
>
>
>
>
>
>
>
>
>
> You can reduce the unsprung weight by cutting back on the beer and donuts!
>
> We didnt have any problems with compression, but were only going 150
> though there. Also I'm pretty sure we are running higher rate spring
> then yours. lets compare notes.
>
> On 9/25/07, Mad Dog Antenucci wrote:
> > Off Roaders & JORN IN NORWAY:
> >
> > Bilstein and Aldan were wrong.....rebuilding the shocks for the Pantera
> with
> 25% more compression and rebound was not enough to stop full compression at
> the
> dips (at WOT) at Silver State in the Pantera....you couldn't have pulled a
> greased string out of my backside on the hardest hit so its back to the
> drawing
> board.;-]>
> >
> > In the last ORR I had another great run....engine although it had too much
> compression ;-]> ran great....the Pantera is handling better then it ever
> has.....but hitting full compression broke the ABS side skirts and bottom of
> the air dam in the dips. Shock mounts and chassis all look good and the
> Pantera
> stayed straight and true on full compression so no handling problem. Te ABS
> was
> meant to provide some added hi-speed stability which it did until it broke
> ;-]>
> but the ABS was also meant tobe the 'sacraficial lamb' which it also did but
> bottom line I still got full compression in dips above 145 mph
> >
> > So, as part of this winter's projects (MORE engine compression) ;-]> I
> need
> some customized shocks with added compression to handle these dips (aka
> WOOPS).
> I don't think there are any plans in 2008 to regrade the course dips so the
> challenge is to build shocks around the course conditions.
> >
> > No Col. I still can't afford those high tech $5 grand computerized units
> but
> a couple people I spoke too suggested adding a stop on top of springs to
> eliminate the 'full compression'.... the negative to that suggestion is
> others
> have suggested it could also cause wheel hop 'at speed' on full compression
> which could lead to loss of control and an off road 4x4 excursion. ;-]> So
> goal
> is to STOP full compression.
> >
> > If YOU have a contact name of anyone you have personally dealed with on
> customized shocks for off-road conditions send it to me. I gotta figure
> those
> guys who are running offroad at 150 mph can help where roundy-rounders
> can't.
> >
> > JORN, SEND ME contact infor on the VIKINGS that ran 200 MPH last week.
> >
> > MD
> >
> >
> > Mad Dawg Antenucci
> > Team Pantera Racing
> > The 1st & still the only vintage race team in open road racing
> > www.teampanteraracing.com
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