rec.autos.simulators

by **Gregor Vebl** » Fri, 01 Jun 2001 16:59:08

Hi Sebastien,

> Waow, i'm far from this ( 0.075 m/s ) ... Well, the problem in rally is that
> we need to have good setting for off/road ( dirt/snow ) and for tarmac (
> corsica/spain )... So we need to setting up the car for a wide range of
> application !!

Well, 0.075 isn't that far off from 0.1 ;). I think if it works, it's
probably what should be used (and would most likely work in real life as
well). I would also imagine that, apart from the tyres, the dampers are
the main setup component when preparing a rally car for different
surfaces, and different values should be used, i.e. lower for the rough
surfaces.

Just my own project at the time; it was the only car I got data on (as
they're in the Millikens' book).

-Gregor

by **Sébastien Tixi** » Fri, 01 Jun 2001 22:01:25

That's how i started ;o) I worked for my own projects and know it's not my
projects anymore, but a full time job ;o)

--
Seb - Le nain, des sensations biens.
Game Developer
http://www.eden-studios.fr
GPLRank -41.68
http://magicfr.multimania.com

by **Doug Millike** » Sat, 02 Jun 2001 09:16:12

> A bit of racing sim philosophy; what's amusing is that, once you create
> a good physics model, you are then given the role of a car engineer in
> that you need to find the best suited springs, dampers, tyres etc. so

...

Amusing for you, but serious business for us! We often go to great lengths
($$$) to get good data...when we model a car with one of our simulations
(these are detailed "analysis programs", not driving simulators).

BTW, you won't find any data from off-road or rally car dampers in RCVD, we
really weren't addressing those parts of motorsports. OTOH, the first part
of the damper chapter is a pretty good review of dampers and should let you
do some simple calcs to get in the ballpark.

-- Doug

Milliken Research Associates, Inc.

by **J. Todd Wass** » Sat, 02 Jun 2001 16:39:47

Gregor, I just did a Champ car a few days ago and aside from being
hyperactive and twitchy, it's very driveable with downforce. My tire model
isn't good yet, but it accelerates properly, spins the wheels at about the same
speed range as the real cars, gets about the right top speed, and pulls the
right G forces at about the right speeds. With better performance specs off
the real cars, I bet I could get it really close, aside from transient behavior
from my goofy tire model. If I you want to compare data, let me know.

Todd Wasson
---
Performance Simulations
Drag Racing and Top Speed Prediction
Software
http://PerformanceSimulations.Com

by **Gregor Vebl** » Sat, 02 Jun 2001 17:27:22

Hi Doug,

I'd be willing to bet that your serious business is also very much
amusing for you as well ;).

I realize that off-road dampers aren't in RCVD, but I figured they'd be
similar, only much softer (as are the springs). Making them linear and
adjust the stiffness to create just the critical dampening is probably a
good starting point for a aerodynamically less dependent cars. I might
be missing something here, though, and I am very much open to
suggestions :).

-Gregor

> Amusing for you, but serious business for us! We often go to great lengths
> ($$$) to get good data...when we model a car with one of our simulations
> (these are detailed "analysis programs", not driving simulators).

> BTW, you won't find any data from off-road or rally car dampers in RCVD, we
> really weren't addressing those parts of motorsports. OTOH, the first part
> of the damper chapter is a pretty good review of dampers and should let you
> do some simple calcs to get in the ballpark.

> -- Doug

> Milliken Research Associates, Inc.

by **Gregor Vebl** » Sat, 02 Jun 2001 17:34:35

Hi Todd,

of course I'd be want to compare! What I mostly lack in data for a
generic champ car are the drag/lift coefficients, which are an educated
guess from some data gathered from RCVD (a large part of the other
physics parameters are conveniently given in a nice table). If you have
any other source, please let me know.

In general the car behaves OK, but it would still require a lot of setup
tweaking to make it driveable. For example, currently it understeers
like a pig at low speeds, but any attempt at serious throttle steering
at larger speeds on the small generic oval I have sends it into a spin,
although that is in part due to the rather small steering ratio I
currently use. It's obvious I'm no Penske ;).

-Gregor

> Gregor, I just did a Champ car a few days ago and aside from being
> hyperactive and twitchy, it's very driveable with downforce. My tire model
> isn't good yet, but it accelerates properly, spins the wheels at about the same
> speed range as the real cars, gets about the right top speed, and pulls the
> right G forces at about the right speeds. With better performance specs off
> the real cars, I bet I could get it really close, aside from transient behavior
> from my goofy tire model. If I you want to compare data, let me know.

> Todd Wasson
> ---
> Performance Simulations
> Drag Racing and Top Speed Prediction
> Software
> http://PerformanceSimulations.Com

by **Matthew V. Jessic** » Sat, 02 Jun 2001 12:55:11

Keep in mind what you are using the dampers to control.
A lot of the lore of dampers in racing is for controlling the
wheel hop mode. I imagine most game simulations won't have a
wheel hop mode, so you would concentrate on controlling
the rigid body motions.

- Matt

by **Gregor Vebl** » Sat, 02 Jun 2001 17:58:49

Hi Matthew,

thanks for the info. I wonder, is it only the high speed behaviour of
the damper that affects the wheel hopping mode (which is what I would
guess), or is the low speed behaviour tweaked to suit this as well?

-Gregor

> Keep in mind what you are using the dampers to control.
> A lot of the lore of dampers in racing is for controlling the
> wheel hop mode. I imagine most game simulations won't have a
> wheel hop mode, so you would concentrate on controlling
> the rigid body motions.

> - Matt

by **J. Todd Wass** » Sat, 02 Jun 2001 19:13:36

>Hi Todd,

It's in the mail.

Todd Wasson
---
Performance Simulations
Drag Racing and Top Speed Prediction
Software
http://PerformanceSimulations.Com

by **Elvo** » Mon, 04 Jun 2001 02:40:26

<SNIP> I realize that off-road dampers aren't in RCVD, but I figured they'd
be

Well, you are missing something :-P High-speed damping is critical for
off-road cars.

For more info, have a look at http://gallery.uunet.be/heremanss/c2/index.htm
for some comments on off-road damping, and
http://gallery.uunet.be/heremanss/sg.htm for a comparison between on - and
off-road.

HTH!

<SNIP> > BTW, you won't find any data from off-road or rally car dampers in
RCVD, we

Right!

Elvo

by **Matthew V. Jessic** » Tue, 05 Jun 2001 00:28:54

> Hi Matthew,

> thanks for the info. I wonder, is it only the high speed behaviour of
> the damper that affects the wheel hopping mode (which is what I would
> guess), or is the low speed behaviour tweaked to suit this as well?

The wheel hop mode is a high frequency (10 to 15 Hz or so)
mode where the wheel is moving as the tire flexs. At those
frequencies it would spend most of its time in the
higher speed range of the damper.

The sprung mass heave frequency is much less for most cars
except that with heavy use of aerodynamics can lead to
much stiffer cars. Also the pitch mode can be much faster
than the heave in certain situations if care isn't taken. So in
general the sprung mss heave would excercise the slower
speeds of the damper.

Other than that general stuff I don't have enough experience
to really answer the question :)

- Matt

> > Keep in mind what you are using the dampers to control.
> > A lot of the lore of dampers in racing is for controlling the
> > wheel hop mode. I imagine most game simulations won't have a
> > wheel hop mode, so you would concentrate on controlling
> > the rigid body motions.

> > - Matt

by **Ruud van Ga** » Tue, 05 Jun 2001 22:56:52

...

While I'm here for a moment, is it really correct that having just 2
values (fast/slow bump/rebound) would be the right physical way (well,
close)?
Or would a curve approach the workings of the shocks better? I mean,
now you have linear lines which suddenly get a different grade. Isn't
this really a very gradual change? (a polynomial function for example)
Or is it that suddenly extra valves open up and you do get relatively
sudden differences in bump/rebound coefficients?

Great site on a lot of things btw.

Cheers,

Ruud van Gaal, GPL Rank +53.25
Pencil art : http://www.marketgraph.nl/gallery/
Free car sim : http://www.marketgraph.nl/gallery/racer/

by **Doug Millike** » Wed, 06 Jun 2001 12:20:13

Big things happen when the damper changes direction...because there is
often quite a bit of stick-slip (stiction) in the motion. Better dampers
(afaik) are designed to reduce this, but all(?) these dampers have passive
shaft seals and piston rings so there will be stiction (non-rate-dependent
friction).

As far as the characteristic curve of force vs stroke-velocity, this will
have different shapes depending on the actual construction of the damper
valves. Some valves open progressively (see the Penske damper plots
in RCVD), while others are more sudden.

Best Wishes,

-- Doug

Milliken Research Associates Inc.

Get Race Car Vehicle Dynamics from the bookstore at <www.sae.org>!

> ...
> >Well, you are missing something :-P High-speed damping is critical for
> >off-road cars.

> While I'm here for a moment, is it really correct that having just 2
> values (fast/slow bump/rebound) would be the right physical way (well,
> close)?
> Or would a curve approach the workings of the shocks better? I mean,
> now you have linear lines which suddenly get a different grade. Isn't
> this really a very gradual change? (a polynomial function for example)
> Or is it that suddenly extra valves open up and you do get relatively
> sudden differences in bump/rebound coefficients?

> >For more info, have a look at http://gallery.uunet.be/heremanss/c2/index.htm

> Great site on a lot of things btw.

> Cheers,

> Ruud van Gaal, GPL Rank +53.25
> Pencil art : http://www.marketgraph.nl/gallery/
> Free car sim : http://www.marketgraph.nl/gallery/racer/

by **Gregor Vebl** » Wed, 06 Jun 2001 15:24:02

Hi Doug,

> As far as the characteristic curve of force vs stroke-velocity, this will
> have different shapes depending on the actual construction of the damper
> valves. Some valves open progressively (see the Penske damper plots
> in RCVD), while others are more sudden.

that's what my impression was. I remember reading an interview with one
of the Peugeot engineers, where he explained how on the 306 model (one
of the best looking hatchbacks ever IMHO), the dampers are softer at
slow speeds, then get progressively stiffer at a medium range speed for
handling purposes, and then open up at high speeds again for bumps. I
don't remember the exact reasoning, but the point is if one is clever
enough one can create just about any damper one pleases.

So, to Sebastien, you've got a lot of unexplored ground to cover to come
up with the best solution :).

And get it now ! :) (I really do mean it)

-Gregor

by **Jon Crook** » Thu, 07 Jun 2001 23:07:19

> Although I'd very much like to, I have no experience in karts. I have however
> spent some time in a Formula Ford. We're talking matters of degree here Jon,
> and also in the context of driving a feedback lacking computer simulation as
> opposed to driving a real car. In a sim wheel, the emphasis on centering
> weight
> needs to be on giving some useful feedback and less on mimicking the actual
> feel of a real car, not to mention that the force is going to vary so much for
> different types of real cars that no one sim wheel is going to mimick them all
> anyway. Whether the centering force on a sim wheel is strong or light is
> personal preference and not really my point.

Yes I agree, it is personal preference and the fact that drivers like Richie
Hearn, the late and great Greg Moore, Stefan Johansson, Frank Biela and
Russell Ingall all choose to own and drive Hyper Stimulators is because they
prefer the Hyper's steering feel over all others including the TSW and ECCI.

Why ??? Some of the world's top sim drivers own Hyper's and use the full
turn (travel) of the wheel.

Like I said in my last post, there must have been something wrong with that
particular wheel. Did you back off the rear***as well ??

We tried ball bearings in a prototype Hyper back in 1991 and found it
unrealistic in it's feel {resistance). The adjustable 'plastic techlite'
blocks in the Hyper allow the driver to adjust the resistance (from nil to
heavy) in the steering to his/her personal preference. In fact its a shame
that bearings don't work as well as our 'plastic techlite' bushes because
bearings are a much cheaper solution. But Hyper's policy has always been the
best solution even if it costs more.

Yes it is personal preference. But Richie, Stefan, Frank and Russell all
disagree with you.

- Show quoted text -

> Don't get me wrong Jon, I think Hypers are a fantastic product. The quality of
> constuction, seating position and comfort, and particulary the pedal design,
> feel, and adjustability are outstanding. There is however a bit of room for
> improvement.

> Don Scurlock
> Vancouver,B.C.

>> Hi Don
>> I'm the person responsible for designing the Hyper Stimulator including the
>> centering feel of the Hyper Stimulator wheel. I based my design parameters
>> on my own extensive experience of driving Formula 2 ground effects (National
>> Champion) and non-ground effects cars, Formula Fords, Formula Vee's and V8
>> Supercars (Works Mobil/Brock driver). All the open wheeler cars displayed
>> very little centering due to the low castor angles used. The V8 Supercar had
>> only slightly more centering weight. I think where some people get confused
>> with centering weight is that their experience with driving a racing vehicle
>> is in a Go-Kart. Go-Karts run very high castor angles and as a result
>> provide very strong centering.

>> You must have tested a steering box that had the external***adjusters
>> too tight. The steering has been designed so that it can be easily and
>> quickly adjusted by the driver so that there is no friction at all.

rec.autos.simulators

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