Suspension Programs

[Will98Cobra]

What suspension programs are most teams using and what are your thoughts on how they work and what are there advantages. We currently have 3D suspension designer. Im currently having some mixed feelings which have almost caused me to launch my laptop across our shop http://fsae.com/groupee_common/emoticons/icon_mad.gif Any suggestions would be great.

William Austin
ODU Motorsports
Chassis/Suspension/Controls

[Will98Cobra]

What suspension programs are most teams using and what are your thoughts on how they work and what are there advantages. We currently have 3D suspension designer. Im currently having some mixed feelings which have almost caused me to launch my laptop across our shop http://fsae.com/groupee_common/emoticons/icon_mad.gif Any suggestions would be great.

William Austin
ODU Motorsports
Chassis/Suspension/Controls

[Didier Beaudoin]

We use MSD Adams. It is good for all kinematics.

Didier Beaudoin
Team Leader -
École Nationale d'Aérotechnique

[Bob Wright]

Use whatever drawing program you use and then sort out point deflections and inst. centres and all that stuff usings matricies. Its a bit slow, but you learn a lot and when it comes time to make dynamic models using shock potentiometer and strian guages, you can just work the matricies backward from the shock pot with a loged csv file. It a bit of work, but then when you get some ground plane censors on the chassis to tell you what the tire bag is doing (geometrically), then you know EVERYTHING. Suspension programs wont give enything that a few hours on matlab or even excell cant. Although Susprog 3d is a start if you're struggling. http://fsae.com/groupee_common/emoticons/icon_cool.gif

Bob Wright
Monash University
Australia

[Will98Cobra]

Thanks for the info guys. I have currently drawn all my geometry up and have it like i want, but our advisor wants it proven with a suspension program. How usuer friendly is Adams, i have looked at that i think the team is leaning toward that. Thanks again

William Austin
ODU Motorsports
Chassis/Suspension/Controls

[ben]

If you're using the template based ADMAS/Car it will be quite easy as templates exist for double wishbone, etc. If you're using ADAMS/View it will be a little more difficult.

On the plus side, the ADAMS user community (ask.adams.com - not a www) is very helpful and used to FSAE questions.

Ben

[Marc Jaxa-Rozen]

ADAMS/Car is very easy to use with the existing FSAE templates...just move the hardpoints around to suit your design and you're good to go.

IIRC there are templates for pushrod front and rear suspensions and a pushrod/3rd spring front suspension. I used ADAMS/View for our front monoshock- the templates' geometry can be a bit tricky to modify- but again I felt it was pretty simple to set up for a basic simulation, even with a minimal background in kinematics.

ADAMS can be used to run full-vehicle analyses as well, but I don't think it's worth the trouble without a solid base of physical data to back the simulation up- it would be pretty pointless to use an unvalidated model for development, and full validation would probably fall outside the realm of possibility for a time-restricted FSAE team.

[Schumi_Jr]

The post-processor in ADAMS is excellent at cranking out loads of useful data. Keep in mind that ADAMS was designed as a dynamic solver and was later adapted to use for suspension/vehicle analysis. One strange limitation is that ADAMS measures camber with respect to the vehicle and not the ground. Try increasing your FVSAL and watch you camber change in both ride and roll decrease! None the less it's a powerful program, it's free and we continue to use it.

Aaron Johnston
University of Waterloo FSAE

www.eng.uwaterloo.ca/~fsae (http://www.eng.uwaterloo.ca/~fsae)

[gug]

my team is about to get their first shot with ADAMS, but the license goes for 120 days only. at that time the program will uninstall itself. ive been talking with the MSC software ppl, and they have pretty much told me that the license agreement is firm, and i cant get the software for the 6 months of design that we had planned. do other teams have this problem with the sponsorship of ADAMS software? according to the adams people "Since we need to be fair to all Formula SAE-A teams please stick to the
standard agreement which runs for 120 days." dont quite see how this is fair when some unis must have the full license...
also, a question for those who have ADAMS, do you believe it is more useful for testing out ideas (ie initial design) or finetuning your suspension setup etc? we need to decide if the license should run from the start of the design time to test those initial ideas with or right to the end for fine-tuning.
i just wish the MSC people would respect the fact that we are going to be out in the workplace soon enough and requesting their software cause we use it now, rather than giving us what is basically a demo, then bugging us to get the uni to buy their software. dont get me wrong, i am grateful for the software, just annoyed at all the restrictions

"I come from a land down under,
Where beer does flow and men chunder"

[woollymoof]

Our Team designed this years suspension in less than four months, more like 2 (mostly fine tuning)using SusProg which is apparently a bastard to use.

That licence should be sufficient to do both ideas and fine tuning as long as you work hard, assuming it's not a bastard to use!

[MercerFSAE C. Burch]

I'm going through the same problems as a first year team and first time suspension designer. I found this neat little program while looking at Google tonight - suspen 2d (http://users.erols.com/smitch/Suspen/). It models a basic wireframe suspension in dos programming. You should give it a try, it might save hours of hair-pulling and keep thoughts of expensive laptop destruction to a minimum.

Chris
Mercer University - Drive!
Coming to an autocross course near you, May 2004!

[awhittle]

Try this one I wrote it 20 years ago in Dos

http://www.ncs-stl.com/Files/Suspension/suspend.zip

2D only but I naver seen it give the wrong answer. Put all the files in the same dir. Start by playing with aframe.exe. aframe2.exe is less documented on the screen but you get more info. macstrut calcs macpherson struts for all you rice car lovers(PS:I own 4 of them) The *.bas files are basic files readable in wordpad

Nope this helps

Andy

[dancin stu]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Bob Wright:
Use whatever drawing program you use and then sort out point deflections and inst. centres and all that stuff usings matricies. Its a bit slow, but you learn a lot and when it comes time to make dynamic models using shock potentiometer and strian guages, you can just work the matricies backward from the shock pot with a loged csv file. It a bit of work, but then when you get some ground plane censors on the chassis to tell you what the tire bag is doing (geometrically), then you know EVERYTHING. Suspension programs wont give enything that a few hours on matlab or even excell cant. Although Susprog 3d is a start if you're struggling. http://fsae.com/groupee_common/emoticons/icon_cool.gif

Bob Wright
Monash University
Australia


<HR></BLOCKQUOTE>

would you care to elaborate on this some more if you have the time please?. I have seen this done before but have never eally understood how it works.

cheers

[gug]

Bob, do you think you could also point us towards a good text on this method? thanks.

"I come from a land down under,
Where beer does flow and men chunder"

[awhittle]

What part is throwing you off. Do you have a copy of Prepare to Win by Carrol Smith.

Try downloading my program and I can talk you thru a lot of the basics.

This all works from the class kinomatics and the position loop equasions to solve a 4 bar linkage.

AW

[dancin stu]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by awhittle:
What part is throwing you off. Do you have a copy of Prepare to Win by Carrol Smith.

Try downloading my program and I can talk you thru a lot of the basics.

This all works from the class kinomatics and the position loop equasions to solve a 4 bar linkage.

AW<HR></BLOCKQUOTE>

i have downloaded your program and have understood it, probably cos ive written one that is practically identical in excel! assumes the same rules and everything, havnt figured out how to model scrub in roll yet, but am working on it.

prepare to win is the only Carroll Smith book that i do not own, but understand what your on about regarding the four bar link, i presume you just write a matrix from simultaneous equations, am i right? and then solve the matrix, using matlab, to get the variables?

[dancin stu]

woops, talking about the wrong download! my program is very similar to the first link, will download yours now

[awhittle]

When you talk about "scrub" are youb refering about the contact patch moving lt/rt due to suspension travel? I ignore that movement of the tire. I figure by the time the chassis gets to say two degrees of roll, the entire car has moved over several feet and that 1/8" or so of tire scrub is insignificant.

AW

[dancin stu]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by awhittle:
When you talk about "scrub" are youb refering about the contact patch moving lt/rt due to suspension travel? I ignore that movement of the tire. I figure by the time the chassis gets to say two degrees of roll, the entire car has moved over several feet and that 1/8" or so of tire scrub is insignificant.

AW<HR></BLOCKQUOTE>

yeah thats what im on about. i suppose when you put it like that, it isnt really that significant really! i suppose also it depends on how accurate you want your roll centre movement analysis to be, if you ignore the scrub in roll your roll centre will not quite be accurate, but when you consider that the vast amounts oif chassis are welded were talking about 1-2mm distortion so its not all thats ignificant.

if you pm me your email address i'll send you a copyhttp://fsae.com/groupee_common/emoticons/icon_smile.gif

[Denny Trimble]

I think scrub is important. Imagine a car with a very high roll center. The car is nice and happy at steady-state in a corner, and the tires are at "optimum" slip angle.

Then, the car hits a bump. The outside wheel scrubs outward, increasing the slip angle and sending the tire over the limit. This has to be a bad thing!

However, off-road trucks have huge amounts of scrub, but I don't think their tires (in dirt)are as sensitive as ours (on pavement) to slip angle.

Comments?

University of Washington Formula SAE ('98, '99, '03)

[dancin stu]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Denny Trimble:
I think scrub is important. Imagine a car with a very high roll center. The car is nice and happy at steady-state in a corner, and the tires are at "optimum" slip angle.

Then, the car hits a bump. The outside wheel scrubs outward, increasing the slip angle and sending the tire over the limit. This has to be a bad thing!

However, off-road trucks have huge amounts of scrub, but I don't think their tires (in dirt)are as sensitive as ours (on pavement) to slip angle.

Comments?

University of Washington Formula SAE ('98, '99, '03)<HR></BLOCKQUOTE>

yeah i agree, i think you might have misunderstood me a little, i was referring to scrub in roll. of course i agree that scrub in bump is a bad thing, although we're gonna run a few tests to see if an idea we have might work concerning massive scrub

[Bob Wright]

Ill get onto puting some example stuff on our website after Ive finished exams. http://fsae.com/groupee_common/emoticons/icon_smile.gif

Bob Wright
Monash University
Australia

[MercerFSAE C. Burch]

Has anyone used SuspensionGen from Altair? If you have, what are your thoughts about it?

Chris
Mercer University - Drive!

[V2 - Italy]

I used it.
It is not so easy at the beginning, but at the end useful.

Then we had the chance to use ADAMS/Motorsports (A/Car) that is more complex, but you can gain a lot understanding all his features.

Firenze Race Team V2

http://www.firenzerace.too.it

DUCATI POWER at the UniversitÃ* di Firenze