Suspension system for the First Year car

[Damped]

Hi ! all the geeks out here...
I am designing the suspension systems for the first year car of our varsity to compete in FSAE-A 2008.
I have studied Race Car Vehicle Dynamics which blew my brains and what was left of it was blown away by the forum.
I am confused that to which depths should i expose myself ?
like for the first time should i consider different RCH front and rear or a horizontal Roll Axis to keep things simple...
Should I experiment with monoshock suspension which will keep costs down or the conventional coilover unit for each wheel with pushrod actuation?
How much you people did for your first time ?
PS : We do not have automotive engineering discipline at our uni.

And i am in a lot of confusion.
PLEASE HELP ME OUT

regards,
Himanshu

[Damped]

Hi ! all the geeks out here...
I am designing the suspension systems for the first year car of our varsity to compete in FSAE-A 2008.
I have studied Race Car Vehicle Dynamics which blew my brains and what was left of it was blown away by the forum.
I am confused that to which depths should i expose myself ?
like for the first time should i consider different RCH front and rear or a horizontal Roll Axis to keep things simple...
Should I experiment with monoshock suspension which will keep costs down or the conventional coilover unit for each wheel with pushrod actuation?
How much you people did for your first time ?
PS : We do not have automotive engineering discipline at our uni.

And i am in a lot of confusion.
PLEASE HELP ME OUT

regards,
Himanshu

[A Richards]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Damped:
Hi ! all the geeks out here...
I am designing the suspension systems for the first year car of our varsity to compete in FSAE-A 2008.
I have studied Race Car Vehicle Dynamics which blew my brains and what was left of it was blown away by the forum.
I am confused that to which depths should i expose myself ?
like for the first time should i consider different RCH front and rear or a horizontal Roll Axis to keep things simple...
Should I experiment with monoshock suspension which will keep costs down or the conventional coilover unit for each wheel with pushrod actuation?
How much you people did for your first time ?
PS : We do not have automotive engineering discipline at our uni.

And i am in a lot of confusion.
PLEASE HELP ME OUT

regards,
Himanshu </div></BLOCKQUOTE>

Well i suggest you go looking for all the pieces of your small brain and keep plugging away at it. There are no simple answers in FSAE and your wasting time looking for them.

You can run any roll axis you desire and its your job to justify how you arrived there and why its more suitable then any alternatives. Figure out what you know and is in your own capabilities and start there.

[exFSAE]

Check out the Carroll Smith series of books.. Tune to Win, Engineer to Win, etc. They are much easier to understand than RCVD.

[Anvit Garg]

Should one feel guilty for not being able to really understand RCVD over the Carroll Smith Books?

Im trying to make it through the RCVD and the supplemental problems book and yeah...its like adding 2 more classes to my full load.

[Chuckster]

As a long time slave to solo car suspension design (not FSAE)-and having been somewhat successful with 5 National championships, I offer this advice:

This is an iterative process:
Read expert texts, dredge forum threads for interpretations/practical experience, design/build it, try it out, rationalize result, repeat entire sequence to optimize.

The part that was missing for me in the 1970's when I started out was: "dredge forum threads for interpretations/practical experience". No Internet.

Some texts are not clear and actully have errors. In the 1980's I found a significant error in one of Smith's books.

Also, remember:
" A single experiment is worth more than a 1000 expert opinions."

[Damped]

Thanks a lot guys...
I tried a lot but cudnt get hold of carroll smith's books. RCVD is interesting but is like a professor who goes on speaking !

[exFSAE]

Couldn't get ahold of Carroll Smith books? Amazon.com?? sae.org??

Get them. IMO, RCVD is a reference book. It has taken me 3 years or so to make sense of most of it, through a combination of reading other sources, doing FSAE, and now working with vehicle dynamics every day. Even now I find it hard to follow sometimes. It isn't a good book to LEARN suspension basics from, but it is an excellent reference for everything.

Smith's books are well written and much easier to get practical knowledge from quickly.

That said, keep in mind that no book or person is absolute gospel.

FWIW, we had no automotive engineering classes at my university either. We had some "general knowledge" passed down from team to team. A lot of it was bullshit. Question everything. In the past couple years we started taking a more legitimate approach to suspension engineering. It pays off. It may seem like a lot of black magic, but suspension and vehicle dynamics aren't that crazy. You have to be able to break it down into simple stuff that you know. It all boils down to springs, masses, dampers, system dynamics and kinematics in general.

Along similar lines of what Chuck said.. best thing to do is iterate. It's ok to not understand everything. No one does. If you're an early-on team, design something robust with a lot of adjustability. Test it, play with it, be comfortable with it. Even if you have no upper-level vehicle dynamics background you can beat a hell of a lot of teams, some with big names, just by having a car that holds together through competition.

[PatClarke]

Himanshu,
Read this
http://www.sae-a.com.au/fsae/downloads/newsletters/fsae_03_2002.pdf

Pat

[Damped]

Thanks a lot sir.
That newsletter gave me some direction to start off.
The real thing is, it is first time in our uni that someone is starting this project so alongwith being a first year team we dont have previous wisdom to be shared.
Any help from experts and other people is really gold for us.
Looking forward for other bits of advice from you all.....

Regards,
Himanshu
Delhi,India

[flavorPacket]

a picture is worth 1000 words. There are thousands of photos posted on here of all kinds of cars. None of them are perfect, but you can learn a lot by reverse engineering.

Just don't put rod ends in bending and you'll be better than basically every other first team out there.

[Chris Lane]

I've just finished the design for our first year car also. I was exactly the same as you in the beginning, lost and confused. I bought a copy of Allan Staniforth's 'Competition Car Suspension' to get me started. Read it cover to cover.

I have found that you simply need to just 'start'. Do some line drawings of your basic geometry in Solidworks/Pro E and play with it.

The first and most important step is to decide what tyres you are going to use. The most popular are the Goodyears and Hoosiers. Everything else grows from here.

As you are drawing these things, ask yourself why things should be done that way. Search in books and on these forums for info and make informed design decisions. Keep a daily journal of new things you've learnt and changes you've made to your system and why (this would have helped me a lot).

Try and speak to local race engineers about the subject. Get involved with some form of track racing (we are heavily involved in Formula Ford, and won the state championship last season).

Ask questions! Don't be afraid to try new things and change it later. As previously mentioned, this is an iterative process. I am on my 7th completely new revision, with countless changes in between.

It will get overwhelming, but don't give up and ask for help from your teammates when you need it.

Best of luck mate!

[Steve O]

As obvious as this sounds, I say your best way to tackle it is to figure out what you want your car to do and why you want it to do it. Then think of the package. From there, go to your RCVD book and look up what setup will fit your needs and look at the pros and cons the book mentions for that setup.

A tip for a simple yet strong design, if you are running front and rear SLA's, is to mirror your from left a-arms to make you rear right and vise versa. Also, as flavor packet said, no rod ends in bending or shear...this is a bad idea. Also another bad idea is to not ensure that your put pull rods are in a direct plane with your rocker arms.

As for your question on the roll axis, to determine what you want for your inclination, you will need to have a good guess as to your weight distribution in your car(and of course CG)...in fact for all your calculations this isn't a bad figure to have around and to attempt to stick to when constructing and assembling your vehicle. To determine where you want your roll centers, determine how you want your car to behave. Simply speaking your roll centers are your levers about your roll axis; interestingly enough, you can make your car roll in on a turn by putting your roll centers above the axis. This is not typically done because it would be a strange sensation in a car. RCVD should discuss how to set up your roll in your car for the type of performance you want to achieve through cornering. For your simple first setup I would put a priority on ackermann, appropriate amount of roll, and eliminating/minimizing bump/droop steer in both the front and rear. I would start without playing with your toe in and out until you at least see where you are after focusing on the stuff above.

Just remember that all of that above is a very simplified explanation of things which I'm sure some people here will argue but maybe either way it will give you something to think about and help you put together the jargon from the book.

Steve

[Mark TMV]

Go to formulastudent.de/academy and look for Pat's Corner "Overview for New Teams" - excellent article, Pat pretty much tells you how to design the car.

But most importantly - get the bloody thing built! A not-so-perfect design that can finish the enduro will get you further in the standings than a "masterpiece of engineering" that you don't finish building till the tech inspection at the event.

[Damped]

Thanks to all who replied.
Every advice was really helpful...
Thanks once again...

[vandit]

hi himanshu

first of all tell me which team you are representing, and which city. also if you are first year then there are like 6 new teams in our country that are coming up this year, hence it is advisable to keep in touch with all of them.

also Regarding RCVD, it's tough book and very hard to deal in first time...but if you dont have access to caroll smith's collection then sit down again with RCVD...but this time take empty pages and pen and go along with their calculations by substituting your data instead of theirs....that's how me and my team mate learnt.....it takes time, but it's worth it....RCVD is bible and if you have patience , it will pay you back......

also send me your email id on vandit_goyal@yahoo.com and i will send you some websites, stuff and pictures of other cars....that will help you ......

but first do the hard work and sit down with RCVD, get your concepts strong ...the more no. of times you will do it, the better you will design you car...

[flavorPacket]

shanky, I'd advise you to scrap the pencil and paper and go right into MATLAB/Excel etc. You can never build models too early. Plus, your work can then help following years' teams get started.

[Chris Lane]

Use pen/paper to get your algebra right then plug straight into Excel.

Start building a suspension spreadsheet. It will be a valuable tool. There is one floating around these forums that was really awesome by a guy named 'Frank'.

Check it out!

[Damped]

Yes i took RCVD again and with a differnet fervour...
I did as you people said....
made a C program to get roll/ride rates using the RCVD formulas and now its a breeze playing with values !!!!
A sincere thanks to all....

[vandit]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Chris Lane:
Use pen/paper to get your algebra right then plug straight into Excel.

</div></BLOCKQUOTE>

Ya, we did that too.. it was really helpful, we got hold on couple of softwares such as suspension analyzer and suspro ......after fiddling around with them, we finally got wingeo...and that was the end of search for everything....

well ya pen and paper can be chucked if you have right stuff from beginning....

[vandit]

hey flavorpacket.....if you are German native then can you please provide your email id ...me and my friend are interested in pursuing higher studies in Germany ....think we can take your help in knowing about the universities....

[Chris Lane]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by shanky:
after fiddling around with them, we finally got wingeo...and that was the end of search for everything.... </div></BLOCKQUOTE>

How do you find WinGeo? I have using Optimum K and it is pretty good. Very easy to understand.

[vandit]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
How do you find WinGeo? I have using Optimum K and it is pretty good. Very easy to understand. </div></BLOCKQUOTE>

it took time ...i had to go through all the help files to understand it ...and also one of our friend bought us "introduction to race car ...... by Warren Rowley"....this book is dedicated to wingeo only....

[Chittad]

When people say let your rodends take a bending load what does it actually mean? If the rodends are used on both sides of the suspension arms, they are very close to the ends where the bending will be anyways small.

Have I misunderstood the whole thing?

Vineet Bhandari
Raftar @ IIT Madras

[Chittad]

I meant dont let your rodends

[fade]

if your ride springs attach to the a arm they will add a shear load into the beam/arm which is reacted at the upright and chassis.

[exFSAE]

Chassis side rod-ends are not a big deal.

Wheel side, as fade said you will have some bending load from the pushrod connecting to the a-arm. You also get a contribution from brake/drive forces.

Truth be told, you can have a perfectly safe, reliable race car that uses rod ends on the outboard end. But to pull it off, either you replace a lot of rod ends, or you oversize them considerably. Not the best or cleanest option.

I much prefer running sphericals.

[Steve O]

Another thing to keep in mind is that when you call the bending forces small, remember that forces through suspension are not as small as you think. Also remember that regardless of magnitude the bending forces, rod ends are meant for a push/pull force, not for any shear/bending forces; therefore, using them in bending is beyond the manufacturing specs which is not typically a great engineering practice.

[Tim.Wright]

Chris,

I'd be interested in hearing your thoughs on OptimumK as a design tool. I used the Eval copy last year for my thesis and found it dead easy to use. However I used it more as an analysis tool. I used Susprog3D to design the suspension because I could change things such as the damper arm length on the bellcrank indpendently. In OptimumK, that would mean resolving for that particular pickup in 3D space, then inputting it. Not too bad if you had a CAD model but still an annoying extra step.

For post processing (eg. graphing, tabling, reports etc) of camber, caster & particularly steering data (which Susprog doesn't analyse very well) it was perfect. Also it allowed simultaneuous inputs of different suspension modes which Susprog does not.

By the way (back on topic), although I belive Susprog3D is a great suspension design tool, it is probably too complicated to use for a first year design unless you are willing to spend a solid month or two learning all the axis systems and other intricacies.

Regards

Tim Wright
Suspension & Vehicle Dynamics
Curtin Motorsport

Curtin University of Technology

[Chris Lane]

Gday Tim,

I have enjoyed using Optimum K for the suspension design. It is an enormously powerful analysis tool, however you do need a parallel CAD model going as well for ground-up design. It does take extra time, but I believe it is worth it in terms of global systems packaging. Optimum G is adding new features for the new version including force analysis on tyres, springs, and ARB's which should make it even better.

I have not had a chance to have a play with Susprog, so I can't really make a comparison there.

For analysing real-life cars, Optimum K is second to none as far as I'm concerned. You just have to be super accurate with your measurements and use high quality height gauges and set-up bars.

If you are ever up in Joondalup, I'd be happy to give you a demo with some Formula Ford data (the SAE data is off-limits, sorry!). Maybe we can organise a BBQ at our new workshop for our teams? I hope CMT is on track to compete this year?

EDIT: I actually live in St James, so I could even swing past Curtin if you are keen to have a look.