Geometry for IFS?

racer7674

racer7674

New Member
 
Hey how do you figuare out IFS geometry if i wanna fabricate a long travel front suspension? Like dimensions of upper and lower a arms and knuckles and how can i cycle it on paper or solidworks?
Thanks
Josh
 
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spaceoden

New Member
 
First you have to make some decisions. Like how much travel you want, what kind of camber change is desired, what KPI you want, what kind of caster you want, if you want to design adjustabliity into any of these parameters. A good starting point would be to find stock specs for all of these for your truck and decide how much you want to change each one. Take alot of pictures of your stock suspension, mounting points steering, and detailed measurements. That gives you a base to design your modifications from.
 
scottm

scottm

Well-Known Member
 
About every tenth post in here is 'how do I build a long travel suspension'. People spend years learning how to design suspension, so they may not be willing to share everything with you. Search for keywords like camber, caster, J-arm, bumpsteer, etc.
 
racer7674

racer7674

New Member
 
I know noboby wants to give away secrets.All im asking is for a basic set up or idea of what i need to do for measurements i can do the rest.
Thanks
 
CRAIG_HALL

CRAIG_HALL

Well-Known Member
 
Lol-if you don't know the basics.. then you CAN'T do the rest..
 
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spaceoden

New Member
 
If you really want to start learning about suspension design Fundamentals of Vehicle Dynamics by Thomas D. Gillespie is a good starting point
 
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D.Mavis

Well-Known Member
 
The Gilespie book is pretty in depth. There are some good easier to read books out there. There were a lot at barns and nobles a few years back, they seemed to all be larger soft cover books with lots of diagrams and pictures, and are actually not too bad to read. Check out carol smiths books. They are all titled "... to win". herb adams has a book called chassis engineering. Theres a lot more I have forgotten about. everything you will find will be about asphalt racers not much about off road, but most of the concepts apply. I'd stick to the soft covers first if you still want more and are the engineering type the undisputed bible is "race car vehicle dynamics" by miliken
 
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atomicjoe23

Well-Known Member
 
I would recommend Herb Adams book as a starter. . .I haven't read the other books by Carrol Smith or Milliken yet, but I was able to design a set of front upper and lower control arms for a single seat buggy that me and 3 of my friends built and raced with 17" of travel. . .we designed and built some rear semi-trailing arms for IRS for the back and got 15.5" of travel. . .we could get 36" of vertical separation between the two front wheels and still keep all 4 tires on the ground and we were able to score a 966 RTI before we ran out of ramp. . .I designed that suspension with pretty much only what I learned from the Herb Adams "Chassis Engineering" book. . .I want to learn more and get more in depth so I'm gonna go ahead and get the other books, but I think Adams' book is a good start. . .

. . .Good Luck!!!
 
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atomicjoe23

Well-Known Member
 
OK. . .I hadn't looked at those books in a while and I forgot how expensive "Fundamentals of Vehicle Dynamics" and "Race Car Vehicle Dynamics" are. . .

. . .so I already have "Chassis Engineering" by Herb Adams (an extremely useful book by the way) and it doesn't sound like "Engineer to Win" by Carrol Smith has a lot to do with suspension design. . .correct me if I'm wrong, I'm just going by the Amazon.com description of the book. . .so what what book would those of you in the know suggest as a supplement to "Chassis Engineering" as I get deeper into suspension design???

If I need to spend the bucks for one of the other two I will. . .but are there any other books that I don't know of that aren't $100 and are either equal to or more in depth than "Chassis Engineering"?

Thanks!
 
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D.Mavis

Well-Known Member
 
I looked through those books. Tune to win is similar to chassis engineering in scope but probably more indpth. engineer to win is more about general real world construction of race cars, its good but not about suspension geometry.

I'd agree that if you were going to buy one book, the herb adams book would be it to start with.

I would not but the gilespie book, its mostly about passenger cars.

Race car vehicle dynamics-- is great but its very dry and probably very excessive for off road vehicle design. it goes in depth into all aspects of ground vehicle dynamics not just suspension geometry.
 
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Tech Tim

Well-Known Member
 
scottm said:
Search for keywords like camber, caster, J-arm, bumpsteer, etc.
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racer7674 said:
spaceoden said:
If you really want to start learning about suspension design Fundamentals of Vehicle Dynamics by Thomas D. Gillespie is a good starting point
Click to expand...
I appreciate your help. Your the only that really did so thank you.
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Josh,

Scottm was very helpfull in giving you keywords to search for. This BB has some fantastic threads on here about different aspects of long travel, BUT you need to know the basics before you can digest much of it.

Do you know what these terms mean and how they relate to IFS?

KPI
Bumpsteer
J-arm vs A-arm
Caster or camber
Brake dive
Roll center
Roll axis
Instant center

If any of those terms are new to you, you need to learn more about the basics. No one is going to want to spell out everything for you, nor can they, it would take pages and pages of posts to even get you remotely close and then there are multiple thoughts of what works best. Do a search for some of those terms and read the threads, you'll see how they go from one end of thought to another.


D.Mavis said:
I'd agree that if you were going to buy one book, the herb adams book would be it to start with.
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x3 on the Herb Adams book, he does a great job on laying out the basics in easy to understand terms and diagrams.
 
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atomicjoe23

Well-Known Member
 
Herb Adams "Chassis Engineering" will explain each of those terms and what affect they have on an IFS. . .with the exception of A-arm vs. J-arm. . .I'm gonna have to look that one up myself. . .
 
CRAIG_HALL

CRAIG_HALL

Well-Known Member
 
atomicjoe23 said:
Herb Adams "Chassis Engineering" will explain each of those terms and what affect they have on an IFS. . .with the exception of A-arm vs. J-arm. . .I'm gonna have to look that one up myself. . .
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No differance in geometry, just packaging.
 
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