Help me find a 3 link rear suspension?

[Offroad Outlaw]

Bassically I have been thrown from my original plans and now Im sitting here trying to figure out what dirrection i wanna go... As some of you know this is my first venture unto the Pro Touring obis.... I come from the world of dirt modifieds so my knowledge of making a car not slide into the corners and keep weight on all 4 tires is very limited... Not to mention assfault itself being the surface...

Here is a grate writeup about the types of suspensions and what im usually tryin ti make them do.... PLEASE go read... might even give urselfs a new idea or 2
http://www.hotrod.com/how-to/chassis-suspension/ctrp-0403-dirt-car-setup-tips/
My project hasnt gotten past paper except a spare bedroom and shop to collect parts n pieces till plans are set in stone and I can thrash like crazy for a few months b4 summer gets here

I have been learning about setups for diffrent styles of big track road course racin... including the pro touring campain and the autocross/rallycross stuff and even good ol rally racing.... ive also always tuned on grand turismo(i know... i know... its just a game) but its a game about physics and geometry... and thats "sometimes" universal... with that being said ive often looked at other forms of racing and tried incorperating it into the dirt world with a fair ammount of success...

I would love to try to do that again... but in this strange new world ive fallen in love with.... So yes i will have a few questions pertaining to ur thaughts on trying a few things.... like have you seen anyone else ever try it? What happened? If u could change it and try again...would you?

Heres the catch... i like custom.... im not a out of the box kinda guy... and i dont build my stuff to look like it came out of the box... i have a pure hate for heims... and id perfer NOT to have a Jbar or panhard or watts link... or any other lateral link... unless there is a damn good reason i should...
EXAMPLES AND QUESTIONS COMING SOON

[LS7 Z/28]

Bassically I have been thrown from my original plans and now Im sitting here trying to figure out what dirrection i wanna go... As some of you know this is my first venture unto the Pro Touring obis.... I come from the world of dirt modifieds so my knowledge of making a car not slide into the corners and keep weight on all 4 tires is very limited... Not to mention assfault itself being the surface...

Here is a grate writeup about the types of suspensions and what im usually tryin ti make them do.... PLEASE go read... might even give urselfs a new idea or 2
http://www.hotrod.com/how-to/chassis-suspension/ctrp-0403-dirt-car-setup-tips/
My project hasnt gotten past paper except a spare bedroom and shop to collect parts n pieces till plans are set in stone and I can thrash like crazy for a few months b4 summer gets here

I have been learning about setups for diffrent styles of big track road course racin... including the pro touring campain and the autocross/rallycross stuff and even good ol rally racing.... ive also always tuned on grand turismo(i know... i know... its just a game) but its a game about physics and geometry... and thats "sometimes" universal... with that being said ive often looked at other forms of racing and tried incorperating it into the dirt world with a fair ammount of success...

I would love to try to do that again... but in this strange new world ive fallen in love with.... So yes i will have a few questions pertaining to ur thaughts on trying a few things.... like have you seen anyone else ever try it? What happened? If u could change it and try again...would you?

Heres the catch... i like custom.... im not a out of the box kinda guy... and i dont build my stuff to look like it came out of the box... i have a pure hate for heims... and id perfer NOT to have a Jbar or panhard or watts link... or any other lateral link... unless there is a damn good reason i should...
EXAMPLES AND QUESTIONS COMING SOON

I've been around Dirt Late Models and Modifieds for over 25 years so I can understand some of what you are thinking but there are very few things that are transferable from Dirt oval racing to asphalt road racing and autocross. The concepts of weight transfer, rear steer etc. are all way different.

Have you read through Ron Suttons threads on suspension on this forum? They are free knowledge and the best advice you can get from an expert.

https://www.pro-touring.com/threads/111964-Rear-Suspension-amp-Geometry-for-Track-Performance

As far as custom goes, you most definitely will have to build your rear suspension as a one off set up because no one that I know of makes a 3 link rear suspension package that is bolt on, I could be wrong but I don't believe so. This is mostly because of the upper link location and the lack of room in most muscle cars. Your best bet is to talk with Ron Sutton and to pay him to design a suspension system for you that will work with your car, then purchase the parts from him.

As far as not using Heims, I'm not sure why you are against them because you are definitely going to need to use them in order to build a system that works properly.

If you are dead set on using a 3 link, then you have to use either a panhard bar, j bar or watts link. You need something to locate the axle laterally. Without it you will crash and burn before the first turn on a road course because your rear end will be moving side to side.

The only suspension that will work decently without a panhard, j bar or watts would be a triangulated four link. I saw you posted about truck arms in another thread but I didn't read it. I don't think that's the right route to go. I know Nascar Cup cars still run that setup but it's an antiquated and old way of doing things.

Maybe Ron will chime in here and give some free advice, but without help from him, Mike Maier or someone who has experience with road course asphalt 3 link set ups you are going to have a tough time getting it right. I totally understand the need to be different and go your own route but you can still build the car and suspension yourself just get the help you need from a pro and you will be way ahead of the game. Good luck.

[Rod]

i have a pure hate for heims...
???? even custom made racing suspensions use them...well leaf springs don't use them




and id perfer NOT to have a Jbar or panhard or watts link... or any other lateral link... unless there is a damn good reason i should...

ok then, leaf spring it is, they don't use any of those



ive also always tuned on grand turismo
I have no response to that

[LS7 Z/28]

???? even custom made racing suspensions use them...well leaf springs don't use them



ok then, leaf spring it is, they don't use any of those



I have no response to that

Rodney, you're killing me over here. I'm laughing so hard I almost fell off my chair.:rotfl:

[dontlifttoshift]

You will need a lateral link with a 3 link.....no way around it. I've built 3 links and 4 links out of DSE swivel-links. They are rubber bushed but there is a spindle on one end so it can rotate freely.

[ace_xp2]

I feel like I've seen a three link with no lateral via converging lowers before...

[dontlifttoshift]

Just converging the lower links will not hold the rear end in place laterally. Even a triangulated four link doesn't do as good a job of lateral location as a link suspension with a PHB or watts does.

[ace_xp2]

So when you converge the links on a four link the suspension is laterally constrained but not with three? Why would that be?

[dontlifttoshift]

That's a good question that I don't think I can answer, but I'll ramble a bit here anyways.

The triangulated 4 link uses bind to hold the axle laterally, picturing a GM a body here and leaving out body roll for the sake of my sanity.

he converging links forces oppose each other, one loaded in tension, the other in compression when the car is loaded laterally. The LCAs are placed out near the end of the axle and essentially run straight front to back. When the converging links are loaded it will want to pull the axle forward on the side of the tension loaded UCA and push it rearward on the side of the compression loaded UCA. It can't do that because the LCAs effectively hold the axle in place.

With the 3 link, if you ran the LCAs from the axle ends and converged them in the middle with a centered upper link, there is no way to keep the axle end from moving front to back with a lateral load. The axle would be free laterally.

[Rod]

So when you converge the links on a four link the suspension is laterally constrained but not with three? Why would that be?

great question, that's basic physics, lets look at this real simple ....if you wanted to support a 200lb tube, 2 feet in the air mounted on little tubes standing up in your driveway.....using the diagram below.......which one looks more stable


https://static1.pt-content.com/images/pt/2015/02/3vs4_zpsubnipngz-1.jpg




Just converging the lower links will not hold the rear end in place laterally. Even a triangulated four link doesn't do as good a job of lateral location as a link suspension with a PHB or watts does.

I agree.....working on mine

[dontlifttoshift]

BOOM! Pictures, thanks Rodney.

[ace_xp2]

With both converging arms constraining lateral motion the three linked version is the one that has the least bind supporting it off the ground. That seems as though that would be what you want, since when actually under the car you'd be keeping the suspension from "falling down" (towards the chassis) with springs.

Though I must admit, I'm struggling with this as something feels wrong to me as well. But despite mulling it over I can't really put my finger on why, with just one point to provide constraint on whichever side of the axle you choose not to have the converging links it seems that you could get the axle to roll steer more (not in a good way) but on the other hand this provides the opportunity to go to a fully heimed situation since there is now no link fighting the others in pure roll. I almost feel as though heims would be requisite, but that with the converging arms parallel to the ground in pure roll there shouldn't be any roll steer, maybe single wheel bump would would produce too much (single wheel in parallel three also produces some, maybe less)? And in that instance with four converging links the suspension can bind against the additional link and so reduce the chance of getting into that zone?

[Rod]

the Lateral Dynamics 3 link was converging and it still required a lateral location device

https://static1.pt-content.com/images/pt/2015/02/d403cbd89764491d9b167afb8a1a8e12_zpsmage-1.jpg

https://static1.pt-content.com/images/pt/2015/02/0604phr_susp_10_z_zps0euotwnx-1.jpg

https://static1.pt-content.com/images/pt/2015/02/LD2012_zpsoz4skcu7-1.jpg

[ace_xp2]

With those link angles I'd hope so.

In the case of three links not providing lateral constraint (just read dontlift's post 9) If you think of parallel arms then certainly you can "collapse" the suspension forward, but with the arms converged at 45, you're going to need to collapse or extend one of the links to make that happen I'd think. Even with no upper arm and the axle flopping about all over the place, you're still able to rotate the arms, but not pull the axle forward without having a link which could do either under force.

Hmm, one more addendum to this post, thinking on the aforementioned it seems to me that in any case of single wheel bump there will be some amount of bind, in turn, this may force you to use bushings regardless of the lack of constraint via the fourth linkage. And so having one link up top may not provide the benefit of allowing the use of heims.