Custom triangulated 4 - Link questions.

[x-tream]

I am building a custon triangulated 4 - link in a 70 cuda, and a 68 camaro. I am wondering what the proper down angle, and side angle of the top bar is the correct. Also is there an approprate lengh for the bars??

[sinned]

There is no answer. Designing suspension is far complex than just "what angle do the links need to be at". It takes hundreds of hours of both trial and error on the actual chassis combined with taking measurements and analyzing the results via an Excel based program.

I don't mean to sound harsh but if you asking what angle the links should be at you really have no business touching the torch or MIG yet. Spent a few months learning, searching, reading then do some measuring of what you have now and analyze that to get comfortable with the different programs as well as taking very precise measurements of pick-up points. After all that map out a plan and post you results, there are a few who will be happy to take a look at them and give an idea of how it looks on paper.

[markss28]

I personaly would love to see someone build a Tri-4 link with out cutting up there ride so much this has been a dream of mine to do but who knows if it could be done.

[Silver69Camaro]

Originally Posted by markss28

I personaly would love to see someone build a Tri-4 link with out cutting up there ride so much this has been a dream of mine to do but who knows if it could be done.

Give us a call, Mark. We've got a DIY kit that can be installed under most trunk pans. You get to decide where the brackets go, so it's all up to you.

[x-tream]

Well i have built straight 4-link , ladder bar suspention for 500hp plus cars with out trouble before. We know have two cars in are shop that are more interested in pro-touring then drag racing. The reason i am asking this is because every picture i see is different. Since u say there is so much to read and understand, were can i find this information? My other option is to build it and see how it works. Which is not really how i want to do things, that is why i am on here asking people who have done this before.

[sinned]

Milken, Steve Smith, Herb Adams, and Fred Puhn will get you started.

Drag suspension is easy...just run a few parallel links and hang on. Things like roll oversteer/understeer, roll center height, brake hop characteristics, SVSA, and articulation are not usually considered.

[PTAddict]

Here are a few basics to keep in mind as you do your reading

Roll Center Height: If you have one pair of angled links, the roll center height will be located at the virtual intersection of the two angled links. From a practical standpoint, with this design, you want to get this as low as possible. The Morrison designs put the upper, angled links at the height of the axle housing, which is better than most such designs which put brackets on top of the housing (unacceptable, IMO). Even better, as suggested by Herb Adams, is to make the lower links the angled pair, but this is more difficult to pull off from a structural and packaging standpoint.

Side View Swing Arm and Roll Steer: Viewing the suspension from the side, imagine extending the upper and lower links until they intersect in space. The line from this point to the center of the axle is the SVSA. The angle that this SVSA forms with the roll axis is important, because it determines whether you will have roll understeer, oversteer, neutral steer. If the SVSA is angled upward toward the front, you will have roll oversteer, which will make your car unpredictable and twitchy on turn-in. Some amount of roll understeer is generally considered desireable, but there are tradeoffs between achieving this and keeping the instant center higher to get more anti-squat. Also, keep in mind that the shorter the SVSA is, the more likely you are to suffer from brake hop.

Instant Center and Anti-Squat: The intersection of the upper and lower links in the side view, as described above, is the instant center. Draw a line from the point of the rear contact patch through this instant center, and find the intersection point with a horizontal line at the height of the center of gravity of the car. If this intersection point occurs forward of the front contact patch, you have less than 100% anti-squat, if it occurs between the contact patches, you have more than 100% anti-squat. Some amount of anti-squat is desirable, to help the car hook up on acceleration out of the corners. Just how much you want is debated, but if you can get close to 100% AS while still having roll understeer, you're doing pretty well.

Link Length: The shorter the links are, the more all of these parameters will change as the suspension moves, and the greater the chance that the suspension will start to bind up to a significant degree. From a practical standpoint, it's hard to have links that are too long.

Getting the optimum balance of all these parameters - even knowing what the optimum balance is, and what it feels like to the driver - is what makes suspension design hard. Build some adjustability in, for sure.

[Silver69Camaro]

Originally Posted by dennis68

Milken, Steve Smith, Herb Adams, and Fred Puhn will get you started.

Drag suspension is easy...just run a few parallel links and hang on. Things like roll oversteer/understeer, roll center height, brake hop characteristics, SVSA, and articulation are not usually considered.

Dennis,
If the links are parallel that will equate to zero anti-squat, which would be a big disadvantage for drag setups. Because of that, SVSA is of concern when designing a four-link system.

[sinned]

Originally Posted by Silver69Camaro

Dennis,
If the links are parallel that will equate to zero anti-squat, which would be a big disadvantage for drag setups. Because of that, SVSA is of concern when designing a four-link system.

Ahh, the drag guys don't care. Just weld in some tubing in place of the shocks and you'll have all the A/S you want.


BTW, the links being parallel (in plan view which is what a parallel 4-link implies) has no bearing on A/S characteristics.

[Mean 69]

Den, nice response, I was wondering how'd you reply! I guess we are all getting a bit nicer these days, eh?

PTAddict, your response was perfect, outstanding summary. Ahh, the compromises! Decisions, decisions, decisions....

Silver, I am "familiar" with the AME four link kit, but wonder if you guys provide guidelines, or examples with the universal kit, based on the statement of "you get to decide where the brackets go." The universal deal is something we have strayed away from, just simply because it is uncomfortable to let the user (and the wide scope of capabilities comes firmly into play) determine the end geometry? Just wondering how you guys deal with that, without going broke from phone calls!
M