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Yo, Tim-
Weld the coilover mounts on the two-wide tubes that run up either side of the rear bulkhead area, hang the axle on them, 4-link arms to the forward tube of the cockpit, and you's in bizness!

I know, I know, it ain't that simple... But it looks fairly straightforward from that picture. Somebody in here (Modernbeat?) had a Se7en with a similar arrangement. Didn't have much frame aft of the driver's comparment, just enough to hang fenders and rear end bodywork on. The coilovers mounted off the rear bulkhead with some simple br*ckets. If I get a few minutes later, I'll try to locate the pictures.


JD

***EDIT***
Found the thread, but Modernbeat used a 3-link setup, not a 4-link. Sorry, my memory ain't what it used to be... What were we talking about? Any-hoo, the thread with the good pictures is here- http://www.locostusa.com/forums/viewtopic.php?f=5&t=1960&start=0 and you can check out the coilover mounts which are way cool and simple looking, as well as his 3-link setup.
JDK

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JD, father of Quinn, Son of a... Build Log
Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom

I marked the normal mounting tube with red -- as I understand it, that's the normal place to hang the rear radius rods?

And if I understood you, the "4-link arms to the forward tube" is the second arrow? Which would make it kinda look like any number of T-bucket / rat / 'coup / vintage sprint car / vintage Indy car setups? Which of course would be wayyyy cool?

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Geek49203 aka
Tim Wohlford
Louisville, KY
Hayes front, S10 +2 rear, Lalo body.

Some examples of loooong radius rods from roughly the front of the cockpit?





Then just put shocks to the top of the rear bulkhead... the rest after that is just to hold the body, protect the gas tank, etc?

Interesting. And yeah, since this all gets covered by Jack's body (er, the Lola-style body), I don't have to worry about how external radius rods look! hmmmm.....

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Geek49203 aka
Tim Wohlford
Louisville, KY
Hayes front, S10 +2 rear, Lalo body.

It would have both pros and cons. Namely the geometry could be improved throughout the range of travel with the longer links, but the buckling loads on the links are substantially increased on them.

I'd say that they can also definitely compliment the car and add to the badassness of the appearance...Just look at the Mallocks.

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

Yo, Tim-
I don't claim to understand all the "ins and outs" of a 4 link, but look at Mallock's TAM system, as well as the more recent Ford (of Europe) Escort rally cars. Cheapracer has a thread or two going about 4 link rear suspension, here- http://locostusa.com/forums/viewtopic.php?f=5&p=146566#p146566 and some other discussions around and about regarding live-axle set ups. And I'm talking about a true "4 Link" set up, like the kid with the micro sprint car in the picture, not the "wishbone" style from the older Indy car... You know that, right???
Good Luck, and keep us posted-

JDK

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JD, father of Quinn, Son of a... Build Log
Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom

With only a single pivot mount on the front of the Indy Roadster, the car can't allow chassis roll without applying torsion to the trailing links and axle - unless it runs a birdcage or other method to disipitate the bind.

I decided to beef up that area of the frame on Car9. It's probably overkill, but it seems reasonable to put a couple of pounds into this since the axle and engine are much bigger then the original Sevens or Locosts.

Since you already have the basic frame, consider welding another 1" square vertical tube 2" - 3" behind the forward tube you point to. Then add a piece of sheet metal between them, Ideally it would have a wavy shape. That will greatly up the strength and make it possible to mount to the vertical in single shear. Weld short tubes into the new piece of square tubing to take the bolts. On Car9 i show a couple of extra holes above where the bars would be horizontal and that can tune anti-squat and anti-lift. The extra holes don't cost much...

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SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.

So I went out and looked and measured...



And as I said over on another thread: "I looked at my build, and noticed that a 30" radius rod would put it roughly 24" from the back of the lowest point of the rear bulkhead, or about 6-7" behind that last upright (near my knee). I'd also have to make sure the rear axle is wide enough to have the rods/links run alongside the frame. My frame is 44" wide, the inside of an S10 axle is just shy of 50", which means I have a bit under 3" on each side for these trailing arms, which means I probably won't have much room for positive offset tires."

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Geek49203 aka
Tim Wohlford
Louisville, KY
Hayes front, S10 +2 rear, Lalo body.

How far to the yellow geek?

Obvious triangulation there and you can go backwards on the axle mounts a bit, if you can acheive say 27"+ I wouldn't get too pedantic about it.

As I recall, 2", making this a 28" arm. And 28" can be purchased fairly cheap from places like Speedway -- I mean, why make your own stuff when it's cheaper to buy? Ditto for axle brackets too.

Once I get this all in place, and once it's all with lots of adjustment holes on the front end of each rod, how would I know how to adjust it? What am I looking for? Given the torque / weight on this build, I assume I'll always be looking for more forward bite?

Thanks!

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Geek49203 aka
Tim Wohlford
Louisville, KY
Hayes front, S10 +2 rear, Lalo body.

You're laughing then Mate, 28" it is then - good info for the other thread too.




Primarily you're looking for the torque not to upset the chassis balance under hard acceleration and for the car to go in the direction the steering wheel is pointed. Also go around some left and right corners and compare how much the RHS wheel picks up and spins compared to the LHS wheel while accelerating hard out of the corner.

Watch Rod's V8 accelerate at 3.14 and 6.19, note the left rear wheel is driving harder than the right and sending the car sideways, this is what you want to adjust out .. (that's no slight on Rod's great build by the way.)

http://www.youtube.com/watch?v=jqvYJlYc4GU

Of course your starting point should always be everything equal for your baseline and making changes/testing from there.

My opinion on 3 links is very simple, they are for people who can't work out how to setup a superior 4 link and/or (incorrectly) believe 4 links bind.

To boot, that is quite a poor example of how a 3 link should be setup offering none of it's advantages and all of it's disadvantages amazing since the knowledge has been around since the early 1950's starting with the C-Type Jaguar.

"One other interesting innovation appeared at the rear. To help prevent wheelspin in this era when limited-slip differentials were rare, Jaguar designed a torque link that mounted atop the right side of the axle, leading forward.

Normally, in a conventional beam axle, the pinion gear has a tendency to "climb up" the ring gear. This creates a lifting moment that reduces the weight on the right-rear wheel, allowing it to spin just when engine output is highest. That's why powerful cars with this type of rear suspension and no limited-slip often leave just one black streak of rubber when scorching away.

Jaguar's novel link was placed and angled in such a way as to counteract this lifting force and press the right-side wheel back down onto the road. Of course, it also located the axle in a rotational sense, thus reducing any tendency to tramp or judder on acceleration"



Notice where the 3rd link is on the Jag, that it's adjustable laterally and very importantly, that the lower links are mounted as close to the center of the axle as practical to avoid torsional loads on the axle housing.

Is this the same as "Bob is your uncle"?

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Geek49203 aka
Tim Wohlford
Louisville, KY
Hayes front, S10 +2 rear, Lalo body.

Were you ever able to setup your test rig to physically confirm that the lack of binding in the somewhat unconventional (generally appears to incur significant pro-squat) geometry was not at all affected by adding the mathematically-overconstraining lateral control linkage?

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

He hates "Bob" actually, much prefers to be called Robert.

By the way, hope you're going to use a Panhard rod, I'll offer you some thinking on that as well, very good choice for a hi-torque, live axle setup - if done properly.