thanks for the info guys! any goods front roll center options?

 

No

 

I'm having trouble visualizing what you're trying to say... care to elaborate? (or draw something? )

 

and it leaves room for a low flat trunk floor. i know we don't care much, but a good design will satisfy several different criteria



on the front of the arm there is room to do this a little, in the rear though, it would be kind of tricky, just because they mounted it the way they did.

by a little, is like 1/2"

 

the line we want is pivot point to pivot point, so putting the ball joint on the other side of the arm does nothing

 

Does not change the roll center, but does add camber on compression which is normally foreign to a Macstrut car.

I was thinking of making lower ball joint brackets using a 1/2" spherical bearing...that way you could move the spindle relative to the ball joint vertically.

 

if you're just flipping the ball joint to the top of the control arm... it won't. at least nothing significant.

an easy way to add more camber gain is to increase the SAI (ie, camber plates)


also a 1/2" spherical bearing seems awfully small for a ball joint..

 

Eage8...looking at 1/2" spherical bearings...radial load in excess of 25000 lb. Could go up to the 5/8" for 44600 lb rating. I would think that would be enough for my 2700# race car! By using the spherical, you can add shims between the LCA and spindle to change RC.

 

The bearing itself isn't what I would be worried about, it's the 1/2" bolt you're putting through that bearing.

and how do you plan on connecting that bolt to the spindle?

 

Tow ways...drill the spindle for a square hole, or use a tapered bushing. By drilling I think you would want to use the 5/8" bolt.

 

the stock balljoint connects to the spindle with an 18mm pinch stud... there is no taper.

 

Haven't had it apart so I did not know that. In that case, I would machine an 18mm stud on top to accept the 5/8" bearing on the bottom, with a lock nut.

 

+1 i just drew a bolt up in solidworks. its 18mm, like stock, and as you would expect, the longer the bolt the weaker it gets, so spherical bearing + bolt solution has a limit to how long you can make it before the wheel falls off in a turn

material is super important.

TBD on using a larger bearing, and bigger bolt

 

my new and improved (hopefully) idea is to use the AWR ball-joint/bearing retainer and weld/drill out the knuckle to 19mm / 3/4" and use a 3/4" grade 8 bolt with a nut holding everything together. (the AWR ball joint uses a 3/4" bearing)

even though the pinch bolt area is 18mm. the recess where the pinch bolt goes through goes down to 15mm which is where mine broke.

 

with the strength testing i'm not 100% sure i'm using the right numbers, if you have a 2800# car with 50/50 weight distribution, 1600# but add 1g, and i'm just testing #2800lbs.

i'm not sure if that's too much, or not enough...

and of course there is the oddity that if i have the computer add a stress diagonally, vs straight it makes a difference, how that is possible on something round, i do not understand

 

Some guys over at nissanroadracing did something similar with the same size bolt:
HOW TO: Ultimate budget front LCAs - Nissan Road Racing Forums

 

The only problems they've had with the setup is the bolt loosening up... so I just have to make sure it stays tight.

 

oh you know i'm not testing for shear, i'm bending it, that must be the difference. it does look like you could hang a couple S13's from one bolt, and we just played with a 350Z today, and i bet the body would fold/spindle/mutilate before the bolt bent

http://nucor-fastener.com/Files/PDFs...r_Strength.pdf

 

Besides camber, would there be any advantage to making it so the control arm was longer? I'm not talking about camber

 

It changes SAI which helps all kinds of things... (roll center and camber gain) But it also increases track (which is good or bad depending on what you're doing)

I have no idea what it does to bump steer.

 

I just need to see how my wheel fitment is with 17x9 +22 on the shine fenders.

I'm thinking why not drill out 18mm to 19mm or 3/4" and using a huge bolt.

I did not measure the stock thickness of the metal on the ball joint, but I was thinking 3/8" would be ok? I guess the hardest part would be machinging the bore for the bearing.

 

Look at your other thread

https://www.rx7club.com/race-car-tec...cones-1058123/

the stock ball joint is aluminum, so the thickness could be smaller if you make a steel ball joint.

I don't know how thick my AWR ball joint is, but I'd probably say somewhere around 1/4" steel

 

I also wanted to raise the rear for more anti-squat. Ultimately, 1/2" just isn't enough to justify the effort. The frame needs to move at least 2" up to help with the lowered stance and give the increased anti-squat I'm looking for. I've thought about cutting it all apart and just welding brackets to the frame / roll cage to locate the outer control arm mounts and keeping a cut down center section of the subframe to support the camber links, and diff front.

I've also looked at the front roll issue and tried getting the setup from AWR. I'll have to give him a call as e-mail doesn't appear to get his attention (everyone has their best way to contact them).

-Trent

 

Yeah, I only raised my subframe .25" and everything just barely fits, you would need some major fabrication to do more than that. maybe 3/8" tops.

I have the idea of making my own front roll center, but I am too lazy to buy the bearing to figure the size I would need to get machined so I could fit a snap ring, then source a bolt and spacers. I really should right now since I am waiting on my fenders.