[EMWHYR0HEN]

There was too much bind with the stock poly bushings up front because of my desired caster so I decieded to replace the bushing with a heim joint.

I made the LCA on the car adjustable which uses a 4'' turnbuckle with left and right hand threads. On one end of the turnbuckle is a 3/4''-16 heim joint with a 5/8'' bore. On the other end is just used a 3/4''-16 grade 8 bolt.

I made the arms in a way so that smallest adj. size would be the stock length. The arms can extend .625'' and still keep a safe engadgement so that means I can adj. my front track width up to 1.25''. Should that be more than enough to work with? i'm going to raise my pivot point on the X-member I wondering if i should move it out as well.

The turnbuckle is made out of aluminum. Anyone have anything to say about that?

I got everything from www.Midwestcontrol.com
Great prices, huge selection, and the most important thing, they post the SPECS!

The pictures are pretty much step by step.























Stay tuned for my chrom-moly tube rear control arms. I already got a jIg made!

[woldson]

Clever use of the wood to keep things alinged.
Not sure of the strenth of the grade 8 bolt compared to the orignal arm.
Do you really trust the thread in the alluminum turn buckel?
Smart to have the treads deep into it though.

[EMWHYR0HEN]

Grade 8 bolts 1/4-1 1/2'' have a yeild strength of 130,000 PSI.

Yeild strength: The maximum load at which a material exhibits a specific permanent deformation.

I think it's plenty considering the car weighs less than 2300 LBS.

How can I find out the load capacities for the aluminum turnbuckle?

I think i'll have more peace of mind with steel ones...

[1 fast z]

Only thing I would of done differently is, use better than a mig welder. I used 312-16 Stainless rod, which has a VERY high yeild strength.

[buZy]

Very Nice Work Myron!

[jnjdragracing]

I agree, it is nice work Myron. Please keep us posted.

John

[1 tuff z]

nice fabbin' myron-can't wait to see your rear arm pics.

[woldson]

I"AM NO EXPERT!
With that said, how is yeild strenth tested on a bolt verses a frame?
130,000 dose not seem that much when you think of bumping .... oh lets say a curb sideways at 10mph.

The work is fantastic and seems relatively simple hence a good idea. I think the thing that bothers me is going from a frame to a cylender makes me pause to think a momemnt of lateral forces on the compondant.
I'am unsure just interested.

[JMortensen]

woldson said:

I"AM NO EXPERT!
With that said, how is yeild strenth tested on a bolt verses a frame?
130,000 dose not seem that much when you think of bumping .... oh lets say a curb sideways at 10mph.

I don't see how any control arm that uses a rod end is any different, and I'd bet a solid 5/8" bolt is stronger than a sheet metal .080" box. Making suspension arms strong enough that don't deform when the car hits a curb sideways is a bit much I think. I doubt the stockers would handle that very well and its very easy to avoid that situation in practice.

[katman]

Actually the people that whine about threads exposed to cyclic tension loads (myself included) that are also a single load path strucutre are proly more concerned with unnoticed fatigue cracking than they are with one time overloads. A 3/4-16 will probably last forever, even with the approporiate notch factors applied to realistic loads. That said, it makes folks like me and Jon cringe because its ingrained into engineer types that you just don't do stuff like that. The sheet metal control arm is what we'd call more damage tolerant, and a lot of those old Z parts weren't just welded up sheet metal, they were welded up sheet metal that had been normalized, stress relieved, and heat treated afterwards.

Really, I just don't understand this fascination with adjustable control arms. Camber plates are a much better way to do that and in 15 years of racing Z's I never found the need for adjustable front control arms. Rears are a slightly different story because of the need to adjust toe, but on the front????

To each his own. Nice work anyway.

[JMortensen]

katman said:

Really, I just don't understand this fascination with adjustable control arms. Camber plates are a much better way to do that and in 15 years of racing Z's I never found the need for adjustable front control arms. Rears are a slightly different story because of the need to adjust toe, but on the front????

He did say that he did it to get rid of the poly bushing bind from running more caster. I do agree that adjusting camber with the LCA is not the best idea, and a camber plate is a heck of a lot easier to adjust since you don't have to remove the TC rod, but for the purpose stated I see nothing wrong with what he's done.

[TONY C]

I have made my own in a similar fashion with great results. Only using parts from a local circle track shop instead. I have camber plates too.
I have been running them hard for 2.5 years and they have performed excellent.
Mig welded and all. I have put them to the test on the "Dragon" regularly and I believe that 318 continuious kiss your behind curves at full slide on a weekly bases would have shown their weakness if there was 1.
Of course I inspect them regularly.
And as far as camber plates being enough. More adjustment is better than not.
I set my camer plates up to operate in a caster fashion instead of camber. I know. Adjustable tc rods. I made them too.
But if you want -3-4 deg camber and +6-7 degrees of caster and have an MSA II air dam or the like you will have to cut quite a bit off the front wheel well area to get the tires to clear (10" wheels 0 offset). With the plates setup in this fashion I can get all the caster I want with NO trimming or rubbing.
Drop the aluminum turnbuckle for a steel unit and they will perform for a long time.
A+ on the build.

[woldson]

That's what I wanted to know guys, thanks! Great job Emwhy!

[EMWHYR0HEN]

Thanks for the comments guys.

I also agree that using camber plates to adjust camber is more straightforward.

However, having adjustable LCA's w/ a spherical rod end I can now adjust my track width, caster (without bind), and then adjust camber up top with the camber plates. The more adjustability the better.


I also agree that we should be more concerned with stress/strain and fatigue on a part like the LCA.

I think most if not all stock control arms are designed to absorb impact and break before transfering that load to the chassis. With that said my new arms probably don't stand a chance with the extreeme conditions like hitting a curb, but with the design and 3/4'' threads (overkill) I think they'll go the distance. I'll probably end up replacing the aluminum turnbuckle with a steel one.

[katman]

jmortensen said:

He did say that he did it to get rid of the poly bushing bind from running more caster. I do agree that adjusting camber with the LCA is not the best idea, and a camber plate is a heck of a lot easier to adjust since you don't have to remove the TC rod, but for the purpose stated I see nothing wrong with what he's done.

We used Tilton spherical bearings to eliminate the binding issue (caused by poly bushings or additional caster) on the IT cars, and I would have liked to section the control arm and add another 3/4 inch to get more camber (got to be careful you don't run out of tie rod thread!), but we were also limited by the rules on how much track we could run (contact patch could not extend outboard of the fender lip. Instead we did funny things with the strut to get more camber (the rules were more permissive there) since even with camber plates you couldn't get the 3.5-4 degrees a radial Hoosier likes without bending the strut and/or other more creative things.

I don't really see anything wrong with what he's done either.

[EMWHYR0HEN]

I took the stock control arm and made a jig out of 1'' square tubing. I wanted my new arms to have the exact same mounting points as the stock arms only having adjustable end links holding the hub assy.

It turns out the round tube on the stock arm is 1'' OD so I deceided to re use that and use it as my starting point. I attached 2 5/8 - 18 rod ends & threaded tube ends to the jig so basically now I just have to connect everything using 1'' OD x .095 wall Chrom-moly tubing.

I'm going to drill 3 or 4 holes on the tube to plug weld the tube ends. Once every thing is cut I think it might be best that I tack everything here with my mig before I Tig weld everything at my school.

[SkunkTeeth]

Wow, that look really good. Great idea.

And just a point about bolts and yield strength. When designing bolts use the proof strength (generally 90% of the yield in most cases). For a grade 8 bolt the proof is 120ksi. The tensile area of a 3/4" bolt is .334 sqin which means a force of ~40000 lbf would cause the bolt to fail, you should be fine , even with fatigue

[woldson]

Extramly clever and simple, really nice work!!

[74_5.0L_Z]

That is similar to the manner in which I constructed my control arms. Here is a Jig that I made:



On my jig, you weld one side of the control arm, then flip the control arm to the other side and then weld the other.

One issue that I see with your control arm design is that the axis of the two rod ends are not parallel. As you adjust the length of the rear rod end, the spacing between the rod ends will change. This will create a binding situation between the strut and control arm.

[JMortensen]

EMWHYR0HEN said:

What you have is so close to this:

http://forums.hybrid...71&d=1211382074

I think the separate toe link is far superior in terms of letting the strut articulate with no bind.

Here's the post where we hashed that out if you hadn't already seen it:
http://forums.hybrid...ad.php?t=129154