Wow! Now here's a guy who's done some homework! Damn so many good questions. Let's start off with, welcome longhornss. Many of your answers are here. Try using the search feature first off.

Next, should the lca be level? According to many here, yes. Your next question I'm guessing refers to half shaft angle? When the lca is level the HS should be uppward at the wheel. Refrence univesal joints best angle, 3 degrees. Now let me add, Corvette C3 runs their HS's level app. Zero degrees.  And the lca downward out. Pinion, at parallel to trans but 3 degrees univesal angle front and rear matched. Radius rod should be inline to the inner pivot point of the lca.

Ralphy

Last edited by Ralphy (4/22/2014 4:56 pm)

http://s350.photobucket.com/user/acmjg/media/MOV04917.mp4.html

Watts video.

Have fun, that's a lot of stuff to go thru.

Ralphy

Last edited by Ralphy (4/22/2014 5:29 pm)

Here's a good image of a bind situation. The trailing link moves in an arc 90 degrees to the LCA. Pulling or pushing on the lower control arm.



http://car-from-uk.com/sale.php?id=10835

Here's a way to do away with any trailing link. The real issue is no control from above the Halfshafts. Once you pin/stop any fore or aft motion. The LCA can do it's job with less stress.

Here's a more profesional look.


http://www.cobraracing.com/

http://irsforum.boardhost.com/viewtopic.php?pid=4811

Ralphy

Last edited by Ralphy (4/25/2014 2:46 am)

Ralphy wrote:

Here's a more profesional look.


I like the way this one looks.
Ralphy

Ralphy -
Great updates while I've been away.  I have a lot of catching up to do. Those milled billet CAs are fantastic.

Cheers - Jim

Pretty to look at. However it looks to me like they weakened the design by putting the shock bolt through the center of the control arm. Thats the highest stressed area in that type of control arm. The design is all ready weakened by their choice to use aluminum.. The load path begins there and should have been the last place to drill a 1/2 inch hole. To have placed ears above or below the arm would have been superior. Ralphy posted a stock Jag LCA that cracked in half inches from the shock mount. The steel Jag control arms are pretty stout units.  Aluminum fatigues much faster than steel in high stress applications like Jag LCA's.  Pretty to look at, Poor design.Short service life.  

The likelyhood of failure is dependant on many factors. The most damaging would be vehicle weight and engine torque. When that is combined with sticky tires even Jag LCA's can fail.  I can see how these LCA's could survive happily under a Cobra with their light weight. I just see a weak load path where they chose to counter bore the CA with a 3/4 x 3/4 hole combined with I am assuming to be a concentric 1/2 inch hole with 1/2-13 threads.  I am well aware that Aluminum isnt free so they chose to go with a plate thickness that gave the most bang for the buck. It looks like 1.5"  6061 T6 plate using the parts around it for scale and guessing on the alloy.  2.5" plate would have provided enough material for the ears but that would be a high price to pay when the majority of the difference  would have ended up as shavings in the auger of their CNC mills chip evacuation system.  Ralphy, do you know off hand what the rear weight of an average Cobra is?  I am aware that question is vague but it would give me a starting point for some rough calculations.   I cant seem to find this info on line. No one seems to be willing to disclose F/R vehicle weights.only gross weight.  The company I work for now has just purchased a new Haas VF5, They allready had 2 VF4's 2 VF5's and a VF6. They are nice machines and opperator friendly. I have been spending the last 4 months getting my feet wet with the software. We do alot of 3D work with them for a testing lab near our location.  The control arms would be a piece of cake to make. Its kind of funny how people show so much intrest in parts that are so simple to make.  (access to the CNC mill is the hard part)  With a greater understanding of the G codes and general programming,  I can see how simple the Billet cobra would have been to make.  Nearly all of the machine work was done on two planes, X and Y. I didnt see any compounded curves anywhere on it.  Kind of like the the aluminum work supporting the quick change in the 68 vette. All done on two planes and as simple as CNC milling gets.  This is not an insult to these cars just an observation from a new understanding of the programming involved.  As far as the latest designs of Vette rear suspensions. They are all far superior to the Jag design. Period. No more BS half shaft UCA.  They resemble a front suspension with out the rack and pinion. Having an upper control arm, not a fake one that only supports one plane but a real wish bone three point CA makes them leap years ahead of the Jag design as well as the old type vette IRS. No argument.  There only draw back is packaging. They take up more space.

Last edited by tyrellracing (5/11/2014 1:12 pm)

I am familliar with 7000 series aluminum. I got a Tremec 5 spd.out of a 2007 mustang GT for cheap at a swap meet. It had the bell housing integral to the front half of the trans case. The mod engines as well as the coyote 5.0l have a different bell housing bolt pattern from the old classic small block ford. I machined a new front casing with its bearing bores and three rail shifter detented bores minus the bell housing. I did this to make the trans compatable with old school seperate bell housing ford used for decades. The problem I ran into was the foot print was bigger than the old top loader bolt pattern so an adapter was  required. I made the new case out of 7075 for the strength and it was what my boss/ company owner recomended I use. He had a remnant big enough and only wanted $25 for it so how could I refuse?  It was also my first personal project on the Haas mills at work. Learning how to program and getting practice by doing personal projects after hours is encouraged. As long as I pay for any tooling I break out of ignorance. 

As far as the failure of aluminum parts. Any one that has worked with Aluminum in high stress environments knows that the issue is number of cycles and their sevearity of  deflection the part must endure before work hardening occurrs. The wings you described may go through millions of cycles but never bend to the point of deformation. Thats where things go bad and work hardening sets in. Typically this is not an over night problem. It takes time. They may only deform the LCA once in a while but the deformations all add up to a crack in the long term.  I agree with you as far as using steel in app's like this one. If I were racing and had these LCA's under my car, I would just have one more thing to inspect before every race for cracks.  The weight savings may or may not justify the effort. Lower unsprung weight has its advantages on rough tracks but have no real advantages on a smoothe track. Rough tracks would be where the damage takes place so it looks like a catch 22. Weather or not these could be an  advantage would depend on where you race.

Last edited by tyrellracing (5/11/2014 2:42 pm)

I'm just sayin, takes a licken. lol



Ralphy

Last edited by Ralphy (5/11/2014 3:35 pm)

Wings don't plastisize, they?

http://m.youtube.com/results?q=777+wing+test&sm=1

Last edited by Ralphy (5/11/2014 7:08 pm)

But aluminum does flex as you said, that's my point. And it does not fatigue as much as common thought, if made right. If it can stand the rigors of Moto X's constant pounding and a wing flexing millions of times?

By Tyrell, "Nearly all of the machine work was done on two planes, X and Y. I didnt see any compounded curves anywhere on it. Kind of like the the aluminum work supporting the quick change in the 68 vette. All done on two planes and as simple as CNC milling gets."

Where have you seen a CNC "profile" parts? Maybe custom wheel manufactures? That would require many hours with little value.

Question: What is a defect?
Answer: Anything that adds cost that adds no value!

If the guy spent countless hours massaging a practical part you can't see anyhow. Trying to turn it into a show piece/ Gold Bricking? He would have to way up the price. Eliminating buyers and not selling much of anything. This market is limited anyhow.

Ralphy

Last edited by Ralphy (5/16/2014 4:07 am)

Sorry, I'm a little to join the party, but Ralphy has a wealth of information available - and terrylracing has a lot of experience to offer as well as many others here.  For all things IRS - this is the place!

I have been working with the C5/6 uprights in my suspension design for my track/race car for the past few years.  Maybe I can offer a point or 2 you might find useful.
1. The geometry of the pick up points on the frame from C5 to C6 are the same, the uprights and control arms as well (As I all my research has found.)
2.  Also, they are the same from base C6 to C6Z06. We'll have to assume that for the ZR1.  Have you a source for those?  May be just different materials - not design.  I understand that is the difference with the stock vs Z06.
3.  Suspension Analyzer V2.4 has a 2001 vette file in its library (C5). Because the position of the pick up points is the same, you can use that information to locate the control arm pivot points and balljoints if that fits your need.
4.  When you start your build, unfortunately, you'll need to do some work on the uprights to get them to be useful - GM didn't make the Ball Joints replaceable - that is why you see them on eBay. There are approaches you can use, I've posted mine here on this site, as well as vettemod.  I post there as phantomjock. 
I have some dimensions - somewhere - I'll look.

Cheers - Jim
 

Lets back track a little bit here. The primary reason I like using two coil overs per side at the rear of my rig is two fold. I have rebuildable shocks and lots of internal parts( pistons and shims) to play with to find what works best for me. Its real easy to over dampen any suspension if you get too gung ho with the spring shims in the rebuild process. I have found a setting that works best for me with the poor road quality and the way I drive. I dampen the rear shocks more on compression and dampen the fronts more on extension.  This seems to reduce some of the wheel hop. The other reason is I like a fairly soft spring heavy shock type setup. I have always used about 75lbs/in greater spring rate on the rear coil overs than the fronts attached to the LCA for reasons we have covered in other posts. I feel having support both ahead and behind the LCA reduces loading on the inner bushings. I am still using needle bearings at all pivot locations and have zero free play. So far.. I understand how simplicity can be a draw to the single C/O shock per side lay out. If it works for you,and you like the valving, by all means go that route.  I however,spend way too much time on E-bay, I have a tough time letting 2.5 id coil springs go when they are in the range I use and are,listed at $5.00 a pair buy it now  and have cheap shipping. I have accumulated more than a dozen pairs that way. So.. I use them LOL.

Tyrellracing - Did you ever have any luck with the widened LCA's to combat or change any wheel hop?
You had a post about how overcoming the large disk brake for the in board brakes caused the LCA's to twist like spongy corkscrews and while the shock setup helped a bit, the shocks acted like a torque coupling.
I've been curious if anything came from the information.