What is the medium going to be in the flex joint? Is this something similiar to the Currie "Johnny Joint"?

 

Similar to the Johnny Joint style but with different features that - I feel - offer better technical merit. Besides, JJ doesn't come in the 3/4" thread I need. A generic term is 'flex joint'. Used all the time by the rock crawler guys. I have some feedback that the 2.4" is pretty correct. Anybody else care to comment on this sizing question? I hope to firm-up the order by week's end. Thanks.

 

JJ's are available in 3/4" thread. Care to share what features you will be building in that provide better mechanical attributes? Not doubting, just really curious.

It is damn hard to beat the JJ with its amount of articulation (way more than needed), completely rebuildable, etc...

3/4 threaded JJ:
http://www.currieenterprises.com/cestore/Product.aspx?id=1262

 

My super cheap digital calipers measure the stock upper and lower bushing center sleeve at 2.4". So that should be about perfect like you said.
I remember a seeing a 4X4 outfitter that had joints with 3/4 threads on them already. I think this is what I was thinking of http://www.summitmachine.com/index.php?p=customParts&cp=fj

 

Thanks for the info shep 77 :thumbsup: Yes, there are several makers of this joint style, but not with the specs needed for a 3/4" rod end replacement. I ordered some double-adjustable uppers and lowers yesterday. They will come with QA1 XMR & XML chromoly rod ends.

I found that Derek69SS posted a pic of his double-adjustable uppers with the heims and spacers (see frame mount location) here: http://www.chevelles.com/forums/showthread.php?t=156498&highlight="johnny+joint"&page=5 in case you aren't sure what I am referring to.

 

jj's are available in the 3/4 thread, but only in the 2" version. they dont make a 2.46" ball width for the 2" joints, which means you have to get the 1" stud like i did. way to heavy, but they are done and i dont really want to redo them.

Tim

 

Is it possible to use the 2" version of the 3/4 Thread with small bushing spacers to make up the extra width?

 

Tim's right on the money. BTW Tim: Even though you mentioned to me previously that your stock mounts are now modified, your first experience was that the 2.46" was too tight to fit OEM mounts, correct?

 

A Napa rubber bushing is 2.4" wide. Look at p/n NCP2674219

A GM JJ center is 2.44" W:

http://www.currieenterprises.com/CESTORE/Product569.aspx?id=3052

Already mentioned, the GM JJ ball will only fit a 2.5" rod end, which has a 1" shank. It would be easier for me to make my own arms if it were 3/4" based off the free materials I can get.

 

the spacer is a possibility, but some extra work. the ballistic fab stuff should be perfect.

the 2.46" width was tight, but not too tight. they slide in and out without problems or force, but .060 smaller wont be too small either. with proper torque specs, the mount will tighten right up against the joint.

Tim

 

Received my tubular arms yesterday. Built like a tank! Yet heims with spacers = 2.46! It's all press fit, so I can't pop them open right now and inspect. However. the internal bushing holding it all together is at 2.40. Upper arm at axle mount is 2.31 (with powercoat layer). Hmmmmm....

I want to finalize the spec to the machinist Monday and get these new joints made. Would appreciate any additional input by then to run a batch. I will post additional info and pics soon. Thanks for the input so far.

 

How many you making? I might be interested in 4 if the price is right.

 

60

 

I'm also interested in 4 to replace the spherical heims in my UMI lowers if the price is right. Keep us posted please. :yes:

 

Timeout here. I received my tubular arms the other day and here's what I got. Anybody care to comment on this picture? Hint: It's got nothing to do with the tablecloth:

 

I don't imagine those spacers are gonna allow the rod ends to have much movement. Whats up with that?

 

Yes agreed... those spacers will not allow the rod ends to articulate properly.

Can I ask what brand those items are?

They need to look more like this- http://www.umiperformance.com/images/1017a.jpg

 

Yeah, those spacers need to be the same OD as the flat on the spherical ball for MAX mis-alignment.

 

Here's the reply from the race car chassis shop where I purchased:

All of our spacers are 1.5" in diameter now. The size of the spacer will NOT effect anything in the suspension.

My second question was why is one of the six heims polished? I first thought it might be a Midwest Control piece, but they all measure out the same. Newer QA1 XM version? UMI, would you know?

Hey, who you know wants to buy some heims? ...And some spacers? Seriously. Four XMR, two XML.

UMI: I don't want to bash a vendor right now (they are not a site sponsor), but even their own website shows the correctly sized spacers! Additionally, being the nice, courteous, detail-oriented guy I am, I pointed out some $$ product errors on their website they didn't know about. When I specifically requested (and they verified) a 1/2-20 bolt kit, they shipped 1/2-13. I can literally buy zinc G8 course bolts by the pound around here. This is really just too bad, because their upper arms are constructed like a tank and reasonably priced for what it is. Lots of TIG'ing:

Back to the flex joint project. Balls in line to get machined end of next week. Again, want to get a lock on the best width. Would +0.02" be of any significance given the wear on a 40-year old chassis? OEM rubber bushings come in at 2.40". I have to talk more to the machinist to square the deal, get his okay to post details...... and pay him :yes:

 

My second question was why is one of the six heims polished? I first thought it might be a Midwest Control piece, but they all measure out the same. Newer QA1 XM version? UMI, would you know?

Well actually I do think I have the correct answer... and I am pretty sure I am correct here. Over the course of a past few months last year we have noticed the quality of QA1 rod ends to rapidly go down hill. They were coming in with a yellowish tint and the bearings were lose compared to others from the past... some would then come in like they did in the past with the high shine and tight bearing. I contacted QA1 and they didn't really give me answer to why it was happening. I sourced out another rod end brand late last year, the quality of the new rod ends is out standing and the rod ends look great and consistent.

My guess is those are QA1 rod ends because based on your pictures that is exactly what they started looking like for us before we switched brands.

Hope that helps!

 

Any comments on competition eng rod ends?

http://www.competitionengineering.com/catalog/CategoryDisplay.asp?CatCode=16014

 

I never used them. When purchasing watch the lad ratings and lining used for the bearing. Some road ends don't use Teflon linings... this is ok for racing but will be noisy on the street.

 

UMI: I replied to your PM. Thanks for confirming my suspicions on the rod end quality.

 

zookpr:
I got to examine those seals last week. Initially looks like a no-brainer add-on to street heims, but they aren't sealed at the bolt head. So if water managed to enter at that point, how would it get out? And if it's covered up, you'll never see it rusting and then ruining the bearing and so on... It makes sense to me that the original intent of these seals was for dirt racing. Of course the seals got inspected after each race.

 

Adding some sort of seal on a street car is better than just leaving them fully exposed. I don't make them or sell them. Just providing some information that some folks may be interested in. As for sealing around the inner diameter some RTV at assembly will provide seal. I'm not concerned about rust - they don't rust. Just want to keep the road elements off them. For me, I have them on some Caltrac style traction bars on a leaf spring street car. But for others that use rods ends, these things may be holding in the rear like in a Chevelle. Yeah, I know you don't need rod ends on the Caltrac style traction bar - just like you don't need them on a Chevelle 4-link. The single degree of freedom bushed ends that someone posted above are fine.

 

Moving a little closer to finalizing this. A question regarding thread length. Rod ends for 3/4-16 run 1.75". I can bump this to 2.00" to get more engagement.

Many of the exisiting upper double-adjustable arms have this: http://www.midwestcontrol.com/catdisplay_short.php?pg=518

The female depth on 3/4-16 is 1.5". My arm has this adjuster and has an inch threaded in there. Male end is pretty much threaded in with some room for the jam nut.

A 1/4" inch isn't that much of a gain but it's no extra to do it. Going any longer maycause problems on certain bars. Comments?

 

We make our adjusters with 2.00" on the female side and 1.875" on the male threads... we also use 3/4-16" threads. We have never maxed out of adjustment on our applications. The thing I don't like about that Midwest is they are 1018 steel. Our adjusters are machined from 4140 and heat treated.

Hope that helps!
Ryan

 

I ran some calculation based on mild steel as adjusters.

http://www.engineersedge.com/thread_strength/thread_bolt_stress.htm

From the above using this formula for internal thread, ¾ - 16 on mild steel:

3/4" - 16
En max (in) = 0.7159
Ds min (in) = 0.7391
Le (in) = 0.75
n = 16

(Shear Area) An (in^2) = 1.243948724

Shear stress (yield /2) (psi) = 25,000


Shear area x shear stress = Force


Force to strip (lbs) = 31098.7181


So based on a ¾” thread engagement, it will take 30,000 lbs to strip/pull the threads. If I calculated this correctly, this is about the same strength as to what the rod ends are rated to.

 

ive heard anywhere from 1x to 1.5x engagement with x=stud diameter.

 

Yes, that is a good rule of thumb. I wanted to actually find hard numbers.

I plan on doing a FEA on the clevis end for the stock arm. I'm trying to find the weakest link, and over design a bit from there.

 

bochnak-
I guess I'm not sure if that Midwest piece is what I have or not but it measures the same. As Emil Faber would have said: "Thread engagement is good." Since you brought up the engineering math, what would be the calculated strength of aluminum lower control arms? Here's a guy using these on a late-model Camaro: http://www.jonaadland.com/Z28/Mods/LCA/AluminumLCAs.html along with a technical commentary on strength. This company offers the same thing: http://pavlockperformance.com/content.php?id=84 I'm going venture a guess that the reason they work on the Camaro is due to the torque arm design. The torque arm manages the twisting forces and the links just keep the rear in the wheelwells.

Well, here's the Coleman Racing 18" bar: http://www.colemanracing.com/catalo...catalog/product_info.php?products_id=35&osCsid=adc9543368133211a0cad7b36c57cd86 It's a turn-key piece: direct-threaded, perfect length, light weight and $17 each.

 

bochnak-
I guess I'm not sure if that Midwest piece is what I have or not but it measures the same. As Emil Faber would have said: "Thread engagement is good." Since you brought up the engineering math, what would be the calculated strength of aluminum lower control arms? Here's a guy using these on a late-model Camaro: http://www.jonaadland.com/Z28/Mods/LCA/AluminumLCAs.html along with a technical commentary on strength. This company offers the same thing: http://pavlockperformance.com/content.php?id=84 I'm going venture a guess that the reason they work on the Camaro is due to the torque arm design. The torque arm manages the twisting forces and the links just keep the rear in the wheelwells.

Well, here's the Coleman Racing 18" bar: http://www.colemanracing.com/catalo...catalog/product_info.php?products_id=35&osCsid=adc9543368133211a0cad7b36c57cd86 It's a turn-key piece: direct-threaded, perfect length, light weight and $17 each.

I get all my material info at Matweb.com. For shear, just divide the yield by 2.

1018 yield - 53kpsi/2 = 26.5ksi or 26,500 psi shear

6061-T6 - 40ksi/2 = 20,000psi shear

In the initial calc I used 25,000 psi. Re-calc for 26,500 is:

33,000 lbs for .75" engagment for 1018

25,000 lbs for .75" engagment for 6061-T6

http://www.matweb.com/search/DataSheet.aspx?MatGUID=1b8c06d0ca7c456694c7777d9e10be5b&ckck=1



My numbers are very comparable to the link you provided. He does not mention engagement, a variable that is important. Also, a great link, thanks!