Hi Guys: I'm working on spec'ing some flex joints that will screw into the aftermarket 3/4-16 tubular rear control arms in lieu of rod ends. I need to nail down the best width to machine the ball flange :cool: so they fit all six of the OEM mounting brackets. Would 2.400" be the "just right" joint size? Bigger? The bore would retain the stock 1/2" mounting bolt to make it an easy swap. 12mm for the G-Bodys. Thanks.

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.

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=%22johnny+joint%22&page=5 in case you aren't sure what I am referring to.

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

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.

http://www.fquick.com/images/vehicles/full/23712191921.jpg?1221681451
Tim

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.

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.

http://www.fquick.com/images/vehicles/full/23712191921.jpg?1221681451
Tim

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

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:

http://www.chevelles.com/forums/attachment.php?attachmentid=18727&stc=1&d=1233633960

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

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

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

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:

http://www.chevelles.com/forums/attachment.php?attachmentid=18742&stc=1&d=1233716370

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:

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


The rod end spacer OD on the ones I use on my car are smaller diameter, on the order of 7/8-1.0 inch diameter! These allow for all of the available rotation freedom. The only limit would be the spacing between the bracket to which they mount. The rod end cannot hit the bracket though since the spacing is sufficiently wide.

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

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.

The rod end spacer OD on the ones I use on my car are smaller diameter, on the order of 7/8-1.0 inch diameter! These allow for all of the available rotation freedom. The only limit would be the spacing between the bracket to which they mount. The rod end cannot hit the bracket though since the spacing is sufficiently wide.

For any one interested, I checked my rod end spacers, they are 7/8 OD and this diameter clears "rod end seals", if you choose to use them to protect the rod end bearing surface and extend the longevity of the rod end for street use.

Rod end seals - http://store.summitracing.com/partdetail.asp?autofilter=1&part=SIT%2DWS6250&N=700+115&autoview=sku

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

http://www.midwestcontrol.com/photos/273.jpg http://www.midwestcontrol.com/sketches/518.gif

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:



http://www.engineersedge.com/thread_strength/image/asn.gif


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.

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/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/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=1b8c06d0ca7c456694c7777d9e1 0be5b&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!

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.

the pirate4x4 site has a good 4 link excel calculator which allows the use of different materials. it will tell you the safety factor for things like compression (lca), tension (uca), and even failure due to load at the center of the link (not useful unless youre rock crawling with the velle). i went with 1.5" .120 dom, but we already know how f-ing heavy my arms are. at least only half is unsprung weight.

What is the adjustment range on adj. uppers? Stock length for 68-72 is 10.25".

Do lowered cars typically need them longer or shorter for desired pinion angle?

**UPDATE**
I’m having Ballistic Fabrication do a custom run of 60 “Ballistic Joints” (aka flex joints) that will specifically fit 64 – 72 A-Body cars that have aftermarket ¾-16 female tubular upper and/or lower rear control arms. These joints replace the rod ends and associated spacers. Ballistic builds their joints for 4X4 applications so they are tough pieces. Owner has no concerns about building a (smaller!) version to fit the Chevelle. Here are the specs:

1.) 100% machined AND forged in the USA!!!
2.) 2.40” mounting width, ½” bolt hole, (OEM specs)
3.) 2” long threaded male shank (up from 1.75” of typical rod end)
4.) Estimated weight to be just under 3lbs
5.) ¾-16 RH & LH threads available
6.) Clear (silver) zinc coated
7.) New Grade 5 zinc jam nut included
8.) Yield @ 208,000 psi, Tensile @ 238,000 psi - Unbelievable

Here’s a link to the details. Also check out the “Image Gallery”: http://www.ballisticfabrication.com/Forged-Chromolly-263quot-Ballistic-Joint_p_1636.html

http://www.ballisticfabrication.com/assets/images/forging/forging4.jpg

Above pic shown without zinc. One thing that makes these joints outstanding is their adjustable spherical design. Unlike a rod-end or similar joint product with a c-clip, the Ballistic Joint can be tightened if ever need be. NO SLOPPY RATTLES. In addition, opening the joint for inspection is via a spanner wrench since the side entry has no c-clip or need for proprietary tools.

I also have a bolt kit consisting of 3.5" Grade 8 Armor Coat (aka Ultra Coat) bolts/washers along with a clear zinced Grade 8 conical flange lock nut. See this video demo: http://www.jergensinc.com/Spinner-Grip-Flange-Lock-Nut-Video.aspx Set consists of 4 each of bolts, washers & lock nuts for $15 plus shipping. These bolts should physically look better for longer on driver cars.

Looking at this from a TCO (Total Cost of Ownership) perspective, I believe this joint design is a great deal. My ’70 has boxed factory arms and 8 poly bushings. Being located in the Midwest with marginal roads and steep driveways, I can feel the rear binding up. I will be switching to upper and lower double adjustables with 6 flex joints and OEM rubber bushings in the rearend ears and selling the unused QA1s & spacers that came with the tubular arms. If you want to run a poly bushing at the lower axle, UMI sells part #0013. Since my car is lowered, the double adjustables will allow pinion angle adjustment as well as re-centering the axle in the rear wheelwell.

BTW: These will also fit the G-Body metric cars such as Monte Carlo SS & GN Buicks with a bolt hole mod. To the best of my knowledge, these cars use 12mm bolts, the Chevelle bolt is ½” or 12.7mm so drilling out the factory mount holes would be necessary for these cars.

As I said, this is a custom order with additional costs involved to produce. Production is set to begin next week. Price is $48 each plus shipping. Sold in sets of two. I would likely use USPS Priority Flat Rate to keep shipping costs low. Feel free comment , P.M. me, or email direct at steverenox@yahoo.com

Wow those seem to be some really nice pieces. So for $48 you get two joints? Sorry just trying to clarify. The only hesitation I could see people have here would be the availability of a replacement or replacement parts should something happen. I realize these things are basically bullet proof but just thought I'd ask.

Neal:
They are $48 each.

Available in LH or RH threads?

What is the distance from joint center to end of shank?

Steve, been out of town a couple days, missed your PM until now.

Those look like some nice pieces!

Available in LH or RH threads?

What is the distance from joint center to end of shank?

They do look like real nice pieces. Any way you can answer the Q's I have above?

bochnak - Your question regarding joint center to shank end is proving to be an issue. Some 3/4 shanks were run on these new forgings yesterday and here are the current results measuring joint centerline to thread beginning:

Rod End: 1.125"
Forging Estimate: 1.500" - 1.625"
Forging Actual: 2.000"

So this increased distance (plus thread length) is just is too long. Even if you reduced threads to 1.50", not good enough. (BTW: Shank lengths have not been cut down at this time). Although this is a really nice joint, I'm sure it will require custom designed uppers and lowers and will likely NOT be a simple retrofit item.

A relatively inexpensive design would be direct-threaded DOM females on the uppers like the DM Products design: http://www.d-mproducts.com/dbladjuppercontrolarms.htm Same design as the Edelbrock and Currie models. Example: You could find out how deep DM threads each end as well as be willing to shorten the tubing as needed. Which shouldn't be a problem since his arms come in raw steel. I would estimate the lowers needing to be shorter than the 18" end-to-end versions I have due to the 0.875" increase on each rod end's body size. Lighter weight, shorter tubing with tube adapters would cure this.

P.M. me on your thoughts. I will need to take action ASAP.

I was able to do an FEA on a stock arm. I simulated the clevis end, which turns out to be the weakest portion.

I used .09" mild steel (I believe this is stock ga), which yields at 30,000 psi. I applied a 5,000 lb load on bolt holes in tension:

http://img3.imageshack.us/img3/5102/feastockarmym6.jpg

You can see that the material will yield at this point.

I guess what I'm trying to say is....those joints are really nice, and way too strong for our application. Is there any way they can scale it down a bit? The first thing that will fail is the clevis, then stripping of threads, and lastly the rod end (assuming QA1 of equivalent chromoly)

Here are 3D model snapshots of what I have built just a few days ago (minus the rod end, spacers, and jam nuts):

http://img22.imageshack.us/img22/4193/adjarm3eb3.jpg

It's real simple since I used a GR8 bolt and nut welded to the clevis. So far I have $6 invested since I deal with stuff like this at work.

Nominal thread engagement is .75 for a 10.25" length. Min is .5", and max is 1". This gives a range of 9.25-11.25 of adjustment.

I will have to make a new clevis since it may interfere with the rear end housing. Totally forgot to account for rubber bushing deflection....D'OH

Matt,can you retest the clevis end for yield point using 1/4 inch steel in place of .090 stock.Like this attachment.

Matt,can you retest the clevis end for yield point using 1/4 inch steel in place of .090 stock.Like this attachment.

Well, w/o doing a whole FEA, and simply comparing bolt contact patch, a .25” THK clevis vs. .09” THK clevis has 2.7x more area. Stress=Force/Area….therefore stress will be roughly 3x less on a .25” clevis.

In essence it will be 3x stronger in tension.

BTW, .187" THK (7 ga) will be 2x stronger. This is what I used due to availability of shop materials:thumbsup:

Thanks Matt;
2 1/2 x3 DOM rectangular tubing is available in .90,.120, .188 and .250 wall thickness.Just thinking about eliminating the clevis as a weak point for upper arms. Malibru's Balistic Fab flex joints would be great to replace rod ends. Grease fitting,rebuildable, super strong.

Is this a situation where the ends justify the means?

Thanks Matt;
2 1/2 x3 DOM rectangular tubing is available in .90,.120, .188 and .250 wall thickness.Just thinking about eliminating the clevis as a weak point for upper arms. Malibru's Balistic Fab flex joints would be great to replace rod ends. Grease fitting,rebuildable, super strong.

So you would hog the c/s out to form a "u" or "c" shape. I don't think I follow how you plan to construct a clevis from a rectangle.

Is this a situation where the ends justify the means?

Not sure what end you are talking about? Clevis, rod end, or both? Please be a little more specific.

Are these studded clevis's (clevi?) something you guys can produce? bochnak has a nice three-break design with two welds. A typical bolt would be RHT, so Joint would have to be LHT - opposite of typical. (Just kidding with you Matt. But I saw the LHT ring detail on the tubing).

Would you need a 0.250" wall to direct-thread? Then you could machine some wrench flats instead of adding the welded nut.

Yes, a RH bolt and nut is cheaper than a LH. Rod end price is same for RH & LH.

Ideally, I would have used 1" AL 6061-T6 hex for the turnbuckle. I do not have this material available at the moment.

That rod end in my pic is a midwest control piece. They have 3D models that you can download.

I‘ve been quite busy for awhile on other things. Here’s an update on this project. Joints are ready to go. Because of their size, they will not interchange with a typical aftermarket 18” tubular lower arm. Optimum tube length with this set-up is 15” therefore custom lower arms are in order. No problem making them, but need to know what you guys want. All of this would be direct-threaded tubing offering 2” of thread grip:


1020 0.188 wall = 1-3/16 OD


4130N Unsure on spec


7075-T651 solid rod w/ 1.25 OD
From what I gather, threading 4130 is not popular or recommended. And welding tube adapters is costly and requires heat treating afterwards. The 7075 has a significant up-charge over the DOM tube and I am concerned about the amount of material around the threads (approx 3/16). Need some commentary on this.

Am upgrading from 3/4 to 7/8 thread shanks for safety sake. Largest cost increase is the jam nuts! Try that with a rod end.

Keep the PMs coming and/or post with your comments.

i ran 1.5" .120 dom. not sure which is stronger. mines bigger in dia, yours is thicker. it wouldnt be hard to find out though.

a link with threaded bungs wouldnt be that hard at all. all the cost in is the joints.

why the 7/8? its going to add a lot to the weight.

Tim

No problem doing the typical 3/4-16 shank either, but here is how skinny she looks:

http://www.chevelles.com/forums/attachment.php?attachmentid=19874&stc=1&d=1237864736

With the 3/4, the 7075 would have a nicer thick wall, get clear anodized. 2-inches of thread grip. Again, this is for the lowers.

Is this a situation where the ends justify the means?

Not sure what end you are talking about? Clevis, rod end, or both? Please be a little more specific.

It's a common idiom denoting that the action called for is driven by the situation.

Several questions about sizing. Attachment is drawing with dimensions: