barnett468 wrote:

.
a johnny joint is basically a heim joint.
 

Basically .. with some fundamental differences which makes it not at all like a heim joint.

This was the other one thats basically a heim joint too with a nice comparison video .. that includes a real heim joint.

Last edited by afnid (2/13/2015 6:05 AM)

Sure, I don't think that your elastomere joint, or the johnny joint are any rod end bearing with any dampning ability is synonymous with a heim joint other than they are all rod end bearings.  It may be splitting hairs on a term that doesn't have a formal definition other than a 65+ year old http://monstertower.com/HeimJoint.htm">patent.

I don't think any of the clevis type strut rods use a rod end with any significant vibration dampning?  A reason could be the size constraints for significant dampning with the end having to fit in the clevis, but even the commercial through-bolt style strut rods are using heim joints (0 dampning).

Like I said before, not seeing any first-hand experience whether the dampning in this style of rod end bearing is significant enough in this application, but seems like it should help.

barnett468 wrote:

afnid wrote:

Sure, I don't think that your elastomere joint, or the johnny joint are any rod end bearing with any dampning ability is synonymous with a heim joint other than they are all rod end bearings.  It may be splitting hairs on a term that doesn't have a formal definition other than a 65+ year old http://monstertower.com/HeimJoint.htm">patent.

I don't think any of the clevis type strut rods use a rod end with any significant vibration dampning?  A reason could be the size constraints for significant dampning with the end having to fit in the clevis, but even the commercial through-bolt style strut rods are using heim joints (0 dampning).

Like I said before, not seeing any first-hand experience whether the dampning in this style of rod end bearing is significant enough in this application, but seems like it should help.

thanks for the reply, unfortunately i'm still not quite understanding everything you sare saying but the one i posted does in fact serve a similar function to the johnny joint . . below is a different view of the one i posted . . nothing wrong with the johnny joint at all when used within its design limits and they are kinda cool, but i can assure you that neither of these joints dampen a lot of the forces from the road, but they will reduce or eliminate the klunking sound that mustangsteve complained about.

it also comes with a female end.






 

Thanks to both of you.  This has been an eye opening experience for me, and it reinforces my belief that I need to return to a stock configuration. 
 

This is the alternate mounting system that I was looking at that uses a simple through-bolt so does require drilling a hole: Simple home made strut rods , most with this type of setup mount it to where the strut-rod is shorter.

And agreed, ride is so subjective that it is near meaningless, so I really won't know untill I can experience it first hand.

Jon Richard wrote:

Most of this is hard to make out, rotational axis in plan view? Top view?

It is a non sequitur regardless, a longer strut rod will exhibit less for/ aft migration of the LBJ as the suspension cycles, and the difference between the RRS units I posted vs. adjustable units that use a rod end is more like 2”. I never assigned much stock in this single attribute but it is at least a move in the right direction for most street applications.

That Johnny Joint belongs at the LCA pivot where it sees movement both vertical and for/ aft, you’d have to do surgery to the strut rod insulator mount to use it as the rod pivot. It can be done but not sure it offers anything over already existing solutions. The off road guys claim that it is “smooth” has nothing to do with NVH and everything to do with better articulation with long travel.

Anyway, that minor point detracts from the main attribute of the RRS units, that being the benefits of a bearing with a better service life over the standard rod end adjustable units. If one’s priorities are NVH and service life go with Steve’s suggestion and get MOOG bits.

The rotational axis is defined by the two pivot points of the control arm and is a vector in 3d space that moves with the body.  Intersect that axis 90 degrees to the ball joint and you have the center of the arc the ball joint moves.  With zero shims on the car, the uppper and lower control arm axis appear to share the same plane.  But the front of the uca will require more shims in order to get any meaningful caster.  A shorter strut rod brings them closer to being in the same plane, or looking like they are parallel if looking at a top down view.

You can't treat the strut rod pivot as a single point, it is just part of what defines the rotational axis of the control arm.  There may be physical limitations of the oem design, but in the limited movement of the suspension, it should not push/pull the lower ball-joint except for maybe under heavy braking.  For the lower, the 90 degree from the lbj intersects with the rear pivot point and the strut-rod forms the side of a cone as the suspension cycles.

It is hard to make out, and difficult to visualize all thats going on, and wasn't trivial to model from scratch.  I am trying to look at it as a whole knowing I at least plan to lower the uca and I added lower camber adjusters.  I can see what combination of modifications will result in but what is an ideal caster/camber with the front compressed 1", or the car in a turn with just one side compressed 1"?  What if with some other changes I do the shelby drop a little more or adjust the upper control arm angle?  I can see the stats change, but for better or worse?  Maybe finding a better handling car could provide baseline numbers?  Do the coil-over systems alter the upper/lower control arm geometry?



 

Hence the mis-information..  It is statements like this in multiple forums that caused me to model this in the first place.  But it was really when you stated this in another thread that I started looking at this deeper:

barnett468 wrote:

the farther apart the mounting points are on the strut rod the less affect it will have on the caster as the lower arm moves it and down.

This really confused me when the all-knowing barnett said something that appeared to defy the fundamental laws of math and physics.  Surely I must have been wrong .. but the math doesn't lie.

Your statement was absolutely false, when the suspension is treated as a whole, the longer arm increases the affect on caster, even though it is very small.

My initial interpretation was the same as yours, but after reading some conflicting information and thinking it through, realized it was quite different.  I needed to model it to see it as a complete system and was still surprised about certain aspects of what actually occurs.
 

barnett468 wrote:

coil over shocks have no affect on steering or suspension ie castor camber or toe. 

The coil-over kits all come with new lower control arms and uppper control arms.  Any change to the position of the static location of the ball joints affects all of those things and will require additional shims and adjustment to return to the desired settings.  In addition any change of the ball joints relative to the steering is going to affect ackerman and bump-steer which can't be adjusted out.

Of course you could be absolutely correct if the developers of these kits have not made any geometry improvements to the 50 year old slide-rule built suspension and I should expect to slap one of those on and not even have to change my alignment shims?

Maybe you assumed I was just going to change my shock and spring and keep eveything else the same, but then why would i bother even posing the question..
 

barnett468 wrote:

If the strut rod has no give front to rear which is the case if a rod end beraring is used in place of the stock bushings, the lower control arm will in fact travel in a slight arc as was mentioned . . it has no choice.

This one is profound, yes the ball joints do move in arcs, and there is no choice in that, but the center of the arc is absolutely not the rod end bearing.  The arc is about the rotation axis, and there is only one, and the center of that arc in the lower control arm is the rear pivot.  Excluding deformation of the suspension bushings, there is only one fixed rotation axis, and only one center that the ball joint rotates about relative to the body.

The stock strut rod likely changes effective length under heavy braking or cornering where strong lateral forces are involved.  In all other cases the effective length should not change and provides a fixed pivot point.  It absolutely does not act as the center of rotation for the lower control arm when it does change length.  What changes is the rotation axis which will affect any points being rotated about that new axis, which will appear to move the lower ball joint forward and back.

When/if the strut rod changes length, the rotation axis changes, but the center of the arc for the lower ball-joint is still the rear-pivot because that is the 90 degree intercept.  The amount of caster change is minscule compared to the amount that comes in from the suspension being compressed under hard braking.

barnett468 wrote:

Lowering or raising the upper control arm has no affect on the castor.

Absolutely false.  If you follow the shelby drop template for a 65-66, it drops straight down, and any change to the upper control arm rotation plane most definitely affects not only the static caster that has to be adjusted for, but also has an affect on the dynamic caster amount added during compresion..

The upper control arm axis is mounted at an angle relative to the lower axis.  The 67-70 template keeps it in the same plane so in theory it could be shimmed and the upper ball joint would be in the exact same previous position.  But any small error here is magnified at the ball joint.

barnett468 wrote:

the strut rad can be eliminated if a lower a arm is used in place of the single arm.

Surely, whats the point?  An a-arm achieves the same exact thing, you define a fixed rotation axis and a point of rotation about that axis for the ball joint.  Still a wishbone style suspension that will have a lot less flex than the mustang design but abides by the same geometry rules.

Sorry to hammer you on this barnett, I like reading your responses, you seem knowledgeable in a lot of areas, and the only reason I am on these forums is to learn from guys like you, but basic laws of math and physics do apply.

So many questions, so zero answers.

I’m a little rusty at this, I’ve moved on from suspension on my current build, but I’ll take another crack.

First off, this whole tangent is a thread derail, so to kdgt500 and Steve- apologies.

Now, I don’t have the energy to go point for point in a quote/ respond fashion, nor do I believe doing so would prove constructive as we have factors dealt with in both isolation and collectively.

afnid- The way you have your front tuned the whole damned wheel is migrating for/aft as it jounces, so perhaps reassess your stance on the LBJ not migrating, I’ll elaborate in the next paragraph. You basically splayed both the upper and lower control arm rotational axis away from parallel because stacking spacers behind the front upper A-arm shaft was your solution for obtaining your desired static castor. Personally I would have opted to either reposition the shaft on the control arm or re-drill the holes in the shock tower before canting the arm to that noticeable of a degree if it was still that far out of whack after running out of adjustment in the strut rod.

Now the LBJ for/aft movement issue. You said “The rotational axis is defined by the two pivot points of the control arm” and “You can't treat the strut rod pivot as a single point” Well, I agree, but If one uses a strut rod having a pivot rearward of the factory potion you see that the pivot has also moved outboard in top view, now the arc is no longer at right angle to the chassis and thus it migrates for and aft through jounce. I know you follow me here because you described this exactly, but I don’t see every mustang needing this wonky shim stack for correct castor so your argument is a straw man unless talking about your car set up specifically.

And really you can count on the LCA almost never ending up at a perfect right angle to the chassis which is why I say that’s the place for a Johnny joint or just stick with the factory bushing.

I can't get enough of this topic, thanks guys.

Bob

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First of all, I readily admit that I am not the most knowledgeable person on suspension and steering, but I have worked with both a lot over the years.

Most of the info I post are facts that are based on things that have already been tested and proven by others and in dome cases have been tested and proven by myself as well.
 
One example is if I say 2 plus 2 = 4 or E = MC2 then these are proven facts . . I am not claiming to have invented these facts nor am I ever claiming to be the one that dIscovered many of the things I post . . Some people used to think the world was round but it obviously wasn’t, and no matter how many people thought it was round, it still didn’t make it true.
 
Many people think that adjusting the push rod length so it causes the rocker to sweep/travel an equal distance on both sides of the center line on the tip of the valve stem is the correct way to set up valve train geometry but it is incorrect and has absolutely nothing to do with valve train geometry . . If everyone was required to supply proofs or some sort of scientific evidence to support every single thing they say to prove what they are saying is correct, then a simple recommendation to set the spark plug gap at .032” would need to be followed by pages of text showing actual test results of voltage vs gap vs compression vs fuel ignition temp etc which is simply unrealistic, however, some of these tests on spark plug gap do exist and I have actually seen some of them.
 
I also occasionally offer opinions but this is actually rare because I prefer to offer known facts because I think it is more helpful.
 
If someone has proof that something I said is wrong then I am happy to look at it and if I am then I have no problem admitting I was because my goal is to learn more about the things I am interested in . . I am not one to ever say I know it all and I dislike people like that immensely . . I tried that a time or two when I was young and stupid and it didn’t work out too well, lol.
 
Now, none of this is to say or imply that I know it all because I certainly don’t, but I started working on cars and motorcycles when I was around 14 and did it as a side line for many years for extra money then started doing it as a full time job for around the last 27 or so, so I certainly hope I learned something doing this in the last 45 years . . This being said, I readily admit that I don't know diddly squat about computer programming, or quantum physics or how to make a perfect soufle' etc, nor would I ever pretend to . . I'll leave those things to Bill Gates, Steven Hawking and Martha Stewarrt [or Betty Crocker] respectively . . Also, I certainly understand that sometimes there are more than one way to fix a problem or "skin a cat" as the saying goes.
 
My posts are simply direct and to the point but are not intentionally written in a way to make it appear that I know it all, it’s just the way I write . . I have written over 1,000 reports so my posting “style” is simply from doing that.
 
As far as the strut rod arm changing the caster, I made simple example that anyone can test to prove it. Also to say that I am wrong regarding this without simply physically trying it yourself makes no sense to me . . in addition, as mentioned, Jon Richards said the same thing so you not only have 2 against your 1. But you also singled me out on this issue and intentionally failed to include him . . I don’t know why you did this and I don’t know why you are not asking him the same questions you are asking me . . This seems a bit odd to me.
 
I am not a computer programmer and have no fancy cad program to show or prove what I am saying, but it sounds to me by reading your comments that you have at least some experience in this area, therefore, I suggest that you simply make a cad program that shows exactly what you are talking about and load it on youtube and post a link to it here.
 
I would be happy to look at it and it hopefully it would help me to understand what you are talking about . . I read what you are saying and based on that, and how I understand/interpret what you are saying, it is incorrect, but the cad program, should make your point more clear to everyone thereby eliminating any potential for anyone to misinterpret it.

Last edited by barnett468 (2/15/2015 5:06 PM)

rpm

I had a moment to flip thru, when I get a chance I aim to read through the entire build thread but WOW- respect!
I'm recovering from a divorce myself and feel for you, glad to see your progress. The only machine I have is a Sherline table top and welding is limited to wire feed until I get a GTAW, thinking about those new fangled compact square wave inverter jobs from Miller.

Anyway, thank you- very inspirational!

barnett468

I want to try and clarify using your example with the 10' and 1' bars. If you take the 10' bar and raise one end off the ground 1', then add that 1' bar under the lifted end and tac it, then you basically have the unitized LCA with the 10' bar being the strut rod and the 1' bar being the LCA, with the tac'ed end being the ball joint and the ground serving as the pivot axis.

That is how I understood it anyway. What I was conveying to arnid was that if you use a shorter strut rod you change the front pivot axis away from paralell with the chassis, thereby changing the arc perscribed by the lower ball joint making the it migrate for/ aft a little as the suspension cycles.

arnid wasn't seeing it that way because he canted his UCA shaft to be paralell with his lower. It didn't make sense to me either because he assumed that was a typical set up.

Anyway as I said that is how I understood it. You seem a knowlegable and experienced fellow so I am open to correction should you believe otherwise.

Jon Richard wrote:

rpm

I had a moment to flip thru, when I get a chance I aim to read through the entire build thread but WOW- respect!
I'm recovering from a divorce myself and feel for you, glad to see your progress. The only machine I have is a Sherline table top and welding is limited to wire feed until I get a GTAW, thinking about those new fangled compact square wave inverter jobs from Miller.

Anyway, thank you- very inspirational!

 
Thanks for the kind words Jon Richard. My Miller Diversion 180 tig does everything I need it to do. Used machine equipment can be had for $500 to $1,000.

Bob

Thank you for doing this afnid, I have a cold and worked 11 hours today- really wasn't looking forward to ripping the upper out of my ride to take a video. Translation- wasn't going to happen.

afnid wrote:

barnett, wasn't really sure where jon stood on each topic, but definitely know where you stand, and I like you more, sorry jon.

Ouch! And this is how I have to find out

Seriously though, the communication breakdown is understandable when we have a static 2-D format to discuss 3-D objects in motion, but to be clear I never thought of the strut rod/ LCA as anything other than one A arm. In order for the strut rod to pull the LCA for/ aft they would have to change they’re angular relationship to one another and the fact that they’re bolted together makes that impossible, they’re one member. Thought I had made it clear with this-

Jon Richard wrote:

I want to try and clarify using your example with the 10' and 1' bars. If you take the 10' bar and raise one end off the ground 1', then add that 1' bar under the lifted end and tac it, then you basically have the unitized LCA with the 10' bar being the strut rod and the 1' bar being the LCA, with the tac'ed end being the ball joint and the ground serving as the pivot axis.

My stance about the shorter rod imparting for/aft movement on the LBJ was always in regards to skewing the axis of rotation away from parallel to the chassis, speaking under the assumption that the upper remained parallel.

Still not crazy about how you have your upper and lower axis splayed. Here’s and excellent thread that covers this topic with some great tech on how the chassis will handle loads with that arrangement in case you haven‘t read it- It has a couple pics that demonstrate your paper analogy too.

http://www.corner-carvers.com/forums/showthread.php?t=210

Last edited by Jon Richard (2/17/2015 12:16 AM)

afnid wrote:

.

 I think there are a couple of things in your demonstration (impressive as it is) that you have not taken into consideration: the bushings compress, and the suspension is not loaded.  The strut rod can be thought of as being the radius of a circle, with its connection to the frame being the center of the circle.   As the LCA moves up and down, its connection to the LCA should describe the perimeter of a circle - it has to since the length of the strut rod doesn't change and the frame end is fixed.  Since this is a fairly large diameter circle, that change, within the arc you made, is pretty small - but should still be measurable.  In other words, in reference to the front of the car, and assuming the LCA starts in the middle of your experiment, the LCA should move forward slightly as it moves up, then backward as it moves back down to the middle position, and then forward again as it moves down.

Steve69 wrote:

I know these are pricey but what do the experts think of this design for the lower control arms?

http://www.ebay.com/itm/67-70-Ford-Mustang-RideTech-Front-Lower-Control-Arms-StrongArms-Pair-/350572089537?pt=Vintage_Car_Truck_Parts_Accessories&fits=Year%3A1969%7CModel%3AMustang&hash=item519fb990c1&vxp=mtr

Those are actually discussed a fair extent in the link I provided above. Personally I don't like them, the forward pivot is still rearward of the factory position and the rear pivot is a radial bushing, you still adjust at the front for castor so unless you just happen to end up with the rear joint perfectly aligned it will bind like any stock LCA.

But those do bring up an interesting point. Since it is obviously a one piece unit how do those that propose the strut rod pulls/ pushes the LCA feel these would react? The only difference is one is welded and the other is bolted.

The example with lifting a fork off the table is apples to oranges- it demonstrates what a trailing link does, moving in a vertical motion having a radial pivot at each end.

A strut rod is fixed at one end, moves dynamically at the other, and prescribes a circle. Just like drawing a circle with a compass with the radius being the LCA and the hypotenuse being the strut rod, the compass will not grow taller or shorter as you rotate it.