Suspension travel upgrades on an 80

[Walking Eagle]

WE
I'm curious how 59 and 66 differ. They shouldn't

try reading - I know it's not your strong suit - from post 66

" changed one of the assumptions from dropping the axle brackets and putting the axle where it would be without dropping them to going out the full arm length and then dropping."

I'm curious how my drawing 118 is "wrong". You even used it. I'm curious how your CAD got picture 101, it doesn't reflect the proper axle mount or arcs (specifically it's missing lift axle pivot).

what the hell is a lift axle pivot? Ya', I used 118, but I think you're looking at the picture wrong. How can you not see that the black arc and the green arc aren't the same path?

I'm curious how your cardboard only addresses a single rod on a dual rod articulating axle. I'm curious how your cardboard arcs don't intersect properly to reflect axle lift..

One last time - we're not looking at articulation. We're only looking at the path the axle takes - do you understand this or not? You do NOT have to look at both sides to understand or simulate this. The cardboard arcs DO intersect properly. There is only one way for two arcs, of the same raduis with those two mounting points to intersect. Guess what, they'll intersect 180 degrees from there too! The orange is for a leading arm - or radius arm mounted lower on the frame. The black is for a leading arm mounted at the stock location on the frame. You can see where each is pivoted by the pin. You can see that each has the same amount of lift by the lovely green springs that put the center of the axle, the little black circles, the same distance vertically from the frame. You can see that the arms are the same distance, cause it's the same darn piece of carboard to represent the leading arm. Let me rephrase that, everyone else can see that...

I'm a curious guy by nature. I can handle you being pissed off.

I'm sure you're happy to think you've pissed me off. That's the whole reason you keep posting the way you do and continue to use WE after I've asked you not to. Maybe I'll start refuring to you as DS.

I don't think you have much of this right, nor are your posts consistent. To help educate a "clueless" guy like me, you can:
* make your posts consistent (and continue to delete the others)

My posts are consistent. The only ones that I changed anything between, I said why right in the post! The only ones I've deleted is because those are the ones that I swore in.

* correct my geometry and conclusions in 118
* reread the givens in the story problem to see my posts as
consistent
* Use Cad to 'fix' 118 *and* come to a different conclusion
regarding articulation arcs of 2 static level axle rods. That should
also disprove my articulation arc formula in the lower right

I've already corrected your conclusions.

Yes, you're posts are consistent - consistently vague, consistantly wrong, and consistantly misguided.

I don't know what you're trying to prove by the arc formula in the lower right, but it certainly has nothing to do with the topic of "Does an axle with lifted axle mounts take the same path through it's suspension travel as a dropped frame mount?" Which the answer to, in cause you didn't read it another posts, is NO.

There's a lot of folks watching this thread. It might be nice to get it cleared up? Since you keep wanting to 'add' to 118, not claim it's wrong, why don't we start there?

Thanks for your continued efforts on behalf of this ascribed clueless

Scott Justusson

I'm not adding anything to 118. I'm just saying you don't know what your looking at or your trying to answer a question that no body asked, and nobody else seems to know what that question is. Seems your trying to prove that for whatever amount the right front wheel goes up, the left front wheel goes down. Which is just silly.

How about you start by answering the questions I've already asked?

"what suspension have you ever designed?"

Here's one more for you.

1. What determines the path that the axle moves as it goes through it's travel (80 series front)?

If you can answer that one correctly, we'll move on. ok DS?

 

[T Y L E R]

Maybe when we sort this all out someone can create a thread that has some flow. Take whatever truths they can sift out of this discussion and lay out some clear, linear information for the newbs that decide to take a look.

The simple spirit of this thread got buried quite some time ago .. it's like a patient asking which medication will help him with his problem, and a medic, RN, cancer Dr, research scientist and surgeon all start jabbering away, disseminating what 'will' work .. thats great and all and I'm all for mental masturbation, but where does that leave the patient .. the newb. Confused as hell


As you were gentlemen.




TY

 

[reffug]

Maybe when we sort this all out someone can create a thread that has some flow. Take whatever truths they can sift out of this discussion and lay out some clear, linear information for the newbs that decide to take a look.


TY

It'll probably have to be Romer T, even though I have 2 years of engineering he's the one who actually has a degree and does it day in day out for a living. Sides dat I don't have the patience for it, I still can't believe I have waided through the 4 pages of this that I already have. I need some coffee.

 

[Walking Eagle]

If someone can get me the specs on the leading arms, I can work out the details of each configuration.

 

[SUMOTOY]

hummm... they don't pivot anywhere but at the frame. They twist a little in the bushings, and so does the axle, but they certainly don't pivot under the axle.

Since they aren't rigidly mounted, and they "twist a little" in the bushing, more if you make extreme angles of them under load, they certainly should be considered a pivot, because that is the definition? Most likely negating 'any' measureable change in arc would be my thinking. Let me know what you want to call a limited pivot mount Walking Eagle, it really doesn't matter to the exercise.

SJ

 

[SUMOTOY]

try reading - I know it's not your strong suit - from post 66
what the hell is a lift axle pivot? Ya', I used 118, but I think you're looking at the picture wrong. How can you not see that the black arc and the green arc aren't the same path?

Then the formula in the lower right hand corner of the picture is correct? Or not? I believe it is.

One last time - we're not looking at articulation. We're only looking at the path the axle takes - do you understand this or not? You do NOT have to look at both sides to understand or simulate this. The cardboard arcs DO intersect properly. There is only one way for two arcs, of the same raduis with those two mounting points to intersect. Guess what, they'll intersect 180 degrees from there too! The orange is for a leading arm - or radius arm mounted lower on the frame. The black is for a leading arm mounted at the stock location on the frame. You can see where each is pivoted by the pin. You can see that each has the same amount of lift by the lovely green springs that put the center of the axle, the little black circles, the same distance vertically from the frame. You can see that the arms are the same distance, cause it's the same darn piece of carboard to represent the leading arm. Let me rephrase that, everyone else can see that...

Er, post 118 is the story problem 3in of lift, 3 inches of articulation, level rods, 2 mounting differences. In your cardboard pic 1-5, you show the intersecting arcs level with the frame bracket pivot point. That's not the design of the lifted axle mount sir. For that intersection to be true, you have to lower the upper rear pivot by 1.5inches given 3in lift and 3 in articulation.

I'm sure you're happy to think you've pissed me off. That's the whole reason you keep posting the way you do and continue to use WE after I've asked you not to. Maybe I'll start refuring to you as DS.

Please call me whatever you feel comfortable with, I just abbrev Walking Eagle. I don't insult your intelligence, I disagree with your supporting documentation, and claim it isn't consistent with itself, or an articulating axle with 3in of spring lift.

My posts are consistent. The only ones that I changed anything between, I said why right in the post! The only ones I've deleted is because those are the ones that I swore in.

A great start, since this thread has a lot of views. 59 and 66 aren't the same are they? In fact, in 59, you have the same axle rod dimension, both horizontal, and yet the upper rod is shorter. How can that be?

I don't know what you're trying to prove by the arc formula in the lower right, but it certainly has nothing to do with the topic of "Does an axle with lifted axle mounts take the same path through it's suspension travel as a dropped frame mount?" Which the answer to, in cause you didn't read it another posts, is NO.

Bingo: "mounts". That's more than 1. Then the answer certainly is yes with the givens of 2 rods equal length in the scenario provided. The *axle* will have 2 arcs during articulation, 1 side up, one side down (as in one wheel attached to a rigid axle up, the other whee.l attached to a rigid axle down). It can't have 1 arc, because you have 2 mounts. 2 mounts = 2 arcs. The axle is the same, it's just no longer level during articulation. You are only addressing 2 wheel compression or 2 wheel drop if you want to use 1 arc. That's not articulation, which is a given in the story problem.

I'm not adding anything to 118. I'm just saying you don't know what your looking at or your trying to answer a question that no body asked, and nobody else seems to know what that question is. Seems your trying to prove that for whatever amount the right front wheel goes up, the left front wheel goes down. Which is just silly.

"Does an axle with lifted axle mounts take the same path through it's suspension travel as a dropped frame mount?"

2 mounts, 1 goes up the other down during articulation. It's not silly, you only present half the answer in your own question. The 2 arcs the *"mounts*" follow during articulation net to zero differences between the two mounting scenarios.

How about you start by answering the questions I've already asked?

"what suspension have you ever designed?"

Does it matter to this exercise? I'd rather stick to the topic, as I suspect would most viewing this thread. If you are *really* interested, please fee free to contact me offline.

Here's one more for you.

1. What determines the path that the axle moves as it goes through it's travel (80 series front)?

If you can answer that one correctly, we'll move on. ok DS?

Care to get more specific? There is more than 1 plane of travel on the front axle. At 3in of lift and 3 in of articulation in a single plane, it would be the mounting of the axle rods. Given two horizontal rods of the same length, mounting so that the axle centerline doesn't change with lift, during articulation, see 118.

SJ

 

[Walking Eagle]

Does it matter to this exercise? I'd rather stick to the topic, as I suspect would most viewing this thread. If you are *really* interested, please fee free to contact me offline.

It must matter to this excercise that you've designed suspensions, since you're the one posting that you have. If it doesn't matter to the exercise, delete it.

Care to get more specific? There is more than 1 plane of travel on the front axle. At 3in of lift and 3 in of articulation in a single plane, it would be the mounting of the axle rods. Given two horizontal rods of the same length, mounting so that the axle centerline doesn't change with lift, during articulation, see 118.

SJ

Stop throwing articulation in and answer the straight forward question. Can you do that? Ignore the flex in the bushings and answer the question!

 

[Walking Eagle]

Er, post 118 is the story problem 3in of lift, 3 inches of articulation, level rods, 2 mounting differences. In your cardboard pic 1-5, you show the intersecting arcs level with the frame bracket pivot point. That's not the design of the lifted axle mount sir. For that intersection to be true, you have to lower the upper rear pivot by 1.5inches given 3in lift and 3 in articulation.SJ

humm.. NO. The question is, and always has been, in my posts that you so kindly said you had to correct, and that I'd done "carnage" with, does lowering the frame mounts have the same effect as lowering the axle mounts

 

[Hayes]

I told myself that I was done with this thread, but I'd really like to try and extinguish some of the flames.
Again, I'm going on my understanding of the problem, and I make no claims to perfection.

It seems to me that there is some confusion between what SUMOTOY and Walking Eagle are calling "arcs," or at least in the way they each are comparing the arcs of stock vs. dropped frame mounts.

To clarify:

We're talking about the "arcs" of the front axle and/or each end of the axle.
The "dropped frame mount" is referring to the point where the front radius arms (leading arms, lower control arms, rods, whatever) attach to the frame.

The confusion (as I currently understand it):

When Walking Eagle is talking about the arcs of the axle (or ends of the axle), he is talking about the actual PATH through space, from full droop to full compression.
When you look at any and all of the diagrams in this thread (SUMOTOY's or Walking Eagle's), it is clear that the axle, or ends of the axle during articulation follow different paths during equal compression and/or articulation.

SUMO's main diagram:

The green arms A & B (stock mount) follow paths A & B for compression and droop, respectively. During articulation (one up, one down) the respective ends still follow paths A or B.

The black arms C & D (dropped mount) follow paths C & D for copression and droop, respectively. During articulation (one up, one down) the respective ends still follow paths C & D.

The PATHS are different. At any position of compression or droop along the arcs, the locations of the ends of the axle in each of the two scenarios will be in DIFFERENT LOCATIONS, except for at one point where the paths intersect.

This is how I interepreted the the same/different arc question.

When SUMOTOY answers the same/different arc question, he is comparing the actual ARCS--meaning the arc described by the motion of the axle defined by the length of the radius arm. As far as the actual arcs go, they are identical in as much as they have the same radius, and are essentially the same size and have the same dimensions, regardless of where the focus (frame mounting point) is. SUMO's equation shows that the arcs are identical, but it doesn't say anything about the paths or location of any end of the axle at any point during compression or droop.


Cliff-notes:
The dimensions of the arcs are identical, but the paths through space along the arcs are different.

Both of you are correct.


Hayes

 

[SUMOTOY]

It must matter to this excercise that you've designed suspensions, since you're the one posting that you have. If it doesn't matter to the exercise, delete it.

W.E., your personal attacks obfuscate the thread. I understand suspensions and suspension theory, because I've designed several, including modifications to mulitlink types. That practical experience helps me understand that oversimplified single mounting axle arcs on a rigid axle, are exactly half the equation, and not properly defining the accepted definition of articulation. With my experience in suspension theory and application, I looked specifically at your drawing 59, and find it doesn't properly picture 2 axle rods of the same length mounted horizontally. With my experience in suspension theory and application, I can look specifically at your cardboard exercise and find some inconsistencies to the givens, and then back to your own drawings in 59 and 66. Since these inconsistencies directly apply to the thread, shouldn't we be trying to figure how the upper rod got shorter in 59, or that the cardboard intersecting lines don't reflect axle mount lift?

Stop throwing articulation in and answer the straight forward question. Can you do that? Ignore the flex in the bushings and answer the question!

Exactly responding to your "straight forward question": it depends. I claim not enough information, and it's not just flex in the bushings. If you want to put the givens that are dictated in the thread and plotted in 118, I certainly can narrow down the variables, and give a better answer to your very broad and open ended question.

I appreciate your frustration during such a high profile exchange. Since I want to avoid any obfuscation myself, I'd like to stick exactly to defining things like articulation, and addressing any 'variances' to the givens in the story problem, in terms of pic 118, and the formula contained in it.

Thanks
ascribed DS

 

[Walking Eagle]

A little Q & A and I'll even give the A's. See if you can follow along...



Q: What does the front axle on a 80 series rotate around?

A: The mounting point of the radius arm / leading arm.


Q: How is the radius of the arc the axle moves through determined?

A: The radius of the arc is the distance from the center of the axle to the mounting point of the leading arm.


Q: What determines the PATH the axle moves through?

A: The radius and the center point.


Q: Can the path be the same if the center point of the arc is different (like dropped brackets vs. stock brackets)?

A: No - because the center point that it rotates around is changed.


Q: Other than changing the mounting point of the radius arm, how else can the path be changed?

A: Longer radius arms (like Slee arms) Or anything else that changes the radius - like changing the mounts on the stock arms. Or mounting portal axles on the stock arms - cause again, the radius is determined by the axle center to the mounting point - independent of the shape of the connector.


Q: Given that two arcs can't have the same path unless the have the same center, is raising the mounting on the axle the same as dropping the mounting point (which by the way, changes the center of the arc)?

A: No it is not.


Q: Was Walking Eagle correct in his statements?

A: Yes, he was.

 

[Hayes]

This agrees with my interpretation in post #169.

Now, can there be agreement on what SUMO is talking about, and can we all agree that it is different?

Hayes

A little Q & A and I'll even give the A's. See if you can follow along...



Q: What does the front axle on a 80 series rotate around?

A: The mounting point of the radius arm / leading arm.


Q: How is the radius of the arc the axle moves through determined?

A: The radius of the arc is the distance from the center of the axle to the mounting point of the leading arm.


Q: What determines the PATH the axle moves through?

A: The radius and the center point.


Q: Can the path be the same if the center point of the arc is different (like dropped brackets vs. stock brackets)?

A: No - because the center point that it rotates around is changed.


Q: Other than changing the mounting point of the radius arm, how else can the path be changed?

A: Longer radius arms (like Slee arms) Or anything else that changes the radius - like changing the mounts on the stock arms. Or mounting portal axles on the stock arms - cause again, the radius is determined by the axle center to the mounting point - independent of the shape of the connector.


Q: Given that two arcs can't have the same path unless the have the same center, is raising the mounting on the axle the same as dropping the mounting point (which by the way, changes the center of the arc)?

A: No it is not.


Q: Was Walking Eagle correct in his statements?

A: Yes, he was.

 

[SUMOTOY]

The PATHS are different. At any position of compression or droop along the arcs, the locations of the ends of the axle in each of the two scenarios will be in DIFFERENT LOCATIONS, except for at one point where the paths intersect.

This is how I interepreted the the same/different arc question.

When SUMOTOY answers the same/different arc question, he is comparing the actual ARCS--meaning the arc described by the motion of the axle defined by the length of the radius arm. As far as the actual arcs go, they are identical in as much as they have the same radius, and are essentially the same size and have the same dimensions, regardless of where the focus (frame mounting point) is.


Cliff-notes:
The dimensions of the arcs are identical, but the paths through space along the arcs are different.

Both of you are correct.
Hayes

Problem. If we define articulation as 2 axle rods travelling in opposite directions up to interference/bind, the formula in the lower right of pic 118 is correct. IOW, single wheel centerline arc can't be defined independently on a rigid axle suspension during articulation.

If we define articulation as one wheel up and one down (up to bind/interference) and "mounts" as more than one, the formula and drawing 118 is the full picture of 'articulation' as described regarding axle rod arcS in relation to mountS. And properly assesses Nay's conclusion that the "effect" can indeed be the same under articulation given 2 mounts.

Drawing 1 wheel travel arc during articulation, is only half the equation. Since the question is "mounts" we have to have 2 rod travels for each scenario (2 rods during axle mount lift, and 2 rods during frame axle drop). Every single drawing and cardboard exercise W.E. has relates to a single mount on a dual mount axle. That means best case scenario in a trig class is half credit.

Then again, if you accept 118 as correct, specifically 59,and 98 can't be. Since they aren't consistent with each other or 118, I don't come to the same conclusion that we are both right.

SJ

 

[Hayes]

Thinking through your articulation arguments a little further...

With the understanding that the 80's leading arms are not known for great lateral or pivoting motion (the bushings and mounts are limiting), the lateral (left/right) movement of the radius arm will be minimal.

And,

aknowledging that any lateral movement will affect the arc in the vertical plane longitudinal to the frame (basically the plane represented by all the diagrams here), then articulation will make the arc deviate from the arc described in all the diagrams.

However,

1. Deflection of the leading arms (according to what I've read around here) is very limited. I can't concieve of how this deflection could affect the arc significantly.

2. The available deflection in BOTH cases would be identical.

3. This would not affect the difference in paths at all.

Again, referring to your diagram, when one end of the axle goes up, it follows the path described. When the other end goes down, it follows the path described.
The paths in your diagram are different.

I'm only trying to point out where the actual conflict is.
The arcs are the same, but the paths are different.

Hayes

 

[SUMOTOY]

A little Q & A and I'll even give the A's. See if you can follow along...

ok

Q: What does the front axle on a 80 series rotate around?
A: The mounting point of the radius arm / leading arm.

ok

Q: How is the radius of the arc the axle moves through determined?
A: The radius of the arc is the distance from the center of the axle to the mounting point of the leading arm.

No. The radius of the arc is the distance from the exact center of two axle mounting points to the mounting point of the leading arm. You can't say it's from the center of the axle, because the arms can be level with the axle above or below it. The above is ONLY true if the axle mounting points are exactly on the axle centerline. Problem, they aren't on an 80.

Q: What determines the PATH the axle moves through?
A: The radius and the center point.

Radius and the center point of 2 axle mounts. The centerline of the axle will follow that path if the 2 axle mounts are exactly equal distant horizontally from the centerline of the axle, and equal distance vertically from the centerline of the axle.

Q: Can the path be the same if the center point of the arc is different (like dropped brackets vs. stock brackets)?
A: No - because the center point that it rotates around is changed.

No, the actual arc is dictated by the centerline of the 2 axle mount. It's location in relation to the centerline of the axle can be different. If the 2 mounting points of the axle are 1/4in below the axle, the path will be the same 1/4 inch above the axle. Look at it this way, in either scenario the axle ROD will be 90degrees before the wheel centerline upper mount travelling up, or lower mount travelling down.

Q: Given that two arcs can't have the same path unless the have the same center, is raising the mounting on the axle the same as dropping the mounting point (which by the way, changes the center of the arc)?
A: No it is not.

They can ideed have the same center. Raise the rod mounting so it is level exactly 1/4in above the axle, or drop the rear pivot so it is level on the lower (stock) mounting points (1/4in below the axle).

I see the confusion you have W.E. Maybe you should take a look at how the arm is mounted on the axle. I have never assumed rigid axle centerline to be the arc. It will travel the arc of the axle rod because it's centered in the path of 2 axle rod mounts. I'll try to give you a drawing to help you out. I won't put it to scale, you can if you want.

SJ

 

[Hayes]

Let's take the concept of changing the leading arm frame mount to the extreme.

Consider a 10 foot lift with a leading arm frame bracket dropped 10 feet. Are you going to tell me that the path of each wheel (articulated or otherwise), or the center point of the two axle mounts, will be the same as the path of the wheels in a stock arrangement?

Sure, if the geometry defined by the length of the leading arms and the position of the center of the two axle mounts are identical, then the dimensions of the arcs will be the same. But if you move the attachment points of the leading arms and the position of the center point of the axle mounts, then the path of the axle through space will be different relative to the rest of the truck.

This is all just plain silly.

I'm trying to clarify your differences so this thread can move on or rest in peace.

Hayes

 

[concretejungle]

what a can of worms. . .

 

[landtank]

No, the actual arc is dictated by the centerline of the 2 axle mount. It's location in relation to the centerline of the axle can be different. If the 2 mounting points of the axle are 1/4in below the axle, the path will be the same 1/4 inch above the axle. Look at it this way, in either scenario the axle ROD will be 90degrees before the wheel centerline upper mount travelling up, or lower mount travelling down.

Because contact with either the road or body of the truck is with the tires and they are aligned with the center of the axle it is the center of the concerned arc. It doesn't matter what shape or where the arms attach to the axle the tires will follow an arc that's radius is equal to the distance of the rear pivot point to the axles center.


Disclaimer: this is assuming the tires are pointing straight ahead. The arcs change slightly when the wheels are turned.

 

[SUMOTOY]

Because contact with either the road or body of the truck is with the tires and they are aligned with the center of the axle it is the center of the concerned arc. It doesn't matter what shape or where the arms attach to the axle the tires will follow an arc that's radius is equal to the distance of the rear pivot point to the axles center.


Disclaimer: this is assuming the tires are pointing straight ahead. The arcs change slightly when the wheels are turned.

I disagree that is phrased properly, because then I couldn't do what's pictured below. What you say is ONLY true, if the rear pivot is in line with the axle. The presentation is exactly and only that the rods are level.

Here' a pic (I'll leave the measures off, but I already took them) Maybe this will help. Look very carefully at the axle rods mounting vs centerline. There is no question you can lift the axle mounting point by x to keep the arms level and the formulas in 118 and in this pic hold true.

Has anyone actually climbed underneath the 80?

Scott Justusson

 

[Walking Eagle]

It doesn't matter what shape or where the arms attach to the axle the tires will follow an arc that's radius is equal to the distance of the rear pivot point to the axles center..

THANK YOU!!!