Quote:
Originally posted by porsche996:
'Nother post for emphasis..



Pay careful attention. I'll speak slowly so TJ can understand.
- (Type slowly...I'm reading...)

Q. What happens to the leaf spring of this flexed Revolver suspension when the tire first gets pushed up into the wheel well, from this position?

A. For the first couple inches, there is very little resistance as the revolver is folding up. The spring is not starting to compress until after the revolver is folded back neatly into place.

- And, the regular shackle swings up as well...the same way...until the regular shackle is seated in its compressed position...so, so far, nothing new...about the same as a regular lift shackle.

Q. If there were a normal shackle in that photo, what would happen as soon as the tire started being pushed up into place?

A. The leaf spring would begin compressing instantaneously, providing a resistant force...

- No, it would not, and I have watched shackles swing...its how they provide most of the additiona droop...the swing of the regular shackle is analogous to the unfolding of the Revolver...So, NO, the leaf is NOT instantly compressed, watch a compression cycle for a lift shackled pack...there is shackle swing, THEN compression.

Q. How does a leaf spring work?

A. When a force is applied, either upwards or downwards, a spring flexes based on it's spring constant, to resist the force...

- So far, so good.

Q. If the leaf spring does not compress, as the tire was raised, was any force being resisted?

- Of course there's force - , See Mr. Kren's explanation for example, several hundred pounds of down force in fact...and, additionally...there is a degree of leverage inherent in a live axle system....so that stuffing one side can force down the other.

A. No. It was dangling in it's natural state...see all above.

Q. How is traction generated?

A. It's the normal force (perpendicular) to the ground, multiplied by the friction coefficient of the two surfaces....

- so far, so good.

Q. What would the traction (aka, friction) be as soon as the tire began to be compressed in the revolver situation as in that picture?

- Several hundred pounds of down force, as described above.

A. The weight of the tire, hub, axle, etc. multiplied by the friction coefficient between the tire & the surface. Until the revolver is folded back onto itself, there is no additional force acting downward on the spring...

- Additional force, as in additional to the several hundred pounds of down force...right, and as the leaf spring is slowly loaded, as the leaf comes into its range of resistance...it can support MORE weight....of course, its supporting all the weight there is to support at any given time...so its not a large factor overall. (The tire drooped to follow the terrain...the weight's already elsewhere...etc.)

Q. What would the normal force be in the normal shackle situation as soon as the tire began to be compressed?

A. It would be the weight of the tire, hub, axle, etc., PLUS the force provided by the spring,. all of that multiplied by the friction coefficient...

- If this is correct...at ride height, all I'd have to do to make all 4 tires have more traction, is add a stiffer spring to each corner.

- In real life, that's called a lift. It pushes the rig UP, not the tires down at that point...if there's LESS WEIGHT TO SUPPORT, or the terrain falls away...then the tires droop, and - less weight is supported.

Q. Wouldn't the force of the spring be acting negatively (if down is positive) on the assemblies, therefore negating the regular spring advantage?

A. Yes, but no. [Freak]

Yes, the math of it would show the spring would technically be pulling the axle assembly upwards, (Good stopping point BTW...)

therefore a reduction in traction from the total.

However, since the spring is still connected to the revolver, the revolver can't actually droop w/o taking the spring properties into effect.

- The revolver can droop if the suspension has no weight to support because of morphology...it really has no idea what the leaves are doing.

So at the point the revolver starts opening, it has already reached the maximum up-pull of the leaf spring.

- Not really - I can see the revolvers opening, and the leaf pack bending...the droop continues until the Revolver is fully open, UNLESS the terrain forces opposite side articulation...opposite stuffage can visibly cause additional leaf bend on the DROOPED side.

- Therefore, it's already at it's lowest amount of traction available in the equation. It does not change at any point in the revolver travel. See above, this is actually incorrect...perhaps due to that "Yes but No" issue you had?

So for example, if the spring was pulling -5 lbs of force (remember, up is negative), it reaches that -5 lbs at the exact instant the revolver begins to open up. Whether the revolver is open 0" to 3", the same 5 lbs are pulling up. But on the regular leaf suspension that flexes to the same point, the full -5 lbs of pull is only at the lowest point, aka, the equivalent of the 3" open revolver. As soon as the regular shackle leaf pack begins compressing, this -5 lbs of pull begins to reduce to 0.

- This is flawed, as the forces described are not realistic, and, the instantaneous all or none nature of the transition is not realistic.

- Remember, the wheel/axle/leaf pack is exerting several hundred pounds of down force...and the transition down occurs when the weight needing to be supported starts to drop - literally and figuratively.

- The tire's down force is reduced the second the tire droop starts, for both types of suspension...so both suspensions start to reduce down force as weight is transitioned to other tires.

- The reguar suspension goes from barely pushing down the weight of the axle and tire, but mostly supporting the weight of the leaves...as it starts to hang from its leaves (The regular lift shackle is swinging now, as it has begun to be pulled down by the axle/tire combo...)

- The regular shackled suspension loses traction weighting rapidly for the bottom 1/3 or so of travel...and then at the neutral point, exerts only the weight of the axle/tire, and - then, below that, it starts lightening the weight on the tire...and, the shackle swings the rest of the way out for full droop...and, when reaching it...the tire dangles in mid air.

- For the Revolvered version...its the same, plus the weight of the leaves...and it continues through the barely present range of the regular suspension....passes it, and continues to apply several hundred pounds of downforce based primarily on live axle leverage and tire/axle/leaf weight...including at the point that the regular shackled version dangled at.

- So no, the spring will not negate the advantage of the regular spring. Both a revolver and the leaf pack have the most amount of traction at the point the spring force is 0. You did not mean to say most, least maybe?

However, the revolver will not even start to begin to reach that point until after it has already closed together...no, several hundred pounds of down force are always present, even when opened...its never zero at the above point.

- I think you are saying that the leaf pulling up, instead of pushing down is not happening between the opening and folding steps?

- It is though, as the range of travel is further...so the point of motion is bracketed, and overlapped...with the remaining point unstated (I think) perhaps being how far the regualr shackled suspension cycles through its downward unweighting process, and lightening process of the tire vs how far the same exact thing happens for the Revolver.

Conclusion:

Through the handy-dandy method of linearity, you can move the origin of force for the spring pack down to the most fully open position (fully flexed out) of the wheel, and begin from there.

This makes it easier to visualize (except for TJ, which will probably argue this point, though he would be wrong to do so.

Frankly - there's nothing stated to argue with...the physics are correct, its the application we're discussing. laugh

This is simple statics/dynamics at work, here, and the calculations/rules for doing this are taught in 100 level engineering classes; in other words, it ain't rocket science.)

Once you do this, you will find the revolver doesn't start adding traction from the spring until it's fully closed, but the regular leaf spring starts adding traction from the moment it starts compressing.

- OK - this is partly correct, in that the word "adding" is accurate, but...the DEGREE is the entire bone of contention from the beginning...as as each above point was essentially involving a foundation point for the conclusion, but partially flawed in application/interpretation of the effects...the entire argument is built upon a shaky foundation.

In other words, and one more time for those that have fallen asleep: (We may be the only ones who read the entire thing...)

[b]IF YOU WANT FLEX WITH TRACTION, GET A REAL LEAF PACK. IF YOU WANT FLEX FOR AN RTI RAMP, USE REVOLVERS.[/b]
[Freak]

Hell, no one's probably awake anymore anyway. [Sleep]

I do appreciate that you at least expressed what you were trying to get across though.

(For the rest of you, I'll type quietly to avoid waking anyone...)

OK - I think it comes down to a difference in opinion/experiences....I've measured and observed, and know what's important to me, and how it really works.

We essentially are only really at odds about the narrow range - about 3" of travel, where your leaf has a faint push left, and then hangs the tire..and mine had the same several hundred pounds of down force all the way through, and down a bit more...and you prefer the faint push of the almost fully extended leaf plus axle/tire...and I prefer the weight of the axle/tire /leaves, through the same point, w/o a reduction in weight against the leaves...

You'd like a little more weight/followed by progressively less, and I'd prefer a little less at first, and more later.

eh.

Maybe its just subjective.

It works on the Jeeps and Toys, and now the X...and for me.

It doesn't do what you're ("Yes and No") calculations would indicate, mostly because of the way you applied them.

So - You are correct in some assumptions...its not like you're nutz...its just that you over estimated the actual effects that do occur.

If I had to do it over again, sure, in a heart beat.

Would I advize everyone to do it? - Only if they are willing to set up a long travel suspension properly, especially if limited in flex by needing stiff spring packs for support/street sharpness, etc.

Same advice for ANY long travel suspension mod, including leaves that can give the same flex, etc.

laugh

Think about shackle swing...its missing from all of your above concepts...and, its about as close to Revolver behavior as you're going to get (Unless you are now running out to get Revolvers...)

wink


OK - the rest of you can wake up now...)

eek
_________________________
- TJ

2001 Xterra '03 VG33, SE 5 spd, 305/70/16's, Revolvers, UBSkidderz, Doubled AAL's, 3"SL/2"BL, winch/bumpers, skids, sliders, OBA, Snorkel, pine stripes....

Friends don't let friends drive stock.

http://www.gifsoup.com/view/501230/tj-tackling-crawlers-ridge-o.gif