Scott, in your diagram you not only moved the arm on top of the axle but also moved the pivot point as well. A different pivot point will cause a different path.
Suspension travel upgrades on an 80
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Man... this has been quite ammusing but the sad truth is that the ONLY 2 points in space that matter are the center of the pivot and the reference point in space I.E. the center of the axle. The size, shape, weight, color, scent, taste, material, mounting location or anything else related to the (raduis arm, axle rod, lateral arm, etc) has absolutely NO bearing on the arc that the axle swings assuming that the axle is rigidly mounted to the arm.
Case... I take my axle and attach it hillbilly style with some hose clamps to the (raduis arm, axle rod, lateral arm, etc) exactly midway between the frame mount and the center of the 2 axle mount points on the arm... the arc will be defined by only the frame pivot and the center of the axle. I could also suspend the axle in front of the (raduis arm, axle rod, lateral arm, etc) by extending them hillbilly style with some leftover fence posts and just like before... the arc will be defined by only the frame pivot and the center of the axle.
Case... I take my axle and attach it hillbilly style with some hose clamps to the (raduis arm, axle rod, lateral arm, etc) exactly midway between the frame mount and the center of the 2 axle mount points on the arm... the arc will be defined by only the frame pivot and the center of the axle. I could also suspend the axle in front of the (raduis arm, axle rod, lateral arm, etc) by extending them hillbilly style with some leftover fence posts and just like before... the arc will be defined by only the frame pivot and the center of the axle.
So that's what, 3 or 4 of us that get it and sumotoy still doesn't....
black line, red line, yellow line, they all begin and end at the same point, and are going to scribe the same circle. Though, I went physcadellic 60's rather than hillbilly
black line, red line, yellow line, they all begin and end at the same point, and are going to scribe the same circle. Though, I went physcadellic 60's rather than hillbilly
Walking Eagle said:So that's what, 3 or 4 of us that get it and sumotoy still doesn't....
black line, red line, yellow line, they all begin and end at the same point, and are going to scribe the same circle. Though, I went physcadellic 60's rather than hillbilly
Yeah, and if you move the focus of that arc (a circle is just an arc of 360 degrees, right?) then you'll get an identical circle IN A DIFFERENT POSITION.
The arcs will be in different locations and whatever is travelling on these arcs will ALWAYS be in different locations except for the maximum of 2 points where the arcs intersect. It doesn't matter what you're calling the focus, as long as it's in a different place, the arcs will be in different locations.
SUMO, the arcs have the same dimensions (an arc is defined by its radius and angle, no?) but they are in different locations.
The paths are different.
Puuuhhleeezz recognize this fundamental fact of nature.
This kind of debate doesn't have to end up being a battle to save one's ego. Either recognize your error, or recognize that you were talking about apples while Walking Eagle is talking about oranges.
Seriously, the folks around here are very reasonable. If you say, "s***, I was wrong," or "doh, I misunderstood what you were talking about" nobody is going to hold it against you.
Hayes
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And if you move the center of the circle (like dropping the frame mounts), Sumotoy can run around his little magenta circle, and I can run aroung my little green circle, and we'll only run into each other twice. CAUSE WE'RE FOLLOWING DIFFERENT PATHS!
Hayes said:
Funny, I was working on that while you wrote this..... The stick figures really help don't they?
Walking Eagle said:
...and if you put a 10' lift and drop-bracket on your 80, we'll never run into each other...
Hayes said:
I've done it.... from another thread - had to make sure I was right before I dug in - I didn't dig in....
Walking Eagle said:
Hayes said:
But if we articulate we'll end up on the same path?
SUMOTOY said:
I'm going to quote you back the same answer I gave you like three posts ago
"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.""
How can it be? Hummm.... geometry? Shortest distance between to points is a straight line, not out 3 and down 4 - across 5 (that would be a 3,4,5 triangle from 8th grade geometry).
I made an assumption when I drew it the first time, and I changed that assumption and told everyone who could read it, that I'd done so when I did it! It's not some big secret, nor slight of hand. or anything else.
How many times are you going to ask this same question and get the same answer? What are you trying to get at? If you're trying to prove my inconsistancy, it's not working - I changed something, I told everyone I changed something. What's the big deal?
RECONCILING 118 to 179
Boys:
Take a look at the arcs I drew in for ya'll. It certainly would dictate that the axle center is NOT the arc origination (ever) on a 80 axle rod in either scenario, drop frame pivot or raised axle mount (or even stock for that matter).
The only question is what is X. Requires tape measure and a dirty knee.
The arcs radius starts at the midpoint between the two axle mounts, (and in all this we are speaking to mm and fractions of inches) and no two axle rod mount radius arc will ever cross the axle centerline exactly on an 80 with a stock axle rod. Unless you change the design of the rod so the end is the effective Center of the axle.
On the 80 it's not.
Please feel free to chop away.
Isn't indeed the arc dictated by the vertical and horizontal centerline of the axle rods two front mounting points? Doesn't that indeed show that 179 is correct for x?
Thanks for helping me out. I'm sure I have this wrong.
Scott Justusson
Boys:
Take a look at the arcs I drew in for ya'll. It certainly would dictate that the axle center is NOT the arc origination (ever) on a 80 axle rod in either scenario, drop frame pivot or raised axle mount (or even stock for that matter).
The only question is what is X. Requires tape measure and a dirty knee.
The arcs radius starts at the midpoint between the two axle mounts, (and in all this we are speaking to mm and fractions of inches) and no two axle rod mount radius arc will ever cross the axle centerline exactly on an 80 with a stock axle rod. Unless you change the design of the rod so the end is the effective Center of the axle.
On the 80 it's not.
Please feel free to chop away.
Isn't indeed the arc dictated by the vertical and horizontal centerline of the axle rods two front mounting points? Doesn't that indeed show that 179 is correct for x?
Thanks for helping me out. I'm sure I have this wrong.
Scott Justusson
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landtank said:
Again, we need to speak to 2 axle rods during articulation. The path of one up, is the same as the path of the other down. What's the difference in the arcs? Well if you look at 1, you can find a difference. If you look at 2 as in "articulation" (we have to go a ways back to find that given, but it's there all along), you must use the formula presented up to bind/interference.
When an axle articulates, arcs happen. 2 of them with 2 mounts actually. We can't speak to 1, and we can't speak to the axle centerline, because there are 2 front mounts to the axle, and their centerline and arcs never crosses the axle centerline or arc.
I'm focusing on articulation of an axle rod that has a pivot point. I can't see ANY scenario where a stock axle rod ever follows the same pivot arc as the axle. Nor do I see a single axle rod ever articulating with an axle without the other axle rod attached to that same axle also articulating.
Hopefully someone will solve for X instead of trying to follow a rigid axle arc that doesn't appear to be a valid arc at all. The actual axle arc can be considered a constant to either mounting arcs, but it is not the same. Hence my objections to any claim, drawing or art to the contrary. You can take articulation out of the equation, and fire away. Then I'll directly focus on all assumptions presented that axle centerline and arc = axle rod centerline and arc.
Fire away boys, I already solved for x, and it sure appears to do exactly what I've been proposing all along. Again, I'm sure I have this wrong.
Scott Justusson
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Ignoring that you still don't have this right -
or this -
A does not equal C. If they were equal, they would cover one another. Which means, the axle is going to follow a different path if the mount is in a different location. Which also means - if you don't mind me quoting post 15 that you say you needed to correct -
"When you move the frame mounts, then you move the motion of the axle/tire relative to the frame. So it's not "the exact same effect"
Here's what you said "A bit of baseline regarding WE thoughts on frame drop vs axle mounting lift contains errors we should correct. Specifically referencing WE comments in posts 15 and 18. - snip - In the case of the front, you are correct, the instant center (the pivot point for drawing the tire radius arc) is the mounting point of the arms at the frame."
So - the pivot point for drawing the tire radius arc (which I'm translating as the path of the tire) is the mounting of the arms on the frame. So, if you move the mounting of the arms on the frame, you move the pivot point. If you move the pivot point, you change the PATH, even if the radius is the same!
It's really that simple!!!
SUMOTOY said:
or this -
SUMOTOY said:
A does not equal C. If they were equal, they would cover one another. Which means, the axle is going to follow a different path if the mount is in a different location. Which also means - if you don't mind me quoting post 15 that you say you needed to correct -
"When you move the frame mounts, then you move the motion of the axle/tire relative to the frame. So it's not "the exact same effect"
Here's what you said "A bit of baseline regarding WE thoughts on frame drop vs axle mounting lift contains errors we should correct. Specifically referencing WE comments in posts 15 and 18. - snip - In the case of the front, you are correct, the instant center (the pivot point for drawing the tire radius arc) is the mounting point of the arms at the frame."
So - the pivot point for drawing the tire radius arc (which I'm translating as the path of the tire) is the mounting of the arms on the frame. So, if you move the mounting of the arms on the frame, you move the pivot point. If you move the pivot point, you change the PATH, even if the radius is the same!
It's really that simple!!!
SUMOTOY said:
So the radius starts at the midpoint between the two axle mounts. So if I move one of the axle mounts (but don't move the axle) the radius of the path of the tire is going to change? If I put the blue mount in, in place of the left/ front mount, - the new path of the axle is going to be half way between the two mounts? Once again - no. I can put the mounts on top, or bottom or front, or back - the radius is still from the center of the axle to the pivot point - frame mount.
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sleeoffroad
Supporting Vendor
Hey, if this goes on a couple more weeks we will have a complete 80 suspension drawn up 
sleeoffroad said:Hey, if this goes on a couple more weeks we will have a complete 80 suspension drawn up
Ya', How about you give me the dimensions on your fixture for pressing in bushings and I'll draw the mounts to scale?
I'm half kidding, I wouldn't expect you or any other manufacture of parts to share.
I keep going back to your site to look at the OME install, it helped alot with guessing the right shape.
Hopefully my wife will deliever soon, and I can get back to real life rather than hiding from the infernal waiting by coming here!
That's all well and good... but back to what I said before. You have chosen an arbitrary point in space. You're reference point is midway between the bushings in line with the axle rod. That point is going to follow an arc that swings around the frame mount. The front bushing is going to follow a different arc. The rear bushing is going to follow an arc different to the other two. And the axle, being a different radius from the previous points will follow an arc different from all the others.SUMOTOY said:
What I am trying to understand is why you have chosen your reference point. On your drawing you have chosen a point with little significance in the operation of a front suspension. The air gap between the axle rod and the axle is not what is going to hit the bumpstop, which in my opinion is the only criteria that anyone should be concerned with. When the suspension cycles up fully, is the axle going to be centered under the bumpstop where Mr. T designed it to be. Sure... you can calculate where the axle is in relation to your hypothetical reference, but why bother when you can measure the arc of the axle directly quite simply. Do me a favor and draw your same pic again with an axle rod that looks like one of those silly straws you used to drink juice out of. You know the one that looks like 3 pretzels tied in a knot. You'll see that the AXLE still follows the same arc.
In a practical sense, the arc swung by your arbitrary point in space between the two bushings is completely irrelevant. The arc swung by the axle is the only relevant arc... and they are all valid.SUMOTOY said:
This is correct... the axle arc IS constant because the frame mounting point is the same whether the arm is right side up or upside down.SUMOTOY said:
As a hypothetical question... what if the front ear of the arm was extended 24 inches, with a corresponding 24 inch bracket welded onto the front of the axle, while retaining the stock rear mount, in essence creating a situation like this which is completely valid:
o.............X.........( )..o
The X is the arbitrary position midway between the mounts that you have chosen. Tell me what significance this point has when it swings an arc that probably would take it right into the bumper???
Walking Eagle said:
No, and that is really the problem you will have with my formulas and math, and why you can't grasp 15 and 18, and your drawing problems. Again, you need to get the tape measure out and put it to your truck W.E. Your drawing is not correct. Do a close up drawing of the two mounts, like I did above. The centerline of the axle and the centerline of tha axle rod pivots are NOT the same, nor are they ever (axle lift, axle drop, or stock). Put in actual dimensions for x, y and z and rod length,, and you can give a measure of exactly *how far forward* of the axle rod pivot point, the axle centerline is. I specifically deleted giving you all the information, so you could work it through.
Specifically, the actual centerline axle arc will always be larger than either axle rod arc. You would need to add yet another orb. The ONLY scenario where what you stated is true, is if the line drawn between the axle pivot and the mounting centerline crosses the axle centerline.
It may on other vehicles with in line axle mounts, it doesn't ever on the 80
Put the measures in and solve for X. The rest of the drawing will make more sense.
I also strongly suspect, you are hardly the only one to make this error. Luckily the error correction isn't major, but I suspect there are a lot of caster corrections that aren't exactly right on lifted 80's.
Scott Justusson
SUMOTOY said:
There is no problem with my drawing - ask any of the other people on the thread. Ask an engineer.
I can pick any point on the radius arm, or the axle, or even the tire, and as I track that point as the suspension moves, it's going to draw a circle centered on the frame mount - just as I've drawn. Can't we get past this point.
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ElJefe said:
Then there's the other side during articulation
It's only not geometrically correct to arc. I'm just plotting arc correctly to the axle rod. That's significant, relavent and correct. Your opinion on interference or bind not withstanding.
Not sure the point, please feel free to do so.
Are we measuring axle rod length or axle centerline to axle pivot? The space between the 2 bushings is completely relevent. Because the effective RADIUS is the exact midpoint between the two.
You lost me there. The frame pivot point raises or lowers by x
The point is exactly that the position midway between two axle mounts on centerline is EXACTLY the vertical and horizontal centerline to draw arc. Which allows the formulas to be valid during articulation.
Guys, draw out the dimensions, solve for x. Kill the formula or the drawing. Don't add to it other than to solve for x, don't tell me the centerline isn't right or valid. Puleeese don't draw another set of orbs.
Arbitrary? No, just trying to get some of the geometry correct regarding arc and radius of 2 axle rods during articulation.
SJ
