sleeoffroad
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The link attachment point to the axle center line changes. It is moved from below the axle center line to above it, so it has to change how the link and axle behave.
Front control arm flip
- Thread starter LCAdvocate
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The link attachment point to the axle center line changes. It is moved from below the axle center line to above it, so it has to change how the link and axle behave.
Depending on where you weld the mounts in, you may or may not have the axle in the same location.
Remember, this is also an opportunity to adjust for caster which many people do, which means your mounts won't be in the exact same spot.
If you're welding to the top of the axle, I don't think you don't need to go as far (shorter distance). Since the arm's aren't changing in length, this should push the axle (very slightly) forward. Take a tape and measure from the frame mount to the middle of the bottom of the axle, then measure to the middle of the top. The top should be a shorter distance.
Lowering it in the rear is essentially the same effect as raising it in the front. This is why a lot of the better wheelbarrows out there have the arms mount quite high, at least on top of the axle and sometimes even higher than that. That lets you hold the arms higher (where you have more strength/force) without tipping the arms at too much of an angle.
The more angle you have, the more it's going to want to push down when you encounter an obstacle. By reducing that angle you're reducing the downward force, which at least in theory should help you get that tire up and over the obstacle.
Dropping the back of the arms should have the same effect as flipping them. I often see that on lifted trucks around here. I also often think "gee, that looks like it'd be easy to rip off...."
Stock Truck:
Lifted Truck, stock arms:
Lifted Truck, flipped arms:
By flipping the arms you're going back to the more 'neutral' position where the force will go more back than down.
The force is being transferred from the axle to the frame mount. The force doesn't care which way the connecting bar curves, unless that bar is flexible. The force will not follow the bar. The only very slight advantage I could see is the difference of where the control arm actually bolts to the axle if you flip it, which would be maybe an inch higher than stock. I'm not even sure that makes a difference.
Well after having a hand in and watching the result of several linked front suspension on rockcrawling rigs, believe what you want, but the geometry is there. As mentioned later in this thread, the force doesn't change, just the angle of that force.
The wheelbarrow is not just about "leveraging" the load. Go out back and load up the wheelbarrow, now hold the handles up near your chest and try and take the wheel over an obstacle, doesn't have to be that big, after you dump that load and feel the handles in your armpits, load it up again, lower the handles back down below your waist, hit the obstacle again and see whether the wheel rolls over it this time or not. I await the results.
Simple example in the way/angle that force is transmitted, simple geometry.
Now having said all of that, I have no intention of "flipping" the arms on my 80.
Jack
Your example mimics what happens when you lift the truck, and has nothing to do with changing the curve of the arms. You can put all the curve in the handles of your wheelbarrow you want, it will not change the thrust angle. That angle is defined by the axle and the end point which the handles pivot on.
that's my problem, if the distance and elevation between the axle's center and the frame mount is the same then the flip accomplished nothing. The forces applied to the spring is the same throughout it's motion.
At least that's how I'm seeing it.
It's far more than an inch.
The mounting points alone move it up an inch or two. Then in addition to that you have the arm being flipped, which is going to add another inch or two.
Even if it's only a net of 2", that's enough to compensate for 2" of your 4" to 6" lift (33%-50%). That's not insignificant.
The arm is essentially a giant lever, so the curve, position, and the way it mounts absolutely has an effect. If you have a straight piece of steel bar, and someone pushes on one end while you hold the other, it's easy for you to control as it moves straight back. Now bend the steel bar. The other person is still pushing straight back, but the bend in the bar will also cause it to have an up/down leveraging effect because the force that is coming in (the person pushing on it) is at a different plane than where it's "mounted" (you holding it).
The more the rod is bent, the more that force is transfered into up/down instead of straight back. It's the same amount of force, but it's partially being transfered in a different direction.
By flipping the arm you're leveraging physics to assist you with lifting the wheel up when it is pressed back. A lift (with stock arms) does the opposite, it increases the angle of the arms which applies more force down.
the reason i did it on my 75 was cause it waas all new suspension redesign and dropped radius arms for an 80 series werent correct when i transferred it to my 75,plus their expensive as hell, so i just flipped the arms,i think it performs better now. i think pics speak for themselves.
these are two members that have done it off outerlimits4x4.
these are two members that have done it off outerlimits4x4.
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I agree the load points remain the same. IMHO most of the improvement would come from the radius arm to axle mount. When more travel is added, the arms are allowed to droop more and when flexed, the drooped arm becomes effectively shorter, stuffed arm longer. This tries to angle the axle compared to rig centerline, pulls the drooped side of the axle back and pushes the stuffed side forward. Due to the relatively long, narrow arm mount boxes, the arms contact the mount boxes stopping flex travel.
In our experimenting, more arm angle, wider the arm, smaller arm to mount box clearance, all equal less flex and more force need to flex, regardless of spring, sway bar, etc. Flatter arms would have less effective length difference, so would have less arm-mount bind, would flex easier. In my experience freeing up the front makes a huge difference in ride comfort.
If the mount boxes get cut off of my axle the new ones will be wider, with spacers/spuds welded in, to center the bushings. This would allow for more arm movement before bind.
IMHO the advantages of arms on top would be better clearance, easier/more flex making for a better ride. The disadvantages are the amount of work, the stock arms aren’t shaped the best for the job, so fitting sway bars, etc, would be a trick. Having run a rig with easier front flex, I wouldn’t want to drive it much on the highway without a sway bar. IIRC Dobbins(?) in Australia made/makes custom arms for the arms on top mod?
This pic shows what I’m referring to. Should have shot it with a straight edge on the bracket, it’s hard to see, but the lower corner of the bracket is flexed out. The front end of the arm is jammed into the other side of the bracket. The next pic is my arm, it is .3” narrower than stock, flexes much more and never hits, but they only use 3 axle end bushings, so pretty much moot point.
In our experimenting, more arm angle, wider the arm, smaller arm to mount box clearance, all equal less flex and more force need to flex, regardless of spring, sway bar, etc. Flatter arms would have less effective length difference, so would have less arm-mount bind, would flex easier. In my experience freeing up the front makes a huge difference in ride comfort.
If the mount boxes get cut off of my axle the new ones will be wider, with spacers/spuds welded in, to center the bushings. This would allow for more arm movement before bind.
IMHO the advantages of arms on top would be better clearance, easier/more flex making for a better ride. The disadvantages are the amount of work, the stock arms aren’t shaped the best for the job, so fitting sway bars, etc, would be a trick. Having run a rig with easier front flex, I wouldn’t want to drive it much on the highway without a sway bar. IIRC Dobbins(?) in Australia made/makes custom arms for the arms on top mod?
This pic shows what I’m referring to. Should have shot it with a straight edge on the bracket, it’s hard to see, but the lower corner of the bracket is flexed out. The front end of the arm is jammed into the other side of the bracket. The next pic is my arm, it is .3” narrower than stock, flexes much more and never hits, but they only use 3 axle end bushings, so pretty much moot point.
Who said anything about changing the curves or adding curves into the arms?
The force flows in a strait line. That is why "Z" steering arms don't work and you still end up with "bumpsteer." Again the same reasoning and functuality of true "hi-steer" or "crossover" steering. The more parallel to the ground the draglink is, the less bumpsteer. Same principle with front control arms.
Think about it.
Jack
The supposed advantage of flipping the arms is to put the curve of the arms up, supposedly directing the force up.
I don't see how moving the mounting bolts to the top of the axle is going to help anything either, as the force is still originating at the center of the axle.
I'm destined not to get this. Good luck with your flips.
Spike, again this is just my understanding of it, so I very well could be wrong.
However, try this. Take an item that's bent/curved in some way (a crowbar would work excellent). If you grab the end, and the other person pushes straight back on the straight part, the force goes straight back. If they push straight back at the end of the curved part, the force doesn't go straight back, it'll go up/down. Flip it over, and it reverses.
I really doubt that we're talking about huge amounts of force here, but I believe that's at least part of where the more supple/flexible feel comes from. If you're trying to climb a rock/ledge, and part of the force is being pushed downwards, then the more you try and get over that rock, the harder the wheel gets pushed down. With a flatter angle, less force is being transferred down, which means it's easier to get over that rock. (Again, goes back to the wheelbarrow example.)
Yes the force originates at the center of the axle, but it will be transfered differently if it's mounted above or below the axle. It's really more a factor of the less distance between the frame mount and the axle mount than where it's located. Again, using a drop mount on the frame side will very nearly mimic this.
Don't take my word for it, try it out for yourself (the crowbar example, though if you really want to cut and weld your arms feel free.
).
Excellent. Try it yourself. The force is transposed between the opposing forces, not along the crowbar. The other force is the weight of the crowbar downward, which won't change when you flip it.
I had some cheapie closed end wrenches that are offset that I was playing with at work today, while I was trying to figure this out. And so yes, I have tried it myself.
I think that what you're forgetting is that the force isn't coming straight back linearly. The force is coming straight back....but is offset from the receiving end. The causes a bias in whatever direction it is offset in. It's a lever, plain and simple.
I agree with Tools at least on the articulation side. I don't know about the forces, but for me it would be about the articulation. Having run long leaf springs on a minitruck showed that one of the limiting factors was the torsional force on the spring mounts/shackles. Using softer bushings or orbit eye/johnny joints allowed for more flex and articluation. Same principle applies here.
How does the angle of the force change? The force is still being applied from the horizontal center line of the tire and transferred to the rear control arm mounting point. You have to lower the mounting point for the wheel-barrow analogy to work. Hold the wheel barrow handles high and it's harder for the front wheel to come up. Hold the handles low and it's easier for the front wheel to come up. Whether you attach the handle above or below the axle, the axle height off the ground remains the same.
What might be happening is it alters the arc the axle travels. The closer the control arm gets to horizontal, the axle should start moving up and back instead of up and forward. Arcing the axle back should be beneficial for getting over objects that hit at the horizontal centerline of the tire.
I aint trained in engineering and geometry though so I could be wrong.
I cant see doing all that fab work and still having a bindy radius arm system. Might as well do a 3 or 4 link if you are going to do that much work.
Got X Link?
And just so I'm not posting solely to harrass Spike (as fun as that may be), several of the 80's I saw on the Aussie forum with flipped arms had X-Link setups.
edit x dos
Truck with flipped arm's and stock setup (7" suspension lift, 2" body):
Truck with stock arm's and X-Link (looks like 4" coils and 750 mm shocks):
Truck with flipped arms and X-Link:
38" tires dropping below the door sills.
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LOL, me and Ebag have been hashing this out in PM's all evening. 
We've agreed to disagree, neither one of us can explain our points in text well enough to convince the other that he's wrong. The X Link came up in that conversation. And his odd cooking ingredients.
Basically I said I'm still thinking of flipping the arms in combination with an X Link, to get the X Link up higher out of the rocks.
We've agreed to disagree, neither one of us can explain our points in text well enough to convince the other that he's wrong. The X Link came up in that conversation. And his odd cooking ingredients.Basically I said I'm still thinking of flipping the arms in combination with an X Link, to get the X Link up higher out of the rocks.
