Front control arm flip

[Ebag333]

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.

See, that starts to make more sense to me then.

I'm not sure just flipping the arms are worth it, but if you do an X Link at the same time....

 

[80t0ylc]

I've been lurking and reading all these opinions of forces and angles applied to the axle when the front end of a rig is trying to go over a ledge. I think it's really a moot point for this whether control arm is above or below. I think the big advantage for higher lifted rigs would be as tools mentioned for articulation in mounting above the axle. Proper articulation seems like it would be more valuable as a climbing tool. When that front tire contacts the vertical ledge, the torque that's applied to the tire and the traction of said tire is going to determine if it climbs the ledge, not the tendency of the control arms first movement. Successfully transferring that torque to traction is the name of the game. And that is where proper articulation gets the job done and all imitations fall by the wayside. I think another advantage for high lifted rigs with the control arm mounted on top is a better handle on correct castor. Just an opinion.

 

[LC80Ducati996]

nothing gain in articulation from a flip. It just has an effect like dropped radius arm frame side mounts.

IMHO 3 link or parallel 4 link it!

https://forum.ih8mud.com/80-series-tech/119989-3-link-ala-action-jackson-2.html#post2319303

 

[locrwln1]

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.

We are both right, but the wheelbarrow analogy is to show how the forward force works against an obstacle when moving forward with a wheeled vehicle. A lifted 80 or any other linked front suspension in esence becomes a wheelbarrow with the rear handles lifted. Again the forward momentum of you pushing on the raised handles causes you to want to continue forward and "over" the axle of the wheelbarrow when you hit an obstacle. The forces on the wheel want to make the wheel "fold" under the pivot point, i.e. your raised handles.

Now if you lower the rear handles, merely to get the handles parallel, then when you hit that same obstacle, it tire rides up and over the obstacle, because the force isn't being applied at a downward angle (your pushing on the handles).

Now obviously there is a limit to this and as a certain point of lift is doesn't matter whether you raise either point, the centerline of the axle is too low and the vehicle will still try to travel "over" the axle when traveling forward.

That is why you see all of the "long arm" kits for Jeeps and other long arms suspensions. They are an attempt to keep the controlling links as parallel to the ground as possible. And why you see all of the crossover steering system available for lifted vehicles. All are attempts to keep the arms parallel to the ground so that the leverage is kept to a minimum.

Jack

 

[concretejungle]

x-link and flipping the arms are not the same... not comparing apples to apples.

 

[Ebag333]

x-link and flipping the arms are not the same... not comparing apples to apples.

Who said they were?

 

[lt1fire]

Can someone explain in very simple terms what the advantages of this would be???

 

[Ebag333]

Can someone explain in very simple terms what the advantages of this would be???

No.

The flipped arms, or the X Link?

 

[LC80Ducati996]

]
That is why you see all of the "long arm" kits for Jeeps and other long arms suspensions. They are an attempt to keep the controlling links as parallel to the ground as possible. And why you see all of the crossover steering system available for lifted vehicles. All are attempts to keep the arms parallel to the ground so that the leverage is kept to a minimum.

I disagree that it is because of leverage. A longer arm actually has the potential of more leverage. Either above or below the axle the stock radius arms are the same effective length.

Think about tourqing a fastene with a crowfoot on a tq wrench. As long as the crowfoot is at a 90* angle to the handle of the wrench the tq dialed into wrench will be what is delivered to the bolt. It makes no difference if it is 90* to the left or right of the handle.

The biggest gain from longer arms is the redued angle so that as the suspension cycles there is a lesser change in alignment. one term for one measurement is dybamic caster. Also with drop brackets or a flipped arm mount setup the angle of the arms is reduced and closer to parallel means less change.

 

[concretejungle]

Who said they were?

well, we are talking about flipping the arms, and now in two posts pics have been posted stating that it flexes better because of the flipped arms and yet they have the x-link system in place.

Just wanted to make sure we are comparing apples to apples so to speak.

 

[Ebag333]

well, we are talking about flipping the arms, and now in two posts pics have been posted stating that it flexes better because of the flipped arms and yet they have the x-link system in place.

Just wanted to make sure we are comparing apples to apples so to speak.

The pics were merely a comparison.

The flipped arms do seem to allow more flex (or at least more droop), but the X-Link seems to do as much if not more than simply flipping the arms. The "ultimate" seems to be flipping the arms and doing the X-Link.

It is an apples to oranges comparison because they function differently, but both allow for more suppleness/flex, and both will help restore the control bits to a more neutral/flat position. Two different ways of tackling the same (or at least similar) problem, just like a body lift and suspension lift will let you clear bigger tires. Comparing a body lift to a suspension lift is an apples to oranges comparison, but both can achieve the same (limited) goal.

 

[CreeperSleeper]

Okay, I will take a stab at it... One of the reasons why you would want the control arms to be as parellel to the ground as possible at ride hight is when you go to climb something. The control arm travels in an arc. If the arm is parellel to the ground, your tire will climb up and over the obstical easier. If the arms are pointed down, the axle needs to travel forward a bit (until the arms are parellel) for it to start climbing. This is the same reason running shackles in front of the axle on a leaf sprung rig is a good way to bend leaf springs. Play with a protractor a while and you will see what I mean.

Reason number 2 would be the range of articulation would be greater. You only have so much articulation so you want to put that range where it is usable. In theory, flipping the arms would not change the amount of possible motion, but it will change where that motion is.

 

[Nay]

That is why you see all of the "long arm" kits for Jeeps and other long arms suspensions. They are an attempt to keep the controlling links as parallel to the ground as possible. And why you see all of the crossover steering system available for lifted vehicles. All are attempts to keep the arms parallel to the ground so that the leverage is kept to a minimum.

The 80 already has a 30"+ long radius arm that has very little angle on a typical 4" lift, plus it offers virtually no droop as you prepare to climb an obstacle. This is why it is so easy to put the 80's front end up on just about anything as long as you can clear your approach angle.

Flipping the arms to help the 80 climb better re: the "wheelbarrow" example will have no practical advantage - in fact, adding flex to the system will create more droop on one side, which will cause the angle/leverage argument to come into play in certain situations. This is exactly what happens on Jeeps with very flexy long arm conversions - the tire still wants to push down and back when it drops into a hole and has to climb even with a 36" radius arm (a flat arm with a ton of droop will ultimately have more issues than a slightly angled arm that doesn't flex).

The price that is paid for this front end rigidity is of course rigidity as it's not terribly comfortable offroad, and it can force a lot of lean in some cases, but it will climb rather than pushing down pretty effortlessly. On an 80, this is not a problem that needs to be solved unless you are bringing significantly increased flex into the equation.

This is a good example showing what happens when you add flex to the front end - you get a tire in a hole, and it wants to push down and back even with a long radius arm suspension.

Now compare to the non-flexy 80. The tire doesn't drop into the hole (the whole rig leans into the hole, but the radius arm is keeping relatively little angle), so the front end climb is effortless, but because of the rigid front end it forces a lot of lean to take that line and the rear suspension has to take all of the flex. The 80 will feel much more tippy here, but leverage on the arm/wheel is not an issue whereas more flexy rigs really have to climb out of that hole against the natural tendency of the suspension.

"Flex" is never an independent variable, and it is not always in your favor on a large rig. Even if it makes for great poser pics on forklifts and curbs.

 

[CreeperSleeper]

*DISCLAIMER ON WHAT I SAID ABOVE*

Maybe 2% of you guys would benifit from doing this. My rig isn't even tall enough for this to be a good move. I was just explaining why parellel arms are "correct"... That being said, I agree with Nay. It is not needed unless you are running taller than any aftermarket lift available to us.

 

[lt1fire]

Quote:
Originally Posted by lt1fire
Can someone explain in very simple terms what the advantages of this would be???

No.

The flipped arms, or the X Link?

The flipped arms

 

[Ebag333]

*DISCLAIMER ON WHAT I SAID ABOVE*

Maybe 2% of you guys would benifit from doing this. My rig isn't even tall enough for this to be a good move. I was just explaining why parellel arms are "correct"... That being said, I agree with Nay. It is not needed unless you are running taller than any aftermarket lift available to us.

According to what I've read on the Aussie forums, 4" is minimum to do it and a lot of the people who have done it are at 6". From what I've read, it's more popular to do a shorter suspension lift and a bigger body lift (IE: 2"/2" is common).

Maybe their 4" and 6" means something different than ours.....

Flipping the arms to help the 80 climb better re: the "wheelbarrow" example will have no practical advantage - in fact, adding flex to the system will create more droop on one side, which will cause the angle/leverage argument to come into play in certain situations. This is exactly what happens on Jeeps with very flexy long arm conversions - the tire still wants to push down and back when it drops into a hole and has to climb even with a 36" radius arm (a flat arm with a ton of droop will ultimately have more issues than a slightly angled arm that doesn't flex).

I disagree and here's why...

You're not changing the length of the arm's when doing this mod. (Or rather, you can but it's not a requirement to, and if you do it's very slight.)

OK guys this time I bring a picture,

The top diagram shows the relationship between the axle centre and the RA chassis mount as a dotted radius line, it is set by the length of the RA and the spring height, it has and angle between the radius line and the chassis of say 30 degrees in this example.

The middle diagram shows a traditional underslung RA with the same RA length and the same spring height and same angle of 30 degrees.

The bottom diagram shows a flipped radius arm with the same spring height, it is the same radius arm so the same RA length, therefore the same angle of 30 degrees.

The key to my point is the dotted radius line, it does not change when you flip the RA, nor does the spring height or the angle, so the dynamics of the axle moving forward as it moves up are exactly the same as they were before the RA flip.

Moving the axle forward when doing an RA flip will have two effects, it will overcome the fact that the axle moved rearward when a lift was fitted and it will lengthen the radius of the axles arc when travelling up or down which is also the same effect as fitting drop boxes to a very small degree.

In my case I am deciding whether or not to RA flip on an SAS that hasn't reached fabrication stage yet and moving the front axles forward is a necessity anyway.

If you flipped on a standard 80 you would fab your RA to axle brackets to bring the axle forward slightly and yes this would increase (slightly) subtleness in the suspension.

Cheers

The point is that flipping the arm's has almost the exact same effect as doing a drop bracket on the frame. All you're doing is restoring the arm to a more neutral/flat position.

 

[CreeperSleeper]

After playing with a measuring tape for hours under my 80, I would think that the bare min amount of lift to make this "worth it" would be 6"... However, even then I don't think it's the best plan of attack on an 80 Series. Now if you had, lets say, 10"s of lift on your 80, then it would be worth it. But who would want to be that top-heavy?!?

 

[BrotherRob]

I won't claim to be a guru here, but I do see the benefit. Let me throw a simple example out.

Take a stock and lifted truck over a good sized speed bump. On the stock truck, the springs will compress allowing the truck to cross the bump with limited body movement. On the lifted truck, some of the force from the bump will be transferred up the arm to the frame. This will reduce spring compression and increase body movement. The force transferred to the frame will also have a jarring effect on the driver.

On a larger obsticle, the angled arm with have a lever effect and will try to push the front end up rather than allowing the springs to compress. This can also happen with a staight arm but it's less likely because the forces are roughly perpendicular.

 

[Ebag333]

The flipped arms

All of this is copy/pasted from: Outer Limits 4x4 Board :: View topic - Flipped Radius arms

When you have big lift, it allows you to run stock arms and bushes and have stock caster (Biggest advantage I can see)

One advantage of the flipped arm is the added clearance of the tie rod, standard arms hit when underneath with a big lift.

before i done the arm flip i was bending the arm with an 7.5"lift the arm sat at about the 45 deg angle so when you hit a log or rock in comp or winching instead of the diff moving up it wanted to go back because of the angle of the arms using my cruiser in comps i was bending the arms each event and was a pain in the ass so now putting the arms on top of the diff they become level as if they were back to standard and since the arms have been on top NO arms have been bent last year i competed in the toperi challenge and powering up a hill and hit a large rock if the arms were on the bottom i would have bent them good but now there on the top no problems even thow i hit this rock thet hard running 38.5"tires and broke my Longfield axel (not the CV) from the tire hitting a 3 foot step but with my arms on top i had to raise the panhard rod any way to suit my high steer.

It'll save me roughly £250 (Aus $550) on the cost of castor plates and should push the axle forward back to where is should be.

advantages I see of the flipped arms is:
- it returns the arm to a more horizontal position,
- moves the diff housing forward (spring lift will make the housing move rearward slightly as the downward angle on the radius arm increases with lift),
- allows caster correction to be done at the same time (or rotate knuckles as well to correct caster and pinion angles)
- gives a little improvement in ground clearance
- eliminates issues with tie rod hitting radius arms (as when caster plates are fitted)
- can be done for far less $$$ compared to buying dropped arms ( a few bucks in steel and some fab vs $12-1300 for drop arms)

Yeah another good point I missed, raising the mounting point relative to the link and chassis will create a flatter link resulting in more controlled suspension, and reduce the inevitable pig rootin bunny hoppin that is common on lifted cars with stock suspension.

Take it all with a grain of salt, much of it is web wheeling.

 

[CreeperSleeper]

I won't claim to be a guru here, but I do see the benefit. Let me throw a simple example out.

Take a stock and lifted truck over a good sized speed bump. On the stock truck, the springs will compress allowing the truck to cross the bump with limited body movement. On the lifted truck, some of the force from the bump will be transferred up the arm to the frame. This will reduce spring compression and increase body movement. The force transferred to the frame will also have a jarring effect on the driver.

On a larger obsticle, the angled arm with have a lever effect and will try to push the front end up rather than allowing the springs to compress. This can also happen with a staight arm but it's less likely because the forces are roughly perpendicular.

Um... That's pretty much what I said...