Dropped Pitman Arms

[rickcdewitt]

That's not leverage on the gearbox. It's leverage on the mounting bolts.

call it what you want but thats the downside of a dropped arm.although i don't know if a super runner steering would reduce the leverage that much especially with big tires and curbs involved

 

[4x4junkie]

No, the Superrunner (K-link) puts MUCH less leverage on the box (the forces are split between the pitman arm and the centerlink's idler arm).

I also agree, the added leverage is the downside of dropped pitman arms. Most also reduce the steering ratio due to being longer as well (which makes the power steering work harder to turn that longer lever).

Any time you put more force on the steering box, it transfers right into the mounting bolts too.

 

[Sasquatch_Ryda]

My dropped pitman arm also makes the the frame horn twist pretty good when you turn the tires, just havn't gotten around to building a brace for it yet.

 

[rickcdewitt]

i had the mega drop arm on a 6" skycracker lifted POS 88 ranger.it was a little scary looking at the frame rail on that used up truck when the wheel turned.it got me into rbv's but was a scary drive with no sway bars.my current rig has a slight amount of movement and the frames been bent before so i built this-

the steering box has a flat side towards the front and shaped just right on the back for a u-bolt.i used a big exhaust u-bolt and would have used two or a bigger one if i did it again but it hasent slipped any so i guess its fine.i bolted the 1/4" tabs to the truck and then cut a pipe to length,hammered the ends closed and tack welded it for fit.if you think about it though the bottom of the frame is held in place pretty well and doesn't move a whole lot its the top that goes in and out.since the crank pulley is in the way its a little harder to brace across the top.my trucks no prerunner even though i drive it that way sometimes so i guess it will be fine.

 

[Todd]

That's not leverage on the gearbox. It's leverage on the mounting bolts.

The bolts dont fail the frame fails.

So use bigger mounting bolts and reinforce the frame.... IF it's really a problem. I have a very hard time believing that it's anywhere near as bad as you say -- most drops less than double the distance, so those bolts would have to be marginal in stock form. Or your buddy spun his truck out and whanged a curb.

After having the bolts tear throught the frame I have reinforced the frame with 3/8" plate. Also my pitman arm is longer then most. This is due to running my soft XJ coils and needing the steering links dead nuts level. Also I have had some major impacts with logs, rocks, ect.

 

[Dishtowel]

No, the Superrunner (K-link) puts MUCH less leverage on the box (the forces are split between the pitman arm and the centerlink's idler arm).

I also agree, the added leverage is the downside of dropped pitman arms. Most also reduce the steering ratio due to being longer as well (which makes the power steering work harder to turn that longer lever).

Any time you put more force on the steering box, it transfers right into the mounting bolts too.

First off, I wanna say I have alot of respect for you junkie, i'm not trying to call you down/out. whateve'

but, whether we look at the bolts or the steering box, or the pitman arm. all they are doing is transmitting the force. they all see the same force. the steering system does is transmit force from the rigid frame to the tires. the frame sees the force too, but hopefully something else will fail before it. the tires see the force to, therefore they move. statics and dynamics.

I don't know how think the superrunner system puts less force on the box by including an idler arm. The very nature of the name "idler arm" means no load. only guidance, think of an idler pully on a belt, it sees belt tension, but that is not a load in that system, if the bearing is seized on the idler THEN it is introducing a load to that system. the idler arm is free to move where-ever and whenever it is acted upon.

anywho, just my 0.02

 

[4x4junkie]

First off, I wanna say I have alot of respect for you junkie, i'm not trying to call you down/out. whateve'

but, whether we look at the bolts or the steering box, or the pitman arm. all they are doing is transmitting the force. they all see the same force. the steering system does is transmit force from the rigid frame to the tires. the frame sees the force too, but hopefully something else will fail before it. the tires see the force to, therefore they move. statics and dynamics.

I don't know how think the superrunner system puts less force on the box by including an idler arm. The very nature of the name "idler arm" means no load. only guidance, think of an idler pully on a belt, it sees belt tension, but that is not a load in that system, if the bearing is seized on the idler THEN it is introducing a load to that system. the idler arm is free to move where-ever and whenever it is acted upon.

anywho, just my 0.02

You probably aren't realizing there is a vertical distance between where the centerlink mounts to the idler & pitman arms, and where the tierods are attached to the centerlink (especially after modification of the centerlink to drop it down more).
If the tierods were mounted on the same plane as the pitman arm TRE, then your statement would be true, but that's not the case here.

 

[Dishtowel]

After putting some more thought into it I have come to the conclusion that the superrunner setup does help in sharing the vertical load on the steering box. (when looking at the front of the truck) The horizontal loading on the steering box and frame remain the same.

Do you agree? Are we talking about the same thing? lol

 

[4x4junkie]

Well, sortof...

Looking back through the post here, seems there's been a lot of confusion about the pitman arms and leverage.
Where the confusion came from I'm not sure... reaally long drop arms DO put a much bigger bending moment on the sector shaft (and consequently, the box and mounting bolts). How this isn't obvious here I can't figure out.

What the Superrunner kit (or K-link) does is greatly reduce the amount of bending force from using such a huge drop pitman arm. If the K-link is made to use the stock pitman arm (or a normal drop arm, as in the case of the Superlift kit), the moment on the sector shaft (along with the effective overall steering ratio) is basically the same as when using the same arm by itself. The centerlink then converts that extra leverage into a much less destructive vertical force placed on both the idlerarm and pitman arm.

Hopefully I'm explaining it right...