Solid Axle Chevy Steering

K5Blazer

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In my quest to make a desert truck out of my K5 I am stumped on what type of steering to run. The stock front to back draglink doesnt seem to work to well in my opinion by allowing too much bumpsteer. I want to run crossover, but I have been told it is not the hot setup for the desert. Can anybody help me?
 

ntsqd

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If you have custom front springs made I can see the stock arrangment working pretty good. What you would need the springs to do is to be very stiff in the section forward of the axle. Effectively turning that portion of the spring into a trailing arm. The length from the front spring eye to the spring pin would need to be adjusted to be exactly the same length as the draglink's joint to joint distance, and they would both need to be operating in a parallelogram. Then to compensate for the stiff front 'half'' of the spring I would make the rear 'half' of the springs very long. Move the shackle back at least a foot. The only issue I can see with this would be in exceeding the angularity of the TRE's. LA 4wd Toyota's are notorious for troubles with this.

Where the bumpsteer in the stock linkage comes from is due to the draglink's fixed length vs. the front half of the spring varying in length depending on where in it's cycle it is.
With cross-over the geometry of the whole system will determine if you've made the bumpsteer better or worse. If the draglink is parallel to the axle housing, or even slightly leading at the knuckle end, then as the springs flatten and get longer the draglink will be in the sweetspot of it's arc and not effect the tire's direction as much.
If, on the other hand, the pitman arm end of the draglink is leading the knuckle end by a significant amount then as the springs' flatten and get longer the draglink will be pulled further away from the sweet spot/zone which could have a drastic effect on the tire direction.
Whether the suspension will cycle enough for the arc of the draglink, as viewed from the front, to affect tire direction is probably the Achilles Heel of the project. In it's favor the draglink of a cross-over is comparitively long. Working against it is that it is hard to get the angle (as viewed from the front) to a reasonably flat position.

There is an unsprung mass consideration in that cross-over will marginally increase it. If you're worried about that little change (relative to the current unsprung mass) I think you're worrying about the wrong thing(s). Not that unsprung mass shouldn't be considered and reduced where possible, but that this change is a pretty small percentage.

Who told you that cross-over doesn't work in the dez ? I'm curious as to what their reasoning or experience is/was.

TS

I used swerve around my halucinations, now I drive right thru them.
 

K5Blazer

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ntsqd, your reasoning makes perfect sense. But the one thing I dont get is how you would make the front half of the spring stiff with relatively no movement compared to the rear half of the spring. I would just like to know what to tell Deaver when I go to get my front springs done. The person that told me that crossover was not the hot setup was one of my fellow K5er's.

BRB, is that an idler arm setup on the second picture you posted?
 

K5Blazer

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I pulled this off an old solid axle chevy thread, can someone clarify this please?

"Fabricate left frame mount track (panhard) rod from Dodge BR/3500 and convert steering linkage to transverse links drag link with Haltenberger type linkage. for front axle."
 

drtdevil93

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what we usually do is flatten out the front of the spring. the front of the spring is already stiffer due to the length compared with the back. i usually dont flatten it all the way, but set it up so at ride height it will be in the "sweet spot".

erik
 

ntsqd

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The way those Nationals were built was that on the front end of the spring each leaf's tip came within ~1/4"-1/2" of the next upper leaf. The truck I saw phis done on worked reasonably well when the driver could be convinced to keep his foot in it. The gal showing her bare upper half just down from S/F @ B-Stow sure did that.......

From the looks of it I'll guess that the second pic is an idler arm. The first draglink appears to run btwn the pitman and the idler, the second draglink btwn the ider and the steering arm. It's purpose is to get the frame end of the second draglink forward enough to create that parallelogram I mentioned earlier.

The post you quoted has to be Bob Sheaves. Give serious thought to his advice. I think what he's saying is that if you do a cross-over (& appearently he feels that is the correct thing to do), then you should also make a panhard rod. I think I see where he's going with this. By forcing the axle to move in a lateral arc with the panhard you can remove or reduce bumpsteer if you can get the arcs of the panhard and the draglink to coincide.

Not being familiar with Haltenberger Linkage I tried a google search and got 7 hits. This:
"HALTENBERGER
A steering system consisting of a drag link that connects the passenger side steering arm to the Pitman arm. It is unique to Ford vans and light trucks." from: http://www.niat-training.com/OnLine/glossary/glossaryH-Q.htm
And this: " STEERING
Type Haltenberger linkage (4x2), cross-tie linkage (4x4)"
from: http://www.springfieldford.org/trucks/commercial/fseries/superduty/specs2_features.html

This leads me to believe that Haltenberger Linkage is the typical linkage found on TIB & TTB Ford trucks. On a live axle I think this would generate toe-out in the bump portion of the cycle so I'm not clear on why he suggests it in particular.





TS

I used swerve around my halucinations, now I drive right thru them.
 

K5Blazer

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I'll have to look at my friends Bronco tommorrow to get an idea of the Haltenberger type linkage.

I remember reading something about the ORD K5 and how he was running a panhard rod and he broke the mount off the frame. This makes me think that im either going to be breaking the mount or im going to be really hard on parts because as the suspension compresses its going to want to make the springs travel in a different arc than they were designed to. But of course I may be wrong since im just digging into the surface on this stuff.
 

Bob_Sheaves

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Hi guys...

Yep, that's the idea. Also, you need to make sure the lengths through the mounts (NOT necessarily the centerline of the link, but the straightline dimention between piviots) is equal and the angle relative to the ground in the front view and the angle fore and aft in the plan view are the same (this creates a parallelogram between the draglink and the track bar).

The Haltenberger linkage is also used on the BR 4x4's to allow for a longer track bar and draglink (longer radius for the induced curve of motion). It is not necessary unless there is a difference in the length between the panhard (track) bar and the drag link. A small benifit is that the steering response is slightly better on the Haltenberger, due to the non-90 degree placement of the compression springs located in the tie rod ends that occurs in a conventional system where the tierod runs knuckle to knuckle, and the draglink attaches somewhere to the tierod.

As far as breaking the mount off the frame-that is a risk if someone doesn't know what they are doing and creates a bad design. As you noted, the loads on the springs are increased (generally not to the failure point), but more importantly, a lateral vector is now added to the frame rail, twisting it normal to the centerline of the vehicle-not good. That is why a proper design will add a crossmember from the left to the right rail near the panhard bar frame mount-to transfer loading between the 2 frame rails.

Best as always....

Bob

<P ID="edit"><FONT SIZE=-1>Edited by Bob_Sheaves on 01/13/03 06:22 AM (server time).</FONT></P>
 

Bob_Sheaves

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OOPS- I meant "twisting it PARALLEL" not "normal". Sorry for the oops....the vector is normal, but the resultant (axis of rotation) is parallel.

Bob
 

K5Blazer

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Alright Im starting to get this. So If I switch from the stock style steering like Bob is suggesting to do, Im going to want to run a panhard rod that is an exact duplicate as the draglink at ride height with the steering centered. I also might want to consider running the haltenberger type linkage to get better steering response. I would also want to make sure the frame and panhard rod mounts are gussetted and braced very well in order to resist frame flex and to keep things from breaking from the added stress of the panhard rod. Is that what he said? cause it went right over my head.
 

Bob_Sheaves

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You have understood the concept..... a couple of caveats however....

1. The Haltenberger linkage is used to create toe-in during rebound (commonly called "droop"-incorrectly) to increase the overall vehicle stability when launched airborne. This is one reason the TTB/TIB Fords are so easy to control when they land hard. Until the suspension moves to full jounce ("compression"), the vehicle understeers (travels straight and requires greater input at the steering wheel for the same amount of wheel turn) for that instant that the driver is bouncing around wailing on the steering wheel uncontrollably (or almost uncontrollably...LOL) from the impact of landing. The downside of this effect is that ntsqd is quite correct-the full jounce (full "compression") position can induce a dynamic toe-out condition to the front tires, leading to an oversteer condition.

By adjusting the distance between the right hand tierod end on the draglink and the "center" attachment tierod end on the tierod (which connects the left tire to the right in this discussion case) you can alter the amount of toe change and the sensitivity to the vehicle suspension dynamics.

2. To have a neutral suspension, you need to use a conventional "T"-shaped draglink/tierod configuration, with the draglink "ball" of the connecting tierod end on centerline of the 2 knuckle tierod ends (this means that you CANNOT have a straight tierod). This configuration will give you a neutral change, but be aware it is VERY tricky to handle on the street, as you have a uniform amount of steering wheel input, regardless of suspension compression or extension. Most manufacturers design in approximately 10 to 18 percent understeer to keep the driver out of trouble in "high suspension travel" conditions (one of the primary differences between a purpose-built race car and a street piece).

3.An engine cage will transfer the track bar loading (if properly designed) from the left to the right framerail and provide you with an alternative mounting position for the upper shock end (or coil over end if you replace the leafs with trailing or leading links-look under a Jeep XJ Cherokee or a Dodge BR fullsize pickup 4x4 for ideas here).

Best as always,

Bob
 

ntsqd

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Bob,
Given that you could only have one but not both, which would you choose for stability; Castor gain in both jounce & rebound, or toe-in in rebound ?
I'd assumed until now that castor gain would be the preference, but your comment about the TTB/TIB stability with rebound toe-in (coupled with their obvious castor loss in rebound) has left me wondering if my assumption was correct.

Thom

TS

I used swerve around my halucinations, now I drive right thru them.
 

Bob_Sheaves

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Simply put-caster gain has a higher priority than toe change for an offroad vehicle. For a street dirven vehicle, the reverse is true.

That being said, my PERSONAL preference is to design in (on a race car that does NOT use a TTB or TIB) a caster change to increase the castor about 25 percent at the limits of travel. In otherwords, if you have (at static ride height) 2 degrees negative caster, the increase at the limits goes to a negative 2.5 degrees (25% of the starting point). This is NOT to imply that I shoot for 2 degrees (the real number is higher than that, depending on the driver I am working with) but rather to illustrate the principle.

Best as always,

Bob
 

ntsqd

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Bob,
Thanks for confirming my conclusion.

TS

I used swerve around my halucinations, now I drive right thru them.
 

Stephen

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This is kind of an old one but since there's a bit more action on straight axle GM's going on I brought it back.
One thought on using stock steering with long travel springs: I tried the stock steering with a set of custom springs I designed a few years ago and the big problem wasn't bumpsteer but roll steer. This is the reason so many rock crawler/recreational offroad types go to crossover steering. The factory steering system places the draglink a few inches outboard of the leaf spring so when the axle articulates under the truck (steering the axle as a result) the draglink can't keep up. I tried running a locating bar from in the factory swaybar mounting locations on the frame and ubolt plate and the bumpsteer was minimal but the roll steer was still terrible. One solution I've seen was turning the box sideways like a dodge truck and running the draglink very close to the leaf spring.

The crossover system with a panhard bar referred to earlier was mine and despite a pretty nice mount on the frame it still tried to crack out until I field welded it to the crossmember that was touching it anyway. One inch of chicken poop applied with a battery welder ended the cracking problem. There is a problem with running a panhard with leaves in that leaves don't really want to move side to side very much so you're going to induce a lot of bind into the system. I had a sliding bushing at the front of the spring to give it about 5/8" of side to side motion without bind and it cycled through about 12" of travel pretty easily. I have some ideas on how to get that side to side motion in a more durable way but it doesn't take very much messing around with it to justify the universal answer: link and coil or coilovers.
 

NTRoffroad

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I've read all this post and I think I am more confused than when I started. I am in the process of building a 78 Blazer. It will keep leafs all around for now and steering is a big concern. After talking with alot of people it sounded like x-over was the way to go if I really wanted to stay with leafs. Now what??
 

Stephen

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go with crossover and live with bumpsteer (personally unacceptable but as always YMMV)
Add a panhard bar to crossover and have great steering at the expense of some spring bind. (probably the best overall solution)
Figure out some way to let the spring move side to side so that it doesn't bind with the track bar. (maybe barely practical)
Link it up and double shackle it and steer front to back with the steering box under the seat. (not really practical)

Stick with stock type steering and have some bumpsteer and probably a good bit of roll steer.
 

ntsqd

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Stephen said:
snip.....
Link it up and double shackle it and steer front to back with the steering box under the seat. (not really practical)
I've seen that type of steering done cleanly, and I still wouldn't want to race it. Too many failure modes.

My vote is also for cross-over, w/ or w/o the panhard bar.
 
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