Rockwells make your sac swell!

Neal3000 · Aug 13, 2013

So it made a significant difference, thats pretty cool......just curious, what angle caster do you have front vs rear?

patooyee · Aug 13, 2013

Re:

I've never measured.

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Skidkid · Aug 14, 2013

toreadorranger said:
Pulled this from billavista's article on (Billavista.com)

The way I understand it, your still subjecting the hardware to a shear force which eventually shears studs. With the cone washers you minimize this effect. Thus preventing or extending their life in this situation. Which is why I bet with the proper cone washer setup and the double shear tie rod bolt, there shouldn't be a problem.

Pretty much this ^

Studs with tapered nuts into steering arm countersunk holes helps with this as well.

Buddy of mine ran a high steer arm with running just bolts holding it on. I told him it would fail running it like this and he did not believe me. After a couple trips it sheared off all but one bolt. Then he listened to my suggestion using studs and tapered nuts. He tapered the holes in the steering arm and went this route. Five years later and its still holding up fine and it gets beat to fawk hard every trip out.

Skidkid · Aug 14, 2013

patooyee said:
Its not front / rear that matters. Its tie rod mount inboard vs. outboard of kingpin.

Rockwell knuckles have the tie rod inboard of the kingpin. That means for rockwell knuckles, on a front axle, the arms have to point backwards to get correct Ackerman.

Dana knuckles have the tie rod hole outboard of the kingpin so that correct Ackerman is obtained with the arms pointing forwards. If you swapped sides with Dana knuckles so that the arms pointed backwards you would get incorrect Ackerman.

I tried to find a good pic of a d60 knuckle and can't. The best one I can find that demonstrates all this is a CAD model pic:

Notice how the tie rod hole is obviously outboard of the kingpin?

Now see hoe the rockwell tie rod hole is obviously inboard of the kingpin:

If you looked at a birds eye view of the knuckles and draw a vertical line from kingpin to rear axle and then another line from kingpin through tie rod hole, the angle between these two lines is your Ackerman angle. Ideally when you do this on both sides the lines intersect in the center of your rear axle. But if you draw this same diagram with rockwell knuckles pointing forwards that is not what happens. Instead the lines intersect somewhere in front of the vehicle giving you crap steering.

And this isn't just for race cars. I immediately noticed the difference just pulling out of the shop today at .5 mph. The rig turns noticeably sharper.

Gotcha, thanks.

photos show it pretty well and I'm going to take a look at one of my D60's for my minds eye comparison too.

I'll have a backwards Ackerman up front but probably do a lot of steering with the rear. I can't change my front without going through major refab hell.

Neal3000 · Aug 14, 2013

Re:

patooyee said:
I've never measured.

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I may be totally off base here but i would guess that you have positive caster in the front and negative in the rear, that might be a contributing factor in the rear turning sharper than the front

patooyee · Aug 14, 2013

Re:

Neal3000 said:
I may be totally off base here but i would guess that you have positive caster in the front and negative in the rear, that might be a contributing factor in the rear turning sharper than the front

My understanding is that Rockwells have very little caster actually built into them and my axles are pretty much perfectly flat at ride height, so not much if any additional caster has been added or subtracted. So I'm betting I have whatever is built into the rocks and that's it. I'll measure on Fri. when I go to the shop though.

My front tires you used to be able to visually tell weren't turning as sharp as the rear. My shop mate even mentioned it when he would watch me crab walk for any distance because I would end up slowly turning as the rear out-steered the front going the same direction. I didn't have time or space last night to try a crab walk but I am looking forward to it ...

Here's the pics of the new setup:

Elliott · Aug 14, 2013

Doesn't the mounting of the double ended ram come into play into all this also?

patooyee · Aug 14, 2013

Not with Ackerman angle that I am aware of.

Neal3000 · Aug 14, 2013

my theory is crap......i googled 2.5 rockwell caster and it looks like they came with -4 degrees in the front to make the trucks easier to turn with manual steering

Skidkid · Aug 14, 2013

Re:

patooyee said:
My understanding is that Rockwells have very little caster actually built into them and my axles are pretty much perfectly flat at ride height, so not much if any additional caster has been added or subtracted. So I'm betting I have whatever is built into the rocks and that's it. I'll measure on Fri. when I go to the shop though.

My front tires you used to be able to visually tell weren't turning as sharp as the rear. My shop mate even mentioned it when he would watch me crab walk for any distance because I would end up slowly turning as the rear out-steered the front going the same direction. I didn't have time or space last night to try a crab walk but I am looking forward to it ...

Here's the pics of the new setup:

How are your tie rod heims mounted to the knuckles now?

How are you measuring caster angle? Axle housing or flat top of knuckle < not sure if either are different out comes.

NTIDWELL · Aug 14, 2013

:

toreadorranger said:
Pulled this from billavista's article on (Billavista.com)

The way I understand it, your still subjecting the hardware to a shear force which eventually shears studs. With the cone washers you minimize this effect. Thus preventing or extending their life in this situation. Which is why I bet with the proper cone washer setup and the double shear tie rod bolt, there shouldn't be a problem.

i would agree with that 100% but like I said before the studs did not come loose there in not a loose fit on arm to stud your tapered nuts or cone washer does not make the same stud stronger it makes improper drilled holes not work back and forth on your studs and keeps em tight correct

patooyee · Aug 14, 2013

The heims on my knuckles just go directly on top of the knuckles single shear with a bolt through them. There wasn't even enough angularity to need spacers, just knuckle, heim, bolt. I did have to grind down some of the inside corner on the tie rod mounting boss simply because it was too big and wouldn't let the heim move, hit the body of them heim. We're talking 1 minute of grinder work just to take off the sharp edge a little bit.

For what its worth, every hi-steer arm I've ever had on a rockwell has somehow tied into the stock tie rod hole and / or the knuckle stop bolt hole. I've never used studs or conical washers, just quality gr. 9 bolts and Loctite, and I've never had a single bolt come loose or sheer. I check them now and again to make sure just to stay on top of them. Bill's article is correct, but we all know that we can get away with a lot of stuff that engineers say is "incorrect."

TBItoy · Aug 14, 2013

Re: Re: Re: Rockwells make your sac swell!

NTIDWELL said:
:i would agree with that 100% but like I said before the studs did not come loose there in not a loose fit on arm to stud your tapered nuts or cone washer does not make the same stud stronger it makes improper drilled holes not work back and forth on your studs and keeps em tight correct

The cone washer or tapered nut converts part of the shear force into axial force (tension).

Skidkid · Aug 15, 2013

Re: Re: Re: Rockwells make your sac swell!

TBItoy said:
The cone washer or tapered nut converts part of the shear force into axial force (tension).

This plus preventing the high steer arm from any possible side to side movement leading up to shearing the bolts.

Nuts · Aug 15, 2013

Back to the ackerman angle... If the steering axle(s) are spooled or welded one tire will be scrubbing anyway so all the ackerman jazz wouldn't matter and you could mount the steering infront of or behind the axle????

fordcontraption01 · Aug 15, 2013

Nuts said:
Back to the ackerman angle... If the steering axle(s) are spooled or welded one tire will be scrubbing anyway so all the ackerman jazz wouldn't matter and you could mount the steering infront of or behind the axle????

x2 mine has a welded rear and a Detroit in the front with both tie rods behind the axels and my rear will appear to turn deeper than my front. The only thing I can think of that is changing this because my rear end is pointing up for driveline angle and my front is pointing up the opposite way for driveline angle? :dunno:

I do know that I'm taking out the Detroit and welding it due it breaking a front axel and thus no front brake due to the Detroit opening resulting in it trying to kill me backing off tailgate hill at Harlan. :****:

patooyee · Aug 15, 2013

Nuts said:
Back to the ackerman angle... If the steering axle(s) are spooled or welded one tire will be scrubbing anyway so all the ackerman jazz wouldn't matter and you could mount the steering infront of or behind the axle????

I don't know that it doesn't matter. I think it just matters less. Because before I had correct Ackerman in the front my rear still out-turned the front despite being in 2wd with my Ouverson locker in front and spool in rear. This is just my sophisticated wild-ass guess though.

xjpaddler · Aug 15, 2013

Neal3000 said:
my theory is crap......i googled 2.5 rockwell caster and it looks like they came with -4 degrees in the front to make the trucks easier to turn with manual steering

you just answered your own??

Neal3000 · Aug 15, 2013

xjpaddler said:
you just answered your own??

Yes, yes i did.

Eddyj · Aug 20, 2013

My old driveshafts are set up for 1350 u joints on the axle end. Who sells a good flange to attach driveshaft to axle? Should I upgrade to 1410. I don't see the need to.