Castor problem?

[ntsqd]

If you're going to quote me, at least quote all of what I said and don't take the part that you want out of context.
There is nothing mechanical done on a vehicle that hasn't already been done on some other mechanical contrivance or some other vehicle. If we can not learn from similar arrangements that did not work or work well, we are doomed. The swivel ball's bolt flange is not something totally unique that only ever exists on that particular design. Slotted holes in that type of assembly, loaded in that fashion, absolutely require some other means to insure the desired orientation. And the bolts are still at risk.

 

[marc olivares]

If you're going to quote me, at least quote all of what I said and don't take the part that you want out of context.

yeah you're right
there, fixed it.

This particular, exact mod, no...fluff

thank you

 

[Steve Rupp]

I'm really surprised that in the 75000 miles of driving back and forth from Chicago and Utah and being offroad for 2 weeks at a time on those trips I have not had a catastrophic failure. That's it the stock balls are going on and i'm blowing 1200 on sexy castor corrected arms and 500 on a multi DC shaft.

 

[Mike_rupp]

Steve, Thom, Marc: you must understand, this isn't about being right. It is about respecting everyone else's opinions, no matter if it is based on theory and not empirical evidence. The fact that between the three of you, 200,000 miles or so without a failure doesn't mean a hill of beans.

Just respect their objections, no matter how misguided they may be, and move along. This isn't the nasty and mean Discoweb.

As a side note: what is the difference between an Engineer and an engineer?

 

[R_Lefebvre]

I'm just revelling in the irony that the same people who would look at a vehicle with 10,000's of copies on the road and very few (*maybe* 3) failures would deem it to be junk, yet on the other hand, would claim that a modification was OK because they have 3 vehicles that have done it with no problems. That's hubris.

 

[Mike_rupp]

There is one glaring difference: the LR3 suspension component is on a stock vehicle. Out of the box, the suspension component isn't sturdy. You have even stated yourself that the vehicle isn't as durable as a Discovery.

The caster angle solution, redrilled swivel balls, is a method to correct problems associated with a lift. Since you are an engineer, what would you do to solve the lost caster associated with a lift?

Don't you understand that with the redrilled swivel balls that the upside outweighs the downside? With negative caster, the likelihood of losing control is greater than a failure related to the elongated swivel bolt holes.

 

[Mike_rupp]

Given the response that the swivel bolts are not under significant shear stress because the locating ring takes all the load, and that I clearly don't know what I'm talking about because I wouldn't do the mod my self, I will never take advice from the two individuals who advocate this hole slotting method. Those bolts are under eneormous stress, especially the bottom ones, which carry large tensile loads as the weight of the vehicle tries to bend the axle and separate the challace laterallyfrom the axle flange. Removing material from under one side of the bolt head means the bolt is unevenly stressed, with a similar effect to having a wedge section washer under the head. This vastly increases the chances of bolt failure. It's not the swivel housing that runs the risk of failure, it's the bolts.

The internet is chock-a-block with self-assured amateur mechanics advocating all sorts of dangerous botches. Given the results of what would happen if these bolts failed on a motorway/highway, it's not a shortcut that I think is worht the risk.

Corrected radius arms are the way to go, in my opinion, and many of the after-market models are both lighter and stronger than the originals, such as those by Equipe and QT.

Your opinion is wrong. I have never seen a failure of a stock radius arm on a Discovery, yet here is a pic of a broken aftermarket arm. Do you still want to stick by your statement that those aftermarket arms are stronger than the original?

 

[Hank]

Hundreds of thousands of miles have been placed on the drilled swivels. I don't know of a single failure. None. Never heard of any wearing or mushrooming out, either.

There is more of a rotational force on the swivels than anything. The 7 bolts that mount the swivel to the axle are only acting as a clamp. The inner lip of the swivel is holding the grunt of the directional load. Even if you took out 3 or 4 of the swivel ball bolts, you would probably still never break anything (not that I'd want to try).

So I'm not real sure what you anti-ball-drillers are debating. Are you claiming that by removing some of the "meat" from the swivel ball flange you're reducing the clamping force on the swivel? Or are you saying that by removing some of the "meat" from the swivel ball flange you're allowing the swivel to rotate? Or, maybe you're saying that by removing the "meat" the swivel could crack and fall off?

I don't get it.....that ball is not going anywhere. The swivel is not being "pulled" away from the axle tube. If anything, under braking, it's being twisted. If the swivel was engineered to have a load "pulling" the swivel away from the axle tube, a Grade 8 bolt would have been installed from the factory; not a Grade 5.

Here is a video of the forces the swivel would typically see daily and on the trail http://www.youtube.com/watch?v=OwkGl3wXEcM
That's a LOT of rotational force. And that's why that sweet QT radius arm broke.

 

[david despain]

The internet is chock-a-block with self-assured amateur mechanics advocating all sorts of dangerous botches.

http://expeditionportal.com/forum/member.php?u=1535


Occupation
grease monkey

if you get paid to wrench then you are not an amateur

 

[greenmeanie]

I'm just revelling in the irony that the same people who would look at a vehicle with 10,000's of copies on the road and very few (*maybe* 3) failures would deem it to be junk, yet on the other hand, would claim that a modification was OK because they have 3 vehicles that have done it with no problems. That's hubris.

X2.

Nobody is arguing that correcting the caster is a good thing. It is how you correct it that is the point. Ntqsd said it well. Redrilling them is fine. Slotting them increases stress, reduces margins of safety and could allow the swivel to rotate unexpectedly, changing the castor on one side, and changing the steering characteristics unexpectedly. If you must slot you should also drill an extra hole for a pin or bolt to eliminate the ability to rotate.

Mark,
Unless you have a control to compare it against, showing one broken arm is pretty useless as there is nothing to say that a stock control arm subjected to the exact same conditions over its life would not have failed too. If you could show a series of failures it would lend evidence to weakness but a single event is insufficient to base an arguement on.

You will also find a different attitude towards modifications in the UK than the US. Our insurance companies are far more finicky about vehicle modification and the courts less sympathetic to accidents involving modified vehicles based on the standard of engineering behind it. An MOT tester can easily fail your vehicle for such a modification if they decide it affects safety. For evidence look at the consequence of the recent tragic accident involving the Defender that ended up in a canal.

 

[Mike_rupp]

It is useless arguing here. Knocking my head against the wall would make more sense. I'm headed out to the garage to modify my Disco. I'm sure all of you Engineers would be critical of what I'm doing.

 

[Antichrist]

....OK because they have 3 vehicles that have done it with no problems. That's hubris.

RTE has been doing the castor correcting swivel ball modification for about 10 years. I suspect, though I have no proof, that they've done a fair few more than 3 sets.

Unless you have a control to compare it against, showing one broken arm is pretty useless as there is nothing to say that a stock control arm subjected to the exact same conditions over its life would not have failed too.

True statement. I'm guessing there are a lot more stock radius arms on (and off) the road than there are aftermarket, and for a lot more miles. Have you ever heard of a stock radius arm failing in that location. I find it difficult to believe that in the many millions of miles driven on stock arms, none have ever been subjected to the same stresses as the one pictured.

As for the castor corrected swivel balls, given how litigious the US is as a society, I have a feeling RTE is pretty confident in the safety of their products.

 

[marc olivares]

Mark,
Unless you have a control to compare it against, showing one broken arm is pretty useless as there is nothing to say that a stock control arm subjected to the exact same conditions over its life would not have failed too. If you could show a series of failures it would lend evidence to weakness but a single event is insufficient to base an arguement on.

you sure this statement should be directed towards me?
i'm fairly certain i've made no such claim, as i am certain that i have not participated in the LR3 thread that Monsieur Lefebvre is inferring in his silly statement.
no, i'm just a guy with castor corrected swivel balls, that's actually speaking from "experience", that's calling out misinformation and conjecture when i see it. oh and yeah, i just so happen to turn wrenches for a living.

:wavey:

 

[greenmeanie]

Marc,
My apologies to you. I made a mistake and should have said Mike.

 

[R_Lefebvre]

if you get paid to wrench then you are not an amateur

I wish that were true. (NOT directed at Marc in any way. Just the statement by itself. There are scores of completely clueless "Professional Mechanics" out there.)