Jump to content

Custom rig for redrilling swivel ball housing


Disty

Recommended Posts

From other peoples replies it seems castor corrected arms are definitely not an ideal solution..

As you can see, I've not done any welding at all- you're right about how it would affect the steel. It was also my understanding that Tomcat no longer offered these. Does anybody know any different?

I have not checked lately, but I know everyone's favourite purveyor of blue boxed LR spares were offering swivels with holes positioned to correct the castor for a 2" lift.

Whether they were of suitable quality that you'd want to fit them is a separate issue.

If I was deadly serious about doing a real proper job, I think I would fit swivels with adjusted holes [just for a moment forget the issue of how these holes were adjusted], and also correct the spring mounting seat angle. Most brackets for the axles are now available as repair pieces for you to weld on.

Granted, it's not a straight forward bolt together solution, but it at least covers the areas of castor correction, favourable UJ angles, and the spring seat alignment issue.

Link to comment
Share on other sites

Yeah I followed that thread with interest a while ago. It seems they are no longer offered? A quick google reveals that paddocks don't stock them, and I can't see anybody else that does.

I'm going to stress test some of these to find out how much weaker they are after drilling. I suspect there is not much in it, but a reliability engineer will be able to tell me for sure!

Link to comment
Share on other sites

One way of doing this is to use 6 hole swivels, to drill 7 offset holes or vice versa, and not bother with welding them up. I was intending to do this at some stage, but never bothered in the end. I believe that castor correction is a nicety but no necesity. It is worth having for comp safari for sure, so you put more camber on in corners, but for challenge cars it never is a problem. If anything, it reduces the groundclearance under the steering rod and there fore gives you more bend steering rods.

daan

Link to comment
Share on other sites

Your not putting the pinion angles back to standard. Parallel pinions are recommended for a 3 or 4 link setup. however the front end is a ladder bar system, the front axle sweeps in an arc from the chasis mounting not perpendicular like a 3 or 4 link system. The front uj on the front axle is only really there to take up the misalignment when the axle twists etc. the rear u.j does most of the work when the axle moves up an down. Using caster corrected arms is just a backyard solution which increases the angles at both joints, therefore increasing the vibration and wear.

If the chasis pivot and the gearbox u.j were perfectly ( :lol: :lol: not in land rover world) aligned then you could fit a solid joint at the axle end without any problems (if the axle were to travel in a vertical axis only obviously).

Hi,

It seems from this post that either I have totally misunderstood what you are saying OR you are not understanding the workings of Universal joints!

These not being "constant velocity" joints, You can or "should" NEVER use only one UJ in a drive-line. It causes massive torque reversals and would cause (like you get without caster corrected arms or adjustments to the diff angle) bad drive-line vibrations as the UJ accelerates and decelerates without the equalising UJ on the other end during it's rotation cycle.

It is however extremely hard to see what is correct or not as the Defender is not setup with even uj angles to start with, and some models (TD5 etc) are not setup with 180 deg opposing UJs to counter this but this only makes it harder to judge what is right and what is wrong.

Not an easy one to answer 100% correctly!

I personally like the steering feel at the altered angle and see no reason to alter the actual steering caster angle back to standard, Prop angle yes, because as you point out, the gearbox end is changing out of sync to the axle end on the Defender front axle, and as it is only setup from the factory as "optimum position" at the designed ride height, this needs addressing for vibration free cruising. But strange to do steering caster only!

Lara

Link to comment
Share on other sites

Lara, I think you misunderstand why castor corrected radius arms are bad.

Castor corrected radius arms are designed to fix the CASTOR angle- the steering angle which the swivels are designed to aslo fix.

The key difference is that in fixing the castor angle, these radius arms worsen the PINION angle. They do not fix it. This makes driveline vibrations worse, hence the need for a better solution, hence the redrilled swivel balls.

I'm not sure what redneck is saying about 1 UJ, but the latter part of his post is certainly correct.

Link to comment
Share on other sites

Hi,

It seems from this post that either I have totally misunderstood what you are saying OR you are not understanding the workings of Universal joints!

These not being "constant velocity" joints, You can or "should" NEVER use only one UJ in a drive-line. It causes massive torque reversals and would cause (like you get without caster corrected arms or adjustments to the diff angle) bad drive-line vibrations as the UJ accelerates and decelerates without the equalising UJ on the other end during it's rotation cycle.

It is however extremely hard to see what is correct or not as the Defender is not setup with even uj angles to start with, and some models (TD5 etc) are not setup with 180 deg opposing UJs to counter this but this only makes it harder to judge what is right and what is wrong.

Not an easy one to answer 100% correctly!

I personally like the steering feel at the altered angle and see no reason to alter the actual steering caster angle back to standard, Prop angle yes, because as you point out, the gearbox end is changing out of sync to the axle end on the Defender front axle, and as it is only setup from the factory as "optimum position" at the designed ride height, this needs addressing for vibration free cruising. But strange to do steering caster only!

Lara

My fault for not explaining myself very well.

My comment about using one u.j was to try and explain that the front u.j. is not there because of the travel in the suspension but to take up manufacturing misalignment, twist of the axle and as you say torque reversal. The front end on a land rover is effectively the same as a torque tube axle as fitted on the model 'T' ford.

A double carden shaft is the ideal solution.

My real problem is the fact there are numerous manufacturers selling a bent bit of metal as a solution to a problem that needs a lot of thought and considerably more work than they would have you believe.

Link to comment
Share on other sites

IMHO slotting the swivel balls is a better method to correct castor than castor correction bushes or radius arms, because the last mentioned methods have an adverse affect on the pinion angle and worsen uni-joint operating angles etc.

Disty, in post #13 provided a link to one place (there are others here in Aus) that have been slotting the swivel balls for a great many years. This has proven to be a very suitable method, with no associated problems. Some people have tried adding extra bolts in normal round holes between the existing, but this has proven unnecessary.

Some people (possibly those advocating welding the old holes) may think that slots are bad because the bolts can't carry the shear load in the direction of the slot. The facts are that the proper bolt pre-tension ensures that the joint carries the shear load through friction - even with stock standard holes, if the friction fails allowing the joint to slip so that the sides of the hole bear against the bolt shank so the bolt carries the shear load, then the bolts must have become loose and joint failure with missing or broken bolts is likely to follow.

Small clearance holes are better than slots, but the reason is not so bolts instead of friction carry the shear load - but this is digressing too far of topic and the explanation is too technical for many. However I must emphasise slotting the holes only enough to rotate the swivel ball sufficient to fix the castor problem.

Link to comment
Share on other sites

If i remember correcly most Simmbugghini's and i know for a fact my one has redrilled swivels and most have been and still will race for years as they are

A, the weigh an awful lot less than a fully loaded Land Rover

B, the do an awful lot less miles than the average land Rover

C, most if not all are not sharing the roads with cars carrying other people and their kids.

If you are going to affect castor correction on the cheap then far better to alter the axle case as Les did (and reinforce the joint) than start hacking around at the swivel joint.

Does anyone know how swivels are made? because if they are cast then the modification should be an MOT fail! Just ask yourself why part modified in thsi way are not sold commercially if it's such a cheap modification.

Link to comment
Share on other sites

I'm going to get some reliability engineering done on these before maybe selling them, so we should see what the reduction in strength is then. I would suspect they are not far off stock.

If they prove themselves to be strong, I would say we're better off with people driving on these than on stock if they have a lift- wandering steering on the roads is definitely not a good thing...

p.s. these parts were available commercially from britpart. Nobody is sure if they still sell them, but there doesn't seem to be any horror stories like there are with castor corrected radius arms. Do those pass MOT??!

Also, these are first cast and then machined. You can see the marks from the machining device quite clearly on both sides of the base. Clearly when they are made the manufacturer has no problem machining them down- and for that matter neither do I!

Link to comment
Share on other sites

Hi, just thought I would add a little note to this on longevity, I have been running my '77 bobtail with a 2" lift and slotted swivels for 20 years! When I did my lift the first time, the option to buy all these off the shelf kits,arms,bushes etc just simply did not exist so the only way was to look at the problem from an engineering/goemetry viewpoint.

Considered cutting the axle tubes and rotating ala Les,but the potential catastrophic failure if all the welds failed at once was the end of the axle plus wheel coming off. Not that I am doubting the quality of Les' welding at all or the fact that it is/was a very common way for comp safari builders to do the mod, just not for me on my road going toy.

As my motor has 6 bolt swivels I slotted for 3 degrees and added a 7th plain drilled hole with a dowel pin to lock the rotation but as bush65 correctly points out, the rotation is prevented by the face to face friction not the shear loading of the bolts so long as the bolts are at the correct torque.

Link to comment
Share on other sites

Just another idea, but for the sake of developing bolt on kits, could one not create a "wedge" to sit under the spring seat and level it out? Not sure if the shock mounting would become too short for this, but it might help a little?

Thanks for the input pitmole- clearly the longevity of this solution is fine!! How did you drill into your axle casing?

Link to comment
Share on other sites

I think if you 'just' put a wedge under the spring seat, then it would fight the radius arm, which would be the winner out of the two. Rotating the swivel ball , cuttng the axle, or cranked radius arms seem to be the only way to do it as far as I can see, as they are the main things that set the castor.

Les.

Link to comment
Share on other sites

Slotted, welded, remanufactured - however your slotted swivels, fabricated radius arms or aftermarket window winders were created, if you fit them and their failure contributes to a fatality you will go to prison.

That's why the big boys do a great deal of analysis and materials testing to make sure that their components won't fail, or to prove that a failure would be genuinely unexpected if it does occur. Hats off to Disty for looking at some reliability engineering, but you might eventually need to satisfy a jury that your testing was sufficient to show a failure would never occur in service. The issue here is usually in understanding the maximum loads that the item could see in service.

Link to comment
Share on other sites

...

The real question is, is anybody interested in laying down the bucks for these? (If not, I may as well stop here!!)

Picture attached.

swivel-top.jpg

I strongly advise against making the slots oversize in width as well as length - from the machining marks it looks like they may have been. The fatigue strength of bolts is reduced when oversize holes are used, which is why my previous post said that the length of the slot should be just enough to correct the castor.

When the bolt is pre-tensioned a region of metal around the hole in the flange is compressed by the underside of the bolt head. It is important that the cross sectional area the region in compression is greater than the cross sectional area of the bolt. The ratio of these area affect how much the tension fluctuates in the bolts, which directly affects the fatigue life of the bolts.

Link to comment
Share on other sites

I think if you 'just' put a wedge under the spring seat, then it would fight the radius arm, which would be the winner out of the two. Rotating the swivel ball , cuttng the axle, or cranked radius arms seem to be the only way to do it as far as I can see, as they are the main things that set the castor.

Les, I only meant in addition to another method (other than your pretty much perfect rewelded axle!)

In response to Bush65, the holes are elongated to the absolute minimum and not more. Is that what you were referring to?

To Turbocharger: I suppose this then becomes the crucial stage. It seems if you fit somebody like QT's radius arms you shift the blame to them, whereas a homegrown solution could be a problem. I very strongly doubt that anything would happen to these, but I think I will do some testing to check whether under normal conditions they perform any worse than standard, just to be sure!

Link to comment
Share on other sites

...

In response to Bush65, the holes are elongated to the absolute minimum and not more. Is that what you were referring to?

...

I was referring to 2 different dimensions of the slot.

One was the length of the slot arc - if for example 3* of castor correction is required, then the slot should only be 3* and no more.

From your post it seems as this is what was done, but I was concerned that someone else may also do this and make the slot 6* so that they could go more if they fit a bigger lift later. If they were to then bolt it up with the bolts in the middle of the slot amount of material in the flange under the bolt head is greatly reduced and this will reduce the fatigue strength of the bolts.

The second dimension I was referring to was the width of the slot. From memory (I stand to be corrected) the stock bolt holes are 10.25 mm diameter. Whatever the diameter of the stock hole is, then that is how wide the slot should be. It should not be opened out by using a larger diameter slot drill (assuming that type of cutter was used in the milling machine and that is the terminology used in the UK to identify that particular type of milling cutter). As I have said, oversize holes reduce the fatigue strength of bolts.

In the pic I can't detect any of the original hole surface, which suggests that a larger diameter slot drill was used.

Link to comment
Share on other sites

Ah, I see your confusion now! The holes are NOT oversized- it's just that the teflon coating doesn't seem to go down into the bolt hole, making the original holes look enlarged, when they are in fact not touched at all. There is a slight W shape from the second hole not meeting the first at the widest part.

I see your points though and they are of course valid. I'm just glad I didn't make those mistakes in hindsight!

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy