Cracked Swivel Housing, How Common ?

[bill van snorkle]

Here're four pics from Mr. Bill with his own notes

From left to right:

1. View from front of portal/swivel housing assembly and showing extra kingpin strut.

2. Worms eye view of steering arm stiffening rod and stiffening bracket from portal box to bottom swivel pin.

3. At right of photo, stiffening rod from steering arm to portal box.

4. Ear welded onto swivel ball and axle housing flange to prevent torque from loosening or shearing off the 6 flange bolts.

Some may notice the double thickness swivel ball flange.

Thank you Michele. These photos were taken some time ago after I fitted the stiffening rod between the steering arm and the portal box, and at the time I didn't notice the crack on the bottom of the swivel casting emanating from the inner front bolt hole, which is just visible if one clicks on photo number 2.

Anyway, it should be clear that I haven't taken any short cuts when it came to compensating for the extra leverage applied by portal hubs

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The weld on the ear on photo number 4 is strong enough but isn't pretty because my petrol powered 240 volt generator set had a bit of a cough part way through the weld. I will re do it while I am fitting the 'new improved' swivel housing.

[Team Idris]

The third king pin isn't sufficient. Although it looks to hold the assembly in plain when loaded by hand, it won't be strong enough to take stress off the lower OE kingpin under driving forces. This is because the single sheer third kingpin will have more flex than the other two for a number of reasons. If it is given an extra brace to make the third kingpin double sheer, any flex from the Young's modulus of the steel will be reduced giving the OE bearings an easier time. Coupled with the swivel housing work you are already doing, it will then be a very resilient set up

[bill van snorkle]

The third king pin isn't sufficient. Although it looks to hold the assembly in plain when loaded by hand, it won't be strong enough to take stress off the lower OE kingpin under driving forces. This is because the single sheer third kingpin will have more flex than the other two for a number of reasons. If it is given an extra brace to make the third kingpin double sheer, any flex from the Young's modulus of the steel will be reduced giving the OE bearings an easier time. Coupled with the swivel housing work you are already doing, it will then be a very resilient set up

The 3rd kingpin is 19mm heat treated 4140 and also replaces the original, and I couldn't make it flex if I tried. You missed (I didn't mention) that the strut is adjustable with a left and right hand thread for pre tensioning purposes.It is also angled upwards towards the axle, which places the bolts and swivel pin bracket in compression because the rose joint slides up the king pin when the rod is tensioned.As I mentioned earlier, if I remove the top swivel pin altogether I still can't rock the assembly even with the leverage of a 36" diameter tyre. Try that with a standard axle for comparison.

[Soren Frimodt]

What if you stopped using the lower kingpin for the trackrod and fabbed up some stronger arms to bolt/weld onto the portals, making the trackrod connect directly to the portal boxes instead? You sort of are half way there with the short arms you've already fitted from portal box to steering arm

[bill van snorkle]

What if you stopped using the lower kingpin for the trackrod and fabbed up some stronger arms to bolt/weld onto the portals, making the trackrod connect directly to the portal boxes instead? You sort of are half way there with the short arms you've already fitted from portal box to steering arm

The lower king pin is used for the drag link. the upper kingpins do the track rod. The thing stopping me from doing that Soren is insufficient space within the confines of the wheel rim, and that it is not permissible to make ones own steering arms here. And it's not the arms that need to be stronger on later vehicles, its the studs. I have sheared the steering arm studs on a normal non portalled series 3 when winching out of a deep hole without bending the steering arm.If you plot the stress path from the steering arm , through the strut to the portal box, you will see that this does relieve the studs of much of the shearing force from steering input. At any rate I am now convinced that the crack started in the one thousand odd miles before I introduced the strut between the steering arm and portal box, and I just didn't pick it up all those years ago. I'll let you know if I am correct in another decade or so.Lol.

PS. a right hand side steering arm from a left hand drive series 3 would allow me to fit it on top, thus relieving the bottom studs from steering shear forces also. But I haven't got one, hence the short strut to the portal box.

[Snagger]

If there is even the slightest misalignment of that lower swivel rose joint, due to manufacturing tolerances as much as any other cause, then you could have it applying unwanted forces to the original swivel points. Regardless, the bracing between the portal and the swivel is applying all its lateral force to the lower pin securing studs, and thus their fitting holes in the swivel housing that have broken. I'm sure the cracking is as a result of the combination of the portals' moment and the incorrect Ackerman angle.

[bill van snorkle]

If there is even the slightest misalignment of that lower swivel rose joint, due to manufacturing tolerances as much as any other cause, then you could have it applying unwanted forces to the original swivel points. Regardless, the bracing between the portal and the swivel is applying all its lateral force to the lower pin securing studs, and thus their fitting holes in the swivel housing that have broken. I'm sure the cracking is as a result of the combination of the portals' moment and the incorrect Ackerman angle.

What misalignment are you referring to Snagger ? The bottom swivel pin is a straight one piece shaft, longer than the original and replaces the original, in addition to providing a pivot for the rose joint. It is much harder to machine an out of true shaft than a straight one, and the pin reads true on both ends with a dial indicator when I swing the arm in a lathe. Even if the rose joint was manufactured out of true, the pin is a neat but sliding fit inside it and can turn inside the ball.The brace between the portal box and the swivel is fastened by the 2 outer studs, which are undamaged nor their threaded holes. The cracks emanate from the 2 inner studs, which were dowell studs and obviously bore the brunt of the steering shear forces prior to me fitting the strut between the steering arm and portal box. Regardless, I have to work with what I have, and having the actual components in my hands as opposed to mere photos, I am better able to ascertain why the failure occurred and how to prevent it occurring in the future. With the backups I put in place, the swivel assembly was still rigid and probably would have survived indefinitely had I not been determined to track down the persistant source of oil seepage that has plagued that swivel assembly for the past decade. The thicker stiffer oil seal retainer, plus dowell bolts everywhere and deburring stress concentrators should optimise the strength of the basic design.

Thanks for your interest, but as you say, we will agree to disagree on the affects of parallel steering vs Ackerman angles. According to the book on suspension principals that I have," Ackermans theory is based on a false premise, as he ignored the slip angles that a tyre develops when cornering". Large section, low pressure offroad tyres develop much greater slip angles than the tyres back in Ackermans day. I could have, and still can easily convert back to standard Ackerman angles if I was unhappy with the result, but after extensive testing with and without (5 minutes work to change the trackrod ) I was convinced.

[Phil Hancock]

AFAIR the 2 dowel studs should be on opposite diagonal corners.

[bill van snorkle]

AFAIR the 2 dowel studs should be on opposite diagonal corners.

You are correct. But as you can see, the portal brace is 3/8" thick and required longer studs on the outer 2 holes. Lacking longer dowell bolts at the time I moved the other original dowell stud to the other inner hole. Anyway, I now have 4 x M10 dowell bolts and lock tabs on the replacement, The oversize swivel pin hole in the Stage One casting would have caused an unequal sharing of the load on the studs. The replacement is a neater fit, and as there is no need to have the bottom steering arm easily removable, the unit can be more permanently assembled with high strength Loctite.