Polyurethane Bushings?

[David T]

While a full plate may be the strongest option, a few stiff pieces across the bottom can achieve the same effect with less weight and allow you to see inside and not trap dirt and water. Anyone attempting to modify or weld a critical part of the suspension must know what he is doing or you can damage the part in such a way as to cause it to fail. Better to leave it alone if you don't know what you are doing. The biggest cause of damage to the lower control arm is tow operators hooking their recovery hooks to them and pulling on them to move or secure the car. Next comes hitting things in the road followed by improper procedures removing and installing ball joints and/or wrong ball joints. I haven't seen one rot to the point of collapse, the frame gets there way before the LCA but I suppose it can happen.

[MikeWard]

The UK show 'For The Love of Cars' which was shown a couple of years ago, used a full plate with several holes in it for added drainage. So that is an alternative single piece strengthening plate if someone felt that added drainage was required.
lca_plate_holes.jpg
Given that the LCA is open at each end, plus the hole in the middle there should be more than enough drainage for any water which may get in there. Weight wise it would be a very insignificant saving using two piece vs one piece.

Agreed though, given that it is a critical part, any work like this needs to be undertaken by someone who knows what they are doing.

[Morpheus]

I'm putting my front suspension back together and I had a few questions for the group:

Is there a particular orientation these lower ball joints should be installed? I can't see that there are any alignment marks on them. They are from DMC Europe, which i presume are DOCUK units.
IMG_0175.jpg

Should I use silicone spray lube when pressing in my poly LCA bushings? The poly ends went in fairly easy by hand, but the inner sleeve seems to be a bit oversized. Should I insert the sleeve before putting in the bushing?
IMG_0176.jpg

I have the lower ball joint reinforcement collars as well. They are flat on one side and have a beveled edge on the other. Which way should these be installed on the LCA?
IMG_0177.jpg

Appreciate the help, guys.

[MikeWard]

They are from DMC Europe, which i presume are DCUK units.

Ed has had his own ball joints made, they are not the UK lower ball joints.

[ed uding]

There is no direction for the ball joint it work in any direction, it is not a cheap after market product.
Silicone is ok to install the bushing.
I dont know your source of the collar ring, but we don,t use/sale it.

Regards Ed
www.delorean.eu

QUOTE=Morpheus;212379]I'm putting my front suspension back together and I had a few questions for the group:

Is there a particular orientation these lower ball joints should be installed? I can't see that there are any alignment marks on them. They are from DMC Europe, which i presume are DOCUK units.
IMG_0175.jpg

Should I use silicone spray lube when pressing in my poly LCA bushings? The poly ends went in fairly easy by hand, but the inner sleeve seems to be a bit oversized. Should I insert the sleeve before putting in the bushing?
IMG_0176.jpg

I have the lower ball joint reinforcement collars as well. They are flat on one side and have a beveled edge on the other. Which way should these be installed on the LCA?
IMG_0177.jpg

Appreciate the help, guys.[/QUOTE]

[DCUK Martin]

Someone on the old forum FEA modeled the system and proved the lower arms do not benefit from being "boxed", something that is pretty obvious with a bit of basic structural analysis. All the "boxing" does is increase bending strength in the XZ plane* - ie carrying the car's weight, and I don't think you'll find any instances of a failure there. It also improves torsional rigidity which is perhaps a bad thing as the arm is put under torsion as the suspension moves up and down thanks to the roll bar. Boxing can also create lovely moisture traps.

Most are damaged by improper use as tie-downs or a failure of the roll bar bushes to prevent excess rearward swing when under heavy braking.

Get Toby's bush kit and other than corrosion protection, leave the lower arms alone is my advice.

(X is left/right, Y is front/back, Z is up/down)

[Morpheus]

Someone on the old forum FEA modeled the system and proved the lower arms do not benefit from being "boxed", something that is pretty obvious with a bit of basic structural analysis. All the "boxing" does is increase bending strength in the XZ plane* - ie carrying the car's weight, and I don't think you'll find any instances of a failure there. It also improves torsional rigidity which is perhaps a bad thing as the arm is put under torsion as the suspension moves up and down thanks to the roll bar. Boxing can also create lovely moisture traps.

Most are damaged by improper use as tie-downs or a failure of the roll bar bushes to prevent excess rearward swing when under heavy braking.

Get Toby's bush kit and other than corrosion protection, leave the lower arms alone is my advice.

(X is left/right, Y is front/back, Z is up/down)

Thats all I did... had the arms blasted and powder coated and re-assembled with Toby's and Ed's poly bushings. Also added Ed's stainless LCA braces for added support.

[Drive Stainless]

All the "boxing" does is increase bending strength in the XZ plane* - ie carrying the car's weight, and I don't think you'll find any instances of a failure there.
(X is left/right, Y is front/back, Z is up/down)

I find it very difficult to believe that boxing does not increase bending strength in all three planes.

For example, if I place the LCA on its side in a 50-ton press and apply force, the LCA will bend in a "U-shape" until the ball joint is almost touching the bushing. If I had boxed the arm and applied the same procedure, it would require more force since the added sheet metal will deform. As we know, metal does not deform without resistance, which makes it suitable as a material for construction generally.

If it were true that boxing did not increase strength in the Y plane, then you should be able to perform the aforementioned pressing procedure without incurring any damage to the added sheet metal; you cannot.

I would agree with you only if you could show that the arm could be bent in the Y plane without causing damage to the added sheet metal.

[DCUK Martin]

I find it very difficult to believe that boxing does not increase bending strength in all three planes.

Indeed. Can you explain how the arm is loaded along its length in anything other than bending (carrying the car's weight), and along its own axis in compression and tension?

All the failures I've seen relate to the arm being dragged rearward too far. Boxing will, if anything, make breakage more likely in this scenario.

To clarify: Yes, boxing does make the arm stronger but not in any way that's of use on the car. The original design is good, but assumed the continued health of the roll bar bushes and the sympathy of people tying the car down.

[David T]

Indeed. Can you explain how the arm is loaded along its length in anything other than bending (carrying the car's weight), and along its own axis in compression and tension?

All the failures I've seen relate to the arm being dragged rearward too far. Boxing will, if anything, make breakage more likely in this scenario.

To clarify: Yes, boxing does make the arm stronger but not in any way that's of use on the car. The original design is good, but assumed the continued health of the roll bar bushes and the sympathy of people tying the car down.

"Boxing" the LCA's will add a lot of rigidity in all planes. It will also add "Unsprung Weight". The LCA's were intentionally designed for maximum strength where they needed it and not as much were it wasn't needed. Lotus was, and is, all about "adding lightness" and in this case not adding weight were it isn't necessary. IMHO it can't hurt to box them but you do have to take precautions so you don't trap water and dirt. The LCA's won't be strong of they rot! BTW the LCA's are also twisting under braking loads and boxing them would certainly help with that.