Lower Control Arm, More Caster

I have ruminated on this for quite some time. A while back I gave in to the mocking from the spare set of arms leaning against the shop wall.
It's a work in progress and this 1st post will likely be the place for updates, maybe subsequent posts, not sure. Not even sure on the title.

The original thought was to drill out the outer two rivets and pivot the forged ball joint mount arm forward, file out the over lap and replace with bolts. A tentative project name "The Rivet Pivot" sounded good. That soon changed. A lot of thought went into the differences between the functional properties of a large, hot industrial rivet vs a nut/bolt.

Yellow X's, drilled out.
Arm swung forward closing the gap at the white arrow.


To be continued.

 

The rest of the story will reside in this post......I think.

This stalled project got revived when @Squeaky Penguin started this thread.
https://www.tacomaworld.com/threads/so-you-push-your-1st-gen-offroad-what-cracks-next.631359/

Below, the actual work begins.

Drilling out the gnarly rivets.
I had no idea what the rivet shank diameter was.
Supporting the CA on the drill press table would be easiest right side up so the drilling would commence from the top side. I figured removing a rivet head would reveal the shank diameter. After the head laughed at an air chisel, I drilled into the rivet head about 3/8" with a 7/16" bit then carefully ground off the remainder. 9/16" looked to be the drill choice. At this point I figured "just beat the rest of it out". Not happening, I tried this after drilling to numerous depths. Not until most of the shank was drilled would the mallet prevail.
I started thinking about the relevance of how this type of rivet both clamps the parts together and expands inside the hole, filling irregularities. Notice below, a step just under the rivet heads. This shows how the rivet had swelled into the slightly larger hole in the sheet metal.





The forged arm was pounded forward but was surprisingly tight. Then I noticed the irregular head overlap and just how small it was. Check the lower hole in the above pic and the heads below, 3/32" on one and a "light" 1/16" on another. Might have something to do with the hard core folks finding cracks radiating out from the hole. One point in favor of a bolt.






At this point obsession kicked in. Did the remaining rivet loosen? What does the hidden part of the forging really look like anyway?
With the third rivet out, wiggling the forging out was still amazingly tight, unbelievably tight. This was a good thing.





Attention now shifted to the bolts and "fit".
I considered boring the BJ arm holes to tightly fit some bolt, metric or SAE. Even gave some thought to knurling a bolt shank to effectively expand it to a good press fit.
An SAE grade 8, fine thread 9/16" bolt was just a few thou undersized, so I went with it for now. I originally had envisioned flanged bolts but they proved difficult to find. 3" length "partially threaded" provided close to an optimal amount of unthreaded length, extra length would be cut off.
With the arm in it's intended position it was time to rat tail file the overlap. After a few strokes it was apparent the sheet metal was more than "mild steel". The fresh US made file seemed to slide across rather than cut very fast. A die grinder and a 3/8" solid carbide burr made short work of that.







This shows the elongation of all the holes. The inner is left alone. The upper and lower rear were getting a little close to the edge.
The arrows point to where Toyota skimped on welding. Easy enough to continue that to the end.
Hmm, welding hardened steel. I'll think about that later.





Time to see what all had been gained.
With the modified left LCA sitting on top of and mirroring a stock right, the ball joint taper is just shy of 9/16" further to the front. A bit more than anticipated.





So what does 9/16" mean in terms of caster degrees?
The distance between the center of the upper and lower BJ ball is the figure needed to calculate the now "built in" caster degree change.
The total length from BJ tip to tip was measured at 22.5". Two naked OE upper and lower balls from the visual aids bin were placed at the 22.5" figure. This resulted in a nice round 17" center to center. Call the 17" figure the radius of a circle. Figure the circumference, divide by 360 and the result is inches per degree.
R=17"
C=106.814"
1°=.2967"
So 9/16" would represent 1.8958°. For simplicity not talking arc length here.





Pretty happy with where this was going, thoughts turned toward strength and overall strength of the area. A plate to spread the loads seemed appropriate. Welded on or not, yet to be determined.

Cut from 3/16" hot rolled, freehand with a jig saw and "tight radius" blade. Mill scale dissolved with a quick swim in the acid bath. Edges dressed and broken, holes lightly chamfered and ready for some whimsy.
I know, it's just a dumb little plate.






I opted for "nuts up" to guard against damage because....





As it sits now with more whimsy.





Future thoughts.
Weld the nuts to the plate with no washers for a bit more CV clearance.
Think about plating the bottom.
Determine the largest diameter at the right spot on a shock that will still clear the CV without moving the lower shock mount forward. My second revision 2" SAW looks to clear fine.
Try it out without welding the plate just to see if anything would move. Same for the now oblong holes.
To try this out, I need to do it to the other side and buy some Whiteline bushings.

That's all for now.

 

I definitely think that plate (top and bottom) would need to be welded to keep the forged arm from pivoting back into stock position after repeated wheel impacts.

Otherwise, ~2 degrees caster gain is terrific - a lot of folks could retain the factory upper BJ position with that gain at the bottom, I'd think...

one question - I see that the forged arm is asymmetrical - any benefit to swapping sides? Perhaps you could gain a non-slotted hole with maybe more plate material around it? (I'm having trouble visualizing it without drawing it up.)

 

Super interested in how this comes out!

 

Interesting.

I could be talking completely out of my ass, but my thinking says if you change the position of where the LBJ meets with the LCA, but the LBJ itself remains in the same position, isn't the LBJ under constant tension/stress?

 

No, Moving the LCA arm takes the LBJ/bottom of spindle/CV shaft with it creating more "built in" caster over the stock adjustment cams, the whole point. Just like moving the upper ball joint to the rear with after market upper arms. Working with the lower arm, the caster increase also moves the tire forward instead of rearward into the fender well (pinch weld pounding) as with aftermarket upper arms. Along with cost that's another major point of the surgery.
As far as steering geometry goes the only real detriment here is screwing with what is known as "Ackermann Geometry". Google that, I don't think this small change will be noticed. Ackermann angles mostly come into play in tight turning situations. Also note that Toyota makes no compensation to this geometry between long wheelbase, ex/doub cabs vs reg cabs other than very slight alignment specs.

I will be explaining all of this as it progresses.

 

this.

 

You did see where I said I could be talking out my ass right?

You got me interested in this.

 

Post #2 brings things to the present.
It's a longy because........... heck I don't know.

 

Being I'm not good with exact measurements - did you measure how much this pulled the ball joint in as well? Guessing it's not enough to matter? You also now have me wondering about my welding of cracks on the stock LCA.

I'd also wonder about those bolt heads catching on rocks.

Probably should have just bought the Solo LCAs when they were on sale.

 

Digging on the whole idea of this. I'm watching to see where your head is at after installation.

 

If there was a plate on top and bottom that was welded into place then it would stay in the forward position for sure.

 

Don't sell yourself short, you understand the big picture beyond most.

The LBJ does move "in" but it is insignificant. I did consider it. To visualize for yourself try this. The distance from the inner of the three bolts (pivot point) to the BJ taper is just under 6". So take a ruler or anything that can represent a 6" line. Hold one end stationary and swing the other 9/16"ish. Not much "in" can be seen.

I wouldn't sweat welding on the LCA, just something to keep in mind. Like welding on the frame. Not too much in one spot at one time like with say, a rear frame plate. I suspect the LCA and frame are very similar grades if not the same.

The bolt "headus protrudus" is definitely a concern and why I went "nuts up". The nuts are significantly taller than the bolt head. If someone wanted to try this mod and have it be a "once and done" then heck, just weld them to the arm after torquing or go with any number of protective methods. Think skid plate fasteners or diff drain plug protection. There should be no reason to ever remove these bolts. By the way, max torque on these bolts is 129 lbs.

Another thing I might not have stressed enough is CV clearance to the lower shock. The exact brand specific shape/profile could be the difference between hit and miss. The big diameter shock body folks would have additional concerns. With that comes moving the lower shock mount forward. That's fine but it also effectively increases CV angle just like additional ride height.

Absolutely
When I think about strengths/stresses, I keep coming back to the seemingly ridiculously small "clamping area" of the factory rivets and I feel better.

Not sure when or if I will take this further. I embarked on the project out of curiosity and I don't really need the additional caster. At this point I am satisfied that it is a viable concept.
For now it's a decoration on the shop wall.





Shot of a ground down jig saw blade for tight radius cuts.

 

Sorry, must have missed your reply.
Yes, I considered swapping sides. I made a template and any way I positioned it would not yield a virgin hole. Further, the overlap on the existing holes would be 3X as bad and include some cutting on the inner hole. Further still, it looked as if the forged arm itself would hit the front of the control arm before any caster gains, so that area would need a little cutting as well.

 

Definitely need to weld that. LCAs take most of the stress on impacts (which is why they're much heavier than the upper) and you can't tension bolts hard enough to keep them from sliding. The force on the lower ball joint will be rearward which means they'll be out of alignment after just a few hits. Otherwise this is a solid strategy.

Not sure if it was mentioned above but you can't swap sides because of the strut mounting point.

It changes the angle exactly as much as you gain in caster. This wouldn't put any additional stress on the balljoints compared to an upper that offsets the upper just as much. Ball joints aren't really stressed from position until they start reaching the limit of how far they can pivot when they start to use the edge of the socket as a lever.

 

Nice work OP...the real genius is the Binford branding though.

 

Welding or not welding is not a question here.
I have no issues with welding the plate/s and would definitely do it, just after some testing for fit, function and curiosity. Might just want to move that BJ back an eighth just to be safe, because of that shock in the way. Thought that was implied.
Filling the little "crescents" with weld would be another equally important thing and was in the original plan.

Reread 3rd to last line in post#2

 

I was talking about swapping the forged part from one LCA to the other - is that what you were talking about as well?

 

Oh I thought you meant the complete arm. Looking at the picture, I think the insert piece is pitched forward on each side so of you swap, you will likely end up with the opposite of what you're looking for.

 

yeah I thought that pitch difference might allow for a clean (non-slotted) hole - but the OP investigated that.