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TC rod pivot relocation / Bad Dog subframe connectors / Slotted Crossmember


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Not too much time to play in the garage today, but I did get the seat bracket modded and in. I had to cut loose the brace that went from the front of the bracket to the rear. Luckily it was only tacked in place, I had planned on welding it in solidly later. So, cut the tacks, get it situated nicely right above the frame rail, and tack it back in place. Then I added a second tube on the other side, so now the seat is effectively attached to both sides of the subframe connector. Then I laid a big weld right through the floor into the frame rails. This was quick and easy to do, and I'm stoked on it. My original welds to the floor were kind of messy because I hadn't straightened out the floor yet. I'm sure it would have done the job the other way, but now it really looks like I know WTF I'm doing! Just a few pics today.

 

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Thanks for the positive feedback Mat, it is appreciated!

 

OK more stuff for everybody. Took some measurements, and here's what I came up with.

 

Stock LCA pivot height from frame rail: 3 3/4"

LCA pivot height after I adjusted out bumpsteer: 3 5/16"

Difference: 7/16" (makes you wonder about all those up 3/4" and up 15/16" bumpsteer mods, eh?)

 

Max adjustment allowed by my slotted crossmember: 2 5/8". So the MAX I can move the LCA pivot up is 1 1/8" from stock.

 

Stock TC rod height from frame 2 3/4". This surprised me. For some reason I had assumed that the LCA and TC pivots were going to be level. They are not. Luckily, the TC pivot is 1" closer to the frame than the LCA, so it's pretty easy to do the math to figure out where everything needs to be.

 

The problem is that with the pivots where I had them before at 3 5/16" above the frame, I don't have enough room inside the 2x3 tubing to put the TC pivot in the correct spot. Here's a pic to illustrate the problem: DSCN0907.jpg

You can see in this picture that if the pivot were centered at 2 5/16" the top of the bolt would be right at 2 5/8" which means it's right where the tube starts to bend. So a sleeve would not fit there. I could probably get away with raised the pivot another 1/8" closer to the frame, but I won't be able to preserve the factory geometry exactly. Also I was hoping to use a cone shaped spacer to spread the load on the box, instead of a 1/8" wall tube which would barely fit if I raised the pivot.

 

While I don't think that this is a terrible problem since none of the other factory geometry has been held sacred in the past, I'm now starting to wonder about getting different tubing for the TC rods. If I got a 2" x 4" tube I could definitely get the geometry right, and also could play with MORE dive as well as less. My concern in using a bigger tube is that the TC mount would be inherently less stiff. The 2x3 tube is HEAVY, so I really don't want to increase the wall thickness past 3/16" to try and make it stiffer.

 

So, what do you all think? Go with the 2x4, or stick with the 2x3?

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I was kind of considering something like that Cary. I was thinking instead of making the angled area of the frame flat like I had originally planned, if in instead made a 1" tall pedestal and then put the 2x3 tube on top of it, then I'd get basically the same effect. Problem is then I'd have to build a pedestal.

 

If I took your suggestion and got a 2x2 square tube, then I guess I'd have to make a mount to put on top... or were you suggesting that I could then put the 2x3 tubing on top of the 2x2 tubing? I guess I don't know what you have in your mind when you say "the mount".

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If I took your suggestion and got a 2x2 square tube, then I guess I'd have to make a mount to put on top... or were you suggesting that I could then put the 2x3 tubing on top of the 2x2 tubing? I guess I don't know what you have in your mind when you say "the mount".

 

Sorry, I guess part of the confusion is that we're upside down here. What I was thinking is that you'd have a u-bracket the bolted to the bottom (top in your picture) of the square tube. Then you can offset this bracket using a spacer to adjust dive.

 

Does that help?

 

Cary

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Yeah that would work but it would limit the amount of adjustability I think. Plus the guy who built the clevises that I used in my previous setup made them too narrow and they bind at a little less than full droop, so I'd be reluctant to use them again, and if I'm going to make a new clevis I figure I might as well just get a taller tube and retain the adjustability.

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I know this might sound a little crazy, but what about making a circle track adjustable panhard rod mount at the TC rod pivot? It basically a high strength vertical slot that has a post/clevis with the post riding in the slot and adjustable vertically via a jackscrew. The clevis captures the rod end on your TC rod.

 

Speedway engineering has examples of what I'm talking about, part numbers 916-45000, 916-45585, 916-45493.

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Found it: http://www.speedwaymotors.com/xq/aspx/paging.yes/dept_id.103/display_id.3393/qx/Product.htm

Looks interesting, and I have some 1 1/2" square tube. Unfortunately it also looks really tall, so if it were mounted under the Z it would be a ground clearance issue. Maybe there is a way to shorten the threaded section. Then again... $250??? Maybe I'll just keep working on something else.

 

Interesting idea John. Very interesting.

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I was thinking more llike this:

 

http://www.speedwaymotors.com/xq/aspx/display_id.3392/qx/Product.htm

 

You can't use these products because, as you said, there would be ground clearance issues. But I think the design can be incorporated in an adjustable height TC rod mount.

 

And I meant Speedway Motors not Speedway Engineering. My mind was thinking one thing while my fingers were typing another.

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I see the merit in that type of system, but for the money I think I can slot the hole and adjust it the hard way. This is probably going to be a lot like the slotted crossmember, where you figure out what works best, set it and never touch it again. I don't anticipate adjusting the dive or anti-dive between autox runs. If something like that were used for the control arm pivot location, that might be a different story...

 

I did some checking and I can get 2x4 tube in .25 wall (can you say heavy?) or .120 wall. I feel like the .120 wall might be too thin. Still thinking about putting the 2x3 tubing up on a pedestal.

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Think I got it all figgered out. :D

 

I think I'm going with the pedestal idea. I measured, and the actual width of the frame rail right above the TC rod bucket is 2.5" across, the frame rail narrows right there so that there is more clearance for the TC rod to swing. The lip there is .5" so basically the frame part is 2" with a .5" piece of sheet metal sticking out the side. You can see how it narrows in this picture:

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I have a whole bunch of this 1x1x.063 tubing, so I had this idea: why not contour the tubing to fit the curve of the frame rail, and weld 2 sections right next to each other. I can already hear John, "that's using almost twice as much material as necessary. True, but it's easy and it only weighs maybe 1 lb. I cut the shape with a jigsaw, for those interested. So here's my first attempt at it:

 

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I think this will provide a solid base to attach the TC bucket to. I'm also considering cutting the flange off of the frame rail so that I can weld the outside tube directly to the vertical part of the frame, instead of just the flat sheet metal flange.

 

Looking for opinions on this course of action good, bad, or otherwise before I proceed.

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Maybe this will help. Got out there yesterday and used my cheesy HF band saw to cut the tube into the TC brackets. MAN, THEY CAME OUT BITCHIN!!! I'm really impressed! I tightened up the spring on the saw so it would cut slowly, and it did. It took about 45 minutes to cut through this tube. Granted, it was cutting it the long way. Also had to clamp the piece in, because the angle I was working at was beyond what the band saw was set up for. I had cut some other pieces with this saw and the cuts weren't straight at all. Maybe it was the size of the piece, or the reduced spring pressure, but the cut is straight as an arrow. Anyway, very happy with how the pieces came out.

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Got the slot cut on one of them, but my 5/8" drill bit gave out after 5 holes so I need to go get a new bit to finish the other side. There's only about 3/16" around the front bottom edge of the hole, but I'm kinda thinking that isn't going to be a problem. I could redo the brackets and give a longer flat surface on the bottom so that the hole would be farther away if necessary. Pics of the slotted bracket:

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This is what the parts look like just kinda stacked on each other roughly in place. I still haven't trimmed the forward end of the pedestal thingy. Gonna need to take a couple inches off the end.

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It'll be hell for stout. :flamedevi

 

There's only about 3/16" around the front bottom edge of the hole, but I'm kinda thinking that isn't going to be a problem. I could redo the brackets and give a longer flat surface on the bottom so that the hole would be farther away if necessary.

 

An easy thing you can do is find the maximum droop of the TC rod as installed and then weld a small plate across the angle you cut in the tube, tying in the sides near the ends of the slot with the bottom of the bracket. This bracket will mostly see compression loads coming in from the TC rod and it looks plenty strong enough to handle the minor tension loads as the LCA moves up and down.

 

I have a whole bunch of this 1x1x.063 tubing, so I had this idea: why not contour the tubing to fit the curve of the frame rail, and weld 2 sections right next to each other. I can already hear John, "that's using almost twice as much material as necessary. True, but it's easy and it only weighs maybe 1 lb. I cut the shape with a jigsaw, for those interested. So here's my first attempt at it:

 

Personally I would have gone with your idea of using the bracket tube (2 x 3) in a bigger size like 2 x 4 or 2 x 5 and contoured the bottom of it to match the frame rail at the angle you calculated, eliminating the 1 x 1 tubing. But that tube would be harder to work with given the tools you have.

 

Either way, your doing the right thing. Hopefully with no springs, shocks, or ARBs installed you'll be able to easily move the front suspension up and down with one hand and it will move through a good arc (as good as it can get using the basic 240Z design).

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It'll be hell for stout. :flamedevi

THAT'S what I wanted to hear! :-P

An easy thing you can do is find the maximum droop of the TC rod as installed and then weld a small plate across the angle you cut in the tube, tying in the sides near the ends of the slot with the bottom of the bracket. This bracket will mostly see compression loads coming in from the TC rod and it looks plenty strong enough to handle the minor tension loads as the LCA moves up and down.

Yeah, the more I look at it the more I think it's going to be strong enough as is.

Personally I would have gone with your idea of using the bracket tube (2 x 3) in a bigger size like 2 x 4 or 2 x 5 and contoured the bottom of it to match the frame rail at the angle you calculated' date=' eliminating the 1 x 1 tubing. But that tube would be harder to work with given the tools you have.

 

Either way, your doing the right thing. Hopefully with no springs, shocks, or ARBs installed you'll be able to easily move the front suspension up and down with one hand and it will move through a good arc (as good as it can get using the basic 240Z design).[/quote']

I'm still considering the larger tubing actually. This 2x3 looks like it will work, but the range of adjustment is only about an inch and a half, and what really concerns me is that I think the rod end is going to hit the top or bottom of the tube, possibly limiting the travel even further. I really don't want to go with 2x4 .25 wall tubing, that's just ridiculous overkill, so if I do have to get bigger tube I'll probably have to mail order it from somewhere. I don't think the contouring of the tube will be too bad. I cut the slots really easily with a jigsaw.

 

Unfortunately right now I only have Illuminas, so they're a bit harder to take through the travel, but the goal is minimal stiction and no binding. As it sits with no strut in there the thing that stops the control arm first is the end of the TC bucket. If I remove the bracket it can go about another 1/2", then the tie rod hits the frame rail. Next step is to put a strut in and compress it to see where it bottoms first, then modify as necessary.

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I think it's mostly a lack of skill that would keep me from doing that. The one other guy I know who did something like this on his 510 used 3/16" too, so that was also a motivating factor to use thicker stuff. I can get 2x4 .120 wall tube here locally, but that's a tall tube and I was feeling a little sketchy about it's stiffness. Do you think I'm wrong on that?

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