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JMortensen

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

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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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Maybe speedway or one of the other stock car suppliers has serated slotted plates you can buy. Those are used on a number of panhard bars.

 

John, I'm assuming you'd need two of the adjusters to make the mount double shear?

 

Cary

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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:

DSCN0856.jpg

 

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:

DSCN0923.jpg

 

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.

DSCN0924.jpg

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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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Well, it looks like 2x4 tubing is definitely going to be the route to take. I installed the strut and took it through the range of motion. No binding at all if the rod end was right in the middle of the slot. It actually worked really nicely right there. When I moved the rod end down as far as I could I found that I couldn't utilize the whole slot because the rod end hit the top of the bracket. This limits my total adjustment to about 3/4" which is less than I was hoping for. Also, I couldn't move the suspension all the way through it's range before the TC rod hit the bracket. 2x4 tubing will definitely solve both of these problems. I took some more pics:

 

This shows how far I can move the rod end before it hits the top of the bracket.

DSCN0928.jpg

 

LCA angles at FULL droop. Should be just slightly pointing down at race ride height.

DSCN0929.jpg

 

TC rod hitting bracket at less than full bump.

DSCN0931.jpg

 

So with that in mind, any opinions on the 1/8" tube for the 2x4? Stiff enough? I was still going to brace it to the rockers, so maybe with that in mind it would be enough?

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Attempt #2: This time using .120 wall 2x4 tubing. Changed up the design just a bit. I left more meat out back and I decided to contour the tube like John suggested. This will allow the the tubing to connect on the top and the side.

 

Haven't cut the slot yet as I haven't gotten a new 5/8" bit, but I did get one side kinda roughed in. Cut the shape with a cutoff wheel. I'm going to clean it up with a grinder and then the dremel. I have to say that it looks like it's gonna work out really smoothly.

 

DSCN0932.jpg

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Bad news: Getting a little fed up with this project.

Good news: It's almost done.

 

I welded on my TC brackets today, along with a support that attaches to the rocker for each side. When I welded the brackets to the frame I grabbed one and wiggled and you could SEE the frame rail flex. That frame rail is sheet metal thin!!! Kinda scary... :weird:

 

I'm glad I did the braces to the rockers. Where I attached to the rocker is actually pretty thick and strong, so that part at least should give some support. Once I got the braces welded on I could no longer sense any flexion, but being that the frame rail was that weak I gotta assume its there. I'm still thinking of other ways to make it stronger, like turning the crossmember into a K member. I don't want to do it though, then find out that my oil pan or exhaust doesn't clear or something stupid like that.

 

My brackets ended up having only 1 1/8" of adjustability in them due to interference issues with the frame rail. The nice part is that it coincided perfectly with my previous crossmember slotting. The crossmember slot went from 3 3/4" to 2 5/8". The new TC bracket is slotted from 2 3/4" to 1 5/8". So they're just right, since the stock setting was to have the TC pivot one inch higher than the LCA pivot.

 

I still have to connect the subframe connectors to the bracket. That got a little tricky because of the curve of the frame rail down towards the bracket, but I think I've got a handle on it. I did have to leave a little gap to allow room for the bolt head fit in the slot when the TC rod is all the way up.

 

I think this will be done in a day or two, then I can move onto something else... finally. Maybe I'll get back into the roll bar... :D

 

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What about a gusset underneath the TC bracket, 90 degrees to the frame rail, attaching it to yet another side of the frame rail?

Funny you should mention that. I was going to do that tomorrow with a piece of angle iron, just welding it in from the top of the frame rail down to the bracket.

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Didn't quite get it all done today, but it's 95% there. Got both subframe connectors done. Need to finish patching the rail in front of the TC box, and I didn't get to the angle iron that I mentioned yesterday.

 

I think I figured out why my car was so twitchy under braking today. The passenger side frame rail above the TC rod had a 1" long crack! The crack was hidden under some of the factory undercoat. And that's thin sheetmetal that was cracked!!! I think this came about from the damage that the car had on the passenger frame rail. It looked like the PO had ran over a curb or something. I never paid too much attention because it aligned out OK even before I had all the adjustable suspension. I guess that is a word of warning for anyone else who has banged up frame rails. So I welded up the crack and got the frame rails done. Had to bend the frame rails to follow the curve of the Datsun rails, and I also had to patch a long triangular section because the frame rail curves in near the TC box, and my Bad Dog special order parts did not. Thanks John, they worked GREAT. Again, if I weren't doing this freaky TC rod modification I think it would have been a couple hours labor to put these things on, and I really feel that they will add a lot of rigidity to the structure of the car. :2thumbs:

 

Check out the crack!

DSCN0957.jpg

 

See it NOW?

DSCN0958.jpg

 

This before shot is just UGLY! Lot of filling with the welder, but I didn't really see another option...

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After:

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Yeah, my gut tells me that crack was actually pretty significant. So what do you think about the overall fix? It's kind of hard to get a plate in there to cover that crack because it's a weird curved surface there, so I didn't, but I figure with the reinforced frame rail/subframe connector, the planned angle iron gusset on top and the thicker TC bracket and the brace to the rockers it should be OK. Do you think I did OK?

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If the damage is from an accident, the repair you've done will be fine. One trick on crack repair is to drill the very end of the crack (the root) with a 1/8" bit to spread out the concentration of force where the crack is continuing to grow. Then weld from that point back to the start of the crack.

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Well, I do believe the TC rod pivot relocation project is officially done! :D

 

I was thinking this morning about patching the frame rail in front of the TC bracket, then it suddenly occured to me that I still had the end of the Bad Dog rails. Remember these?

DSCN0855.jpg

 

So I figured if I was going to cut the shape in the bottom of the frame rail into a piece of steel, it might as well be those! Line the angled section up to the TC bracket, and now I'd have gusset in another direction. So that's what I did. The angled section was about 3/4 of an inch too tall, and about 5 inches too long, so I trimmed it down for length on the chop saw and cut the angle on the band saw. I did also do the angle iron gusset that was previously discussed. Pics:

 

DSCN0973.jpg

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All in all I think this whole thing turned out pretty damn good. Figure a 10 - 12 lb weight gain, but I got subframe connectors, I can adjust dive and anti-dive a bit, got what looks to be a MUCH stronger than stock TC mount, strengthened my seat bracket, and found and fixed a crack in the frame. Not too bad!

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