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HybridZ

240z SCCA vintage race car, restoration


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11 minutes ago, Alexander240z said:

Physically yes its being held on by one side of the box. Structurally the bottom plate that the nut is welded to is being held by the 2 lateral sides. One of those lateral sides being held by spot welds. Unfortunately for these cars you have to assume rust is already eating at the spot welds. So the structural integrity might not be fully there. If you weld a spreader plate that encompasses the top section of the rail, that'll work too. This is for a factory situation as in Aydin's case he redid the entire front rail. 


i can tell ya, on mine it was completely rusted out. So much so, that the die-pressed steel gusset supporting the nuts and sway bar mount inside the frame rail, was half gone. Meanwhile, there was little surface rust on the outside of the rail. Another classic situation where water had worked its way in between the lap joints, and the PO had no idea it was happening until holes showed up in the usual spots. 

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1 hour ago, AydinZ71 said:


i can tell ya, on mine it was completely rusted out. So much so, that the die-pressed steel gusset supporting the nuts and sway bar mount inside the frame rail, was half gone. Meanwhile, there was little surface rust on the outside of the rail. Another classic situation where water had worked its way in between the lap joints, and the PO had no idea it was happening until holes showed up in the usual spots. 

I'm not sure what condition mine is in but my sway bar bolts broke the nuts so I hardly had a sway bar to begin with. Need to put the floors in and attach the rail to it before I start messing with the driver side lower rail and firewall so that I don't mess up the location of the tension rod. 

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1 hour ago, Alexander240z said:

Physically yes its being held on by one side of the box. Structurally the bottom plate that the nut is welded to is being held by the 2 lateral sides. One of those lateral sides being held by spot welds. Unfortunately for these cars you have to assume rust is already eating at the spot welds. So the structural integrity might not be fully there. If you weld a spreader plate that encompasses the top section of the rail, that'll work too. This is for a factory situation as in Aydin's case he redid the entire front rail. 

 

The frame rails help support the entire front of that car. If your sway bar is bending your entire frame, you've got issues with more than sway bar mounting. I think the sheer number of cars with upgraded bars that have torn sheet metal around the mounting nuts shows where the weak point is. 

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3 minutes ago, calZ said:

 

The frame rails help support the entire front of that car. If your sway bar is bending your entire frame, you've got issues with more than sway bar mounting. I think the sheer number of cars with upgraded bars that have torn sheet metal around the mounting nuts shows where the weak point is. 

Yes you are right. I just have concerns with the factory spot welds and I don't trust them at all. You can easily see when the sheet metal round the mounting nuts fail but the spot welds hold the entire rail together might be breaking under it all without visible evidence unless you look really hard. Seems like my concern might be something that occurs after hundreds of hours of driving. 

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Your solution is valid. You don't need a lot of support around that bearing.. many of the comments above reference putting a standard "clamp" bearing to the stock frame rail, which is a little sketchy, but a reinforcement plate solves that. And the aluminum heating info sounds like what I researched. That is how I ended up thinking about a sledgehammer. If you read the internet, you will find various opinions recommending steel arms due to flexing. That all depends on how stiff/thick your bar is of course. I figured my bar is not 400lb or above so I opted for aluminum and 3/8 rod end arms. I will put a camera in there at some point during testing to watch it. So in the end I think press is the best way to bend them. But my un tried sledgehammer should work also.

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Different material but I tried bending the steel ones with BFH and got nothing. Put in my 12 ton press and was able to deflect the end about 1/8" before I gave up for fear of my life. Then found a machine shop with BIG machinery and they put the arms in a 50 ton press and bent them easily. Your standard auto shop press ain't gonna cut it. The double shear end link mounts are so that I can use a clevis and not have to worry about the clevis leaning in the hole. Pro-tip: if you're making them double shear, take a piece of plastic from the last tool you bought, or a razor or anything that comes in a blister pack, and put that between the rod end and the arm. That will give you an extra .005" or whatever and it allows the rod end to slide easily into the mount. Last time I did this I didn't use a spacer and it was a real bitch to get the rod ends into position for the clevis pin. Will probably clunk a little, but hey, racecar. :D



I think AL is stiffer and more brittle. Someone mentioned spring rates, and the higher the spring rate the less sway bar you need, so you can get away with less strong arms as a result. Before I decided to make boxed arms, I had an engineer friend I used to autox with 20 years ago suggest milling down the arms to 3/8" thick so that they could be bent more easily. That would be another way to fix and would reduce weight.

The strength of the arm as delivered is more than capable of withstanding the thickest sway bars that you would use on a 3000 lb dirt track car with soft springs and (WAG) 7" of travel, so a lot more force on those arms than what they'll see in a stiffly sprung ~2500 lb car that moves a couple inches at most.

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Edited by JMortensen
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@JMortensen thanks as always Jon! So I still have not gotten to trying to bend the AL arms, but more on that later. At 3/4” thick and 1-1.5” wide where it meets the link, I agree it’s plenty stiff to resist whatever motion my 350lb springs don’t already resist. And as you said, if they deflect more than I want, I can just up the wall thickness of the sway bar itself. Where did you get your bar from? Speedway engineering makes these bars for dirt, autoX, even nascar, and for vehicles much heavier than a Z. In fact, the bar looks to be the beefiest single suspension component on the car. I am optimistic.

 

the end links I got are a Clevis on the LCA side and a cantilevered (single sheer?) rod end on the sway bar arm side. If they fail, I can always consider doing a clevis-like joint like the one you have, but would need to switch to steel arms for that. 

 

Today I put the rack back on to establish clearance. It will be close. As I was fiddling around, I realized how much easier this would be without the fenders on. But, I have not yet tried to mate my inspection lids and naturally they don’t fit anymore with all the modifications and rust repair I have made to the cowl and fenders. Shit… after spending 30 min trying yo make them fit, I gave up and decided to just weld a sheet of 20-gauge to the fenders to close out the hole. I still need to stiffen it a bit so it doesn’t flop in the wind, but the fitment works with the hood. Il finish the other side tomorrow, then I can toss the fenders aside and get back to the sway bar. 

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I got my bar from colemanracing.com, but aside from spline count variations they're basically the same idea, and my understanding is that we can buy arms from other suppliers like Speedway and as long as the spline count is the same, they'll fit. Coleman sells a 48 and a 49 spline, mine are 48, FWIW.

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Don't forget ebay for these too.  You can search for NASCAR sway bar and find lots of options.  Ideally you test these as they often take a different rate after being used a few times.  I wasn't aware of this until I saw it in a youtube video explaining how to use bars with bump rubbers.  You can also look at some of the big race teams for used parts.  Really high end stuff for pennies on the dollar.

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@JMortensen ah cool! I figured from the emphasis on spline count that the industry has more or less standardized. Since they only sold one OD for the “standard” bar, I also assume this was for swapping convenience. What I’m really missing is tangible experience on how critical the sway bar is in the overall handling of the car for a road coarse. I have a bit of experience on just how important it is an autoX, since you are constantly changing directions. I need to get on a track! 
 

@tube80z absolutely! I have not experienced swapping out bars with different spring rates myself, but it makes total sense. I assume this has to be based on “feel” after a test drive, since it’s hard to factor in so many variables ahead of time. Precise length of arms from mounting hole to bar, bar material and dimensions (AL in my case), how orthogonal the forces from the links are relevant to the radius of the arm/bar, so on… 

 

I have noticed some great deals on eBay race shops, in my case for instruments. I got this (pic) CF panel complete with auto meter electric gauges (most of which I need) for $200. Two gauges would have easily cost that much. I just need to buy the sensors/transducers, which are also sold at deep discounts. 
 

Updates, finished the silly inspection door delete. I still have steel fenders so this was as easy as welding 20-gauge to the fender, adding an 18-gauge stiffening rib to the underside, and checking contour and fitment. Only saved me 1lb overall, but my issue here was fitment of the OEM doors, not weight. This ended up eating my whole weekend though, but now I can toss the fenders asside and get back to the bar. 

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Man I have really struck out on finding a way to get these aluminum sway bar arms bent. Had one shop lined up, but once they saw the part they declined (didn’t have the right die).

 

i did do a ton of research into bending 6061. Without a 7X radius to thickness and the right tooling, it is very hard to bend in it’s tempered (t4, t6) states, so you HAVE to anneal it. The tempered states have a tight gap between yield and ultimate, so they tend to crack. Heating the part as you apply pressure will reduce the temper. There are some tips on how to get to the annealing temp, but they are difficult on something as thick as 3/4”. 
 

I might just have to buy a HF press and give it a try myself 

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Edited by AydinZ71
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Man don't try that. As soon as you start jacking and hear it creaking you will think man this thing can kill me fast if something slips. I get scared pressing bearings sometimes with a sketchy socket jammed in there.

 You could probably design some tooling to make it safe, but that will also be a hassle.

 

I'm still thinking sledgehammer with it secured to something solid.

 

Unless you can find a way to bend the aluminum, I think you have 3 options and they all involve a steel arm. 

1. John's welded up arm with a splined steel stub cut from another arm.  It's a real cool idea. Another take on this is the Speedway Motors stubs. They are pretty cheap and you can weld to them. This is what I used in rear of mine.

https://www.speedwaymotors.com/Complete-Torsion-Bar-4130-Rear-Arm-Kit-1-Inch,2141.html

They sell just the stub in a few 48 and 49 spline sizes. The pipes are rather large and a little heavy, but they fit up perfect on rear of mine. The stub is quite heavy also, but that can be fixed.

2. Get a steel arm and apply torch. From what I can gather, most every circle track car does this.

3. You might be able to find a steel and maybe aluminum arm already bent. Google offset sway bar arm and you can find some new options.  Sprint car guys call them torsion bars. And I bought the set for my last car off of eBay. They come up often for sale used but it can take some time to find a matching pair the right size.

 

 

 

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On my 20th try, I struck gold! Thank you to Jon and Clark for the alternate suggestions. I was about to return them for steel as Jon suggested. Clark, I decided against buying my own press for all the same reasons you thought of. 
 

The shop is called Bert’s sheet metal in chatsworth. They heated up the radius, annealed it, and it bent without any noticeable distortion.  After some test mock-ups, drilled some holes and voila. Now all that’s left is welding the attachment to the chassis with the aluminum/brass bearings to hold the bar. 

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