Building a swaybar for the Midget

[Loren]

So, my Midget came without a swaybar. Not sure why. The earlier ones didn't have one, and some years they were optional, but it should have been standard on the 1976 model. But, the car's been repainted, refurbished a bit, so who knows?

I noticed when I first looked at it that it had NEW swaybar brackets on the lower control arms. But, no swaybar. So, I'm guessing some PO in recent history upgraded the swaybar, and then removed it before selling it.

Aaaaanyway. The car handles pretty well without a swaybar. But, when you start getting aggressive with it... yeah, it's got some body roll. Need to add that swaybar.

I've been all down the Internet rabbit holes about what size it should be. 9/16" is the stock size. There are some 5/8" bars available, even more rare is 11/16". The most common is 3/4", but a lot of people who have them say that it's too much for street use and affects ride quality. Given my usage of this car, I figure stock would be a good place to start.

I actually ordered one on eBay. Great deal, somebody accepted my offer of $25... with $27 shipping. The seller was honest enough to contact me when they found that it was bent as they were packaging it. So, I didn't get that one. The next cheapest one I can find is $75. And anything new is around $200. I'm being cheap, I'd just rather not pay that much... especially when I had one almost in my hands for $50!

Went down the rabbit hole of building a swaybar (again... I've done it before). The naysayers say "OMG, it's got to be made of tempered steel, and if you weld it, you must have it retempered or it will never last!" But, other people who have done otherwise, some of them with metallurgical/engineering experience, will say that any kind of steel will work just fine, and heat treating is not required as long as you don't deform the bar beyond its yield limit... and that's generally more than a swaybar needs to bend or twist. I'm sufficiently convinced that it'll be okay. The bar we modded for the Festiva worked great through a LOT of abuse, the rear bars we built for both the Festiva and the Mirage worked fine... the rear subframe that they were attached to gave up before they did!

Down a couple more rabbit holes, I went...

If I'm building vs. buying, I should make it hollow to save some weight, and adjustable. Dang it, I already ordered the brackets and bushings for it, so... unless I want to waste those bushings (there I go being frugal again), I should make it that 9/16" diameter. No problem. I can get that hollow, and adjust the length of the bar a little bit, and still get the end result that I want. I worked out all the math (using this calculator and some measurements I took from the car. Figured out what materials I needed and what it would cost. Ended up being over $80 after shipping. Not too bad, really. But, I've still got that $50 number in my head.

Can I make it cheaper? Well, yeah! The stock bar should only weigh about 4.5 pounds. The weight savings wouldn't be more than 1.5 pounds. I'm not racing this car, what's a pound and a half??? It doesn't need to be hollow. Reworking the numbers to make it solid and have the same stiffness brought the price down to $42.45. Nice!

So, that's where I am. This is what I'm building:

The center section of the bar will be solid 9/16" bar for exactly 20" (the bushing mounts on the frame are 16"... the stock bar bends are at 26"), that will be the twisty part of the bar to give the proper rate. I'll cut it about an inch longer on each end, and that will fit into a 1" diameter tube that has a 9/16" hole. That piece of tube will be about 1.5" long and cut at a 45 degree angle on the outer end with a piece of 1/4" x 1" flat bar will be welded to it. The end of that flat bar will be bent at 45 degrees and drilled with at least two holes for adjustment. The softest adjustment will be slightly stiffer than the stock 9/16 bar, the stiffer setting should be close to what a 5/8 bar would be. If I go any shorter with the arm length, I'll probably need custom end links. (and since I just bought new stock end links, I don't want to do that just yet)

The thick end tube and the bar stock of the arms should be pretty rigid. The tube is about 10x as stiff as the 9/16 bar... and there's less than 2" of it, so it ain't gonna flex. All of the action in this bar should be in the 9/16 center section.

Oh, and I'll use a couple 1/4" long sections of that same fat tube as stops to keep the bar from sliding in its mounts.

I'm just about to pull the trigger on the $42 worth of materials to build this thing. Shouldn't take too long to put it together once I have all the pieces. A little cutting, a little drilling, a little bending, a little welding... some grinding and some paint... no problem!

Given that I'm not competing in this car, I think it'll work just fine and be joyful thing. And I'll feel good knowing that I saved a few bucks creating something functional.

[Loren]

Here's my sketch that will probably help the above make sense.

[Loren]

FWIW, the math says that a bar with all stock dimensions (disregarding any flex in the arms, which should be minimal) should be:

9/16 = 120 lb/in
5/8 = 182 lb/in
11/16 = 267 lb/in
3/4 = 378 lb/in (no wonder people think that's too stiff, the front spring rate is only 271!)

This bar (arm flex should be even less) should be:

6" arm length = 155 lb/in.
5.25" arm length = 203 lb/in.

And if I adjust one side stiff and the other side soft (yes, you can do that, the forces equalize through the bar), it would be somewhere between the two, around 177.

So, one adjustable bar gives me options equivalent to "almost stock" (30% stiffer) 9/16, a little less than 5/8 (50% stiffer), and a little more than 5/8 (70% stiffer).

With my opinion being that 11/16 and 3/4 would be way too stiff for street use with stock springs, I think that's a good range of adjustment.

Did I mention that 3/4" bars are known to rip the mounting brackets out of the frame and require reinforcement? This bar probably won't do that.

[Loren]

I settled on a design a while back and ordered materials. Materials are here now, will probably start on this tomorrow. Really want to get it done and on the car because the way it flops around without it, the front tires rub. I'd like to be able to actually ENJOY driving the car!

The short pieces of hollow bar that the 9/16" bar fits into, I screwed up and ordered the wrong tube. 9/16 = .5625" and I ordered .625" ID. Oops! So, I'll have to fill in that extra .0625". Not critical, it doesn't have to be perfect. A nice tight fit would have been nice, but I'll live with it. The welds are what's holding it together.

Really shouldn't take long to put this together... maybe I'll get it done tomorrow?

[Loren]

Mocking things up a little tighter now.

With the actual bar in the actual brackets with the actual end links in place... what I'd estimated as a 6" "lever" length is actually max 4.5 and min 3.5. That changes the math.

The bar, I'd planned to make 20", so I got a little extra at 22". So, I can make that at much as 21.5 and get away with it.

Let's see where that gets us...

Just shortening the arm length to 4.5-3.5 gives rates of 276 (okay) and 457 (!!!)

Extending the bar length to 21.5 helps... 257 & 425.

I guess I can always rework the thing if it's too stiff. Materials were only like $40.

So, I'm going to make the bar length 21.5" and set my adjustment holes at 4.5" and 3.75". That will give me 257 max and 370 min with a middle adjustment in the 306 range.

That's more than I wanted (but, I'm sure I'll like it), but still less than the commonly available 3/4" bar... and way cheaper... and adjustable... and I got to make something.

Time to get to the making!

[Loren]

Making progress. Determined that I can put my holes .5" apart, so I can do 4.5" and 4" for my adjustments. 257# and 325#.

The fab is coming along. I couldn't get the tight bend radius that I wanted on the 1/4" arm bar stock without heating it up, and I'm not well-equipped to do that kind of heating (all I have is a propane torch). So, I cut half-way through it, beveled the cut, bent it, and then welded the cut. Nice, tight angle. Good to go!

[Native]

Good times!

[Loren]

Current status:

Bare Bar.jpg (102.64 KiB) Viewed 4833 times

All the welding is done. I did all the welding/shaping/drilling/grinding on the arms first. Then, I laid things out on my fancy welding/fit-up table and tacked it. Verified that everything was correct, and then continued tacking every 10-15 minutes. Trying to not put too much heat into the twisty part of the bar. Theory is that heating it up too much will anneal it and make it soft.

Lots and lots and lots of discussion in various places online about whether this should be heat-treated or not. Technically, it should be, but apparently, even a lot of OE manufacturers don't heat treat swaybars. Cold rolled steel is adequate for the purpose... as long as you don't heat it up.

So, tomorrow, I'll do a test fit to be sure it's all that it's supposed to be. Then, I'll try to do the final grinding to make it pretty and verify that the welds look okay. Then paint it, and it will be ready to go on the car Sunday!

[Loren]

Started my test fit Saturday morning. Quickly found that I'd poorly fitted my stops in the middle of the bar. I knew when I tacked the second one on that it wasn't quite right. Supposed to be a 14.25", was closer to 14.5. I figured it's going in a rubber bushing, should be close enough. It wasn't. Dang it!

After futzing with it and considering modifying brackets... I thought better of it and cut the tack welds on the stop and carefully repositioned it. That's why I'm testing this before I paint it, so I can fix silly stuff like that.

Second attempt. It still doesn't fit! After removing it again, I found my mistake. I did put it on the line that I'd marked... but, I put the stop (just a 1/4" thick piece of tube that fits around the bar) on the WRONG SIDE of the line, thus putting it 1/4" off. So, I'll have to fix it again.

Before removing it, I went ahead and ran the bolts down on the frame brackets. Found that my holes on the bar could be further out than I thought. Maybe close to that originally expected 6". Why? Because when I measured that 3.5-4.5" length, I was thinking in two dimensions. It is 4" back from the bar, but it's also DOWN the length of the end link.

Fortunately, I've not cut the bar ends to final length yet! So, I'll add a couple more adjustment holes and have more flexibility.

[Loren]

After being derailed by inop brake lights, which led to a major electrical rewiring project, and another extensive console refurbishment project... 5 weeks later... I'm back to this!

I drilled an extra set of adjustment holes in the ends of the bar, and pilot holes for another set. Cut the welds on wrongly-positioned slide stop, and welded it back in exactly the right spot.

Fitted it all to the car, and it went together... like it should have the first time had I not fucked it up!

Won't need that last set of holes that I did pilot holes for. The last set is as far as I can go without clearance issues.

So, now that it's finally on the car, of course I took it for a test run! Really doesn't feel all that different... which confirms that the shocks are the real problem. (fortunately, I have a freshly rebuilt set ready to go on) But, the problem that brought this swaybar install to the top of the priority list is that the front tires were rubbing fenders on aggressive turns. I'm still a little gun-shy about that, but I was cornering a little harder today and no rubbing. So, I'll call that a win!

Now, I need to take the bar back off the car, trim the ends, clean it up and paint it. I guess I could send it out to be powder-coated or chromed like all the cool kids. But, have you met me? Black paint will work. Be glad I'm not using red or teal!

Once it's painted, I'll put it back on in one of the stiffer settings and see how it feels. I feel like the stiffer bar in the front is just going to make the weak rear shocks feel even worse. We'll see.

[Native]

That also looks good.

[Loren]

Decided to adjust it to the middle set of holes this afternoon. BIG difference. I mean, it's still got gobs of body roll (soft springs and weak shocks), but the front end feels a lot more precise. I like it! And I can still go a bit stiffer if I want to.

By the numbers, I ended up with adjustment holes at:
4" - 325#
4.5" - 257#
5" - 208#

Compare to commonly available standard bars:
9/16 = 120 lb/in
5/8 = 182 lb/in
11/16 = 267 lb/in
3/4 = 378 lb/in (no wonder people think that's too stiff, the front spring rate is only 271!)

My numbers being all sorts of "approximation", and not taking into account any flex in the bar ends (shouldn't be much), I'll say that my softest setting where I was yesterday is probably something between the stock 9/16" and 5/8" bar. Did the job, but didn't seem like enough. My middle setting is probably close to an 11/16" bar, and feels nice. My stiffest setting still won't be as stiff as the 3/4" bar.

Anyhow, this comes off tomorrow for final clean-up and paint. Should have it back together by Sunday.

[Loren]

Spent about an hour cutting, grinding and sanding this thing. Yes, it's true, I'm more of a grinder than a welder!

In this case, the welds on the arms are pretty decent. (there, I cut 1/2 way through the 1/4" steel to allow for a tight bend, then welded it back together... and then welded a short piece of pipe to the arm as a receiver for the center bar) The welds to the center bar aren't as great because I was trying to be hot enough to get good penetration, but still do it as a series of quick spot-welds in an effort to not put more heat in the bar than absolutely necessary. If you ask a metallurgist, they'll say that this bar should have been heat-treated after welding. But, I've ready enough accounts of garage-builders who have made swaybars just like this with no heat-treating, and never had a problem with them for many years. So, I feel okay about it. Most of the bar never got significantly hot, anyway.

So far, in the little bit of driving I've done with it, it's seen full body roll, which is probably 3" down on one end and 3" up on the other. That's a lot of twist! And when I took it off to paint it, it had no deformation. Good enough!