Fat Man Fab 4 link Scary!!

[ErikLS2]

My June '09 Super Chevy has an article in it installing a Fat Man Fabrications 4 Link kit in a '71 Camaro. I couldn't believe it when I got to the upper arm brackets installation. Quote, " The brackets bolt to the frame rail via SELF TAPPING screws that are sufficient, ....".
YIKES, self tapping screws? They do say they decided to add some welds and Fat Man agreed. How could anyone put somethin like this out there with this type of design? I just don't understand.

[Rhino]

There are a number of examples which don't require welding. It isn't just Fat Man in this instance.
The Air Ride Air bar and Chris alston G-bar are the same.
While I would recommend welding it in, this is exactly as it was designed.
Looking at the first gen kit for the airbar, I can understand why it doesn't require welding. Due to where/how the load is applied. The screws aren't under tremendous tension or shear forces because of the cross member design.

I can't say definitively without seeing it, but I'd be inclined to think it's similar for this kit.

[Vegas69]

I don't care what the manufacturer says. Weld it in....it's a pretty well known fact that the air bar guys ripped a cradle loose in the autocross that was bolted in. If you intend to drive your car, I'd weld it.

[ProTouring442]

I would imagine this also has to do with what type of self tapping screws. Many bolt on parts were installed from the factory with a self tapping bolt (1/4" 5/16" 3/8") and if this is what we are talking about, they are quite stout. On the other hand, if we are talking the TEK screws you normally use to temporarily attach sheet metal, :eek:

Shiny Side Up!
Bill

[Rhino]

I don't care what the manufacturer says. Weld it in....it's a pretty well known fact that the air bar guys ripped a cradle loose in the autocross that was bolted in. If you intend to drive your car, I'd weld it.

Are you refering to Air Ride's '69 Mustang? If so, it was the factory frame rail that let loose, not the screws. It was fatigued metal that failed. That car also got beat on much harder and longer than the majority of the cars here running that setup.

It could be argued that a solid weld around the cradle would distribute the stresses more evenly. With that said, I was rather impressed by how it held up simply bolted in.
If it were my car, I'd weld it simply for piece of mind, but I wouldn't second guess it if I saw someone driving down the street with it.

[Vegas69]

Would it have failed with it welded in? It's just my opinion. I'm sure it's been tested but I'd still weld mine in the car. Wait...mine is welded in my car. :1st:

[ProdigyCustoms]

Yeah, that was the Mustang, and it was the factory sheetmetal that pulled away. The Air Ride Cars still run them bolted.

And if your car can do this.............

https://static1.pt-content.com/images/noimg.gif

[Bryce]

sheet metal screws are that bad, you can get grade 8 sheet metal screws. Like the ones you use on cheap bead lock.
and by design the fsteners are in shear so the threads have minimal loads

[Bryce]

can you describe whats going on in that pic?
is that when it broke? or does it get that much traction and pulls a wheel stand?

[68Formula]

Lightning McQueen - ka chow!


Yeah, that was the Mustang, and it was the factory sheetmetal that pulled away. The Air Ride Cars still run them bolted.

And if your car can do this.............

https://static1.pt-content.com/images/noimg.gif

[silver69camaro]

sheet metal screws are that bad, you can get grade 8 sheet metal screws. Like the ones you use on cheap bead lock.
and by design the fsteners are in shear so the threads have minimal loads

That describes the strength (in shear) of the fastener itself, not it's mechanical bond to the parent materal.

The stock "rails" are 0.045" thick. You guys make the call.

[Bryce]

thats what im saying, the weakest link is the stock sheet metal "frame"

i would always weld

[ErikLS2]

I know nothing about the Fat Man kit itself, just what I saw in the article and am not trying to run them into the ground. Maybe sheet metal screws are only used in a couple locations, I don't know I just can't get my mind around the fact that they would attach any main suspension component to 40 year old sheet metal that way.

I'm not an engineer but I have been working on cars nearly every day of my life for 20 years and have never seen any suspension component secured this way, even on the most basic econo box.

[1969CamaroRS]

Welded mine, worth it for peace of mind.

[chickn]

I wouldn't even hang an exhaust system using self-taping screws never less a suspension system.

[JRouche]

Sounds kinda weak to me. I dont see any use for self tapping screws for a suspension part unless its a cosmetic part. JR

[bret]

A few things to remember when talking about the "self tapping screws" used in the AirBar:

1. The fasteners that we use for the AirBar are bit more refined than the hardware store sheet metal screws. They displace the metal to make the thread, like a rolled thread, rather than cutting the threads into the framerail. The fact that the magazine article described them simply as "sheet metal screws" was more a reflection of my poor explanation of these fasteners to them than anything else.
2. The cradle is designed to load the fasteners in at least 2 planes so the stressed load is carried in shear instead of tension. This was not by accident or convenience.
3. To prove that this was an acceptable way to install the unit during development, we placed a small "witness" tack weld on a couple of spots between the cradle bracket and the framerail to indicate if there was ever any movement. Those tacks are still in place and unmolested. We did this on my Mustang and on the Velocity Camaro.
4. The Mustang did rip the [corrosion thinned] floorboard out of the car...after 3 autocross seasons behind a 630 hp hi revving small block, with a Rankin NASCAR 4 speed, a carbon clutch, racing slicks, and very un-gentle handling. [see Franks picture above] The fasteners were still intact. [I should have taken pictures.]
5. For MOST people, a bolted connection is superior to attempting to weld the clean .188" wall steel of an AirBar cradle to a thinner, dirtier framerail while upside down under a car. That being said, if you posses the resources to successfully weld the cradle into the car, you will likley not burst into flames, so weld away with my blessing.
6. Because of the possible uncertain variances of welding, [weldor skill, metal quality, position of the joint, etc] buildings, bridges, and airplanes are, for the most part, bolted together.

I completely respect anyones decision to weld their AirBar cradle into their car...just trying to clarify the facts so you can make a better informed decision.

[Bryce]

good explanation, thank you.

[Eric Howell]

can you describe whats going on in that pic?
is that when it broke? or does it get that much traction and pulls a wheel stand?I hope they dropped the pressure in the right rear bag to 3 wheel it.

[ErikLS2]

Bret, just to clarify, the article I was talking about was on the Fat Man 2nd gen Camaro 4 link, not yours. Thank you for your articulate explanation and I totally agree with you on the welding variances possible.

[dr.gonzo]

that must have been a hell of a ride in the stang

[chickn]

I was thinking, maybe riv-nuts may be a better solution than self tapping screws. they would be more resistant to tearout and they can be installed without any special tools.

[MonzaRacer]

Actually the rivnuts have less shear strength over the way Bret explained the type of fasteners used. I have to go over and weld one in for a friend in couple of weeks after he gets done blasting all the crud off his underside! He got a new scratch tig Yeah Thermadyne Dragster 85 for a 110 tig VERY awesome unit, now I really want one agian(dreamed about getting one before).
On rivnuts we used them to attach a plate that an upper control arm attached to on a go cart, they pulled out as they had less ability to hold, where as the fasteners that ART use are directly into metal and rivnuts are squeezed down around a thin area of sheet metal, the hole drilled. The sheet metal deformed and the rivnut pulled out and these had large washer heads.
And these went through in 2 angles as through a piece of angle iron to the cart rail.

[fatiger53]

Fatman here. Just to clarify, The four bar in question IS Airride's. We supplied it with QA-1 coilovers for this article, just as we give that same option inour catalog. Airride naturally sells it with their Shockwaves only. Bret's explanation above is right on the money. Personally, I would add some short welds for extra piece of mind, as several guys suggested. We sell the Airride version simply because we see it as being the best, and see no need to build our own or pirate the design from such a fine group of guys as Airride. We just offer the coilover version for those of that mind.

[DarkoNova]

So what was really going on in the pic of the Mustang? I mean I've seen cars lift the inner wheel in a turn, but only like an inch or two. That thing's got like a clean foot of air. :eek:

Matt

[BrianP]

And if your car can do this.............

https://static1.pt-content.com/images/noimg.gif

What's wrong with this setup? Is the rear roll center too low in the rear? It looks pretty dangerous.

[JRouche]

What's wrong with this setup? Is the rear roll center too low in the rear? It looks pretty dangerous.

Dangerous? YES. Thats a given. But odd mostly. The outside front tire is severely unloaded too. Only thing I can see causing that much unloading of the entire front would be some serious traction at the rear with some serious HP!! Either way, its not the fastest way to take a turn and that airborne tire has to come to earth sometime, ouch... JR

[silver69camaro]

Only thing I can see causing that much unloading of the entire front would be some serious traction at the rear with some serious HP!!

That would be the last on my list. My guesses would be:
1. Too high of a front wheel rate
2. Too much front roll stiffness
3. COG too high
4. Too low rear wheel rate
5. Too low rear roll stiffness
6. Improper shock valving

My initial thought is #4 and #5. But honestly, this isn't totally a bad thing. The lift is indeed excessive, a little bit is more justifiable; but if this is the setup that allows Bret to drive the fastest, than so be it. Increasing rear stiffness and spring would cause more oversteer, which may be what he's trying to get away from.

[Steve1968LS2]

Yea, I would chalk this up to bad writing in the SC story.

They made it sound like tec screws from the local Home Depot. lol

Still, I would always choose to weld brackets in place. However that doesn't mean you HAVE to.

Keep in mind that many guys are just driving thier cars, not beating the ever loving snot out of them like we do.

Welding is always great option.. if you can weld. ;)

[Steve1968LS2]

Dangerous? YES. Thats a given. But odd mostly. The outside front tire is severely unloaded too. Only thing I can see causing that much unloading of the entire front would be some serious traction at the rear with some serious HP!! Either way, its not the fastest way to take a turn and that airborne tire has to come to earth sometime, ouch... JR

Did you ever think they the made the car do that just for fun and/or the picture? I mean seriously, do you think that's the way the car is set to be on a regular basis? lol

[thetoystore]

gotta say i'm just gunna chock that pic of to random **** that can happen. just a story but back in highschool i had a 2.2 s10 that was bagged and i could do that all day. i gota find pics of it. was it safe? no was it smart? no. was it fun as hell in an empty parking lot? hell yea

[BRIAN]

Maybe the screws are the better way to go?? Welding on maybe 16 gauge 40 year old metal also has it pitfalls. Plus add corrosion and welding under a car and it can be just as dangerous. Then add guys are mini tubing these cars taking away a chunk of the rail and welding in a patch. That is plain old sheetmetal not HSS in 1969.

If you are going that far into mods buy a AM clip and do it right. No bash on Air Ride just my thoughts.

[bret]

In reference to the picture of my Mustang...that specific tune up is definately not the fast way around the track... but it is great for moral!

I had the front shocks way up on rebound valving, the rear shocks way loose in rebound and compression...and drove it way deep into the corner before steering into a late apex. In other words...it was kind of "on purpose". The track surface way way sticky, the tires were BFG R1's. The landing was certainly harsher than the lift off, but not terribly brutal.

I can't recommend this method for most cars...this car is very light [3000 lbs], mucho torque [600 lb. ft.] with good traction and weight distribution. I also had the benefit of a nicely designed decreasing radius sweeping left hand turn to set this situation up.

In other words...Kids, dont try this at home!

[JRouche]

That would be the last on my list.

Hey lookie there, it was an over powering of the turn and an unloaded front end. :) Revamp the list :machine: Just messin.

But it was obvious there was some serious engine power pulling the front up, you dont just have a car do that with suspension issues. If it was all suspension then the front outside tire would have been in much more of a compression. It was loaded, but stuck do to the compression stiffness he dialed in for the purpose.

Thats why I pointed out the front outside tire was unloaded. It wasnt, it was on a major compression, the inside tire had no where else to go but up, way up.

But all in all it is an interesting pic. Not everyday you see that. And cause it was kinda done on purpose, testing the car, makes it all the better.

I like the idea of taking the car to the track with extremes of suspension adjustments to see what the adjustments do. Only way you will see. Then you creep in on the perfect adjustments. JR

[Vegas69]

You did that with your stock urethane bushings Bret?

[bret]

You did that with your stock urethane bushings Bret?

Actually, we use rubber bushings in the AirBar.

[67LS1T56]

oops. wrong threadhad to delete.

[silver69camaro]

But it was obvious there was some serious engine power pulling the front up, you dont just have a car do that with suspension issues. If it was all suspension then the front outside tire would have been in much more of a compression. It was loaded, but stuck do to the compression stiffness he dialed in for the purpose.



I agree the engine is making some good power, but it pulled the front end up due to suspension "characteristics" rather than the power it makes. I've seen everything from M3s to Miatas get some serious three-wheeler airtime, and it's pretty much due to the vehicle setup.

A common contributor to a situation like that is often #2 on my list (too much front roll stiffness), which can be explained, as you said, why the outer front hub isn't in big-time compression.

[fatiger53]

Fatman Here. Bret said it right. And, Super Chevy kinda confused the issue a little. We did supply our front stub for the project, and then Bret supplied his own Airride rear four bar system. At the time, Bret had not yet developed his own coilovers as he has now, so we supplied it, and still sell their system with QA-1 coilovers rather than Shockwaves. As Bret says, welding is OK as a supplemental, personal peace of mind way to attach the system. Bret deserves the credit for this excellent design, and we are proud to use it here. And now, you can get it with his own design coilovers too.

[1969CamaroRS]

I don't care what the manufacturer says. Weld it in....it's a pretty well known fact that the air bar guys ripped a cradle loose in the autocross that was bolted in. If you intend to drive your car, I'd weld it.

They really beat on it for an entire season, most street cars wouldn't see that abuse. With that said I welded mine in :)