Should I be pissed or is this my fault?

Friction shocks dampen the same in both directions, as in 50/50.

90/10 is a drag race shock, to allow the front end to lift on acceleration.
They are much stiffer in rebound than compression.

50/50 and 60/40 are common for street shocks.

 

I've used the perches before and I am 99 percent sure that they are a one piece casting. The shank is turned down on a lathe then theaded. A huge stress riser. I've switched over to high strength bolt welded to tubing for the eye.

-Kirk

 

45 degrees, I also had the front end aligned after the car was finished by a very reputable alignment shop.

 

If that is really a threaded casting, it is a shame. Lucky77 you could go to the welded/tubing type as a quick repair.

 

Glad you're okay. That's pretty scary.

Were the batwings located correctly so that the shackles were angled correctly on both sides? If maybe the bat wings were located too far apart for that spring, and the shackles were stretched out almost flat, maybe that could have put too much tension on that stud when the weight of the car shifted sideways and yanked on that broken stud. Do you have any "before" pictures of the front end so we could see if something didn't look right with the geometry of the front end in the shackle area?

It's possible if you nailed a curb or chuckhole really hard some other time, that it put a crack in that stud, and it just took a while to propagate until it finally snapped.

Maybe you should check everything to make sure there's no chance something in the suspension was bottoming out -- like see if some parts have marks where they were knocking into each other. It seems like you'd have to bottom out on something to be able to snap that bolt. When the front end is suspended by the springs, it only has to handle the load on the spring, but if it bottoms out metal to metal somewhere, suddenly it's like a jackhammer trying to snap that thing in half.

Maybe it's a defective part, but it would be good to rule out all the other possibilities in case there's something else that caused a perfectly good part to break.

If the inside of the hole in the bat wing is not round anymore, and oval and shiny and chewed up on the inside, that might be evidence that the stud had loosened up and rattled around in there a lot before it broke.

Good luck.

 

They still have pics of their cast Corvair Pitman arms on their site.

 

That entire piece doesn't look like a quality forging. If it's a casting what is it made from? Let's hope it's not cast iron LOL but who knows? Hit the eye hard with a sledge hammer and see if it breaks or bends. Breaks=cast iron, bends=shit or inferior steel. This kind of thing is scary and thank goodness for this website where others can learn from this. Also never use inferior china bolts sold at some of the big box stores-Use grade 5 or grade 8 where safety is concerned. Let us know about that material-obviously all one piece with no strong grain structure though the stud.....

 

Scott, Bring the part to Lunch if you can. I want to take a look if there is any evidence of heat treating. Depending on the construction there should have been a heat treat process applied to the part. If so and it wasn't done (several reasons for this) then the part was essentially a grade 5 part and the failure was "just a matter of time".

Frank

 

^^^^ what lucky77 said.

I'll add that this looks like a poor design to me. having the bolt go sideways puts a whole different stress on it than it would if the bolt was going down.

 

Really ?


How can you be sure?
Maybe they are supposed to break when you hit a bump.

 

Rusty, here's a shot of the part under load. You have to look closely and maybe blow the picture up but you can see the shackle seems to be slightly greater than 45 degrees. That shot was taken doing about 55 mph on a relatively smooth road. Also the batwings come pre welded to the axle, all I did was bolt it all together and bolt it to the perch.

 

I'm no damn engineer but that is only a 1/2" shank on that thing. Just seem's too small for me. I made my spring pivot's out of a grade 8 3/4" bolt and original ford forging's tig welded together. I dont know how your gonna fix it but I would be using something a little beefier. JMO Gregg

 

Counterfeit bolts are a huge problem in any industry that uses them. Even the certified mill test reports are being faked. I would talk to Speedway and find out what they say about the situation. No matter what, remain cool and professional.

 

This is a hell of a dangerous area for a single bolt with no backup plan.

At very minimal this needs to be a two bolt design. In maximum form it should be a complete plate mount system.

 

You could mount this plate to the barrel on the spring then plate mount it.

 

Or completely covert the mount to something like a rear trailing arm mount.

 

Any chance that the nut loosened up a little? It looks like the moment put on the shackle would normally be taken up by the flange where the stud begins. However, if it loosened, the moment would be on the stud only. This could have fatigued it with the ups and downs of normal driving over time (thus the rust at the crack). Just a theory, not pointing any fingers. It could also be in combination with poor part quality as well. I would let speedway know in a nice "I don't plan to sue you" tone to see what they say.

 

I thought bolts were Graded for "pull apart" strength, not "shear"?

As I know it, it's better to run something softer in order to see fatigue, rather than run something that will snap.

I dunno, just thinking(and probably incorrectly).

 

Nothing was lose on the suspension. Everything is painted black so it's easy to see if there was any movement. The hole in the batwing is not elongated, everything was tight. I do check out the suspension regularly, I even get under it to make sure nothing has come lose. Here's another shot of the suspension at rest so you can see the shackle angle.

 

It could of just been a bad part. From the looks of the pic's,it looks like there was a break in it for a while. I'd change them both out for some from SoCal,or something...

 

this tells me more that the bolt was lose and was pounded around the mounting hole reason it did not fall out. also looking at the amount of shank and lack of exposed threads it looks as if the nut had bottomed out.

 

I would be taking the driver side apart to see if there is a evidence of similar prob there . Perhaps it may shed some light on the subject . ​

 

Me - I'd put a different front end on.

I couldn't drive around wondering if a different manufacturer's part was going to the same thing, and when.

But that's just me.

 

Did you use all of the fasteners that came with it including washers? Just grabbing at straws here.

Were they the right grade? In my gut I would want Grade-8, but I've heard some experienced guys say that they would rather Grade-5's because they bend before they break...

 

From looking at the pictures it looks like the body of the bolt doesn't go all the way through the bat wing. It has threads inside the bat wing and that the break is at the end of the thread. The body of the bolt is the main support and the threaded part does little to add strength to the assembly because the thread diameter is smaller than the body of the bolt. Looking at the bat wing and the shackle end it looks like it was pulled up tight on the top but the force was not evenly distributed across the side of the bat wing. For what ever reason the threaded section at the end cracked, the bolt was then able to flex at that point until if finally broke. If the threads were cut in a lathe the have a good chance of creating a stress point at the end of the thread. Rolled threads are better and don't create the same stress point as single point cut threads.

To me the entire assemble is a little small for what it doing and the bolt should be a body fit bolt so that it doesn't have any chance of moving once it is tight. Larger diameter bolt, mating flat surfaces where the two parts meet and threads not long enough to go inside the bat wing would all help reduce the possibility of failure.

I would suggest that you pull the other side and check it, you will probably find a similar problem. Look at the mating surfaces of the two pieces and see what the contact area is, should be close to 100%. Look at the end of the thread and see if a stress crack is present. Look at the bottom of the hole in the bat wing and see if there is any sign of movement of depression in the steel.

Joe

 

I really don't like the fact that the bolt is mounted in shear. if the hole in the batwing was twisted 90 degrees so it was horizontal (or to fix this front end, I'm thinking you could weld a small L shaped bracket over that hole (using the existing hole for a plug weld as well as welding the outer perimeter of the verticle part of the L to the batwing), then drill a hole in the horizontal part of the L to mount the bolt part vertically (putting the bolt in compression instead of shear) while still ending up with the eye portion at the original spot so as to not affect ride height. You would need a shorter spring to do this, but looking at the picture of the front end at speed (I blew it up around 600% to make it clear), it looks to me like the shackle is more verticle than 45 deg., and that you already need a shorter spring.

 

Didn't like the looks of speedways setup so i made my own out of 5/8 grade 8 bolts, so far so good but now I am going to pull them and take a good look. Glad you didn't wreck your car.

 

Take a BIG hammer to the good one, see how far it will bend.

Report back with the results.

 

Yep. I'm amazed it took to page ...whatever page this is....for someone to say it. There are all sorts of reasons why that bolt could have broken but the only one that really matters is that it was used in the wrong application in the first place. That design is the problem. It could have been a grade 27 bolt but it would still have failed...eventually.

You gotta read Carrol Smiths books. It all makes sense.

Good luck on the repair. But don't just replace that broken part. It needs some re-engineering along the lines of Blownfuel's description.

 

When all else fails, look at how Ford did it. Look at a orig Ford perch bolt; the huge wide taper that creates a much bigger diameter of the perch bolt where the forces concentrate....plus the taper holds it all super tight.

Then look at that tiny piece of crap that you have. There is no gentle radius where the bolt shank joins the perch part. That is just lame engineering. It needs to be like a factory front spindle with a nice radius under the inner bearing.

Junk parts and a poor front end design.

Catalog building is a gamble at best.