Should I be pissed or is this my fault?

PLAIN SPRING PIVOTS

<!--googleon:snippet--> Use with 1-3/4" nylon shackle kit. .750 I.D. tube 1/2" fine stud.
Intended for "T" bucket and other short cross-spring front suspensions.

• .750 I.D. tube
• 1/2" fine stud
• Length of the threaded shank is 1"

<table border="0" cellpadding="0" cellspacing="0" width="100%"><tbody><tr><td align="left" valign="top" width="19%">91633005 </td> <td valign="top" width="45%"> <table border="0" cellpadding="0" cellspacing="0"> <tbody><tr> <td> Plain Spring Pivot </td> </tr> <tr> <td>
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</td> </tr> </tbody></table> </td> <td align="center" valign="top" width="7%"> EA </td> <td align="center" valign="top" width="13%" nowrap="nowrap"> $6.99</td></tr></tbody></table>http://www.speedwaymotors.com/p/6970,310_Plain-Spring-Pivots.html

 

The Ford perch bolts are 5/8", where they pass through the axle, IIRC.


Compare the areas, for a 1/2" and 5/8" thread.
Then imagine how many cents you would save making your bolts smaller.

 

I really appreciate everybody's input. I figured because this kit and company had been around so long that the stuff was pretty much fool proof. Guess I was wrong The rear suspension is all 1" tubing with 3/4" rod ends and all the hardware is above grade 8. The local Fastenall dealer showed me the stuff the City uses on all it's dump trucks and that's what I went with. I think it was over $30 for seven nuts/bolts/washers.

Well, I really like the way my car looks, but in all reality its more freakshow than hot rod. I was thinking of relocating the axle back under the frame over the winter and this event today kind of reafirms my thoughts. We'll see, the roadster I'm building is using all Ford parts in the front end except the perches. I was going to buy them from Speedway but I think I'll look elsewhere. Tomorrow I'll take the other mount off and see what it looks like. For right now I'm going to bed and give a little extra thanks to the big guy up above.

 

One more thing I just realized. This is why I didn't jump all over Speedway. Like I said before with me (200 lbs.) and a full tank of fuel (80 lbs.) the car weighs 2,440 lbs. Speedway says maximum weight for their "classic spring behind axle" front end is 2,500 lbs. I'm within 60 lbs. of the maximum, did I cut it too close?

 

The total weight doesn't matter, you are only worried about the weight on the front axle.

 

Your screen name has special meaning in this mishap, and maybe next time "the big guy" will let the cards fall where they may....meaning....

... why all Ford "except the perches"? I am using real Ford perches. Yes, they are too short for those add-on lower shock mounts, but those mounts I don't care for either. I've seen plenty of those shock mounts loose at the shows...no kidding...and it's usually one side only, due to the shocks twisting forces tightening one side, but loosening the other side because they are both right hand threads.

 

NO you didnt cut it too close..there should be at very least a 50&#37; safety margin built into those figures..more really .That bolt in shear could not possibly be considered a reasonable size to hold up a 2500lb car.
put simply ,that component was destined to fail. loaded in shear, all shock forces of the suspension through it, hard radius on the shoulder , it all points to poor design.I dont think that it is your fault, after all, it is offered for sale for this very application, BUT you have to take responsibility for choosing it, to a degree. I know i would not use that system.

I have a spring behind setup, but i use FORGED Ford perch pins, passing through a 1/4" wall sleeve with a taper to match the perch pin, that is then welded through the bones,
and locked up with a big arse 13/16th nut. Im happy with that.

my two cents.

oh, and bolt on shock mounts? fucking stupid, will never fit them again. I weld a bung onto the axle now, much nicer looking and No street rod look. they also dont make an aftermarket perch pin long enough to succesfully use em with a 2 1/4" boss axle.

 

I suppose that could contribute to the failure but I'm more concerned with how the original crack developed. Glad you didn;t cause any damage to yourself and I guess you picked one helluva user name.

 

When you fix it, take the new spring mount, tighten it tight like it should be. Then, make a nice solid weld around the nut on one side of the batwing, and another weld on the other side of the batwing.
Oh... screw four bar systems, radius rods and wishbones have always worked just fine. We've won World War II on point ignition systems and rotoary phones.
Lucky, its just a hot rod thing.

 

speedway cast suspension parts=scary. i dont like those perches they sell, nor the ones for spring over (at least the plain ones).

i had the spring over perches in my 34 p/u and went to romove the nut from one and in snapped right off, no good, so then i had to put a new perch in the damn thing.

I dont like speedways cast parts, cheepo castings.

thank god your ok.

JEFF

 

Another thing I noticed about that front suspension that's not really right is using a tubular axle with hairpin rods. Tubular axles have too much strength against twisting compared to I-beams. It puts way more stress on the hairpin rods when one wheel goes up while the other goes down. With a stock I-beam, the I-beam doesn't have a lot of strength against twisting, and it's pretty springy forged steel, so it twists to let one wheel go up and down in relation to the other one without any severe binding problems. With a tubular front axle, the axle is so stiff against torsion, that it behaves more like a big solid U-shaped piece when you use it with wishbones. 4-bars work better with a tubular axle. Wishbones work fine with an I-beam.

Thinking about it more, I think it's a crummy design putting that little part in single shear like that. It's like somebody was playing with an erector set and figured out a simple way to bolt everything together, but it's not really a well engineered setup. The only purpose to having it bolt on like that is to make it easy to change the caster angle. Instead of that Mickey Mouse stud, maybe you could do something like weld two big triangular gussets to the insides of both batwings and have fishmouths in the points of the gussets that wrap halfway around a piece of DOM tubing. That way it would be welded with lots of weld area and not have to rely on the puny shank of that Speedway part. You'd just have to make sure the piece of DOM tubing wound up parallel to the spring perches with the correct caster angle at ride height so you wouldn't wind up with any binding in the shackles.

When the axle goes up and down over bumps, the axle swings through a big arc that centers on the rear mounts of the hairpin rods. That slight swiveling back and forth might only be a degree or two in normal driving at the shackles, but it seems like it would be easy for that swiveling action to eventually start to loosen that Speedway stud from the nut that's holding it. Once it loosens a little, then it starts to rattle around in there and start banging itself to pieces at the root of the threads. Maybe not loose enough that you'd even notice it, but loose enough that the base of the Speedway part is no longer pulled tight against the batwing -- putting more stress on the threads than they would see if the part was tight against it.

That stud breaking is sort of like when you have the lug nuts loose that are supposed to hold your wheel on. When the lug nuts are pulled tight, the load of the wheel is spread out to the whole hub by the friction between the wheel and the hub, and the studs are mostly just in tension. But when the nuts are loose, the wheel is free to rattle around and hammer at the studs in single shear until they shear right off.

Even if you checked the tightness of that bolt religiously, it seems like the design of that Speedway part in that type of application where the axle is swinging through a gentle arc is bound to try to keep loosening it over and over. Every time the front end dives down, the slight twisting action there is like a wrench trying to loosen it a hair.

Yeah, that Carrol Smith book that someone mentioned is great.

 

Id be more angry that stuff like that is avaliable. Its a bit of a trap for first time builders hat dont have a history in hot rodding. Having it mounted in sheer like that is scary, at first I thought it was a swan neck that had broken in several places. It just didnt cross my mind that it would be mounted like that.
Yeah there may be thousands of em out there but people took Falidimide for years and look at what that shit did to people! Just because its avaliable doesnt mean its good.

Doc.

PS, Is the Carrol Smith book still avaliable?

 

That sucks..Im not going to offer up my speculation..I think its been covered already. I am glad your ok, and that it happened while you were moving slow and close enough to home, that flat bedding it didnt break your piggy bank too.
Winter is on its way. Time to re- think that front end.

at any rate, you say this was a "Kit" from speedway? If so I would send that part back to them and let them know about this failure..they can only correct an issue if they are made aware of it. good luck . I hope all comes out good in the end

 

We use bolts in single shear on race car coilovers all the time. Not the best idea, but that part should sure hold the weight and shock load on a car that light.

I think the problem lies in the design of the shackle mount. I beleive those are actually a one piece forging that are machined down in the stud area. Someone feel free to correct me if I'm wrong. If it had more of a radius on the shoulder where the stud is machined down, it might hold up better.

 

You've most likely checked this - with the batwings welded to the axle angled inward the shackle mount used is usually not straight but one angled 7 or 11 degrees to mate up straight with the spring.

 

All i can say is that I am glad i built my own and used grade 8 bolts, and thats why I use grade 8 on everything. Here's how i did mine.



Glad to hear that you are alright.

 

For what it's worth, probably nothing, did you tighten the nut on that thing while the car was in the air or when it was down on its wheels? Most suspension parts should be snugged up while the car is off the ground and tightened to final torque with the weight of the car is on its wheels. It occurs to me that if you torqued them down while the car was off the ground, when you finally set the car down, the stud had excesive torsional and shear loads on it making it more apt to break like that.

Just my .02.

 

I'm a first time rodder and my "suicide" front is set up that way, except the part that you broke is mounted to a braket that someone welded below the wishbone. I have looked at it more than once thinking that it was a weak point! I saw someone on the forum made weld on brakets with the spring shackel mount built in and then welded to the radius rod, I think I'll do the same thing. Might be worth it to post those photos here if someone knows how (I'm pitiful with computers) They looked like a "C" shaped piece of 1/4 inch plate that fit around the radius rod with the perch tube welded in place then welded to the rod. Looked stout to me.

 

That is a cast steel piece rather than a forged steel piece as Ford made them originally. Cast steel is hell for strong but inspection must be carefully made of each piece when manufactured. The BEST is the forged stuff from Ford. This style stud perch was used on all the Ts in the rear including the TT trucks from 1919-27. The TT forgings are larger than the passenger car pieces but you'll never break one either.
I'd rather use a stud perch made from a steel bolt welded to a piece of steel tubing than a cast piece like you had.

 

Unrelated to the actual technical solution, I think you should add a 3rd column of consideration other than speedway's fault versus your fault. Call it "shit happens".

That part looks an awful lot like the shitty poly bushed rod ends speedway is notorious for selling, and is probably manufactured the same way. You should probably source the replacement (both sides) somewhere else.

Good luck

 

Glad your ok. Seems like a chineese part failure to me. Thats all speedway sells.

 

are any aftermarket hotrod suspension parts controled by DOT testing?, i kinda dont think so, does speedway or any other company have there own "test to destruction" program?, i'd like to thank you for doing this post as now i'm going to take another look at my front end parts before i install them, i look at the bolt coming out of your perch and i think its way to small, should be a 3/4" shaft thats been bored and taped with a washer and a cap screw on the opposite side holding it on, the tab the bolt goes through is way to small, if the bolt had not broken down the road the tab would have. i bet the reason more have not failed is most people dont drive there cars that often, what would the front end look like after 300,000 miles?

 

that would also put torsion on the bolt all the time.with only the spring shackles and rubber spring bushings to allow some play.the idea of setting these up on the ground with full weight on the spring and then checking for bind seems like a good idea.along with the better mounting ideas.

 

When the kit arrived I bolted it all together and put it on the chassis as one unit. After everything was on the car I tightened everything one more time before I hit the road.

 

Looks like it may have come loose and was shaking around in there... Maybe put a little lock tite on the nut next time.

 

But I must say, the threaded shank on that type of perch is much thinner than a normal perch that goes through the axle in a "spring over" set up... Does looks a little scary.

 

It's a bad design (the front axle) to start with. Having all the weight on 2 attachment points in shear (ever wiggle a wire back and forth to break it?) is asking for trouble.

 

Yes, single shear is fine, in the right application;
but would you use 1/2-20 bolts on coil overs ?
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Forgings have wider parting lines than castings.
Makes it easy to spot the difference.
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Adding a larger rad at the shoulder wouldn't help,
because it didn't break there.

 

Like an old feller(his term)told me a long time ago,"Hot rods is like Frankenstein monsters,you gotta tighten up their bolts to get 'em to act right every now and then!"
Glad to hear everything turned out all right for you.Live to rod on another day!
Happy endings are good.

 

Yes, we do use 1/2-20.

Didn't see it the first time, but you're absolutely right, it didn't break at the shoulder, which has me wondering...


I was looking at the fact the broken stud is still flush with the inside of the batwing (as near as I can tell), but there IS some stud left on the perch.

OK, I just went out and looked at that exact assembly we have sitting in the shop, and there is a little shoulder right at the base of the threads (where Lucky's broke) that does NOT fit thru the hole in the batwing. I'm assuming it should pull thru (slight press fit) when tightened?

Lucky, was it pulled all the way tight? Looks like they were touching from the wear marks but it might be worth checking the other side...