Featured Technical Broken Super Bell axle

As hot rodder's we all do "stuff" that's not exactly safe, no front brakes, "fruit jar" master cylinders, no windshield wipers, ETC. An "I" beam axle consists of two flanges and a web. In construction, both steel and LVL wood beams require structural and mathematical formulas to get the right size. In steel I beam construction, drilling or cutting holes in the web is never allowed, legally that is. In wood LVL beams drilling is allowed by following strict formulas as to the size of the beam and hole size. I have seen I beam axles that have holes drilled in them that are too small and it does not look right, so the answer is drill bigger holes. I have seen holes drilled in axles that actually touch the flanges and that vastly changes the structure of the beam. The mathematical formulas are very complex, but I wonder if anyone has ever taken the time to see how drilling different sized holes effect the I beam axle structurally.

 

I have some guys that I work with that could make quick and easy ****ysis of what putting holes in these I beam axles actually does to strength. However, modeling one up to do that would be the first step as well as knowing the actual loads on the axle. Anyway, if someone had an axle modeled up for something like a 32, I would volunteer that we could do the ****ysis and report back. The closest I have done to modeling up an axle so far is when I modeled up a sign for Sid to hold one...

 

I have had several Ch***is Engeneering Forged axle. HRP

 

@ocool25


Hello,

I moved the photo around so the two ends meet or sort of meet. But, I am puzzled as to the goopy stuff on the end of the axle going across. (blue arrows)

But, besides the point, the weakest point of a drilled axle are the holes. The holes nearest the ends seem to get more action and therefore could happen again. It does show the crack right in the hole area...

Yes, thousands of hot rod folks have drilled axles. We had a solid one on our 327 powered 1940 Ford Sedan Delivery. It never cracked over the 1000s of miles we drove all over the West coast and inland portions of California.


Jnaki

At least the axle company stood by their product... good on them.

 

I have slightly less concern about axles that have broken during a crash then I do when axles break before a crash, because those that break before the crash are often the reason for the crash.
Axles are not suppose to break at all, as far as I'm concerned, but I have seen some mangled stuff after crashes.

Back when beam axles were the thing to have on dirt tracks, it was not unusual for the left front tire to be off the ground coming through the turns, when the cars crashed. I've seen beam axles really bent up, and I've see them ripped out from under the cars, but I don't ever remember seeing an axle broken.

 

How an axle is impacted will have great influence on whether it breaks or not. The normal impact is mostly vertically with only a small portion of the load being horizontally. So when your car is traveling down the road hitting bumps most of the impact force is vertical. With this car being struck directly to one front tire by another car all the force was horizontal against the tire and the end of the axle was pushed backwards while the spring held the axle at the perch. Not the usual impact an axle ever sees, thus it stressed it in a direction that caused it to break. Might have been 1 mph, but how much lateral force the heavier car's impact caused would take an engineer to figure out.

 

What a coincidence, so do I!

 

The holes in the OP's axle look like they are drilled high in the web and could be affecting the top flange.
@ocool25 , did you buy the axle drilled or was it drilled after it was purchased?

 

With an axle with that much drop, when the tire hits a solid object it also causes the axle to twist, due to the lever action of the spindle being 6 to more inches above the axle beam.

 

Would probably be fairly easy to figure out the forces involved if you knew the slope, weight of both cars, distance traveled to impact, and distance both cars traveled after impact, and some measurements from impact point to vehicle centrelines. Probably, a few ***umptions needed as well.
Judging by the fact that it fractured where the hole was, it makes sense due to the reduction in cross-sectional area. The fact that the hole centrelines are a little biased upwards I don’t think would have made much difference in this failure mode (horizontal bending moment - I think).

 

With the drop, the holes and the added scrub, lots of stress on that axle when the tire was impacted head on. Even if it were a forged axle, it most likely would have bent.