Technical Structural Analysis software

I’ve got a really super neat front axle I would love to use. I believe it’s not going to be strong enough though.
Anyone have the computer gizmo stuff to confirm or deny my suspicion? Maybe I can beef up the found weak points. Maybe I’ll feel better about it being wall hanger.

 

Here’s a few pics, let me know what info is needed to run it thru.

 

To do an FEA (finite element analysis) You'd first need to to make an accurate 3D model of it in a CAD program like Solidworks. To be meaningful the steel grades, weld quality and other factors would have to be entered and since that information is unknown, then no, you can't do anything useful with "computer gizmo stuff".

 

I'd say that the main issue is the integrity of the welds plus the actual wall thickness of the axle tube are the big issues after cleaning up some of the clutter around the spring mount on the axle plus is there a gusset on the bottom side of the spring mount.

 

For an accurate FEA, you also need to know what input loads and forces are going into that suspension. Generally in the heavy truck world, we use 1.8 x GAWR (Gross Axle Weight Rating) as a worst case scenario, but dynamic events in smaller, lighter cars can often exceed that by a fair amount. The question is by how much, and since this looks like a dragster chassis, coming down off a wheelie could create some very high loads. At least you don't have to worry about braking loads....

 

It can be calculated pretty easily without CAD and FEA. It is really a simple cantilever beam problem. There is a torsion load and a bending load. The bending load is from the shackle mount to the tire patch. The load times distance is the moment. The torsion is the load times the shackle distance. You need the dimensions and the wall thickness. The fail load would depend on the steel but assume mild steel to be on the safe side.

 

Andy is spot on. If you have a handle on the input loads. A few free body diagrams, then calculating the section properties in a few areas, it can all be done by hand.

Everything you need is in here.

 

Oh I’d put some brakes on it,

 

better pics of same axle
Different location

 

For starters, you need to know the exact material(s) you have there before you can determine if it will be safe for your application.....with their respective stress/strain curves. Then, you need to figure out the static and dynamic loads....which will be no easy feat, since you have no way to determine them, short of strain/load instrumentation/testing. And...you need to determine the margins of safety (safety factors) necessary for safe operation in your application. And then...you need someone sufficiently competent to operate an FEA software program, or manually calculate the stresses and deflections of the entire chassis as a system.

Or...you can simply put it on your vehicle and see what happens.......like most hot rodders do.......

 

And then, you have to have a pretty good idea of what the likely loads from your chassis setup would be to apply to that analysis model once built......

 

What do you want to use it in?

 

The wall thickness can be determined without drilling a hole in the tube. All of the welded on parts can be measured and the weight determined from the volume of steel. ( .283 lbs/cubic inch) .The whole axle weight would then have the welded on weight subtracted. It would then be able to calculate the wall thickness from weight and length of the tube.

 

My $0.02.........It appears that the "spring weight/mount" is situated on the front of the axle. Regardless of strength or lack of it, I would think that there will be a constant twisting load on the bushing spring mounts. I realize there are a pair of radius arms mounts back to the frame, but generally speaking, I'd say that basic designs of these sorts of things are configured for symmetrical loads on bushings and other load bearing parts. So the only comment I'd every think of right now, if someone GAVE me that axle to put on anything that I may be building, I would just say, "Thanks anyway"......

 

Too many ground down welds for my liking. Pretty isn't always safe.

 

I'd worry more about the steering arm welded to the spindle. You could always get hamber WAC to make you a new bulletproof axle if you have no faith in this one.

 

On my Vicky
Under that hemi.

 

I would find another axle....this one would be OK on a dragster....

 

I've got a very similar steering arm on the chrome roundbacks that I got for a sweet price and figure that I am going to have to cut all three hand made welded on and chromed arms off and use bolt on arms.

 

Not one grinder mark

 

Random thoughts.
I would find other spindles, switch to a four bar, and weld on mounts for spring over instead of spring ahead.
If you give me the dimensions and weights, I will run the numbers.

 

I'd run that axle as is. I dig it, just keep your eye on it. "If" it fails, it won't fail catastrophically like a cast axle many of the naysayers may run. It may bend, and on the wall it goes. You're already using spindle mounts up front, the unknown but cool axle adds to the fun.

 

You probably should clean off all the welds and dye-check/mag particle inspect them for cracks.......or have your life and casualty insurance paid up to date........

 

Yeah; but Ohio isn't on the east coast; thus the spring is on the wrong side of the axle.

 

I stand corrected. The earlier photos looked like the welds had been ground smooth.

 

I’m guessing the axle itself is probably good enough, but looking at the bracket design for the spring support and that of the radius arms would have me tossing it as is. The radius rod brackets are paper thin, and a better design would have used thicker material that would have incorporated it as a means to wrap around the axle and act as a gusset(s) for the spring bracket. The steering arm also looks suspect.
It would be relatively easy to make some simple hand calculations with enough info about material and static loads, but ultimately, something like this will fail due to dynamic loading which is very complex to model and generally not done by hobbyists.

 

As an old guy currently back in school, pursuing the mechanical engineering degree that I was too lazy to get the first time around, I love all the comments on this thread! Lots of good technical advice.
Modeling/analyzing these things can get really complex, really fast, but the first thing I thought when I saw the pics was that it's really not smart putting the spring mounts out front like that. The other posters noted this already, with the car's weight putting constant torque on the axle, every time you hit a bump your caster would increase, which is the opposite of what you would want for good steering. Sure, on a dragster this might not seem to matter, but in that case, as mentioned above, you have a car coming down off of a wheelie, and then all that weight, magnified by the torque from the offset perch, will put a lot of stress on those welds. So, while it looks really cool (I could see it on a Roth style bubble top!), it might be best for a show car.

 

How about this apprach. Determine the wall thickness of the tube and calculate the section modulus. Then calculate the section modulus of a Ford beam axle and compair it to the tube section modulus. If the tube's is greater then go with it..

 

Funkin run it, if you were to replace the axle with a RE housing and turned it around, it would basically be the same suspension as a T bucket. Welds look fine, Weigh the axle to get close to the wall thickness