Need some engineering help.

[drnickriviera]

I'm making a panhard rod for my car. For those that don't know what one is, a panhard rod locates the rear end of the car side to side. It's used when you have a solid rear axle.

So here's what I need to know.

3/4" diameter .058" wall tubing. 48" long. 4130 Cromoly, Normalized. 90ksi tensile strength.

Car weight 2600lbs. Max 1g skidpad. For a safety factor, let's assume all the weight will be on the rear axle.

The tube will be horizontal with the forces horizontal. How much force can that tubing take before it bends?? I have no idea how to calculate something like this.

 

[drnickriviera]

Any ideas? Or is this simply too complicated?

 

[bonkers325]

you should ask the retailer for that information, usually they have that info readily available

 

[radioouman]

What vehicle are you looking to build this for?

Are you an engineer?
If so, located a book on strength of materials and use the equations to load a hollow column.
Even though I routinely load tubes in my job, I load them in torsion, so I don't have the equation that you need.

For the F-bodies, the aftermarket is using 1.25" diameter tubes. Do you need to go with a tube that is only .75"?

http://www.bmrfabrication.com/F-bodySuspension.htm

 

[drnickriviera]

It's for my 78' MGB that i'm doing a V8 conversion on. I put in a Ford 8" rear end and coil overs. The original setup was leafsprings and had no lateral locating device.

I saw the f-body rods and that's why I posted the question. I have another premade panhard rod someone gave me and it's only 5/8" dia with .125 wall, so i'm confused as to what size it needs to be.

I don't have to use .75" but I already have the tubing, heim joints and threaded tube adapters.

I'm no engineer, but i'm sure I could figure it out with a little guidance. When you say strength of materials, what do I need to find? Modulus of Elasticitiy?

I'm looking at this page, but it's all gibberish to me
http://physics.uwstout.edu/StatStr/statics/Columns/colse62d.htm

 

[kaizersose]

Originally posted by: drnickriviera
I'm making a panhard rod for my car. For those that don't know what one is, a panhard rod locates the rear end of the car side to side. It's used when you have a solid rear axle.

So here's what I need to know.

3/4" diameter .058" wall tubing. 48" long. 4130 Cromoly, Normalized. 90ksi tensile strength.

Car weight 2600lbs. Max 1g skidpad. For a safety factor, let's assume all the weight will be on the rear axle.

The tube will be horizontal with the forces horizontal. How much force can that tubing take before it bends?? I have no idea how to calculate something like this.

clarification: you are saying that the force acting on the tube will be acting only axially, meaning (the force vector is) parallel to the length?

if so, then it is:
sigma=Force/Area, sigmamax=90,000 lbs/inch^2, as long as sigma<sigmamax, you should be good.

my guess is that there is more to it than that. real life loading situations tend to be multidimensional. btw, use generous safety factors. there are flaws you will never be able to otherwise account for.

 

[skyking]

IIRC, a panhard rod is mounted with ball joints on the ends, to fixed pins. Unless you bind or defeat the ball action of the joint itself, the axial load is everything. It won't be subjected to bending loads.

 

[hypn0tik]

Safety factor of 3 FTW!

 

[kaizersose]

Originally posted by: kaizersose

Originally posted by: drnickriviera
I'm making a panhard rod for my car. For those that don't know what one is, a panhard rod locates the rear end of the car side to side. It's used when you have a solid rear axle.

So here's what I need to know.

3/4" diameter .058" wall tubing. 48" long. 4130 Cromoly, Normalized. 90ksi tensile strength.

Car weight 2600lbs. Max 1g skidpad. For a safety factor, let's assume all the weight will be on the rear axle.

The tube will be horizontal with the forces horizontal. How much force can that tubing take before it bends?? I have no idea how to calculate something like this.

clarification: you are saying that the force acting on the tube will be acting only axially, meaning (the force vector is) parallel to the length?

if so, then it is:
sigma=Force/Area, sigmamax=90,000 lbs/inch^2, as long as sigma<sigmamax, you should be good.

my guess is that there is more to it than that. real life loading situations tend to be multidimensional. btw, use generous safety factors. there are flaws you will never be able to otherwise account for.

Originally posted by: skyking
IIRC, a panhard rod is mounted with ball joints on the ends, to fixed pins. Unless you bind or defeat the ball action of the joint itself, the axial load is everything. It won't be subjected to bending loads.

simple enough then. I would use weight*2.5 for the force and you can find the area using the wall thickness and diameter. if it comes out too high, look for a more stiff or thickly walled tube.