XJ_Rudolph
NAXJA Forum User
- Location
- Pleasanton, CA
My "Hero" Blog
- Thread starter Jeep450r
- Start date
Well I finally got material for my crossmember today. I ended up getting it through work. Little did I know that I have access to thousands of pounds of perfectly good material that is left over from previous structural jobs. Better yet, I just gave the shop the dimensions of the steel that I needed and they cut it all to size for me. And it was all free. Even the material. I'm cool with that.
Here's what I got:
28.5" of 2x4x.25 box tube
2ft of 4" flat bar
(2) 16x7x.25 plates.
Thanks to those of you who offered me material for cheap or free. I would have taken you up on it but was already talking to the guys at the shop about the above and wanted to see how it worked out.
Aaron (Rudolph) and I have been drawing the crossmember up in CAD too. We made a little bit of progress last night and he plugged away at it some more while I was at work. Gonna tweak a few things on it tonight and then post some 3D renderings and stress analysis information for your feedback.
Here's what I got:
28.5" of 2x4x.25 box tube
2ft of 4" flat bar
(2) 16x7x.25 plates.
Thanks to those of you who offered me material for cheap or free. I would have taken you up on it but was already talking to the guys at the shop about the above and wanted to see how it worked out.
Aaron (Rudolph) and I have been drawing the crossmember up in CAD too. We made a little bit of progress last night and he plugged away at it some more while I was at work. Gonna tweak a few things on it tonight and then post some 3D renderings and stress analysis information for your feedback.
Mike1331
NAXJA Forum User
- Location
- Folsom, CA
Sick! Way cool you get all that steel for free. That's such a huge cost of building that you are set on.
831_xj
NAXJA Forum User
- Location
- Santa Cruz
Get to it bud! Hope to see you at cantina perhaps??
- Location
- Fort Collins, CO
Hell yeah man! That's awesome. No more drive lines rubbing your floors.
So Aaron and I have been playing with designs and this is what we ended up with. Huge thanks to Aaron for doing the majority of the CAD work and stress analysis. The stress analysis may not be entirely needed, but its fun to do and cool to see.
Here's what we came up with:
We applied a 12,000lb load on a spot in the center of the bottom of the crossmember that was 2" in diameter. The parts of the mounting plates that contact the "frame" rails were fixed as if they were sitting against the frame rail when the load was applied.
Here is the model showing the Von Mises Stress. Note the color bar on the left showing what stresses the different colors represent. Max stress was 239.4 KSI.
The next model shows the displacement. The max displacement was only .2177 in. Not bad for having an applied load of 12,000lbs.
I personally find these numbers a little hard to believe. I would expect more displacement but hell, I'll take it!
Anybody have input on this analysis or design? Did we overlook something obvious? Are we doing it all wrong? Are we color blind?
One thing to note is that we couldn't figure out how to use the weld feature on all of the joints. So that will change things. But this model isn't perfect, and we know that.
And Pat - I'm planning on being there for cantina. Usually the best run of the year if everyone's rigs aren't hacked together. I hope to see you there!
Here's what we came up with:
We applied a 12,000lb load on a spot in the center of the bottom of the crossmember that was 2" in diameter. The parts of the mounting plates that contact the "frame" rails were fixed as if they were sitting against the frame rail when the load was applied.
Here is the model showing the Von Mises Stress. Note the color bar on the left showing what stresses the different colors represent. Max stress was 239.4 KSI.
The next model shows the displacement. The max displacement was only .2177 in. Not bad for having an applied load of 12,000lbs.
I personally find these numbers a little hard to believe. I would expect more displacement but hell, I'll take it!
Anybody have input on this analysis or design? Did we overlook something obvious? Are we doing it all wrong? Are we color blind?
One thing to note is that we couldn't figure out how to use the weld feature on all of the joints. So that will change things. But this model isn't perfect, and we know that.
And Pat - I'm planning on being there for cantina. Usually the best run of the year if everyone's rigs aren't hacked together. I hope to see you there!
831_xj
NAXJA Forum User
- Location
- Santa Cruz
You're still clocking the tcase ya?
Yes. Clocking ring came in the mail today
Also those notches are cut for driveshaft and exhaust clearance.
XJ_Rudolph
NAXJA Forum User
- Location
- Pleasanton, CA
this picture is a little better, its not smooth shading its actual chunks.
So basically the yield strength of mild steel is around 30ksi, so anything in the light blue/green will be permanently damaged since it is above 30ksi. This test is with 12000lbs on the 2in circle in the middle of the xmember (same as the photos jeep450r posted).
So basically the yield strength of mild steel is around 30ksi, so anything in the light blue/green will be permanently damaged since it is above 30ksi. This test is with 12000lbs on the 2in circle in the middle of the xmember (same as the photos jeep450r posted).
blondejoncherokee
NAXJA Member
- Location
- sacramento
Add some 1/4" along the bottom and front and back then ...of course in real life what is 12000 pounds of force ?
XJ_Rudolph
NAXJA Forum User
- Location
- Pleasanton, CA
I just did double the cars heaviest weight. No matter how you hit it there will always be deflection of some type and the force is most likely going to be a lot less because of that. Also usually you have at least another point on the ground that will be able to share the force of impact. These stress tests are worst case senecio, and with .21in of displacement you will easily be able to drive home without worry.
Originally we put some 1/4in plate on the bottom, but that only helped the displacement by .02in
Yeah surprisingly the plate along the bottom and sides did very little to stiffen it up, so we removed them from the simulation and probably won't bother fabbing them up. I'm curious to see how the crossmember reacts when I add link mounts and apply forces to those.
- Location
- Virginia City, NV
Thats very sciency. Wish i knew how to do dat.
knucklehead 61
NAXJA Forum User
- Location
- Cottage Grove, Oregon
it will fold like a taco. :gee:
XJensen
NAXJA Forum User
- Location
- Sacramento
Like a crunch wrap? I know your a taco expert...
831_xj
NAXJA Forum User
- Location
- Santa Cruz
Yeah very cool design! No testing like the real world get to the grinding and welding I wanna see how flat you can get this thingaling!
- Location
- West Sacramento, CA
BigKintheXJ
NAXJA Forum User
- Location
- Cupertino
Is there an opportunity to buy cheap steel through you? What if you welded a thing of c-channel under those areas?
I was only using 1/4" flat bar. I'm trying to use material I already have and I already have the 1/4", no 3/8". The only way I could really do strength by shape would be to add some sort of ribbing to the inside of the crossmember before I box it in. Maybe I could weld some angle in there? I don't want anything welded to the bottom (aside from some plate) because the whole idea here is maximum ground clearance.
Unfortunately no, we don't sell to the public and Im not in a position where I can get material for others.
C channel would be a good idea but the issue is ground clearance. Im afraid it would hang too low for what I want.
XJ_Rudolph
NAXJA Forum User
- Location
- Pleasanton, CA
You might be able to rib the box where the cutouts are...would take some work. It doesnt flex/bend that much anyways. And your always going to get deflection or the steel springing or rock breaking a little to help absorb the impact. As long as you have some good welds where it connects to the ear plates then she will withstand a lot.
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