Can I drill a 2" hole in a 5" C Frame?

I think the only real solution here is to sell the truck ;-P
If the hole is centered in the frame (height) it will have the least effect on strength. I would weld a section of tube inside the hole to give it a little more strength. I would not box it however. If the plate used to box the frame was square, you would have stress concentrations at the corners which could lead to cracking. especially on an old C channel truck frame with riveted in cross members. The frame has some give in it, and a stiffer than the rest section could crack as the whole thing twists.
As far as above the axle not having the most stress... the axle is supported by the leaf springs. The shear force should be greatest at the spring mounts, the bending moment will be greatest in the middle of the span, or above the rear axle. This is why you will see some I beams with a web that gets thicker as it approaches the middle of the span. Pushing the flanges further apart greatly increases the resistance to a bending moment. It has no effect on the shear strength tho, so having a tall I beam at the ends of the span is a waste of steel. For this reason, it would be safer to drill a hole than to notch. Notching effectively brings the flanges closer together which exponentially reduces the resistance to a bending moment where it is most needed. I know it has been done, but plenty of people have built cars with no front brakes. Doesn't mean its a good idea.

 

Ok I think I have it, drill the hole, weld in a pipe, rerun the fuel fill, and sell the truck.
Thanks as always

Probably wont sell it on The HAMB now that this is out there.

 

This is why these "Structural Engineering" questions always turn into a shitstorm.

"Structural engineering is the art of molding materials we do not wholly understand into shapes we cannot precisely analyze, so as to withstand forces we cannot really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance."


'Nuff said.

 

No Surf! That is the poetry, altogether true. And then we best-estimate, what the structure should provide, in terms of wise material use.
One fact of engineering is; we realize 'at times', just how little we know.

 

Don't forget to shoot the engineer, so you can start production.

 

Google Tacoma Narrows bridge! Sometimes they guess wrong.

 

LOL. I am a structural engineer PE. But I do know I don't always have all the best answers.

My wagon parked in the 480' truss bay here at work:

 

I really don't believe the shit on here sometimes ? ? ?
Argue with a fence post ...
And to think my trailer ramp thread got deleted HAA

 

I thought that was scary, too. I'm not a mechanical engineer, so who knows. I saved this link for future reference though. I though it was interesting. I don't mean to highjack the thread.

http://67-72chevytrucks.com/vboard/showthread.php?t=457037

 

why are all of the pedestrians and the cathedral leaning to the left?

 

belled hole. sometimes you can find a dimple die used. kind of like an electricians knockout punch that puts the flare in the hole for strength. 2" hole in frame is no big deal.

 

I would really be impressed if those trusses ran North/South instead of East/West! LOL

 

Wouldn't it take some serious heat to get much bell out of a hole like that without cracking?

 

That is what I was thinking. while I love that idea I am fairly confident I cant produce that. I suspect the right dies on a hydraulic punch setup would produce that.

An alternative would be to weld a pipe on the hole.

 

How about you drill the hole and make a diamond shape plate with a hole in it to weld around the hole.
Hay I have been to the top of that leaning tower.

 

HOLY SHIT! I wouldn't park MY car under that! LOOKIT those HOLES in those trusses!!!

 

Probably shouldn't ask if I can drill 17 or so 1" holes in a 2" axle then should I?

So how many things are wrong with this ?
Lets see:
The area between the spring mounts is most critical. We know where the spring mounts are on this right ? Oops
% taken out doesn't equate to the % left oops
To close to the flange
Too far out of the neutral axis
Too many holes too close together
No reinforcements
No pipes
No boxing
No holed fish plates
No no no

This seems to defy every single reason or counter offered on this thread.

 

Hey, is that Squirrel out in the middle taking measurements?

 

Wow, I didn't know that the frame in question was made of forged steel. In that case, just load up the 12 gauge and pump a few rounds where you want the hole. You'll achieve the dimple, no problemmo. The removed steel is over rated.

Comparing a hole drilled into a frame by a hobbyist to an ENGINEERED truss system is hilarious. The better comparison would be to go remove one of the chords of that truss, and ask the design engineer to approve it. And let's not even go near the aircraft comparison.....what mechanic in his right mind would dare to drill a 2 inch hole into the structure of a wing? Funny stuff, dudes!

I tend to care about my family and other motorists, so I tend to build with some safety in mind. You are free to do whatever you want, of course.

 

an I beam has a lot more strength than a C channel.... with that being said I would drill my 2" hole in the frame and not worry about it.

 

This thread should have a poll.

 

maybe a disclaimer would be better....

 

agree
I shoulda gone to the vote
thought of that somewhere late in page 2

 

It's all about the moment of inertia

 

I think you still can, go to thread tools at the top.

 

blowby>>>This thread should have a poll.>>>

Just say no to big gasholes!

Jack E/NJ

 

Stress=Mc/I
Ever hear of this one?

 

No resonant frequency effects?

 

Pipe, boxing, heat, belled, sleeved, fish plate, do it, don't do it, trusses, wing spars, girders, Narrows bridge, leaning tower of Pizza...my head hurts...Im off to the shop to cut, shorten and weld my pitman arm