? about placing a bolt through tube?

Post by **alk1174** » Thu Dec 13, 2007 4:17 pm

I am looking to drill through a piece of tube and weld in a sleeve so I can run a bolt through it. I am wondering how this will affect the strength of the tube. I have seen this done without the sleeve and the tube ended up splitting at the hole. Will a sleeve welded into the hole get most of the strength back? Anyone have any knowledge on this?

Like in the PDF below.

Post by **Arya Ebrahimi** » Thu Dec 13, 2007 5:32 pm

I can't speak to the actual strength differences as compared to an undrilled tube, but I know that several sports car manufacturers use this technique to secure their seat belts to the chassis.

Take that for what it's worth I guess.

Post by **Billet Benny** » Thu Dec 13, 2007 8:32 pm

If the tube you stick in is of decent wall thickness (as I'd assume if you're running a bolt through it) you don't have anything to really worry about. Make the sleeve stick out farther on each side of the tube than in the pdf. That way you can weld it a little better and it's an easier weld to pull off. However, I wouldn't do this in a main structural run of tube without a very nearby brace or cluster.

Post by **Steinberg** » Thu Dec 13, 2007 10:43 pm

my engineering take on it: a hole through the tube creates a stress riser which is what leads to the failure. once you weld in a thick-walled sleeve, the extra stress created by that stress riser is distributed across more cross-sectional area, making up for the magnified stress at that location.

my gut instinct says that if you sleeve it you're not gonna have much to worry about.

Post by **alk1174** » Fri Dec 14, 2007 7:08 am

Thanks for the input guys. This is for the top harness mount. It will be on the cross bar about 8" away from the B hoop so from what you are saying it should be ok.

Post by **MILLER** » Fri Dec 14, 2007 9:24 am

Steinberg wrote:my engineering take on it: a hole through the tube creates a stress riser which is what leads to the failure. once you weld in a thick-walled sleeve, the extra stress created by that stress riser is distributed across more cross-sectional area, making up for the magnified stress at that location.

my gut instinct says that if you sleeve it you're not gonna have much to worry about.

True, but Benny didnt elaborate that far. And the hole w/ or w/o a sleeve will weaken the member it is in. The point that should be made here is that if the member is a main structural member, extra steps need to be taken than just sleving the hole. One is better off adding a short piece of tube between two structural member to put the hole with sleeve through.

Post by **Steinberg** » Sat Dec 15, 2007 2:07 am

no comments about me being a nerd and having no life....

I made an FEA model for 3 cases: no hole, hole in tube, sleeved hole.

1.75"x0.125 wall tube
3/8" hole
1/4" wall sleeve
Young's modulus: 29,500 ksi
Poisson's ratio: 0.290
Bending applied so that the hole is in max tension/compression

click below for the pdf with the output plots. note that the color scale is not the same for all plots.

going from plain tube to an un-sleeved hole is 3 times the max stress
going from plain tube to a sleeved hole is 1.25 times max stress

I doubt that 1.25 stress concentration factor is gonna differ much from any other welded joint in the cage.

Post by **shmoken875** » Sun Dec 16, 2007 12:09 am

Steinberg wrote:no comments about me being a nerd and having no life....

I made an FEA model for 3 cases: no hole, hole in tube, sleeved hole.

1.75"x0.125 wall tube
3/8" hole
1/4" wall sleeve
Young's modulus: 29,500 ksi
Poisson's ratio: 0.290
Bending applied so that the hole is in max tension/compression

click below for the pdf with the output plots. note that the color scale is not the same for all plots.

going from plain tube to an un-sleeved hole is 3 times the max stress
going from plain tube to a sleeved hole is 1.25 times max stress

I doubt that 1.25 stress concentration factor is gonna differ much from any other welded joint in the cage.

dude that shits awesome, what are ya? ME? All this time and I never really thought to ask anybody what their majors were

Post by **Steinberg** » Sun Dec 16, 2007 12:33 am

yeah, ME. I occasionally need something like this to remind myself it's useful. thanks Adam!