joining new tube to old tube?'s

[fathead]

I'm cutting the roof of my 4 seater to reconfigure the cage.
This will require joining the new tube to the old tube where I make the cut. I will slip a section of tube inside the old and new to help transfer the load. The chassis is 1 1/2" .120 wall.
My question is, how long should the tube inside the tubes be? How thick should it be? And what is rule as far as drilling a hole in the outer tube, up and down stream of the intersection. How big of a hole, how many etc.
Thanks

[movindirt]

For splice use 1.25 x .120 tube 6" long. Drill 3 holes (.375") in the 1.5" tube about 1.5" from the ends (both sides). Also leave about .125" gap at splice so you can weld all 3 tubes at the same time. Hope that helps...

[fathead]

should it something like this? Would it be better to have the holes staggerd. I know they need to be on the right, back and left side?

[fathead]

For splice use 1.25 x .120 tube 6" long. Drill 3 holes (.375") in the 1.5" tube about 1.5" from the ends (both sides). Also leave about .125" gap at splice so you can weld all 3 tubes at the same time. Hope that helps...

Thanks by the way!

[movindirt]

Sure the way you have them in the pic will work. Not really a hard and fast rule.. Just make sure the holes land on the splice tube and are not to close to the splice. If you lay them out the way you have pictured then you could even go larger (.4375") on the holes to make it a bit easier to weld.

[partybarge_pilot]

If you are MIG welding it, go larger on the rosette holes.

[Triaged]

Read this starting on p67 of the pdf
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/8ce3f88c034ae31a85256981007848e7/99c827db9baac81b86256b4500596c4e/$FILE/Chapter%2004.pdf

[movindirt]

Great info in that pdf.. I wouldn't worry about making the cut diagonal. My front coil over hoops are sleeved and loaded in tension. They have taking tons of abuse with zero issues. The sleeves you would be putting in your cage will never see tension
loads (about the only way a sleeved joint will fail) as my hoops are unless you are really big (around 4000lbs) and forget to strap in. Don't get me wrong, the diagonal cut method would be stronger just could be a PITA to make happen with what you are doing.

[fathead]

Great info guys, thanks for the help.

One more question,
We will probably be tig welding this, but either way, (mig or tig) is it bad to grind/blend the welds after to make it look seemless?

[movindirt]

Great info guys, thanks for the help.

One more question,
We will probably be tig welding this, but either way, (mig or tig) is it bad to grind/blend the welds after to make it look seemless?

Nope. the welds are not really doing much unless you load the splice in tension. In your case the tube is going to fail on either side of the inner splice tube if it is to fail. Now I am not saying you can get by with sub par welds but to blend them in is not going to hurt anything. And not saying you would allow sub par welding:D

Good luck with your project. Post up some pics if you get a chance.