Aluminum Tig ? for the pros or whoever

[monte55]

I'll try to explain without pics..... I have a 6" diameter aluminum disk x .125 thick. I also have a 6" ID x .125 wall aluminum tube. The disk will fit into the
end of the tube flush with the end. It's a snug fit. I want to tig these together. I also want the weld to be flush. Do I v taper the inside of the tube
and taper the disk so when they come together there will be a V to fill and then grind flush. This has to be perfect. It will be spinning about 1000 rpm
What sequence... do I spot, then weld to have it stay true? Explain. This is the gear enclosure for my helicopter project that will hold oil..
KB hellllllllllllllllllllp!!
Thanks ..............................Nick

[MMW]

It will work the way you are describing with the "v" groove. Six long tacks (about 1" each) evenly spaced & then weld it up.

[MMW]

You can also line up the inside corner of the plate with the inside corner of the tube so will have an "outside corner weld". This leaves you with a nice area to fill up with weld & less sanding.

[kevbooth]

+1 for the outside corner idea. Also it might not be a bad idea to leave a 1/16" gap or so to make sure you get good penetration into the joint, because welding both sides would be difficult given the tight space inside the tube. A gap will make it easier to make it not leak as well.
The outside corner could be "trued" in a lathe, without removing much of the weld, leaving a stronger joint in the end.

If you need help, I'd be glad to lend a hand. I love projects like this, and it makes it even better that it's for a helicopter.

Later,
Kev

[monte55]

I understand the corner but the end plate is only 1/8" thick and it would be difficult to extend it out of the tube to make a corner joint and keep it square with the tube. As far as the gap idea which is good..............I have the problem of keeping the disk centered in the tube without elaborate jigging. This needs to run very true as it spins. The tube is about 5" deep
so welding is out..... at least for me it is.

Another question.......The tube will have about 3" of oil in it. I'm torn between
thinking the oil will be slung to the outside and not having lube in the center where it is needed...............but I'm also thinking the oil can't really grab the walls of the tube and will never reach the speed/force to totally stay at the outside wall. What are your ideas? I guess I need to spin a can with liquid in it and see the results. I might be going with the second thought.
thanks for the replies.
Nick

[Marcel Bauer]

I just made a model with a cordless drill and a plastic cup with water.

The water spins to the outside wall alright! That was only at about 200 rpm. Any faster and the water would have climbed out the top.

I also like the idea of a corner joint/weld. Accuracy in fit-up is no problem, just use three spacers exactly the same length on the inside at 120 deg.

[kcstott]

Tack it up evenly spaced around the diameter taping it into place as you go, Spread your heat out too. Tack one side then the other. you could set the tube upright one end over and other 5" tube or pipe this would hold and support the end cap as you weld.

Penetration should not be and issue with 1/8" material, Blow through maybe but not lack of penetration.

I've done jobs like this before where you just have to shim everything to fit.
It can be done and no elaborate fixture required.

And 1000 RPM's is not that fast considering it's weight. If you were off and 1/8" on the weld you would never see any vibration 3000 rpm maybe but not 1000.
And yes oil will stick to the side of the tube two ways to over come this with out lowering the speed is one use thinner oil or two use more oil.

Exactly what is this thing going to be????

[Broccoli1]

Exactly what is this thing going to be????

"This is the gear enclosure for my helicopter project that will hold oil.. "

[Marcel Bauer]

Nick, how about some more details for the curiosity in all of us? You know we can't possibly do this job justice until we know all the details...

[monte55]

Nick, how about some more details for the curiosity in all of us? You know we can't possibly do this job justice until we know all the details...

See "Flying Project" thread I started on 8-08. Pics there of the rotor head
I'm making.