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RE: [PSUBS-MAILIST] how to machine a big pipe end?
Hi Alec.
Thanks for that. Sounds like it probably was the external stiffener that was the problem. At least you've managed to sort it out without to much trouble.
There isnt any stiffener on mine. Ive got the SS rings made ready to fit in and my plan is to tack them in with plenty of tacks, then i'll weld around into the root and then finally i'm going to weld on the cladding ready for machining.
I was going to use spray transfer for the cladding to get good penetration and a smooth (ish) bead ready for the machining. Im already hampered with the endcaps not fitting over the ring properly so i really dont want any distortion to compound the problem.
Maybe i'll make yet another damn brace to hold it all round.
Cheers
James
Hi James,
The cladding was done before I started welding, so that wouldn't be it.
I don't think it was the join between the 18 inches section and the main
length either, because it was 18 inches away from the SS. The culprit I
think was an external stiffener that's about a foot from the SS. The
stiffener fit over the pipe with some wiggle room. As I welded around
it, my theory is the weld contraction between stiffener and pipe pulled
the pipe out of round. My recommendation, if you have a similar
situation, is to tack weld it on numerous spots before you put in the
heavy passes, to try and prevent uneven pull. The one with the problem
was the second pod I made. I think on the first one I was more careful
with the tacking, and by the time I got to the second was probably a
little too eager to be done.
Good luck!
Alec
-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of James
Frankland
Sent: Monday, December 01, 2008 13:57
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] how to machine a big pipe end?
Hi Alec.
Can you tell me how you ended up with the distortion? Was it due to
welding the 18" bit of pod to the main part? Or as you did the
cladding. Or some other bit?
Im just about to do that lot for mine. Ive made the internal rings that
fit into the pods from stainless to minimise machine work.
The endcaps dont fit over the rings properly so i was going to skim a
bit off the rings at the same time as i machine the cladding.
thanks
James
----- Original Message -----
From: Smyth, Alec [mailto:Alec.Smyth@compuware.com]
To: personal_submersibles@psubs.org
Sent: Mon, 1 Dec 2008 09:11:36 -0500
Subject: RE: [PSUBS-MAILIST] how to machine a big pipe end?
Problem solved!
Here's what I ended up doing. I'm fortunate to have a Harbor Freight
store nearby, so as Dan suggested I went there and got a 20 ton jack
($39) to replace the 2 ton jack I'd been using before. Note for future
reference... they carry 50 ton jacks! With that I was able fairly
quickly to get the thing approximately round. But curiously the diameter
ended up too large all the way around. Only by about 0.004" though, so I
went at it with a hand file and emery paper. Once I got close, test
fittings of the endcap marked the contact spots and told me where to
file. The whole process took about 6 hours.
As always, thank you everyone for the suggestions.
Alec
________________________________
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Daniel Lance
Sent: Friday, November 28, 2008 18:04
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] how to machine a big pipe end?
Alec,
Go to Harbour Freight and buy a bigger hydraulic jack. They have some on
sale right now. Keep working with the jack method. With patience you
should be able to get to within a few thousandths of and inch. I had
this problem with the 12" pipe caps. If you cut , weld and remachine
then reweld you could end up right back to where you are now.
Dan Lance
----- Original Message -----
From: Smyth, Alec <mailto:Alec.Smyth@compuware.com>
To: personal_submersibles@psubs.org
Sent: 11/28/2008 5:53:02 PM
Subject: [PSUBS-MAILIST] how to machine a big pipe end?
I have a typical fabrication difficulty, and am wondering if
anyone can recommend a tool or idea.
The ends of my battery pods that receive removable endcaps have
a SS inside shoulder, and were buttered in SS. The shoulder and SS were
then machined to a close tolerance to seal with a similar SS ring on the
edge of the endcap. When this machining was done, the pod pipe was only
about 18" long so that it would fit on the lathe. That short bit has now
been welded to a much longer one, and I've also welded on external
stiffeners, through-hulls, etc. None of the welding was less than 10"
from the machined end, which I thought would prevent heat distortion.
One of the pods came out fine, but with the other I was wrong, the pipe
end is now an oval.
I've tried stretching the short diameter of the oval with a 2
ton hydralulic jack. That corrected it a bit, but I still have about
0.015" to go. This jack can't stretch the pipe any further, it's reached
its limit. But in any case, that's such an inexact way of fixing the
problem I don't think I could get it properly round to the final few
thousandths this way. I think I need to re-machine this pipe-end in
place, and obviously it isn't going to fit back on a lathe as is.
Ideas:
- Cut the pipe again to put the pipe end on the lathe, and
re-weld.
- Make a jig that will center on the pipe ID and have a
longitudinal shaft, with an adjustable arm mounted to it and a lathe
cutting tool on the end of that. Yuck, a lot of work.
- Is there some specialized tool out there?
Any ideas are welcome! BTW the pipe is 12.75" OD.
thanks,
Alec
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