Author Topic: Ball turning, a different perspective  (Read 4022 times)

Offline madjackghengis

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Ball turning, a different perspective
« on: April 22, 2010, 10:59:58 AM »
I am in need of an oil tank for a custom motorcycle, and have long envisioned exactly what I want, but have given up looking to find it already made.  Working on aircraft in the Marines, I saw a small spherical tank which held compressed nitrogen to operate the 20 mm guns at the wing roots.  Ever since that first time, I've wanted to make a spherical tank for a chopper, but have never gotten around to it.  A couple years ago, I built up a stack of plywood "rounds" on a lathe faceplate, but never finished it.  Last night, being disgusted with my lack of achievement yesterday, I took the faceplate off my non-functioning lathe, and with a bed sheet to protect it, mounted it on my primary lathe, and dug through my array of turning chisels.

After working the roughest off with a couple of gouges, and putting a good solid wire edge on them, so they need complete rework in sharpening, working by eye, I got out my best chisel, about two inches wide, a quarter inch thick at the back of the tapered edge, with a very slight curve to the edge, I got the block pretty well hemispherical, and fairly smooth, excepting the voids in the plywood, and a few spots that are low.

I used a boring bar minus a cutter as support for the chisels, moving it and swiveling it for best support and least chatter, and I will give it a good coat of bondo auto body putty, filling in all the voids and low spots, then do a final turning, and finish with sanding it off, and giving it a good coat of good hard paint that is smooth.  Then I will see if spinning on a lathe is as easy as turning wood on a metal lathe is.  Two of these hemispheres welded together, each about 8 and a half inches in diameter will give me a gallon of oil, and a quart of air space.  Another oddity from a slightly odd fellow. Too much to do, not enough time in life to do it in, mad jack :headbang:

Offline Jasonb

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Re: Ball turning, a different perspective
« Reply #1 on: April 22, 2010, 12:13:49 PM »
I've done a little bit of spinning and found it quiet easy, did have to annela the steel a couple of times though

Also wouldn't recomment the sheet so closeto the work, just one splinter would catch it and wrap it around the chuck

Jason

Offline madjackghengis

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Re: Ball turning, a different perspective
« Reply #2 on: April 23, 2010, 11:56:18 AM »
Thanks for the words of advise, I will be spinning using some 3000 series aluminum, which has very little alloyed in it, and takes a lot to workharden.  As to the sheet, if it grabbed, the spindle would quickly come to a stop, as the flat belt drive on this 1948 lathe won't pull a full half horsepower.  It is good advice though, and would certainly be of concern otherwise.  I expect to be "pushing the metal" with a stout piece of oak, and some wax to lubricate it.  I'm hoping that just pushing it around a hemisphere will let me avoid having to anneal it at all, and just get two pieces spun, and then weld them together, along with a few bungs, a couple of mounts, and the usual odds and ends.  :poke: mad jack

Offline Bernd

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Re: Ball turning, a different perspective
« Reply #3 on: April 23, 2010, 04:07:02 PM »
I'm going to be real interested in the welding part. You going to tig it or gas weld?

I've got some material together to try and gas weld aluminum. Now all I need is some time from my other projects.  ::)

Bernd
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Offline madjackghengis

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Re: Ball turning, a different perspective
« Reply #4 on: April 27, 2010, 11:52:11 AM »
Hi Bernd, I've read about gas welding aluminum, and I've tried it a couple times experimentally, just a couple pieces of scrap together, and while someone who has experience with it may be able to do wonderful things and perhaps things tig won't, I am not that man.  I will be tigging the tank, I've got a nice welder that was top of the line when I bought it fifteen years ago, I just had to replace the water cooled torch, and the new torch is perhaps a third the size of the one it replaced while having greater power capacity.  The old torch was a freebie, and probably sixty or seventy years old.  I like polished aluminum on bikes, and have made quite a few tanks, both fuel and oil, for many other people, but this tank has been on my mind for more than thirty years, the spinning blank has been on the face plate for about five years, glued up but unturned, I ran into a problem in what I was doing the other night, didn't have much time, saw the never cut blank, grabbed a sheet and a chisel, and in about twenty minutes turned the rough blank pretty close to final dimensions all free hand, I'd been kind of putting of turning it until I made a template for the radius, couldn't find a decent piece of carboard, so just decided to wing it, and I think it pretty closely approximates a hemisphere.  Close enough to make a template after the bondo and before the finishing with files, paper and the like.  Did you ever find that after you made something custom for yourself, you didn't want to make a copy of it for someone else, who sees it, and wants one "just like that"?  I'll take pictures as I go, just to make a record.  When I got hit with a virus a couple months ago I lost thirty years of pictures including all my overseas pictures, and all my pictures of my cross country trips, putting it on the internet means its always out there. my best, mad jack