Air Tank Cone Mandrel

[JHCC]

Finding myself in possession of a thick-walled air tank, I decided to try out an idea I’d messed about with previously but never finished: converting it to a cone mandrel. (My apologies for not having taken quite as many photos of the process as I might have.)

 The first step was to torch out the eight  gores that make up the cone. These were isosceles triangles 2” wide at the base and about 15” long, still attached to the main cylinder. I forgot to take a photo, but here’s the offcut, which should give you a good idea:

I heated each of these triangles at its base with the oxypropane torch and bent them inward until the tips meet in the center. Because my cutting skills are somewhat lacking, this required a fair bit of trimming with a cutting disk in the angle grinder, just widening out each joint where it was making contact until all the pieces could come all the way in. As pieces came into alignment, I tacked welded them until everything was in place.

(NB: see that bit of pipe sticking out of the side? Remember that; it will be important later.)

Then I welded all the seams up with FCAW and wire brushed the whole piece.

 Next, I ground off the welds, leaving an octagonal cone with rounded sides. Some more blending with a flap disk smoothed things out and left it fairly round. 

The next step was to torch off the remaining end of the tank and weld the mandrel to a piece of 3/4” plate I had knocking about. 

Then I welded some bars to the base, so that it would fit in the 2” hardy hole on my striking anvil. 

Finally, I filled the cone with sand through that pipe fitting on the side and screwed on an end cap to keep it all inside. That bit of pipe is also quite handy for lifting the cone on and off the striking anvil.

Haven’t had a chance to forge with it yet, but I’ll provide an update later. 

[George N. M.]

Cool project, John.  My only suggestion is to put some file marks on the cone at various diameters, e.g. 3", 3 1/2", 4", etc..And label them with metal stamps or magic marker or something.  I'll be curious as to how much you use the cone mandref in preference to the horn on your anvil(s).

GNM

"By hammer and hand all arts do stand."

[gewoon ik]

Now you have a cone and a crown.

Nicr work

[Frosty]

Pretty slick John, nicely done. I'm with George regarding marking different diameters, maybe you can make a story pole that when rested on the cone's base has marks that indicate diameters. That way they can't wear off the cone. OR you could turn rings of various diameter and just drop the one you want on and mark the mandrel. 

Hmmm, I'm starting to think of a number of different gauges to serve the purpose of marking specific diameters on the cone, a long narrow piece of plywood or sheet metal with marked holes in it could hang on the wall out of the way. 

I like it John, a LOT.

Frosty The Lucky.

[JHCC]

Thanks, Frosty. I'm going to wait to see how much I use it before adding permanent marks. In the mean time, I'll probably just use a pair of outside calipers set to the desired diameter for a specific project to mark the appropriate height with some chalk. 

(By the way, the 3/4" plate was salvaged from some construction debris and had some HUGE beads and the stubs of whatever had been welded to it previously. Had good fun blasting those off with the torch and a #1 tip.)

[Frosty]

I just calls em like I sees em John.  How often you'll use it is always the question isn't it? I lucked into my swage block and have it handy but hardly use it. I think a mandrel cone would be more useful but I don't know, never having had one available. 

A lot depends on what you do, it I turned a lot of rings I'd make a bender or maybe a cone to true them up. It's kind of the same with the swage block there have ben a couple times it's been really useful, turned a couple projects into pretty straight forward instead of a solid PITA. The hex swages come in really handy making Brazeal type slitters and punches, driving the preform into one corner produces the ideal angle. 

I look forward to how it works for you. 

Did I forget to ask what it weighs? I can see myself rigging lift eyes so I can use my engine hoist. 

Frosty The Lucky.

[JHCC]

A bit over 43 pounds, according to the bathroom scale.

The diameter is 5-1/4”, and the height (including the base plate) is about 22”. Since the striking anvil is 28”, that gives a total height of 50”.

21 minutes ago, Frosty said:

I can see myself rigging lift eyes so I can use my engine hois

I did consider building the tip around a nut for an eye bolt. 

[Frosty]

NICE! I'm liking it more all the time! I might have to talk to "Air Liquide" about a dead oxy tank. 

Frosty The Lucky.

[JHCC]

This came to me from HGR a while back and turned out to have pretty thick walls (a fat 1/4”). Consider these four bending jigs I made for the fly press; the one in the far left is made from a piece of this tank. 

[ThomasPowers]

I've stumbled on one "extra" pressure gas cylinder; it's walls are about double the thickness of a "regular" cylinder.  For some reason I kept that one's base for a dishing form. I'm dot sure why as a regular tank's works just fine and when I need to do heavy pounding I do it hot anyway.