Conical Boiler Casing

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daves1459
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Conical Boiler Casing

Post by daves1459 » Fri Nov 01, 2019 11:24 am

Can anyone provide or lead me to a concise yet SIMPLE method for laying out an eccentric cone like used on a boiler casing with conical coarse ahead of the fire box outer wrapper with the seam on the bottom or straight side? I'm stumped! I have a reprint of an early 1900s book on boiler making that describes the making of a boiler conical gusset sheet. However, much of the text is obliterated in the reprint and with my feeble mind I can't follow it. I've tried the internet to no practical avail or I'm asked to pay of a down load. Any lead or assistance will be appreciated.

Thanks, Dave

Glenn Brooks
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Re: Conical Boiler Casing

Post by Glenn Brooks » Fri Nov 01, 2019 11:48 am

Dave, I have no idea how the boiler makers accomplished this. But have wondered the same thing for many years. I am just stripping down my 1904 4-4-0, that has a similar boiler configuration. Discovered the wagon key hole portions were assembled in several pieces - so the conical shaping was accomplished a little bit at a time. Not what I expected, before I removed the lagging. There also is a smallish flared piece riveted to the bottom of the boiler. Pics below...
96D73EA9-1AE1-4D27-9E6D-DBCAA0B784B1.jpeg
FFC0CC65-9478-4BB5-9C33-AAC2CF275AAB.jpeg
7F9E5C4A-AD43-452B-B50B-EDDB73042D8C.jpeg

Also, what size boiler are you building? A friend of mine used a commercial conical pipe fitting to flare from his 7” boiler tube, to a larger size fire box outer shell. Of course all welded in his case. Mine was very likely hot rolled, hand formed, at least in part - then riveted.

Glenn
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....

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cbrew
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Re: Conical Boiler Casing

Post by cbrew » Fri Nov 01, 2019 11:55 am

assuming you are talking about the jacket.
the dumb way I did mine,
i took the circumference of each end, centering end that on the sheet metal with the spacing equal to the run and drew intersecting lines. cut and rolled by hand. surprising, it worked with minor tweaking.
just leave enough to have ears that will slip under of the other two sections then add the bands.
tenwheeler.jpg
if you are referring to the pressure vessel, i would use an eccentric reducer.
If it is not live steam. its not worth it.

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PeterCraymer
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Re: Conical Boiler Casing

Post by PeterCraymer » Fri Nov 01, 2019 2:57 pm

I just used poster-board from the dollar store on top of the cork insulation and solid supports for things like the handrails and drew lines on the poster-board. then i cut it with scissors and secured it with blue painters tape. Worked pretty well with some minor adjustments for the difference of the thickness between the paper and the metal.
posterboard jacket.jpg

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VO4454
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Re: Conical Boiler Casing

Post by VO4454 » Fri Nov 01, 2019 3:05 pm

Dave, I used this calculator for making my jacketing patterns. I then took all the numbers drew it in CAD and had templates printed

Vic
https://www.cmrp.com/cone-calculator
For Duty and Humanity

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gwrdriver
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Re: Conical Boiler Casing

Post by gwrdriver » Sat Nov 02, 2019 11:44 am

On the few boilers I've been tasked to build (copper) which required a tapered course (a "truncated cone") I determined that the internal volume lost was insignificant compared to the time effort and cost of doing a short transitional taper. I built the boilers with straight barrels cosmetically hidden by a tapered wrapper section.
GWRdriver
Nashville TN

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gwrdriver
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Re: Conical Boiler Casing

Post by gwrdriver » Sat Nov 02, 2019 9:51 pm

PS - I actually did the volume calculations for comparison between doing a tapered section and just a straight tube on a typical "wagon-top" boiler to determine how much volume would be lost. On the projects I had to hand that turned out to be a negligible percentage. This short-cut might not be appropriate for every boiler, but it does offer a workable option in some circumstances.
GWRdriver
Nashville TN

daves1459
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Re: Conical Boiler Casing

Post by daves1459 » Sun Nov 03, 2019 8:12 pm

VO4454 wrote:
Fri Nov 01, 2019 3:05 pm
Dave, I used this calculator for making my jacketing patterns. I then took all the numbers drew it in CAD and had templates printed

Vic
https://www.cmrp.com/cone-calculator
Thanks for the calculator. But, it is for concentric diameters. I'm looking for a method for eccentric diameters where the outside of both diameters share the same horizontal plane on the bottom.

Dave

daves1459
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Re: Conical Boiler Casing

Post by daves1459 » Sun Nov 03, 2019 9:02 pm

gwrdriver wrote:
Sat Nov 02, 2019 9:51 pm
PS - I actually did the volume calculations for comparison between doing a tapered section and just a straight tube on a typical "wagon-top" boiler to determine how much volume would be lost. On the projects I had to hand that turned out to be a negligible percentage. This short-cut might not be appropriate for every boiler, but it does offer a workable option in some circumstances.
I need the lay out method for the outer casing. I understand what your saying about throat sheet and made mine flat. I just want to form the outer casing to look like a tapered gusset sheet in under it. I know I can probably fudge it to shape using trial and error. I'd just rather at least try to make it the proper way using a layout method.

Dave

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gwrdriver
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Re: Conical Boiler Casing

Post by gwrdriver » Wed Nov 06, 2019 9:20 pm

I do a lot of things "just 'cause" I want to see if I can do it. And it usually works out OK.
GWRdriver
Nashville TN

10 Wheeler Rob
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Re: Conical Boiler Casing

Post by 10 Wheeler Rob » Sat Nov 09, 2019 10:28 am

I cut two plywood sheets, one the size of each end of the cone. Spaced them apart with some wood blocks. Then cut thin cardboard to fit the the plywood jig. Made a left and right side patterns. The I added 1/2 inch to the pattern beyond the cone. Notched around the cone area where the cone conformed to the adjacent cylindrical sections and formed the notched tabs to conform to the jig. Worked great. Sorry I don't have pictures avialable to show you.

Rob

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