Rolling a Boiler Barrel

[daveburrage]

I know there have been some past posts on this subject but I don't think this has been discussed.

On past boilers I have created a development profile and used bending rolls to produce the cone. There are short unbent lengths left by the bending process. I can't see any way of avoiding them and have manually formed a bend over a bar or pipe to compete the circle.

I'm looking at making the barrel for a 7.25 gauge BR class 2 and
its been suggested to me that a better way would be to add extra width (equivalent to the flat part) to the development and trim off afterwards. Presumably some "springing" of the barrel would be needed during the forming process to stop 2 layers of copper going into the rolls. Anyone tried this or know a better way? m not too keen on a lot of experiments with copper at its current price!

regards

Dave Burrage

[baggo]

Hi Dave,

another way is to use a piece of drawn tube with a diameter the same as the larger diameter of your barrel and cut a vee shape out of it lengthways and then close up the gap to give your taper. This still involves a bit of manual shaping though to get the smaller end round after the gap is closed up. This would be a more expensive option though as seamless tube would be a lot dearer than flat sheet!

The flat left at each end of the sheet is a problem with the 'ordinary' type bending rolls which have the pinch roller on the top. I made a set of the George Thomas type rolls which operate differently. These have two rollers, one above the other, which grip the metal and push it against a third roller at the back which does the actual bending. This type bends the metal right to the very edge but needs the sheet putting through in both directions to bend both edges. I've used mine for smokebox barrels, cab roofs, boiler cleading, etc. and they work a treat - no trimming needed at all.

John

[durhambuilder]

You could use the trimmed off bits to make the butt straps and then nothing is wasted.

[stantheman]

When talking about 'the pinch roller' being at the top I wonder if I am on the same wavelength, if so I assume the two rollers are in a vertical plane with the form roller at the back and adjustable. One little secret I used when in my working life was to start the form off by entering the sheet from the back, this very rarely left a flat to worry about. Bearing in mind the rolling procedure was 'little and often' when adjusting the form roller's position. Very often passer's by would stop and stare when I was doing this and wonder if I knew what I was doing. It worked for me!. Otherwise start the form off by using as thin a backing sheet as possible until the form is getting well established.
Stantheman

[daveburrage]

I turns out that the rollers I'm intending to borrow are of the "George Thomas" type (I can't remember what I used last time).I've not got the copper yet; but I've tried a bit or scrap strip' reversing it as suggested and got an almost perfect cylinder with no flats.

Thanks for everone's help

regards

Dave Burrage

[stantheman]

Only really one thing to be careful of if trying this reverse rolling is that the handle is secured so that it does not unwind all of a suddent. Good to read the idea may have worked for you.
Stantheman.

[steammadman]

george thomas rolls are just the ticket for boiler barrel rolling
i made some some years ago,apart from not putting gears on
the rollers i find them just the ticket.
I made a second set WITH gears and ,what a diference, MAGIC.


I still have the published drawings and write up instructions, i could
look them up if you would like a copy. BUT for 71/4 g boiler work
you will hve to beef em up a fair bit.

[daveburrage]

Article to build the rolls is on line (on baggo's website) but thanks for the offer.

Stuff I only need occasionally I prefer to borrow - there's only so much you can cram in a small workshop.

regards

Dave Burrage