2-6-6-4 vs 2-6-6-6

Thanks bob2, 

Does your 48/ft descriptions give diagrams for building a boiler?  I get the idea from your comment but need some more clarity. Thanks again.

John

Tell you what: School is out, and I need to get off the couch.  I shall rough out my Challenger boiler and try to post some photos.

But basically, all you do is cut the tube longitudinally, and spread it until you get the diameter you need.  It will spring back, so you need to pin it somehow.  And to join different segments, you need an inner flange.

So what you do is make rings of the appropriate diameter, put them inside the slit tube, and pin them with 2-56 screws.

I have found that getting the ends of a tapered section square is challenging.  I use a sanding disc and a machinist's square.  But the Challenger has only one main taper, plus the smokebox taper.  I will get some dimensions forthwith.

Brass tube used to be available in many diameters.  Now you will have a cery difficult time getting much other than 2" tube.  Brass bar rail is ok.  Practice with steel exhaust pipe - it is cheaper.  My first locomotive is still steel boilered.

This is gonna be an interesting thread...

If anyone can pull this off, it's "bob2"...

Mark in Oregon

Thank you Bob.  I look forward to your efforts and photos.  Would you please where you get the blueprints or build specs.  I hope SP's are easier than PRR.  I have a T-1 that I was going to wreck for 2 gear boxes.  But it so magnificently by a quality machinist, I changed my mind.  I have found a boiler.  The state of PENN wants $35 to search the blueprints the PRR gave to the state, but will not return the $$'s if it cannot find them.  Thanks a lot.

John

And to Mark in Oregon-- Thanks for the recommendation.

Here is the first cut:

forget about railroad blueprints.  They are for folks with barns - generally 1/4 scale, expensive, detailed, and generally unwieldy.  Many, many artists have distilled them down to model-size drawings in things called Cyclopediae.

For this project, I have a copy of the MRR drawing of a Challenger from November 1959. It says th boiler barrel is 7 3/8" long, tapering from a diameter of 2 3/16" at one end to 2 5/16" at the other.

As you know, circumference increases quite a bit faster than diameter, so for a 5/16" increase in diameter you are looking at a gap of over 1".

More in a bit.

Nice to here from you, miss your many knowledgable columns in 48/ft.  What are you up to these days?

So what you are saying is that you are making a truncated cone, or in other words a stack of perfect (ideally) circles that start at 2 3/16" and end at 2 5/16" with a  total length of 7 3/8"?

Not trying to be a PITA, just trying to see if I understand your instructions.

Simon

PITA? More like a legitimate question.  Since so far I have not posted any photos, the mental picture may be a bit fuzzy.

Yes, truncated cone. Yes, ideally concentric circles, but some boilers taper only on top or bottom, so the circles would "touch" at one end of the diameter, and step away at the other.  Worrying about this detail would mean certain failure.

The tough part is trimming the ends.  Once you get the end perfectly "square", you have to be at the proper diameter and the proper length.  That is three constraints that work against each other.  A photo is simply the only way.  I need a couple days to get this project underway.

The motivation for a Challenger boiler is two-fold:  the original poster mentioned Lobaugh and Challenger in his first post.  And I need a Challenger boiler.  I will owe him, since I was just going to wait for a Lobaugh boiler (I have six already, and am in no particular hurry).  And I need to get off the couch and do something! (Joke; while I rarely move before ten AM and a full cup of coffee, my typical day involves at least an hour aloft, various aircraft maintenance activities, pedalling all over the airport, preparing lesson plans, and teaching a 3-hour law school course.  Not bad for 73.  Opinion.)

And on that Allegheny: 66" drivers, which are closer to All Nation's 70", especially if you think 17/64.  I should sell mine - it looks ok, but is still not powered.  Early Max Gray, with scratch tender.  Nah, I never sell anything.

Gotta disagree here; that sounds like a fact...

Mark in Oregon

Cut the main section this evening.  Taper is easy.  I cut 8" (better too long than too short) and now wish I had cut 7 1/2".

Thank you for all of your comments.  I have learned a lot from your postings.  I never thought about 17/64.  I will mic the drivers to determine driver diameter.  jwmathew--thank you for the historical derivation of the challenger and bob2--thanks for the hint about the Cyclopediae.

John 

Well, bump!

I have the boiler barrel and smokebox screwed together, and the domes placed temporarily.  I will try to get the firebox started and post some photos in the next few days.

Of course, in just a few more steps, I shall have a boiler almost as good as Lobaugh, which means a genuine Lobaugh boiler will show up pretty soon.

Two things of interest, maybe: one, while I like to think of my tapering technique as originating with me, Fred Icken was teaching the same thing prior to WWII in MRR, in an article building an SP P-13.  And the other - the Challenger boiler has a graceful curve to it, not a taper.  The real thing might have three very slight taper changes, but the Lobaugh model has an almost imperceptible curve.  Most Lobaugh boilers were "spun" by the Cusper Brothers in LA.

Thanks bob2.  Look forward to your pix.  Help me out on the barrels.  First--Where can I find brass tubing to start this process? Wholesalers want to sell in large quantities or very long lengths.   Second--Would copper work?  To show my ignorance which is stronger (least dents/dings)?  Third--Besides a sharp hacksaw, grinder, and files what kind of equipment do you use to square up the ends of the tube? 

I looked at one of my 4-8-4 boilers which was cast brass boiler with a tapered brass (sheet or tube) smoke box.  I am going try you method if I can avoid investing equipment.  

Feel free to contact me about the original boiler.  Thanks again.

Her's a boiler for a Labough challenger, made from copper tubing ,with brass riveted sections overlayed, and sweated on. I used some scrapes from an air conditioning job. the copper is hard copper (worked) and 1.2 mill thick. The tubing was cut down the middle, and a wedge added to create the tapper.     Stephen    (cTr...Choose the Right)

I got some photos.  I shall start a new thread, mainly because your title does not lead to a boiler discussion.

Thank you Stephen Bloy.  As I said earlier i am a newly to O scale brass.  Would you explain "brass riveted sections overlaying.  I think the rivets keep the taper stabilized on one end, but how do control the diameter of the opening at the end of that section? Is it the following riveted section?  I think Bob2 uses 2-56 screws it to hold his taper.  Thanks for your help.

Bob2

Please keep me posted on the new topic so I can follow your advice and pix.  Thanks for your help.