Boiler Construction Questions

[Fender]

If you go the DOM route, suggest using an eccentric 8" to 10" reducer, and cutting into the transitional area where it approximates the diameter of the tubing. But much easier would be to use 8" pipe throughout, and make a dummy jacket to get the boiler profile you want. Very little difference in steaming ability.

[Berkman]

A 8 inch boiler is very small for a pacific. This is more characteristic of 2-6-0s, 4-4-0s, 4-6-0s and small 2-8-0s Even a stock LE pacific uses a 9 inch, 9 3/4 OD boiler and it looks somewhat small. The LE pacific is based on a SP P4 which is very similar in size to a G5. I'd use a 9 3/4 od pipe and then simulate the thicker courses.

[Marty_Knox]

Here are some pictures of a wagon top boiler for an Allen Ten-Wheeler. The first course is 8" pipe (8 5/8" OD), the rear course is 9" pipe (9 5/8" OD), and the tapered course is formed from 5/16" plate on a press brake.

[thunderskunk]

You guys are the greatest, don't let anybody tell ya any different. I should have started asking questions on here years ago.

Berkman, good catch. I've spent a long time wallowing over what locomotive to model, and the only one that grew on me was the light pacific. That, and anything longer or heavier won't fit in the car.

In the end, I might go with the dummy jacket. It helps with a few things. For one, my 'steam dome' on the prototype G5 isn't actually a dome, so it's shorter. I'd get an extra inch under the jacket for dome height.

I almost think that having that space filled with ceramic refractory lining might make the engine more efficient than would having that space for steam. Bad theory? I might try doing the math out when I get closer to the boiler build.

[makinsmoke]

Chuck Hackett actually did some testing some years ago when working on the boiler for his
Northern.

His results were that dead air did as good if not better a job reducing temperature loss between the boiler and the exterior of the jacket.

Chuck, if I don't have that right please correct.

Brian

[makinsmoke]

Here is Chuck's page and test information:

http://www.whitetrout.net/Chuck/844/Tes ... /Index.htm

[Berkman]

The G5 is a nice looking locomotive! Would be a neat one to see modeled.

If it were me... I'd use a 9 3/4 OD pipe, fake the tapered section with welded rings and keep it as air space under the jacket. Use a heavy jacket that you can tap into for the various boiler details.

For the rest of the locomotive: the drive wheels will be the hardest part to find. Not sure anyone makes a scale 70 inch driver casting set or hodges trailing truck set. LE or Roger Goldmann cylinders would work. You'd also be designing the valve gear from prototype drawings if you really wanted to be accurate.

You can always start with little engines 4-6-2 drawings then modify them to fit your G5's wheelbase/axle spacing. It all just depends on how accurate you want it.

Honestly a lot of people wouldn't know the difference if you kitbashed a LE pacific with hodges trailing truck then used the flared jacket plus the various CP G5 details, cab, etc. At least that way you would be sticking to a proven design.

[BClemens]

At least that way you would be sticking to a proven design.

And that is some excellent advice for many, many reasons. You cannot 'cut' without a plan and either you build a locomotive or spend precious time exploring the build. There are too many things to consider and figure if you start from scratch.

bc

[thunderskunk]

It is good advice. I plan to pick my battles, just not 'wisely.' Probably end up faking the rear end of the boiler, as that's probably a little too far above my head. The linkage, on the other hand, will more than likely be the death of me.

Fundamentally, I'm building the engine for me, and while I hope my friends and family get something out of it as well, that's not my end state. It'll be scale 70" drivers with a nicely timed valve gear or bust.

I looked at that test as well. It makes sense, based on the actual width of the lining. In the end, 0 is 0, and an inch is an inch. You'd need a pretty steep difference in the R value to get anything better than still air.

[thunderskunk]

I'm gonna throw this right back in this thread, and bear with me. What's the boiler called in Marty knox's photos above where the firebox is inset from the rest of the boiler, making a keyhole shape at the back, versus the boiler that has the angled mud ring and the firebox walls are tangent to the third coarse walls (such as the one I posted to start with)?

Sorry if that's jumbled. It's hard to research how to do things a particular way when I don't know what said thing is called...

[Marty_Knox]

The one I showed is called a keyhole firebox, the one on the Pacific is called a wide firebox. I put the picture up to show that you can make a tapered course.

[10 Wheeler Rob]

I recommend to build a straight boiler and build the jacketing to the shaped design. My ten wheeler is made that way and steams very good.