# "T" Box Boiler for C P Huntington



## bille1906 (May 2, 2009)

Ever since I first laid eyes on this beauty in the Sacramento Meuseum, I had the desire to build one








I went to the Meuseum Liabrary and was able to get som measured scale drawings like this

This is a standard gauge which would normally be at 1:32 but at that scale, the engine is so small that a live steam version doesn't make sense.
Aster built an standard gauge American in 1:28 and Aristo does all of theirs in 1:29 so i decided to go with 1:29
This still presents several problems. At first, I thought I could do a Ruby bash but the 3/8" ruby cylinders are actually too big for this engine.
If you look at the drawing, you will see that the top of the drive wheel lines up with the center of the boiler which means a Ruby boiler wouldn't even fit between the wheels (1.5")
I think I can use the Ruby valves by cutting 1/4" or so off and making new cylinders. This will save some time.
Now for the boiler. The largest diameter tube I can fit in will be 1-1/4 inside and 1-3/8 outside. I will need to crush it a little near the wheels in order to make room for the Lagging.
I feel I need a 3/4" outside diameter flue tube for the poker burner which leaves little room for water. The bunker won't be free and a tender would spoil the look so an axle pump won't work. My idea is to make a T boiler but because the cab is so small, a cylindrical one won't work. So here is my plan

The box will be just under the cab size. The boiler will be painted black and the windows will be glazed so it should look somewhat natural from that standpoint.
The sight glass and pressure gauge will be between the cab and bunker with the throttle above and center (at the roof peak)
I plan on annealing the copper plate, drill all of the holes and cut out the boiler tube hole slightly undersize. Then bend the pieces as shown so the seam is where the tube goes in.
The stays will have nuts to hold the piece in line while it is soldered. After the seam is soldered, the tube hole will be fitted with the dremmel or spindle sander. 
the top and bottom will be bolted with the stays and soldered on. Then the nuts will be removed and soldered. 
Finally, the tube, flue and front plate will be soldered.
I have never done anything this complicated before and welcome any hints.


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## David Leech (Dec 9, 2008)

Bill, 
I would think that it would work, BUT maybe not too efficiently. 
The water circulation during boiling might be somewhat difficult. 
However, when you have it built, you will be able to show us how it works. 
All the best, 
David Leech, Delta, Canada


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## Semper Vaporo (Jan 2, 2008)

That square bottom leaves some water space that is not near enough or above the fire to do anything but sap energy from the system. Maybe if the front and rear sheets of that box were shaped like Home plate it would be better (eliminate the lower corners).

Also, that square box is going to 'want to' take on a spherical shape when subjected to pressure. I think I see some stays in the drawing will help elimate that, but the junction of the round boiler barrel and the flat sheet and the junction of the flue/firebox in the flat backhead sheet may be subjected to some stress, anyway. I'd recommend thick walls for the flat sheets (double that of the cylindrical parts) or an "L" or "T" shaped stiffener across the sheet to help avoid the deformation stress that will occur.


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## Steve Shyvers (Jan 2, 2008)

Bill, 

I concur with David and Semper Vaporo. There might be some things you could do with internal siphons to get the water to circulate within the "box" section. Also cross tubes at the far end of the flue might help a little bit, but the small boiler diameter probably precludes any huge benefit. Insulation might help too. Think also in terms of the ratio between the boiler's total volume to total surface area. You want that number as large as possible, and volume increases (and decreases) by the cube of it's linear dimensions while area changes by the square. This means a tiny boiler will have a lot more heat loss proportionally though surface radiation than a larger boiler of the same proportions. Another way to view it is that the boiler shape should minimize surface area while retaining as much volume as possible. This was behind Semper Vaporo's "home plate" suggestion. A horseshoe shape would be an alternative. 

First thing, though, is you need to figure out proper staying for the flat sections. Just going to thicker copper will only add to the amount of heat the boiler soaks up that doesn't go into the water. I'd be happy to go through the stay calculations with you, but it's too complicated to do here. In the past I tried to design a "boot" or "T" boiler for a logging loco, but the staying got too complicated for the small boiler size. Internal girders are an alternative approach, but still complicated to build. 

Steve


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## bille1906 (May 2, 2009)

You are right about the lower sides being dead space except that if I get to a low-water situation, the extra water will help to get it home before damaging anything. I thought of a U shapped box but it would be harder to solder. I just sketched the diagram and it is not to scale. The box is quite small only 1.75" x 2.75 x 2.5" outside. The Flue will be ,750" outside diameter by 5-3/4" long which should supply the necessary heat. The material will be 1/16" and stays will be no further apart than 3/4". Your concerns about the circulation are probably over my head. Is the concern that it could cause an air bubble in the tube? 
I wonder what the circulation difference will be vs a T boiler like on the Accucraft Shay


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## Phippsburg Eric (Jan 10, 2008)

If you built a true locomotive style boiler with a ceramic butane burner located down low in the firebox you could get the efficiency up while keeping the boiler diameter down. you could keep one large boiler (flue) tube with cross tubes or use several smaller flue tubes.

have the boiler start down between the drivers as the prototype with a wet sided firebox (with cross tubes possibly)


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## rwjenkins (Jan 2, 2008)

You might want to look at the Wuhu Porter as a starting point instead of a Ruby. Same basic technology, but with a smaller boiler diameter and smaller cylinders.


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## Semper Vaporo (Jan 2, 2008)

Posted By bille1906 on 06 Mar 2012 08:09 AM 
You are right about the lower sides being dead space except that if I get to a low-water situation, the extra water will help to get it home before damaging anything. I thought of a U shapped box but it would be harder to solder. I just sketched the diagram and it is not to scale. The box is quite small only 1.75" x 2.75 x 2.5" outside. The Flue will be ,750" outside diameter by 5-3/4" long which should supply the necessary heat. The material will be 1/16" and stays will be no further apart than 3/4". Your concerns about the circulation are probably over my head. Is the concern that it could cause an air bubble in the tube? 
I wonder what the circulation difference will be vs a T boiler like on the Accucraft Shay 

Extra water "below" the top of the firebox ("Crownsheet") will do nothing to "get you home". The top of the Flue/firebox will glow cherry red and only convection in the metal will heat the water not directlly in contact with the directly (flame) heated metal. Thermal stresses could tear the boiler apart. Sloshing of the water onto the overheated metal will flash to steam which could cause pressure spikes that could damage things too.

Granted, this is a very small boiler and will be well below the size of the "Critical Crack Length" to result in a boiler explosion ("BLEVE") from the thermal stresses and pressure spikes, but why chance the unwanted release of steam from unintended "holes" at inopportune times?

Cross tubes cause circulation to get all the water up to temp so the boiler is more uniform in temperature so the thermal expansion is uniform to reduce stresses. Random cold water turbulance caused by the motion of the locomotive will cause the steam pressure to fluxuate and cause erratic operation. Cross tubes are also additional heating surface and additional volume of water.


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## rwjenkins (Jan 2, 2008)

Another thought, instead of using the cab and/or firebox space for a square extension of the boiler, why not use that space as a water tank and add an axle pump? 

Going back to my earlier suggestion of using Wuhu Porter components instead of a Ruby, the Wuhu boiler is 1.5" outside diameter, the cylinders are 5/8" outside diameter (same as the older Ruby cylinders) but only 1" block length. There is enough water capacity in the boiler to run for about 10 minutes, although the fuel runs out after 6 minutes with the stock tank (I have swapped mine out for a Ruby tank). If you use the cab and firebox space for a water tank, I see no reason why that couldn't be increased to the 30 minute run time you're looking for. The big question is how much fuel capacity are you going to have in that bunker space? That deep underframe below the cab and bunker looks like it could also yield some usable space too, possibly for additional water capacity or to stash a battery and R/C receiver and servos.


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## highpressure (Jan 2, 2008)

This is the boiler I put in my Climax A type. Steams nice even with the offset flue.


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## Shay Gear Head (Jan 3, 2008)

Larry,

Where's the throttle. Also not you usual sight glass!


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## Phippsburg Eric (Jan 10, 2008)

Richard-- I am thinking the box under the frame was a water storage tank. 

I am guessing Larry's throttle was on the other side out of sight in the photo.


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## Amber (Jul 29, 2011)

That's a nice T boiler!


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## bille1906 (May 2, 2009)

Semper 
Got you on the low water issue. I will see of there is any room for cross tubes 
Richard 
I just don't want to fool around with adding a pump to the only drive axle which will already have two eccentrics, a clack valve and a bypass. 
The 1.5" boiler won't work becaise the distance between wheels is 1.5 and I need lagging
I already cut up some Ruby valves and made some cylinders yesterday. They are 3/4" outside and 1/2" bore by .950 long.
I was planning on using the underframe area for the batteries and using the bunker for receiver, servo, fuel and lubricator. Might be able to fit the receiver in the frame somewhere. Throttle will be manual and reverse by RC 
Larry 
That is a nice looking boiler. similar to what I was thinking except with a cylindrical riser vs a rectangular one. I don't see why my design would be much different. Do you? 
Do you have cross tubes? 
What is your flue diameter?


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## Semper Vaporo (Jan 2, 2008)

The difference between the cylindrical and rectangular riser is that the cylindrical one is already in the shape that pressure will try to force it to, thus less stress on the joint where the horizontal barrel of the boiler joins; and there is less surface area from which to radiate and thus lose heat. In the size you are working with, those differences are slight, but still there.


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## bille1906 (May 2, 2009)

Right Semper, thus the need for stays
By the way, I just finished the cylinders

here is one next to the longer 3/8" Ruby cylinder. The flange on the cap is for the four rail crosshead. The need for the shorter cylinder os because of the pilot wheel spacing.


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## highpressure (Jan 2, 2008)

*Climax T boiler has the throttle out of view on the opposite side. It uses a straight 3/4" OD copper flue with a poker.
Here it is installed.







*


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## bille1906 (May 2, 2009)

Larry 
That is an awesome model 
Why is the flue offset? 
It is hard to see from the pictures but is it offset at the T and in the center of the smoke box or offset all of the way?


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## highpressure (Jan 2, 2008)

*The Fire tube is offset to clear the engine which butts right up against the boiler. If it wasn't offset the poker & jet would not be able to be installed.*


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