Union Pacific Big Boy in 3/4 Inch Scale

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Carrdo
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Re: Union Pacific Big Boy in 3/4 Inch Scale

Post by Carrdo » Wed Oct 05, 2011 2:46 pm

What you see is a happy man. The leaking firebox stay and questionable blowdown bushing have now been well and truly re - silver soldered.

It was just a repeat of round 2. Clean the copper, preheat the area with the weed eater propane torch letting the flame wash act as a shielding gas inside the insulating firebrick soaking area, flux and then with a slightly reducing flame flow the silver solder with the oxy acetylene.
Attachments
66 Leaking Firebox Stay and  Blowdown Bushing Fixed.jpg

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cbrew
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Re: Union Pacific Big Boy in 3/4 Inch Scale

Post by cbrew » Wed Oct 05, 2011 2:52 pm

Carrdo wrote:What you see is a happy man. The leaking firebox stay and questionable blowdown bushing have now been well and truly re - silver soldered.

It was just a repeat of round 2. Clean the copper, preheat the area with the weed eater propane torch letting the flame wash act as a shielding gas inside the insulating firebrick soaking area, flux and then with a slightly reducing flame flow the silver solder with the oxy acetylene.
Very Nice, and you must be a man of true patience :!:
If it is not live steam. its not worth it.

RET
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Re: Union Pacific Big Boy in 3/4 Inch Scale

Post by RET » Wed Oct 05, 2011 3:30 pm

Hi,

We're still learning, and we are definitely still amateurs, but our success rate keeps climbing. Hurray!

The combination of using the big "weed eater" torch to provide the main heat plus the oxy/acetylene for the final spot heating is definitely best.

In this configuration, the wash from the propane shields the hot metal and using the oxy/acetylene for the final melt gives fine control over where the solder will melt. When that torch is used with a reducing flame and using just the wash, you get good control without the extra heat that will burn the flux and/or the copper. The black flux also helps a lot. However, the copper still pulls the heat away like crazy.

A smaller boiler could possibly be done with just the two propane torches and we did do some silver soldering on Don's Josslyn Hudson lead truck frame with just those two torches and it went much faster and easier than the copper.

As far as I know, that's the last of the silver soldering for Big Boy. Next we tackle the combustion chamber tube plate.

Still a learning process, but better.

Richard Trounce.

kvom
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Re: Union Pacific Big Boy in 3/4 Inch Scale

Post by kvom » Wed Oct 05, 2011 7:12 pm

cbrew wrote:
Carrdo wrote:What you see is a happy man. The leaking firebox stay and questionable blowdown bushing have now been well and truly re - silver soldered.

It was just a repeat of round 2. Clean the copper, preheat the area with the weed eater propane torch letting the flame wash act as a shielding gas inside the insulating firebrick soaking area, flux and then with a slightly reducing flame flow the silver solder with the oxy acetylene.
Very Nice, and you must be a man of true patience :!:
Seeing Carrdo's Hudson build confirms the patience! :D Nice job on the boiler too.

steamingdon
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Re: Union Pacific Big Boy in 3/4 Inch Scale

Post by steamingdon » Wed Oct 05, 2011 7:24 pm

BIG BOY IN 3/4" built by L. Knight
live steaming in the USA 631.jpg
3/4" BIG BOY
Attachments
live steaming in the USA 632.jpg
Head-on 3/4" BIG BOY
steamer

RET
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Re: Union Pacific Big Boy in 3/4 Inch Scale

Post by RET » Sun Oct 30, 2011 10:15 am

Hi,

On closer inspection, I can see that there is silver solder in the front tubeplate joint. That is very good news. The solder is very hard to see even with the fiber optic unit, but its there. I had put loctite in the joint before because I couldn't see anything, but this last silver soldering "go-round" of ours burned out the loctite and cleaned the joint so now the solder is just visible. Don will post a picture showing what the fiber optic unit sees.

Here is a picture of the boiler & smokebox assembled. These pieces haven't been together for about 6 years, but I'm fitting the outer cladding to the round part of the boiler and I need to have them assembled for proper fitting of the cladding. Its a slow process to get all the holes in the right place and has to be done right because any mistakes will be obvious. I made the cladding heavy enough so I could fasten the catwalks and handrails to it as well as the power reverse, etc. Fun & games time again.

This picture is a still shot taken with my high definition video camera so its smaller. Don's camera takes better pictures for posting (higher resolution), but is 4 x 3 format instead of 9 x 16.
Attachments
Big Boy boiler 2011.jpg
Last edited by RET on Tue Nov 01, 2011 4:11 pm, edited 1 time in total.

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Carrdo
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Re: Union Pacific Big Boy in 3/4 Inch Scale

Post by Carrdo » Sun Oct 30, 2011 3:15 pm

Some additional Big Boy photos taken today.
Attachments
67 Fiber Optic View of Combustion Chamber Front Tubeplate.jpg
70 External View of Combustion Chamber Front Tubeplate Location.jpg
71 Initial Fitting of Boiler Cladding.jpg
72 Boiler with Cladding Domes and Smokebox.jpg

RET
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Re: Union Pacific Big Boy in 3/4 Inch Scale

Post by RET » Sat May 12, 2012 7:46 pm

Hi,

Since the last post, I have been fitting the forward boiler cladding (in front of the firebox). This is a long process which still isn't finished, but I've recently also been working on the propane burner design for the firebox and I have a few pictures of the burners and the insulating brick "hearth" to show that I haven't been wasting my time.

When Gerhardt built the boiler, he put in a 2" id. firehole ring, which isn't conventional. Because the backhead slopes, this ring angles downward toward where the grate would normally be. Its easy to see that Gerhardt also intended to fire with propane; trying to coal fire this locomotive when you are sitting on the wrong end of a 32" long, 3 1/2" gauge tender simply isn't practical.

I've seen several burner designs for propane and all the ones I've seen don't have the ability of supplying the radiant heat you get with a coal fire; nothing gets red or white hot like the coal bed does. Because of this, I decided a different approach was required, so I've designed a Turbotorch (Sievert) style burner that you can turn down to zero without having it flash back as the conventional ones do. I built it and lo and behold it actually works! Just because I come up with a new idea doesn't mean its going to work, but now & then they do.

The idea is to use 3 of these (one smaller so it fits) fitted inside the firehole ring with the burners firing directly onto an insulating refractory brick. The ends of these burners will project into the cab, but this way there is no chance of the burner intake picking up any burned gasses to affect the flame.

The surface of this type of brick gets red to white hot immediately when you put a flame on it, but when you take the flame away, you can put your hand on the heated surface about a minute later. When the flame is on the brick, you can feel the radiant heat from it from several feet away.

Don took these pictures showing the burners and the refractory in its stainless steel box at one of our meetings. I want him to take a couple more shots showing the burner in operation, hopefully with the flame burning on the small inside tube as well as on full fire. On full fire, the burner tips get red hot, but since everything is stainless, they should work OK.

There is always more to do, but this is where we're at now. The winter holidays are over, so outside work etc. gets in the way.

Richard Trounce.
Attachments
IMG_0422.JPG
Burners + brick in stainless cradle
IMG_0424.JPG
Large burners showing inside flame tubes from both ends
IMG_0423.JPG
3 burners showing 2 sizes

RET
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Re: Union Pacific Big Boy in 3/4 Inch Scale

Post by RET » Sat May 12, 2012 7:56 pm

HI,

I still have to build the control valve for the propane supply to these burners; since the plan is to have automatic pressure control, that's why I needed a burner with infinite "turndown." As I probably mentioned before, the idea is to pull off the throttle body intake venturi for a pressure tap and run this to the control body under the cab. There will be two controls in a common body with separate bypass controls for each one. This way, the single burner will be set 5 psi. higher than the two burner control with the bypasses set so none of the burners go out completely.

As I said before, now all I have to do is build the "stuff."

Simple, right?

Richard Trounce.

RET
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Re: Union Pacific Big Boy in 3/4 Inch Scale

Post by RET » Sat May 19, 2012 4:30 pm

Hi again,

Here are a few more of Don's pictures showing one of the burners in action. As I've mentioned before, there will be two burners this size and one smaller and shorter one. All three will fire onto the insulating brick to give the radiant heat to the firebox and the wash will go into the combustion chamber and up the stack in the usual manner. On full fire, the burner puts out a lot of heat and you can see the tip gets bright red. Everything is stainless, so that's OK.

When the burner is firing on the brick, you can feel the radiant heat from several feet away. The heat never penetrates the brick.

Progress is slow, but it helps when things work the way they're supposed to.

Richard Trounce.
Attachments
IMG_0435b.jpg
Burner with flame burning on smallest internal tube.
IMG_0437c.jpg
Burner firing on insulating brick. Note white heat of brick surface.

RET
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Re: Union Pacific Big Boy in 3/4 Inch Scale

Post by RET » Thu Jul 12, 2012 7:05 pm

Hi,

Just a few more pictures to show the firebox with the burners temporarily in place.

In the previous pictures you saw how the burners work & the effect of their firing on the insulating brick. The first picture shows the orientation of the 3 burners in the boiler backhead from the inside. The next picture shows how the burners protrude into the cab space. Not ideal, but necessary.

You can see two bars attached to the mud ring, one at the back and one across the center of the firebox. These two bars will support the stainless box that the insulating firebrick sits in. The box will be clipped to the bars to hold it in place. I will also have to cut and fit a stainless steel baffle plate at the bottom that will only allow a controlled amount of excess air into the firebox. Too much air will lower the temperature in the firebox, tubes and flues. In the pictures, you can also see the 4 stainless superheaters where they will be when in their final position. As I said before, with this model superheating is even more important than usual.

The final picture shows the complete boiler to give an idea of the relative size of things.

That's pretty much where things are at the moment. I have to complete and install the burner assembly. As you can understand, in summer, things go much more slowly with all the other calls on my time.

Richard Trounce.
Attachments
IMG_0441f.jpg
Looking at the inside of the firebox backhead with the burners in place
IMG_0442g.jpg
Looking at the boiler backhead from the outside
IMG_0444e.jpg
View showing the complete boiler underside with some of the cladding in place

RET
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Re: Union Pacific Big Boy in 3/4 Inch Scale

Post by RET » Tue Aug 21, 2012 9:12 pm

Hi,

Just a few more pictures to show what I've been working on lately. The throttle on Big Boy is a direct copy of Roy Johnson's 4 Aces throttle with 4 sequentially opening graduated sized poppets.

As always Gerhardt's work is very good, but rather than trying to get four poppets to seal metal on metal at the same time, I thought it was much more practical to use "O" rings as a soft seat for each one. Installing the "O" rings wasn't that difficult and now the throttle poppets actually seal the way they should.

The first picture shows all the assorted parts with the throttle body in its upside down position. The next picture is a closer view of the throttle without the other parts and the third picture is with the throttle body right side up showing the individual poppets seated on the "O" rings. The final picture shows the throttle assembly with three of the original short superheaters that Gerhardt was planning to use with one of the long "hairpin" style replacements temporarily in place. The original ones stopped just short of the combustion chamber but I found I could just slide the hairpin style through between the water tubes in the combustion chamber into the firebox and as you can see in the previous pictures the plan is to have them go almost to the back of the firebox. They will be MUCH more effective this way.

Progress is slow, but it is happening.

Richard Trounce.
Attachments
IMG_0500.JPG
Big Boy Throttle parts
IMG_0499.JPG
Throttle body upside down
IMG_0498.JPG
Throttle body right side up showing "O" ring seats
IMG_0492.JPG
Throttle body assembly with original short superheaters & one long one

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