Union Pacific Big Boy in 3/4 Inch Scale

[LVRR2095]

Five years is a long time between posts,I think?

But a five year hiatus is not uncommon in the live steam world. I have some projects whose castings have been "normalizing" for close to 50 years now!

Keith

[RET]

Hi,

My personal life got in the way. My "significant other" got sick in 2005 and after a long illness died on New Year's Day in 2010. Somewhere in 2006 the urge to work in the shop just went away so I didn't do anything for 4 or 5 years. I knew it would come back, I just didn't know when. The urge finally came back last year and I've been working slowly ever since. Last year was hard, there were times when I didn't want to do anything at all, but life goes on. This year is better, but I'm still not back to "normal," whatever that may be.

Since I've started work again, I've done some work on Big Boy, but most of my attention has been on "Dart," a part built 7 1/4" chassis I acquired 7 or 8 years ago. I put needle bearings on the main axles and coupling rods and that's turned out well. With grease lubrication, they'll last forever. It runs very smoothly on air.

I've also recently started on rebuilding the little Sherline CNC mill into a much bigger, more precise machine, but still using the same stepper motors so the computer won't know the difference. I'll be interested in seeing how that turns out when its complete, perhaps somewhere around Christmas.

Where Big Boy is concerned, the axle pump pictures were posted on another thread. That turned out quite well, and I've thought a lot about how I would do other things; propane firing, burners, burner control, etc. The more I've looked at these things the more I realize that Gerhardt had the same plans; for example, automatic boiler pressure control. The burners and pressure control require "inventions," but the basic design is done, I just have to make the stuff.

I know how to do everything that still needs to be done, but the big problem is the boiler. When Gerhardt built it, for some unexplained reason, he didn't silver solder the tube plate into the forward end of the combustion chamber, and now you can't even see the area, let alone work on it, because the water tubes are in the way. I've used a bore scope to see the joint & there's no solder there at all.

At some time in the future, I will get Don's help and we will silver solder the blow down bushings in and the top feed plate (under the front sand dome). Once that's done, we'll try to use high temperature soft solder to seal the combustion chamber tube plate joint. From that point, its "downhill all the way," it just takes time, lots of it. I figure I'm going to have to live another 30 years to finish all the projects I've got on the go.

Katherine, I'm very glad to hear from you, thanks for posting. Gerhardt's work is very impressive, and yes, Big Boy is still a "work in progress," but the aim is eventually to have it run under its own steam on the track. I'll be very curious to hear how it sounds with the twin stacks & exhausts.

Hope this helps a bit.

Richard Trounce.

[Hudson Honey]

wow...talk about daunting project...thought mine was bad.... yours is more than twice the locomotive my is....but half the scale.......i cannot imagine some of the difficulties. so many things just do not scale due to the nasty laws of physics.

I wish you all the best fortune bringing this master piece to life


Pamela

[RET]

Hi,

I thought some of you might like a little more information on the engine. After all the chassis changes the engine should be able to negotiate an 18 foot radius curve as a minimum, but we haven't tried it yet. For a model of this size, that is very good (if it works). I've based this assumption on the angle between the front & rear engines at maximum swing.

If you look at the pictures, you will see there are two mechanical lubricators on the front engine and two more on the rear engine. The front two of course are for adding steam oil to the cylinders, one for each side, while the rear lubricators are there to lubricate the chassis. One side lubricates the rear engine, while the other side does the front one including the piston rods and slides.

That is what a lot of the small diameter piping is for that you see in some of the chassis pictures. More of the piping is to operate each of the two brake cylinders that are on each engine (Gerhardt did all this, I just modified things so they would work). Since the front engine swings, its going to be a bit interesting to arrange the piping between the lubricators & the high pressure steam pipes mounted on the boiler.

As I've said before, I'm planning on having automatic boiler pressure control by having the boiler pressure modulate the propane supply to the burners. Because of this, I need a burner that I can turn down to zero without having it "flash back." I think I've figured that out, but I haven't built one yet to test the concept.

When I first looked at Gerhardt's throttle assembly, I was puzzled by the "venturi" that I saw at the throttle/boiler connection. I've since realized that's the perfect point to take off the boiler pressure control tap and that tells me he had the same idea. This way, when the throttle is closed, it reads true boiler pressure, but when the throttle is opened, the "apparent" pressure falls immediately because of the venturi so the burners will go on high fire right away. Similarly, when the throttle is closed, the "apparent" pressure recovers sharply and the burners drop back to low fire. This way the system "anticipates" demand very nicely. Sophisticated, but simple; just good engineering.

The burners will be arranged in a triangular bundle, two on top that fire together and one on the bottom. The bottom one will be controlled separately. That one will never shut off completely and will serve as a pilot burner for the other two. The top two will run on a separate control and will be set to a 5 pound lower pressure than the bottom one. The burners will fire onto a layer of insulating brick (not firebrick) which will get white hot immediately and give the same radiant heat that a coal fire would give. The brick will be in a stainless tray with an upward extending front lip to serve as an arch.

There's more, but this should be enough for a while.

Richard Trounce.

[steamingdon]

Glad to see and hear your back at it. Big Boys take a life time and in 3/4" maybe two. Hope to see it on the track one day.

[mjahn]

@Steamindon:

No need to get depressing about it..

@Richard:

I'm sorry for your loss.

Your Big Boy is amazing! I don't think I know of any modelers even in 1.5 who are force lubing their cross heads and packing glands, though its the prototypical thing to do. Did you add any side movement in the engine truck? How much is currently in it right now?

[RET]

Hi,

Thanks for your understanding. When you lose someone, even when you know what's coming, you are never as prepared as you think you are.

Yes, I guess in a way its now 'my" or "our" (Don & I's) locomotive, but Gerhardt still did the lion's share of the work and my hat's off to him. His workmanship is exceptional (especially when you consider this was only his second locomotive) and I'm trying to make sure anything I do is to the same high standard. It seems that many (especially the more complex ones) locomotives are started by one person and then completed by someone else for many different reasons.

To answer your question, the lead truck on the front engine is a swing-link suspension and has a total side travel of about 1/4". As you can see in a previous post, I added a spring on the lead truck king post to get more vertical travel so it could follow the track better. The lead truck on the tender is also swing link and got the same treatment for the same reason. The tender in particular, really shows the result of these changes; before, it would derail when pushed slowly along a piece of straight track because the suspension wasn't able to move at all. Now, I can shove it as hard as I can down a 60 ft. length of track in the back yard and it won't come off; it rocks & rolls a lot as it sails along the track, but it always stays on.

The changes I've made were necessary to make the engine follow the track; softer coil springs, filing axleboxes so they can move easily on both engine & tender, increasing end float on the tender caterpillar, removing interference between the front engine & the boiler so the engine can swing, etc. While the changes are many, I've tried to make sure they don't show unless you really know where to look and even then, most of them are still invisible.

Over the years I've been lucky enough to acquire several very well built locomotives that were started by someone else but couldn't be finished for different reasons (Boston & Albany, Dart and Big Boy). While not finished completely, Boston & Albany runs very well, but Dart and Big Boy still have a long way to go before they will run under their own power.

I'd like to thank you all for your continued interest in the project. Its really appreciated.

Richard Trounce.

[Carrdo]

Well, there is conventional wisdom and then there is reality coming out of one's experience. Not necessarily the same thing at all.

I promised I would take a few more pictures of Big Boy as things went along.

Today, Richard and I had a session in silver soldering the top feed plate and two blowdown bushings onto the Big Boy boiler. See the attached photos. Concerning the preparation work, things went well.

As you can see, the boiler is heavily oxidized as it has been sitting for a number of years (and as well has a lot residual adhesive from insulation found on the boiler when we got it). We know that copper has to be absolutely clean for silver soldering to have any chance of success at all.

That is when things became interesting and not for the above mentioned facts.

When silver soldering or re silver soldering pieces to large masses of copper such as are in the Big Boy, the conventional rules for silver soldering which have oft been stated here and elsewhere don't quite apply.

I am going to limit my remarks to the use of propane as I do not have or use oxy acetylene (however, Richard does have it and uses it if necessary) as we both feel that it is too easy to burn the copper unless one has had previous experience in this area. To repeat an often used phrase, I will stick with the devil I know.

To be continued.

[Carrdo]

To continue,

The first go round on this was to follow the conventional approach i.e. thoroughly clean the metals, slow indirect heating of the boiler up to silver soldering temperature (a dull red hot), use plenty of flux (Richard prefers the black commercial flux) and use of a high silver content (with cadmium) small dia. wire -1/32" (easy flo 45). The cadmium silver solders, despite being banned, are still the most free flowing and have the lowest melting point of all the high silver content silver solders. While I played the large weed eater torch around the area giving preheat, Richard used the largest Turbotorch tip available (1" dia.) as added point heat. Everything was brought to a dull red preheat (for at least 10 minutes) before silver soldering was attempted.

The result; the silver solder appeared to flow but didn't. It wasn't apparent what was going on as the flux masked the joints both at the blowdown locations and the top feed location.

To make a long story short, to summarize what worked after the initial failure was:

The top feed copper plate was thoroughly recleaned, refluxed and "tinned" separately i.e. a thin layer of silver solder applied to the bottom curved surface using the conventional silver soldering approach.

A more or less enclosed "soaking pit" area was created with insulating firebrick to reflect as much heat back into the copper as possible (see the first photo).

The boiler area was cleaned thoroughly of all previous flux, oxide, etc. as before.

This time the weed eater flame thrower flame was applied directly over the part and osscilated slightly. It was observed that it is important that the flame wash be larger than the area to be silver soldered so the part and part area is completely enveloped inside the propane flame at all times. We observed, contrary to conventional wisdom, that if this was not the case, the area became oxidized almost instantly even with excess flux present. We surmise that inside the flame wash is a area where all of the oxygen has been or is nearly consumed and as such the flame wash acts much like a shielding gas.

The flame was played directly on the part/boiler area at all times including and during preheating and during silver soldering.

The copper boiler in the area of the part was heated to a bright orange which is about 150-200 degrees F higher than dull red hot. It has been my experience that conventional wisdom on how hot to heat a particular metal when silver soldering is wrong and I have found this to be the case not only for copper but for steel, bronze or any metal which I have successfully silver soldered with propane. It does not seem to matter what kind of flux or type of high silver content solder one uses either although the new non cadmium silver solders need to have a much higher silver content to flow at the same temperature as an equivalent cadmium silver solder (i.e. a 56% silver content non cadmium silver solder is equivalent in flow temperature and properties to a 45% cadmium silver solder).

Large copper masses conduct heat away at an astonishing rate. The weed eater flame thrower torch is rated at 210,00 BTU at 30 psi. I had to sock the heat full force into the copper and Richard had his 1" Turbotorch going full blast just to heat the small boiler area within the soaking pit for at least 10 minutes before attempting to apply the silver solder. It was quite a sight and I wish there was a picture but we both had our hands full. I think this was one reason why our first attempt failed. We did close the garage door on our second attempt and used only the small garage light so were in semi darkness. It was a windy cool day and this didn't help either.

The result is what you see in the last photo. It looks like the surface of Mars but the silver solder has fully penetrated everywhere and there is a beautiful (but hard to see) root fillet all the way around the base of the part.

Tomorrow, were will do the blowdown bushings again as they came out under finger pressure. There is silver solder all around the heads but nothing through the joints.

Richard might add some more if I have missed anything.

[RET]

Hi,

Don covered things very well. I'd just like to add that its very satisfying to finally find something that actually works and works well when silver soldering this boiler. Neither Don nor I can really figure out how Gerhardt was able to work on this boiler by himself. It seems to be definitely a two man job.

In this case, as Don says, the key seems to be to play the large "weedeater" flame directly on the area to be soldered and use the wash to protect the heated area. Make sure the wash never leaves the work area because you can see the copper oxidize immediately. Bringing the wash back over the oxidized area does seem to protect it again, however.

It also seems that the flame from the big torch isn't quite as hot as the Turbotorch and so that torch is also necessary to get the area to be worked on up to the actual soldering temperature. When using propane and black flux, it seems to be next to impossible to burn the flux, but getting that much metal up to soldering temperature is a slow process.

I filed the excess solder off the top feed plate this evening and it looks very good. I still have to drill & tap the 4 mounting holes and drill the 5/16" center hole into the boiler. There will be an "O" ring to make the seal for the top feed fitting.

We'll resolder the blowdown bushes tomorrow. With what we know now, it should go much better.

The saga continues.

Richard Trounce

[Carrdo]

Success continues to be a hard won victory as we were only partially successful today.

One of the blowdown bushes was successfully silver soldered in but we have doubts about the second bushing. And there was one leaking stay in the firebox which we thought we had fixed only to find out after all of the flux was removed that we heated the wrong one!

So, back for round three sometime in the near future.

I was also wrong about us not using oxy acetylene. Richard does have it (I don't).

At the location of the blowdown bushings, there is such a concentration of heavy copper sections, the weed eater torch was used to preheat the area and then when it looked like both propane torches going full blast were not giving sufficient heat, Richard carefully used oxy acetylene (with the torch adjusted to give a slightly reducing flame) to do the final silver soldering.

A few comments on the photos.

In the first photo one can see the combustion chamber with its many circulating tubes which also act as structural elements.

The second photo is of the successful bushing. Not pretty, but the solder definitely flowed through and around the bushing.

The third photo shows the top boiler feed fittings. At this point they have been made in brass but we are going to remake them in bronze, just to be sure.

[RET]

Hi,

When it comes to boilers, we are still learning and starting off with a big one is probably not the best way to go. Propane is much more forgiving, but the combination of the big torch and oxy/acetylene is necessary for the blowdown bushes because the large mass of copper pulls the heat away too fast.

We ran out of acetylene, so the one bush will have to be redone & we got the wrong stay, although the two propane torches were just enough to melt the solder on the outside of the firebox. We'll get there, but we sure aren't experts yet.

Fun & games.

Richard Trounce.