Boiler Repair.
Caution: the procedure used to disassemble this boiler will remove the original finish. Keep in mind that all hot metal boiler work on these engines was done prior to final finishing. So don't emulate this unless you plan on losing any finish on the boiler. In this case, there wasn't any original finish to lose.
There is no way this engine will ever run again without a pressure tight boiler. This one has a serious crack where the primary steam valve is located, probably from the engine falling, or something falling on the engine.
To repair the boiler, we must first remove the end cap.
Here it is, safely removed. Heat around the edge, and gently tap with a heavy brass plate at the joint. Work around the edge, the cap will move a little further with each pass around the boiler. Eventually, it will pop off.
And a closeup of the damage. What we will do is:
1. Rough the damaged area back into shape
2. Solder a sleeve on the inside to seal the cracks, and provide a new, stronger mount for the nut.
3. Resolder the valve nut.
4. Replace the end cap.
Hammering the damaged area back into shape required the utmost in caution, as this brass is quite thin. I used a heavy pipe for a rounded backstop, and a brass hammer to flatten the boiler material out. Brass hammers pack quite a punch for the amount of swing you use. This allows localizing the force, so that you flatten out the sharp dents without also flatting the rest of the boiler. The rounded shape of the pipe aided in hammering the pieces back into a semicircular shape.
Once roughed into shape, a piece of thin brass plate was bent until it was the same contour of the boiler. It was then placed on the inside, and soldered into place. Note: the sleeve was essential. While it may seem tempting to slop some heavy solder on the inside to seal the cracks up, this will not be strong enough to withstand pressure. It will blow loose during the first steaming. The sleeve on the inside provides a strong seal. The solder is used only to provide an airtight seal, and to hold the sleeve in place.
Here it is during the first soldering. The sleeve was sanded and is clamped in place. Note the Smith Little Torch being used for a heat source. Being an oxy/acetylene torch, it provides a great amount of heat in a very small flame. Note also the fill plug in place - this insures that the 'nut' for the fill plug does not drop off due to weakening of it's solder.
That got the sleeve in place. But it wasn't airtight, so additional solder was needed.
2nd soldering. Hemostat holds the sleeve in place so that it does not drift during heating. Heat the sleeve, and work fresh solder around the edge. Then, apply heat to the other side, so that it sticks to the boiler as well as the sleeve. Solder and flux was worked around the sides in quantity until a good seal was achieved.
So far, so good. Now, drill a hole through the new sleeve, to locate the nut. Screw the steam valve through the sleeve and down on the nut, to hold it in place while soldering it for a permanent seal.
There it is, sealed in place. Note wet rag - this was used to keep the valve cool, so that solder did not run onto the threads and lock the valve onto the nut. If you look carefully behind the solder area, you can just make out the diamond shaped 'nut' for the fill plug. It's just a scrap of brass plate, not even a proper nut. Contoured, drilled, tapped, and soldered in place, as are the other nuts on the inside of the boiler. This is a construction detail that one doesn't normally see.
Replace the cap, give it a good polishing to show off the effort, and it's ready for steam.
But not completely done yet. This boiler originally had a purplish-brown finish, so let's put that back on, so we're as original as possible.
All done. The crack is still evident, but it will hold steam now. The sleeve on the inside assures a seal that will hold pressure. And, a tip for the aspiring restorer:
Careful with that heat, Eugene. I didn't just plunge in and attack this classic boiler with a torch. First, it was practice, practice. Starting on sheet brass, progressing to an old Fleischmann boiler that was beyond salvage. What I learned is that soldering thin brass was a study in heat management. Too much heat, and the brass will burn. If you see green flame, it's the copper in the brass burning. Back off immediately. Heat it for too long, and the brass will distribute the heat across the entire boiler. Fitting nuts will drop off, and solder can run out of perfectly good joints as well. While this Doll boiler's main body is made from brass tube, others such as Marklin bend a brass sheet over and solder along the bottom for the main tube. You don't want to weaken that joint. So get a very small and very hot torch, preferably one that uses oxygen, and apply the flame sparingly. Don't leave the torch in one place, move it around. Be sure you prep the area with sandpaper and use flux, otherwise the solder will just ball up and roll off. Make a few passes, and apply the solder. If it doesn't melt, make a couple more passes and try again. The trick is to increase the heat incrementally until you have just enough to melt the solder. And heat both sides, to insure the solder sticks.
That's about it for this installation of Boiler Repair 101.