I am building a three truck shay live steam engine in
1 1/2" scale. I need to know what to use for the boiler lagging. I have read several books but none of them say what material to use. Please help??

You don't see this done much but once many years ago someone suggested to me that wool felts would make a good insulator for model boilers. I tried it and it works great. It's relatively thin and a great insulator. You must be sure however that it's wool felt and not a synthetic, which is what you will find at most local cloth & sewing shops. Wool felts are available in many thicknesses and densities/weights. I use 1/8" for larger boilers and 1/16" for smaller ones. There is no problem with saturation. Since it "breathes" through the fibers, any water that might find its way to the fabric gets baked out during steaming.

In building my 1 1/2" scale locomotives, I use alternating layers of heavy duty aluminum foil from the supermarket and woven fiberglass cloth material from marine suppliers. Usually 5 layers of the cloth and 6 of foil. The foil helps to reflect the heat back into the boiler and the gass has insulating value. I make cardboard patterns and cut the materials to size. I use staples to make a seam along the edgeof the panels. The layers of foil help the sandwiches stay in place but I use thin wire to hold them in place until I get the outer wrapper on. This method does not tend to crumble when handled and is easy to remove and replace as needed.

Mike, My experience is in building small scale live steam at near 1/2" to the foot scale and it seems that 1/16 to 3/32 thick ceramic fiber is used most always, although some early locos used asbestos just as the full sized locos did. Ceramic fiber must be available in thicker form for larger scale locos,or perhaps you could use the thinner fiberglas as used for after market water heater up-grade blankets.Might I suggest a call to Little Engines or one of the other advertisers in Live Steam magazine. Any insulation is better than not. GB

Sulphur Springs Steam Models can supply Ceramic fiber blankets for boiler insulation in 1/8" and 1/4" thickness