Try your experiments on something else. In soldering, for instance, solder pieces of brass together until you learn to make a joint.
Don't try your experiments on your model, or you will grow discouraged before you are half through.
A word more about soldering.
Do not touch the metal with the soldering-iron and then take it away. You might be able to solder in that way but the joint would not hold, but fall apart at the first pressure or slight blow.
Soldering on the best work should be used very seldom, and all the fastenings should be either done by riveting, screwing or brazing, and it is hardly necessary to remark that no part of a boiler should be soldered which comes in contact with the flame of the lamp or furnace.
Brazing had better not be attempted by any boy who has not been practically taught the art, unless it be on small joints.
To braze the seams of a model boiler would require a forge fire, or a very powerful gas blast—too expensive for the amateur. Small things such as a broken slide valve, rod, etc., can be brazed by using a gas blowpipe.
This will cost but little to make, and as it will be useful, we explain. See Fig. 1.
To make a blowpipe such as is pictured in Fig. 1, first get a small piece of brass tube, A, of about half an inch diameter, and 5 inches long. Drill a hole at 2 inches from one end, and insert a piece of gas pipe, B, soldering it in place.