Hello all, I am looking for someone who makes and sells bulbs for IOM in Canada or even anywhere in North America? I was going to make my own (i might still do this) but I was going to see first if anyone makes them and what the cost would be?
I have seen some ads for these items at the AMYA web site. AMYA web site has changed to Modelyachts.org for some reason.
I have made my own bulbs with some trepidation. Dealing with hot lead is a dangerous process but not beyond the ability of a careful craftsman. If you cast some lead make doubly sure that there is not the slightest bit of moisture in the mold. A plaster of Paris mold will work very well but you must give the plaster a long time to dry thoroughly, like a week or two.
My molds have been two part affairs. Foundries call these two parts the “cope” and the “drag”. I cast them vertically, that is with the nose down. The reason for that position is so that mold fills better and more homogenously. Pour the lead into the mold from the small end (trailing edge) . That means that the trailing end will not come to a point. Use a wood or plastic cone to finish the back end. Another feature of the mold is that it will need a vent. A small air hole near the top of the mold for air to escape as the pour progresses. The vent will need to be paralell to the centerline of the bulb or the resulting sprue will make extraction from the mold difficult. It helps a lot if the mold is heated while pouring. If it is too cold the lead will freeze before you get the mold filled and that makes an ugly casting.
You can also make a bulb with a single open mold. Use plaster to make a mold that forms the bottom half of the bulb. In this case you are casting horizontally. Cast two of these parts and plane the connecting surfaces into a nice flat surface. Bolt and epoxy the two halves together. This is probably the most practical method. There is more work involved because you have to fit the joining surfaces. In either kind of mold you must build a box around it to avoid damage and possible failure of the mold. Don’t trust the plaster to hold that hot lead by virtue of its’ own strength.
If you do the casting yourself, do so in a well ventilated place. Fumes from molten lead is dangerously toxic. A respirator is needed too. Devastating burns are possible with this stuff so you must be extremely careful.
With all that, it is easy to understand why a lot of people use lead shot and epoxy for bulb making. Not as dense, but a lot safer.