Lid Mechanics

Posted: August 30, 2010 in Furnace Body

Before wrapping up the lid, I figured it’d be a good idea to get the mechanics of the lid wrapped up.  Since this is a Foundry Furnace, a crucible will be inserted into the body filled with metal to be melted.  To trap heat inside, you need an insulated cap to the furnace.   So, it becomes obvious that you need a means to move the cap out-of-the-way when you need to insert or remove the crucible.

The simplest method of doing this is to install a hinge on one side and lift it.     This has its down sides though.   If the lid will tilt up, then it precludes us from using the top for other purposes without moving things.   Ideally, I want to be able to use the top as a “burn-out oven” to vaporize wax in investment flasks or to pre-heat molds so that I am less likely to have an incomplete casting.   Keeping the lid horizontal is preferable if at all possible.

In thinking about it, I decided that  a metal tube in a tight-fitting sleeve would allow vertical movement as well as a horizontal pivot.  I’d be able to lift it up and swing the top out-of-the-way when I need to get at the crucible, or lift it straight up and put in a “doorstop” under the opposite side to open a much larger forge port if I ever had the need to do any scroll-work or other big items.   

A piece of 1/2″ electrical conduit was slid over the mild steel ring and welded together.   The conduit was bent 90 degrees by heating the conduit and using a “cheater pipe” to give additional leverage to make the bend.   The bend was reinforced with significant extra weld material for strength so that it can (hopefully) deal with the cast refractory lid.

On the lower unit, I have a 12″ length of  3/4″ black pipe with an end cap.  I drilled, and ground out, a hole through it just large enough to accommodate the outer diameter of the 1/2″ conduit.   The bottom of the black pipe will utilize a 3/4″ -> 1/2″  reducing 90 degree angle, then I’ll use more electrical conduit to come out and attach it to the base of the furnace.   Additional securing is probably necessary at the top but I can get to that later.

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