# Best way to cast this??



## ohioriverrailway (Jan 2, 2008)

This is an old Lional lamp post. It scales out to about 12 feet, so it's probably close enough for Main Street.

My thought is to make clear resin castings (stuff from TAP). I have a supply of 15 volt bulbs that have a diameter of about 5/32. If I nestle one into a piece of tube, then the bulb would be in the lamp, and the tube would help to strengthen the post and provide a place to run the wires.

But my question is: Should I make the mold in halves, or just try to make a 1 piece mold then cut it down the centerline?


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## Totalwrecker (Feb 26, 2009)

Is the post hollow? 
As I understand it, you want a brass tube to run the length of the post. If you cast as a solid you'd need to drill each post for the tube. If you cut the post lengthwise and made your mold the hollow center (if there is one or the grooves you cut in them) would be repeated with evey casting and would simplify assembly. 

My molding experience is with vulcanised rubber and I always had to cut in to find the piece and then checking my notes I'd cut it out. The notes covered where I wanted the parting seams. Of course I was injecting my molds with melted wax and needed near perfect patterns for lost wax casting. How a mold vented was important too. 

For pouring resin, I'd suggest 1 mold of a tad more than half of the post (instead of cutting down the middle of the flat sides, cut nearer the corners. After the pour has set, then you'd sand the sides until two fit snug on the tube. When you make your mold have a piece of tubing in place, a little longer than the post, so the mold can hold it in place when you pour, plug the tubes ends to keep the mold from seeping inside, or cut it off when cleaning the mold. I think you want to use the clear resin to make the glass top at the same time, so you'll need a bead on top of the tubing so there's a chamber for the light bulb. You might want to put mold release on the tube and bead so you can remove them after the cure. Then sand and install the tubing as you glue the halves together with bulb installed if it won't slip through the tubing. Only flaw this way is changing a bulb. If you made the glass top a seperate piece changing the bulb would be easier. You could also mold the top section as one piece with a plug for the light chamber. 
With a slightly more than half mold there will be some resin higher than the equator, but a pass with a seperating disc along each side of the tube will remove the resin enough to lift the tubing out for sanding your castings. 

Hope this helps. 

John


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## Jerry Barnes (Jan 2, 2008)

You could just mold the top and bottom and use a brass shape for the column. That would be real simple.


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## Jack - Freshwater Models (Feb 17, 2008)

Jerry, 

Just a few thoughts.... 

Why not build your own pattern that is correct scale and isn't just a copy of a major manufacturers part? Yeah it's work but probably worth the effort. 

Casting in clear resin will be a tough one when it comes to bubbles. Presssure casting is the way to go if you can get your hands on a paint pot and compressor. 

I would cast it in two pieces, the pole and the clear top section. I would use a core to provide a hole in the pole for the wires. I would also use a core to make a hollow clear section. If the clear section is separate you can replace the bulb as required. The clear part might also be cast using simple rotational molding technique to make it hollow. 

RTV molds can be poured in one piece and cut in half or poured half at a time. 6 to one half a dozen to the other. If you cut a one piece mold in half you should use a scalpel and make an irregular cut to provide keying. If you pour in two parts you need some Klean Klay to bed the part in and need to cast with keys to maintain registration of the parting line. 

Looks like a fun project!!!!! 

Regards, 

Jack


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## Burl (Jan 2, 2008)

Personally, I'd make a glove mold with a round outside. I'd cut a piece of PVC pipe in half, lengthwise, to make the form for the mold. That way you could re-use the PVC pipe as a mother mold when you cast. Of course, you'd have to cut the mold at least to the bottom of the glass (assuming you're going to cast it upside down) to get it off the pattern. Just my two cents.


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## Havoc (Jan 2, 2008)

Why not just put 2 wires in the mold before you pour?


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## Dan Pierce (Jan 2, 2008)

Why not use a hollow brass tube and 1 wire in the middle as the brass tube is the second wire.


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## Torby (Jan 2, 2008)

LED for the lamp. Just cast it in.


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