Pith Helmet Brass Top Ball Finial and Dome Fitting

[mite5255]

Hi all.....A work mate of mine belongs to this military group http://www.nprsr.qld.gov.au/parks/fort- ... index.html and they wear a pith helmet with a Pith Helmet Brass Top Ball Finial and Dome Fitting, see the first photo.I have been asked if I can made the top ball finial and dome fitting...I propose to make a silicone mold and casting the ball and finial as one piece and the dome separate and cast in pewter, suggestions welcomed

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I cannot use the ball and dome fitting for a pattern as they are rather thin the ball especially is thin and would not stand up to molding in sand at all so I cast a ball using a lead sinker as a pattern and reduced it to the correct size by drilling and tapping a hole for a m5 bolt, I then placed it in my drill press and sanded it to size. For the dome, I took a billet that I had cast to work and asked our shift maintenance fitter it he could turn a dome for me in the lath ( must get a lath one day ) I placed plasticine the ball finial, I then place the ally ball into the finial and pulled the ball into the finial and plasticine with a m5 bolt and nut, i ran the nut down the bolt till the ball was firmly in the finial and was squishing the plasticine out, the I just cleaned the excess off

This is what I have thus far, disregard the nut between the dome and finial, I have no idea why I put it there

This how I propose to make the silicone mold, the orange bit would be my pouring cup. the pouring cup at its widest would be 16mm and 10mm at its narrowest
I will place the pattern in the cup thats below, it has a hole in the bottom and the pattern is bolted to together, I'll then pour the silicone in the cup and when its set I'll remove it and make a pop keeper to stop and distortion when casting, I'll cut the pattern out and that cut will be my parting line.....I have already tried one silicone mold but some dodo mixed the silicone and setting agent by volume and not by weight
Mike

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[Nudge]

Have you got any further on with this?

[mite5255]

Have you got any further on with this?

I hope to get some more done this week nudge, I had to order some more molding silicone and it arrived last friday, so i'm hopeing to get time this week

Mike

[F.C.]

Just a suggestion, Mike... i've attached a pic of a sketch which ought to help you create a mold of that thing you can use to duplicate it in wax massive amount of times. Once cast in wax you can sprue them all together onto a wax rod and cast them in bulk doing lost wax investment.

[mite5255]

I do hope your feeling better Frank , I worked out years ago what causes that hung over feeling, these days I only drink low alcohol beer and I feel sooooo much better

Thanks for the above diagram, I was going to have the parting line vertical but horizontal I think will be heaps better. I've ordered some alginate and it should be here in a few days, I'll then cast up a mold.


Ya know what Frank, one of my biggest disappointments is my Father is not alive, he would of loved this metal casting caper, if he was still alive he would be well into his 80s but he would sit and watch PLUS tell me when I was, in his opinion wrong I miss him

Mike

[mite5255]

I do hope your feeling better Frank , I worked out years ago what causes that hung over feeling, these days I only drink low alcohol beer and I feel sooooo much better

Thanks for the above diagram, I was going to have the parting line vertical but horizontal I think will be heaps better. I've ordered some alginate and it should be here in a few days, I'll then cast up a mold.


Ya know what Frank, one of my biggest disappointments is my Father is not alive, he would of loved this metal casting caper, if he was still alive he would be well into his 80s but he would sit and watch PLUS tell me when I was, in his opinion wrong I miss him

Mike

Alginate finely arrived , the place were I ordered from shut down for four week over Christmas so it arrived yesterday, I'm hoping next week to try and mold the pith hat finial and ball, its raining here today and my work area has water over the floor and I hate having to have duck feet

Mike

[Rasper]

For several years I had a shop that was an old abandoned commercial greenhouse. It had great light. I sorely miss that translucent ceiling. I heated it with a wood heater I made from a 55 gallon drum. In the rainy season I would have several inches of water over the entire floor. I dug a sump hole about two feet deep and put in a sump pump with a float switch and fifty feet of garden hose to carry the water to lower ground.

Richard

[mite5255]

I've been a bit busy of late with work and life so now its time to try and get something done.

Went to start making a new mold using alginate as Frank suggested, I picked up the original silicon mold that I had made but didn't use enough setting agent and it didn't set , well it has set good enough I think to make a few wax castings.

first wax casting

[mite5255]

Just experimenting here
Trying two things , I had some fine grog so I thought it may be better that sand. Mixed twp parts pop to one part grog (ground up fire brick )
the first photo I dipped a wax casting in the mix and when it drys I'll coat it again till a reasonable thickness, please ignore messy work bench maybe work bench is the wrong word place to store assorted tools would be more correct


2nd photo, I filled a piece of PVC tube with the mix and then placed the wax casing in the mix,when it has set I'll cut the PVC tube off

[F.C.]

Are you casting them solid or with a core? If you want that cast to be hollow there needs to be a core inside that wax suspended by a couple pins (at least). If you're casting it solid, that may end up a bit heavy on the helmet, wouldn't you think? And why didn't you use the algenate?.. it's a simple water based mix, sets up quick, easy to vibrate out bubbles, virtually fool proof in my opinion and it's much cheaper to use than the commercial silicon mold compounds.