making a hollow 2 piece mold

[johnny ducketts]

Guys

I am trying to make a 2 piece mold in rtv ala...dahlberg style

But i would like to cast the pieces to be hollow in the middle that way i can add a through wire, ballast, or rattles. Other than cut the master in half, is there any way to do this. I made a 2 piece mold of a nike but its a solid chunk of alumilite and casts like a brick. Any of you guys try to make a hollow 2 piece mold. Rowhunter i hope you have.

Thanks

[Nebe]

Take your model and make a rtv mold of it. once you have your RTV mold, smear some plastic clay like Sculpy inside the cavity of the mold. If you have half of a pouring reservoir in your RTV, complete the other half of the reservoir in clay as well. the plastic clay will simulate the thickness of the material you want to cast. Once your plastic sculpting is done, pour more RTV over the clay to make a "B" side to your "A" side of the RTV... You need to do this to both sides of the first RTV mold.

Once your molds are cured, remove the clay and you will have 2 molds to make 2 halves that you will have to glue together with a serious glue like zapagap.

Make sense?

[Rowhunter]

Unfortunately, I have not attempted this, so I'll be of no help there. If you already have the two piece mold, I'd try to lighten up the resin mixture with microballoons. Set some pins in the mold to hold a pre made through-wire with any weights positioned on the wire. You could try 3oz part A and add 1oz microballoons. Separately, 3oz part B and add 1oz microballoons to it. Calculate the amount needed for the pour, then add the two mixtures accordingly. Im sure this will give you plenty of buoyancy, and will then give you the freedom to place weight where you wish to get your desired action. Other than that, Nebe's above method will put you on the right track for a hollow two piece. If you took the wood master and cut out 1/4" out of the center, and used it to press the clay in the existing mold, it would give you a fairly even 1/8" wall thickness. Hope this helps,

Douglas