Re: Superheavy Assault Walker
Posted: Tue Dec 08, 2009 6:44 am
Mark; as I said, I'm not sure on the texture of the Mr 500 - the 1000 stuff was smooth as so perhaps I didn't use enough thinners for the hot weather. I might post the pic over on the Fichtenfoo forums and ask them. It is indeed sandable - I cleaned it up yesterday using some 1200 grit.
Jon; nope, only a single vacuum stage. The mixed resin is poured into the mould and then the mould placed into the pressure pot. The pressure pot has been modified with two sets of fittings to allow both the vacuum pump and compressor to be connected simultaneously (and selected through the use of some valves). Vacuum is then applied and released (to force the resin into all of the voids) and then pressure is applied (but in my experiment above the pressure stage was skipped).
If you look at the ankle joint parts they have quite a large volume sprue (similar to the volume of the actual parts)and I use this as the resevoir. In reality the resevoir does not have to waste much silicone or resin: the silicone only needs to be a few mm thick around the resevoir. And the sprue doesn't need to be filled with so much resin - I just had exrta mixed up.
I'm told resin is only supposed to expand to around double its volume under vacuum (as opposed to silicone which does more than 3 times).
The pump I'm using is the type a Refrigeration or air conditioning mechanic would use. It probably takes a minute for it to take my pressure pot to full vacuum. Another trick that the caster told me is to fill up your pressure pot with uncompressible crap so that the volume of air that needs to be moved is lowered (and thus vacuum is quicker).
I'm going to pick up the final fittings I need for the simultaneous setup today but won't get a chance to try it out until tomorrow night.
Jon; nope, only a single vacuum stage. The mixed resin is poured into the mould and then the mould placed into the pressure pot. The pressure pot has been modified with two sets of fittings to allow both the vacuum pump and compressor to be connected simultaneously (and selected through the use of some valves). Vacuum is then applied and released (to force the resin into all of the voids) and then pressure is applied (but in my experiment above the pressure stage was skipped).
If you look at the ankle joint parts they have quite a large volume sprue (similar to the volume of the actual parts)and I use this as the resevoir. In reality the resevoir does not have to waste much silicone or resin: the silicone only needs to be a few mm thick around the resevoir. And the sprue doesn't need to be filled with so much resin - I just had exrta mixed up.
I'm told resin is only supposed to expand to around double its volume under vacuum (as opposed to silicone which does more than 3 times).
The pump I'm using is the type a Refrigeration or air conditioning mechanic would use. It probably takes a minute for it to take my pressure pot to full vacuum. Another trick that the caster told me is to fill up your pressure pot with uncompressible crap so that the volume of air that needs to be moved is lowered (and thus vacuum is quicker).
I'm going to pick up the final fittings I need for the simultaneous setup today but won't get a chance to try it out until tomorrow night.