White metal casting - Individual Track links

[Guest]

I'm working on some scratch built vehicles and am coming up to the stage where I need to figure out how to make the track links...

I can make some using a CNC engraver to make some very precise parts but would need to fabricate the parts using various cutout parts. This would be very time consuming...

..as i'd need approx 37 links per side and thats just for the visible links, ideally I'd like to extend the track links under the armour covered parts a bit too.

I was thinking about RTV silicone for the moulds as I could split the mould with a scalpel.

I was thinking it might be nice to cast the link sin white metal rather than resin,

Does anyone have any experience with white metal and could post any of their experience here?

[Guest]

hi alan, i dont personally know anything about white metal but i looked it up. im sure you already know what whikipidea has to say but il post the link anyway.

http://en.wikipedia.org/wiki/White_metal

[Guest]

you can buy high temp RTV silicone, no problem- so mould your master as normal - then rather than resin or whatever use the moulten white metal compound and cast as 'normal',

my experience was you needed a bigger ' fill hole' with white metal type materials- but melt the white metal compound and pour in as usual- the one thing you tend to find is that there is increased chances of bubbles on undercuts with ' hot' compounds' as they cool,

i got more bubbles and defects in white metal castings than i do in 'bi resins'

i generally stick to resins now, its also in my opinion less hassle too- melting the metals on the stove with a blow torch adding extra heat is just hassle !

[Guest]

Hi Alan

Some years ago a shop called Langly minature models in Crawley Sussex did a batch of white metal castings for me I supplied the master in milliput and they did the work. Cost me next to nothing and the results were incredible, im sure if you google them you should find a contact. Most all they do is model railway. White metal is cast in a centrifuge so as not to get voids.

Could be costly to set up for.

kevin

[Guest]

Thanks for the advice, I'll give them a ring and see what they say.

[Guest]

the alternative is to mould then apply vacuum - this should pull out any air bubbles to top of the mould, they do this alot with resin so i guess it should be ok with white metals.......

its just a messy business !- resin is easier IMHO

[Guest]

I've seen resin casting where they allow the resin to cure in a pressure pot, the pressure compresses any small airbubbles, they also refer to degassing equipment when moulding the rtv silicone. I assume a vaccum pump would be used for this. My problem is that with the track links the parts would be so small I'm not sure I'd be able to get them to mould correctly just by using gravity alone.

[Guest]

trying to draw a vacuum on a white metal casting would be like trying to catch a flea's tail you couldnt move fast enough to evacuate the mould before the metal transitioned. resin sets over a long time. The resin is initialy de gassed in a partial vacuum to remove air in solution the resin is then poured and put under pressure to compress any remaining air bubbles.

kevin

[Guest]

I contacted Langley Models regarding the White Metal Casting, they charge £53 to produce the Rubber Moulds and then £3.50 a shot for each pour. They reckon on being able to produce 20-25 track links from each mould.

The original needs to stand up to 130 degrees c as they use an oven to cure the rubber.