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Discussion Starter · #1 ·
Hi all
i hope you guys can help, i am looking to cast a Land Rover defender and a series 2, i have found a couple of good guides on the internet of how to cast but i do not have a clue where is the best place to get the required resins, mould releases and the silicone rubber to make the mould in, any help would be much appreaciated.
Cheers

Reuben
 

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Hi Reuben

I got my casting stuff from www.tiranti.co.uk

They suggested the following products.
T28 Silicone rubber for making your moulds
Either G26 Biresin or Axon F16 polyurethane resins for your bodyshells.

Have only made the one body so far, read the thread "should have stuck to MG, Jimmy" on page 2 of scratchbuilding, which details some of the pitfalls I encountered and might assist your own efforts. The products worked as they should have and gave excelent results - the problem was with the user!
 

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Second that, I use Axon F16 resin. The T28 Silicone is excellent with a high tear strength which is very handy when casting awkward shapes with large undercuts.

Good luck, and let us know how you get on.
 

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Reuben

If you put your Land Rover master in a container with a gap of about 10mm all round then pour water in so that it covers the top again by about 10mm then tip the water into a measuring jug it will give you the amount of silicone required. Add a bit onto the figure to allow for error and final adjustment when you are actually preparing the mould.

David
 

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Discussion Starter · #7 ·
hi
i have the land rover prepared and in a box i aso have the t28 silicone rubber + the axson resin, i beleive pouring the silicone rubber over the top is the next stage but just wanted to confirm this!
Thanks
Reuben
 

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Hi Reuben,

Sounds like pouring the silicon is the next job to me. I would only pour from one corner of your mould box, nice and slowly, and let the silicon find its own way around your pattern, that way there's less chance of any air getting trapped.

Good luck
.

Marlon.
 

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Another useful trick of removing trapped air is to gently vibrate the mould as soon as you have poured the silicone. Just hold the mould box tight on any vibrating surface: vibrosaw, top of a washing machine, etc. for about 30 minutes. A bit boring but it does bring at lot of bubbles to the surface. good luck steve
 

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It's better to vacuum out the air bubbles.
Which can be done fairly simple, you have to work quickly, but the setting time should be enough.

1) Poor 20 ml at a time into a 60ml syringe.
2) Tilt it up and press out excess air.
3) Seal the needle nozzle.
4) Draw out the cylinder.
5) Let go of it.
6) Repeat 4 & 5 a coiple of times.
7) Press out into the mold.
8) Repeat 1-7 until all is used.
 

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I`ve read with interest all the posts above and as I`ve been casting resin and white metal for longer than I can remember I thought I`d just add one idea that I don`t think has been covered. That is using a skin mould with it`s own shaped reinforced liner.

The box mould is only one way of making a mould and it uses too much valuable silicon. Cover your master in cling film and then next cover the master with about 15 mm of plasticine over the top of the cling film and shape it as near as possible to the contours of the master.

Place a small tube at the top most point of the plasticine but not into the area of plasticine, then build a box out of card or plasticard. I use a hot glue gun to stick the box together. Make up a mix of plaster of paris. This is poured into the box so that it makes a good solid box, remember that it is not touching the master here guys. Your tube should be sticking out of the top of the box. Once it is dry, then remove the box. Strip away the plasticine and the cling film.

Replace the master inside the P of P box and seal the bottom of the P of P box, again I use a hot glue gun to do this. Now you can pour your mix of silicone into the tube, it goes down and surrounds the master. The point here is you are now using a lot less silicon than the methods described above and there is another bonus too.To remove the air bubbles (I use a vac chamber) you can get away with using a large Anne Summers Vibrator and holding it against the tub of silicon will remove the bubbles.

Once the silicon is set (try doing this where the room temp is as high as poss, I work in at least 60 degrees) remove the p of p case and what you now have is a thinner mould, more flexible, less costly and it fits like a glove to the p of p case which will ensure that the mould never goes out of shape.
 

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Another trick I've used is to paint on the first coat of silicon. You can be sure you won't get any bubbles that way. With some catalysts you get a very thixotropic rubber that you can actually build up with several coats to make a 'skin' mould as Johnny S describes, which you can then support with plaster of paris.
But generally I've found that if you mix and pour carefully, the very slow setting time means that bubbles generally find their way to the surface anyway. Stirring the catalyst in too violently is usually the mistake- the bubbles come from air you have accidentally stirred in, rather than it getting trapped beneath the master. Use a paddle with an 'L' shape, which mixes the rubber and catalyst below the surface without mixing in too much air. It makes a big difference.
You can also put your jar of mixed rubber inside a fishtank and fix up a vacuum cleaner. If you have a powerful enough draw the rubber will foam up until all the air comes out, then it falls back and you have an airless mix.
But I've never gone to that much trouble for a body shell!
 

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Would it work if you got a small plastic fishtank (cheap), placed your frame inside it, poured the silicone, sealed the top with your vacuum nozzle connected to it then switch it on?

Actually...You can get small plastic tubs about 8"x4"x5" (lxdxh) for spiders and small lizards (for transporting them/temp. accomodation) - you could just connect the vacuum to that and use it as the basis for your mould.

*n
 

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I`ve made a vac chamber out of an old freezer and used a vacum cleaner to suck the air out. It does work and a smaller air tight box would be easier to do. Be careful guys, there is plenty of scope for disaster and by the way keep the vibrator out of your mouth or else you`ll lose your teeth! Not that I`ve ever tried that on a cold Winters night!!
 

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where i used to work, we had a perpose made vacume chamber for resin/rubber moulds, to take the air out.
(we produced vac formed bodies, silicone and latex moulds for various modeling applications)

the vacume chambre was a cylindrical container with a half inch thick perspex lid. the air was then sucked out by a compressor.

tried it with cup of water in it, and it made the water boil at room temp.

i wonder what would happen if you put a spider in it? he he
 

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QUOTE (penski @ 3 Feb 2005, 15:32)Would it work if you got a small plastic fishtank (cheap), placed your frame inside it, poured the silicone, sealed the top with your vacuum nozzle connected to it then switch it on?

NO!

What happens if you do it that way is that the bubbles seek themselves out to the nearest surface.

A very easy to make vacuumchamber is made from:
1) A glassjar with a metal lid.
2) A bicycle valve.
3) A short bit of tube. That goes over both valve and syringe.
4) A large syringe.
5) A magnet and a bit of thin rubber.

A) Drill a hole for the valve in the lid.
Put the valve in backwards, seal it tight and put the tubing on it.
C) Drill a small hole, put the rubber over and seal it with the magnet.
D) Close the jar.
E) Start evacuating with the syringe (attach, pull, detach emty etc).

With this very easily done vacuum chamber I've gotten astonishing results.
On both resin and silicone.
 

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Now that is clever. I`d moved on from the Heath Robinson stuff and bought a vac chamber and all ther gubbings, cost about £1500 but if tou evac the resin and the rubber then you get the best results.
 
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