castable refractory

[ThisOldGarageNJ]

Re: castable refractory

once you have your first one cast,, can you fill it with expandable foam,, take it out then use that as a solid base form ? It could work on the outer surface as well, maybe ?

Mark

[mr g]

Re: castable refractory

I like the way you're thinking. How much foam do you think I'll need? I've never worked with it before.

[david s]

Re: castable refractory

Fibreglass is way more durable and more widely used for casting moulds. But I hate working with the stuff.

[ThisOldGarageNJ]

Re: castable refractory

mr g,

you could probably do the inside mold with 4 or 5 cans,, you could use baloons to fill up some blank space and not waste too much foam,, In the states we have a product called Great Stuff,, They make a high expansion foam for sealing large spaces,, once dry it can be cut shaped etc,,,, Hope this helps,, as for the outside, I guess you could spray it on, maybe smear it down with a spackle knife or it may just take the shape well

Mark

[david s]

Re: castable refractory

The foam is not particularly strong. I would be concerned about it breaking up after the second or third casting. Then you're back to square one.

[ThisOldGarageNJ]

Re: castable refractory

If you have the HILTI brand foam (down under) it is much stronger... and very dense,, you could always foam to get the shape right then fiberglass the foam and you would definitely have a permanent form....

[david s]

Re: castable refractory

Now you're talkin' but run some tests with the foam. Depending on the resin you use, some foam will dissolve on contact.

[david s]

Re: castable refractory

Hey, I used to work for HILTI back in 1970 Their products are the best.

[ThisOldGarageNJ]

Re: castable refractory

Davif S

Hey, I used to work for HILTI back in 1970 Their products are the best.

A Hilti is a tool you buy once and leave to your kids,,Because You will die before your HILTI

Now you're talkin' but run some tests with the foam. Depending on the resin you use, some foam will dissolve on contact.

Maybe the foam could be covered with a cheap painters tarp, plastic, etc.. Stop by an autobody shop that works in fiberglass they may have some ideas, I believe guys that build surfboards also use a foam core, so if theres a surf shop around they may have a few ideas as well..

Im even thinking, for the outside a plaster of paris cast, like a dr. would do on a broken arm, could be applied easily to the shape in strips and if you ever felt a cas it is pretty hard..

Mark

[asiapizza]

Re: castable refractory

looking forward to your pics, awesome job!

[MetalHead]

Re: castable refractory

Did your sand cast get destroyed? You could repair it and make a fiberglass mould over it 3 or 4 layers. Then once it is set you could leave the sand mould under the fiberglass outer shell. You couls also fiberglass in your dividers.

[mr g]

Re: castable refractory

Did your sand cast get destroyed? You could repair it and make a fiberglass mould over it 3 or 4 layers. Then once it is set you could leave the sand mould under the fiberglass outer shell. You couls also fiberglass in your dividers.

No, the sand mould is still holding up. It's more a thought experiment at this stage. If that sand mould gets damaged it should be fairly easy to repair. The fibreglass angle is good but it's a pretty expensive way to go. I'll try a few more and see how we go. I've got a big form building session going on tonight with some buddies so we should be able to get a whols dome cast on Sunday.

[TheOldFox]

Re: castable refractory

i'm loving this thread.. and thinking i could take this route with my limited and zero time limit make-over..

waiting with awe to see more of this method..

regards & great work to mr_g and his friends..

[mr g]

Re: castable refractory

i'm loving this thread.. and thinking i could take this route with my limited and zero time limit make-over..

waiting with awe to see more of this method..

regards & great work to mr_g and his friends..

Thanks mate, I've attached some photos of the form work. As I suggested earlier I've separated the entrance from the dome to make for easier casting. We've settled on a clever little idea to keep the form in place and with the correct slope. The side wall had to be cut to allow for an inward slope and rather than using timber stakes to keep it from bulging out once the concrete is poured we've used a tie down strap that goes all the way round the form. Hopefully the pictures clarify what I'm babbling on about.

Casting a full dome tomorrow. I'm optimistic that we'll do it inside two hours.
Cheers for now.

[mr g]

Re: castable refractory

Forgot to add the pics..... sorry. Here they are. One of the photos show the quarter dome form that I first used under the table.

Mr G.