Molding question

[allenea]

Wasn't really sure where to ask this question so please move if in the wrong location.

I found a perfect Suburban to use with my 1/72 guys for a modern game. Issue is I need like 3 of them and want to cast them here at the house for my own use.

Question is how the heck do I do the mold? Do I remove the tires and try it that way or mold as one piece? I've searched youtube but only seem to come up with the one where the guys is making a copy of a model body.

I've done slot car bodies years and years ago but I'm really stuck on this and don't want to waste product each time I mess up.

Thanks in advance Earle

[6milPhil]

You'll likely have to fill it before you can make a mould.

Post a few photo's of it from various angles and I'll give you more detailed advice.

You an E-6 then?

[snitcythedog]

It would be helpful to see the truck to let you know what you need to do.  It is possible to cast the whole thing at once but it might be better to take apart.  Just depends on the model. 
Snitchy sends.

[allenea]

So here is a pic that I took a few weeks ago. I have to reglue the mirrors back on but the base does come off as it is only on by 2 screws. I want to mold a few of the Nissan in the back also as technical vehicles until I can find a better truck.

I was think about putting the clay up to the wheel wells and then pouring the bottom half for a 2 part mold to cast...

I was a SSG along time ago...now I'm a 1SG

[6milPhil]

I was a SSG along time ago...now I'm a 1SG

Well Sarge I reckon you could do this with a one piece fill mould, sure you could do a two-piece, but that's a bit more convoluted and I'm assuming you don't have a vacuum chamber or pressure pot.

The way I'd do it would be to take it apart so you can fill it to make it solid, this guarantees no rubber gets inside when making the mould and all the problems that can cause. I'd first glue the plastic which makes up the glazing into place, then fill the body down to the plastic which fits on the bottom to give the underside.

Remove the wheels and cast seperately, again these can be fill-moulds with the inside of the tyre flat which won't matter as you typically won't see it. Fill in any holes in the wheel arches left by removing wheels. Also check the gaps around the windows, grille, etc and see if they don't need filling or fixing too.

Then remove any detail on the underside to get it flat and reassemble, then spray paint and spray varnish to give a bit of a seal.

Next would be boxing, you can do it with lego or plasticard, and I reckon you need about 3/4 of a inch all the way around. First fix the now smooth bottomed model to a base board with superglue, put the walls around it and you're ready for mould making.

I'd suggest a long cure rubber for the mould, not because you want to have to wait but so you can work out any bubbles which are most likely going to be in the wheel arches. Now you can, when filling the model, put a bit of a slope into the arches if you want, bearing in mind the wheel fit of course.

On pouring rubber I'd suggest pouring to the floor of the box so the arches fill from the bottom up. First pour to about 3/4 of the way up the arches and let it settle briefly, then gently top it up to about the height of the door handles. Get some right angled tool and have a prod into the depths of the arches and try to drag any air out, then top up a little more and hold the box with one side up and give it a few taps, then the other side. Do this as offten as you feel you might have to. Then fill it up with about half inch of rubber over the top.

If there are bubbles in the arches they'll be at the top back, only you can judge that really.
Good luck!

Btw do you now why the Navy have Marines?

[allenea]

Thanks I'll see how I do on the first run...gotta buy a kit here shortly

[snitcythedog]

6milphil nailed it for the two side.  Another option would be to fill the vehicle, glue it to a base, fill the void under the vehicle and texture the base.  Then you could cast it up as a single sided mold.  Preparation would be a bit more challenging but you end up with a simpler to use mold.  It all depends on how comfortable you are working with silicone and resin. 
Snitchy sends.

[KJoelN]

Hi!

I just made a mold for a fantasy miniature that I just posted:) You can check out the process at http://www.leadandclay.blogspot.se/ maby it can help. I think I would make a block mold of some sort. I would remove the tires, fill the holes with clay and brush on the first layer of silicone to avoid bubbles and then fill it up.

[allenea]

So this is the first run. I molded the mirrors on it and I have the holes but for some reason the resin didn't go into them. I'll push some in with a toothpick on the next one and se how that comes out.

Just gotta sand the bottom and finish the tires.

I thought I sealed all the holes but as you can see my donor now has a mold on the inside.

I think it will be just fine for gaming though. Gotta get rid of a few air bubbles.

[6milPhil]

Excellent, for mirrors I'd do them seperately. or vent to the body.

[allenea]

Thanks the mirrors are proving to be an issue do I'm going to leave it be for right now.

I'm still having issues with bubbles in the resin though. I mix then stir and right before I do all this I heat the mold up for 1 min in the microwave. I pour slow and about a foot up.  Any suggestions?

[6milPhil]

Buubles on the surface of the model or at the bottom of the model?

[snitcythedog]

Thanks the mirrors are proving to be an issue do I'm going to leave it be for right now.
I'm still having issues with bubbles in the resin though. I mix then stir and right before I do all this I heat the mold up for 1 min in the microwave. I pour slow and about a foot up.  Any suggestions?

An undercut like your mirrors tends to trap air bubbles anyway.  Best suggestion that I have is to use a disposable paint brush to paint into the mirror cavity.  Then pour your resin.  This will at least coat the inside of the undercut and give the resin something of a base to work with.  Other options would be to use a vibration table or a vacuum chamber.   A vacuum chamber would be best since it will degauss the mould completely.  If you are in the states then you probably have a ready made vibration table in your house.  Simply throw an old pair of combat boots into the tumble dryer and run them on fluff (no heat).  Then place the mould on top while it is running pour and use the toothpick as normal.  It should help. 
Snitchy sends.

[allenea]

6milPhil , Bubbles are all over in random spots...not large ones and I can fill them with something before I paint

snitcythedog , Nice i'll have to try this "combat boots into the tumble dryer and run them on fluff"

Thanks guys..getting there...I'm going to have an army of suburban's by the time I'm done though  

Earle

[Sinewgrab]

Brushing the inside of the mold with a little talc always helped me when I poured a new cast - and I would also vibrate the entire mold for about 15 to 20 seconds after pouring the resin as well.