How hard would it be to cast this ?

[Greg Myers]

or for that matter any one rack of sprue , i.e. parts pack kit?

Edited May 16, 2014 by Greg Myers

[Ace-Garageguy]

From my experience, I'd say it would be pretty straightforward. Many trees are designed with only 2 mold parts, and so have a single parting line that goes all the way around everything, at the same level.

A silicone mold could be made, up to the parting line for one half, and above the parting line for the other half.

A potential problem is the property that most liquids (including mold materials) have of forming a meniscus where they're in contact with a solid. This would tend to make for a very thin mold-edge at the parting line, easily torn, and could contribute to producing a part with significant parting-line flash.

Edited May 16, 2014 by Ace-Garageguy

[Kit Basher]

I have very limited casting experience, so I could easily be wrong, but I don't think it would work well. I see several potential air pockets, and I wonder how well the resin would flow thru the small spaces where the parts attach to the sprue. I think the difference comes from the pressure of injection molding vs. just gravity for pouring resin. Actually, I hope I am wrong, it would be cool if it would work!

[Mark]

The Aurora engine has separate pistons, but I'd take the Revell engine over the Aurora every day, and twice on Sunday.

[Ace-Garageguy]

... I see several potential air pockets, and I wonder how well the resin would flow thru the small spaces where the parts attach to the sprue. I think the difference comes from the pressure of injection molding vs. just gravity for pouring resin...

Excellent point, but I think if the mold was vented on the non-visible side of the parts, you could probably get a good result. It would take some experimenting, and maybe a minor pressure differential between the resin-in side and the vent side. RTM (resin transfer molding) is a common technique in industrial applications to get good mold filling with liquid resins at low pressures.

Here's more on the process, which could be adapted to small-volume copies of traditionally injection molded parts trees. http://www.rtmcomposites.com/tooling/resin-transfer-molding-rtm

Edited May 17, 2014 by Ace-Garageguy

[Kit Basher]

Thanks for that link, Bill, that is really interesting. I see they are using rigid molds, rather than the silicone held together with rubber bands that I use. Plus a resin injector. On the other hand, for a low-tech guy like me, I wonder if silicone inside a rigid box, and a syringe, would work. Hmmmm.....

[Greg Myers]

The Aurora engine has separate pistons, but I'd take the Revell engine over the Aurora every day, and twice on Sunday.

Why ?

[Mark]

It's way more accurate. Besides the Revell parts pack, their Thunderbolt kit's 427, and several AMT engines, are better than the Aurora piece. The Aurora pistons have "connecting rods" that are just round stalks sticking out from the bottom. The cylinder bores look way small. Parts like the water pump, oil filter, and starter look like whoever sculpted them never looked at a Ford engine, or even a good picture of one. The rocker arm detail just attaches to the upper part of the cylinder heads, not surrounded by any valve cover mounting surface. The valve covers are way too wide. And it isn't even a 427; I can't recall seeing a 427 with a three-twos setup. Yes, the parts should fit, but who ran one? The Revell engine, with larger carburetors and some tweaks to accept the piston/connecting rod parts from the Revell display parts pack, would be a way better engine. Aurora didn't do any other engine packs; that should say something.