How do you do it?

[raildogg]

When one would like to scratch build a master for casting an engine block and heads and the rest, how do you do it? Where do you get the dimensions to accurately make the scale masters from ? Do you just wing it, or take the measurements from another model engine?. Just curious. Also when a master for a tire is made such as, say a MT fatty, how accurate are the treads and side wall profiles, and how were they derived? Most of those dimensions are proprietary as far as I can tell, I've searched often for that data and come up empty. The answer may be in front of me but I can't see it. It's whats stopping me from mastering my own tire molds. Any insight will be appreciated.

[Ace-Garageguy]

Any master for any model that's worth a damm will have its dimensions taken directly from a 1:1 counterpart. You just find a real one of whatever you're going to model and measure it carefully, then divide by the scale you're working in. Make 3-view drawings as rough or as detailed as you think you will need.Taking the measurements for say, a Dodge Hemi 6.1 engine will give you dimensions for a Dodge Hemi 6.1, nothing else, so if you want to cast Dodge Hemi 6.1 engines, use a kit engine as the master. If you're not selling them, no one will care. But "winging it" will only produce poor, not-to-scale models, and though some of the manufacturers seem to take that approach some days, it's not the way to go.

With some understanding of scale and a little math, you can get reasonably accurate dimensions for tires from images on the internet. I say reasonably because very few models are dead-on accurate. In 1/25 scale, if your dimensions are within 1/4 to 1/2 scale inch, in many cases things will look close enough.