Hello all,
I'll try to be as brief as I can. I am currently working on a pedal car project for my kid. I am really tired of seeing on the stores pedal cars that pretend to look like real cars but have no similarities to the pretended thing, so I have decided to build one that looks like the real ones. There will obviously be some differences due to size constraints (no roof, small windshield, etc...).
The chosen car model is a 1970 Ford Mustang fastback (1st image). I am building on my home made CNC milling machine the different body parts out of Expanded Polystyrene from which to make the mold negatives. (The second and third images shows a crappy picture of the left door, left front fender, left rear fender and hood).
I am now starting to think about the molds. My original idea was to make them out of fiber glass, but I am now not so sure and I am more inclined towards the silicon/rubber molds. the main reason is their flexibility so that I need not worry so much about the demolding process, as they can be "flexed out" off corners and bents. I've benn also suggested the posibility of making the molds out of plaster. But I beleive they are too rigid, fragile, heavy and can be damaged easily.
The final dimensions of the body will be 1300 mm (~51 inches) in length, 720 mm (~28 inches) wide and about 310 mm (~12 inches) height. The bigger part is the hood, which is about a third in length of the car: 430 mm (~17 inches) and 500 mm (~19 inches) wide.
I've been reading a little bit about making silicon molds, so the rough general process I am aware of.
Now the questions:
1. What kind of material do you think is the best for making the molds? fiber glass? silicon/rubber? other?
2. Which is cheapest?
3. How many parts can be made (roughly) out of each kind of mold?
4. Expanded Polysytirene is not perfectly smooth, it always has some tiny holes so, before making the mold, I need first to apply some sort of filler and then smooth it out with very fine sand paper. What filler do you recomend?
5. Once the molds are made, I was planning to make the final parts out fiber glass. Is there any restrictions to the material of the molds? I mean, can parts be made of fiber glass using say, silicon molds?
6. Do you recomend a different material for the final parts rather than fiber glass?
The reason for making molds is that there are already several friends that are interested on making a copy of my project for their kids IF mine turns out good, or reasonable good. And I am not planning to mill each time the body parts.
Any help, suggestions, directions will be apreciated. Thank you very much,
Di4l