Battery Vehicle Society

Hi all,

Been racking my brains about this one and thought you may have some bright ideas !

I want to build a large round, curvy instrument pod to sit on my flattish dash-top to house voltmeter, ammeter, sat nav, missile launcher etc. (I dont have any room elsewhere).

Anyone got any ideas how I could build or mould one ? I thought glass-fibre but cant think of what to use as a mould. Was going to cover it in a bit of thin foam and "leatherette" !

Pre-made ones are all too small and very expensive.

Be grateful for any ideas.

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By the way, will the Society be exhibiting at this years Kent kit-car show at Detling ?

Would it be worth looking at other vehicle dashes and locating a dash that might do as a mould ??

As for Detling I would expect so, although I havent seen it in the line up yet

ChrisB

Hi, I have (long ago) made glassfibre things and the way we did moulds was usung polyureathane foam (a 2 part mix) which makes a strong rigid lump which can easilly be shaped with knife/surform etc. you then cover it in a gel coat and then put a mould release agent (usually PVA..like the wood glue) onto it and apply fibreglass cloth and resin to the required thickness. An alternative is to use wax to make a former (a bit more costly bu with skill produces excellent prototype moulds)

All of the kit (resin, cloth, PVA, PU Foam etc.) can be obtained from "Glasplies" in southport who have a very helpfull price list/catalogue and have always been helpfull in the past.

They stock huge amouts of stuff...great if you want to build your own bodyshell etc

Hope this helps

NIck

You can also pick up off cuts of Kingspan insulation from builder's skips, they waste loads of the stuff.
Layer it up and then carve to shape.

Alternatively get a cardboard box of about the right size and squirt it full of expanding foam, you can get it from B+Q, and let it rise to the top of the box. When it has cured rip off the card board and carve.

Have a look at this thread on DIY Electric Car, the guy is building almost all his car body work with foam and glass.

If you're looking at using foam, then it's worth considering the lost foam moulding method, as it's ideal for complex shapes. I've even made aircraft fuel tanks this way.

THe technique is to get some pink or blue insulation foam. The stuff you want is extruded (not expanded) polystyrene, as it's soluble in petrol and easy to carve and sand to shape.

Lightly glue some sheets together to get a thick enough slab, then carve and sand it to a pleasing shape. Cover it with woven glass cloth and epoxy resin, not polyester, as that will attack the foam. Glass cloth will give a fairly smooth external surface and will conform to compound curves well (use a satin or loose weave cloth of around 200g/m² to get good "drapability"). You don't need to worry about getting the foam out at this stage, so can make a completely closed shape if you like.

Once the resin has cured, drill a fairly large (around 1" or so) hole in a convenient place. Carefull start dribbling petrol into the hole. This will gradually melt the foam core and allow it to be poured out of the hole. It's a messy, smelly, business and I normally do a final clean up rinse with cellulose thinners, to get rid of the petrol smell and the final sticky residue.

You'll be left with a hollow shell that can be a very complex shape, with no need for moulds. If you're planning on covering it with cloth, then all it needs is a rough sand on the outside. If you want to paint it, then the glass cloth finish is pretty easy to fill and sand smooth.

I've even made battery boxes with overlapping lids using a modification of this technique; laying up one half of the box on the foam, letting it cure, adding a layer of shiny packing tape around the overlap join and then laying up the other half of the box, including the overlap over the tape. If the foam core is only lightly bonded, I can usually prise the box apart before melting the foam out of each half. The epoxy glass doesn't stick to shiny packing tape.

Another alternative is to cover the foam former with shiny packing tape before covering it with epoxy glass. Once the foam has been meted out, the tape can be removed from the inside, leaving a fairly smooth and shiny internal surface.

Jeremy