Headlamp
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This headlamp shell Is a copy of an LC 250 light unit, I copied this because it is cheap and easy to obtain replacement glass and rim. The mould was made from an old plastic LC[RD250] headlight. I have made lights from scratch, these were made to take Landrover sealed beams, which again are very cheap and no problem to get. This first headlamp shell layed up in this mould was made from
200 gm/metre twill, each layer was 2 pieces. To eliminate the frayed
edge join, I layed the carbon up on a polythene sheet and when the
epoxy had gone tacky I trimmed the frayed edges. This was a very
messy job and there were little pieces of epoxy carbon every where.
I was disappointed when I pulled it from the mould, it was very
badly pinholed. Looking at the surface of the mould it was obvious
that when it had been vacuumed small bubbles in the epoxy had expanded,
when I removed the laminate from the mould the epoxy over the expanded
air bubbles had stayed in the mould leaving a large pinhole in the
laminate, this also left a lattice of extremely thin epoxy on the
mould surface. This headlamp shell was made of 200gm plain weave carbon fibre. Each layer is 3 pieces of carbon fabric, 3 pieces were used so that it would be easy to lay the carbon in the mould. I didnt have to worry about the frayed edges with plain weave, well not as much as twill anyway. There are 4 layers of carbon, so the shell is about 1mm thick and there are another couple of layers around the mounting holes and the bolt holes for fastening the rim in. The rim fastening is by 2 bolts at 4 and 8 o'clock and a rib at 12 o'clock, so a lip was added to the shell to hold the rim. Graff SE epoxy was used, this gave a working time of about half an hour. I mixed the epoxy in a vacuum, so it didn't have any air in it. The pieces of carbon were layed up on a polythene sheet, the resin
was brushed on and squeegeed with a rubber tube roller. Removal from the mould was very difficult, I had managed to get the first one out of the mould without damaging the mould. I was fairly confident that the surface of this was going to be OK so I had made it thicker so it was to stiff to distort and release. I was forced to cut the mould in half. There are several light cuts on the surface of the laminate, but they are insignificant. The moulding got stuck because the release angles were not large enough, the first part that did release was flexible enought to compensate for this. I had problems with the first headlights I made, due to carbon being conductive. The shell had been made the correct size for the light units, when a replacement light unit was fitted the terminals touched the shell. This wasn't noticed until my brother was coming home from the pub, he couldn't understand why dip was brighter than main and the bloke following could smell burning epoxy. The shell had burned around the terminals, I reinfoced the area with several layers of Kevlar around the terminals. |
Figure 1. The plug, prior to painting, this is a plastic H/lamp shell with a few modifications, the yellowy coloured stuff is body filler. All radii were increased, all draft angles were increased, the height was increased to allow some waste and a flange was added to stick the bagging material to. |
Figure 2. Headlamp shell laminate being "bagged", click on image for higher quality image. |
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Figure 3. Headlamp shell and mould after removal of breather cloth and peel ply. The breather/peel ply is in the foreground. |
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Figure 4&5. headlamp shell after removal from the mould. click on above for larger image. |
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by
richard