Monthly Archives: November 2014

wrongness 6 – angle grinder accident

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wrongness 6 – angle grinder dies

So, after 20 years of faithful service, my bosch angle-grinder only goes and dies. Smoke came out of it and that was the last turn it made. I replaced it with a cheap hitachi and kept on going. There’s a lot of steel seam-welded in this car and it can be a real pain to get it all grinded out. Near the end of the day, I was starting to feel like I’d had enough, but was wanting to get one corner finished.

Therein lies the rub :). I was wearing a jumper and managed to get the left sleeve of my jumper caught in the grinder (I think I was holding it in my right). Before I knew it, it had whipped the grinder out of my hand, and as it started to spin on the sleeve, it dragged the grinding disk up my arm. Then it stalled.

I don’t like thinking about what it would be like if I had a slitting disk in there rather than a grinding disk.

Here’s the obligatory photo though:

IMG_0892

Chassis cut out now, ready for part manufacture

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IMG_0894So, now I’ve managed to get the entire squabs and transmission tunnel cut out, ready to take the entire floorpan CF part.

It looks somewhat bare and scary, no? Overall, I’ve cut 22kg of steel and ally out of this arrangement, and some of it was especially difficult to get out. I’ve also cut out the harness mound points out as well – I’m going to reposition these as hard points in the composites when I know where I want the seat.

I’m going to go for post-fit hardpoints, in a sandwich arrangement. What I will do is drill the hole through the tub for the eyebolt hole, then use an allen key in a drill inserted in the hole to worry out the closed-cell foam core, and then I’ll fill this hole with an epoxy/glass bead filler. This will create a hard point to bold through.

In order to be belt and braces, I will also then put a bonded in stainless plate on the front, and the harness mounting plate, bonded on the back. This should give great anchorage. I will make a test panel as well to test this.

Some setbacks of late

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I’ve not gone away or given up on the blog, but have had a bunch of setbacks recently with this composites journey, so I thought I’d get them out here and move on.

Wrongness 1
Firstly, my compressor died (all-in-one motor and pump unit seized). The replacement part isn’t due until tomorrow.

Wrongness 2
The moulds I made for the fuel tank are wrong. I did two things that went wrong:

  • I made a part of the mould with a 180 degree return. No worries, I thought – I’ll just fill the back of the return with expanding foam, then I’ll have a nice sensible surface to envelope-bag against. Nothing like it. Two things broke – firstly putting it under vac meant the trapped gas in the foam needed somewhere to go, so I struggled to get a full vac
  • The return was in essence being crushed by atmospheric pressure, and the mould flange cracked

    • Wrongness 3
    I can’t vac-bag a mould with a 180 degree return – every time you turn it over, the cloth moves about. I need to rethink the way I’ve moulded this part.

    Wrongness 4
    My plan to infuse the transmission tunnel as three separate thin cosmetic parts, and then put the moulds back together and do the remainder of the infusions failed. I’m using a new release agent, and it’s excellent but there way no way I could get the backing materials off the mould with out popping the part out. Then I noticed that I’d got a lot of voids on a sharp return which would have meant a lot of chipping out and filling.

    Wrongness 5
    The tunnel top mould that I had to polish didn’t fare terribly well. The edges on the tunnel top that turn down into the tunnel sides (or up rather, on the mould) chipped a bit under the polishing disk.

    So, get well programme is:

    1. fix the compressor
    2. scrap the tank moulds and make new ones
    3. scrap the transmission tunnel moulds
    4. cut out the seat squabs and footwells, and make a single composite tub