OK, some more progress today.... First job was to work out the clearances for the conrods. So, using a wax offcut, I roughly milled out a segment - with many trial fits to the engine. Eventually, the hole was big enough:
This was then measured, and a second piece marked out & cut with a bandsaw, just to verify that my measurements were, in fact, sound:
That white tape is holding the wax together; it broke at a boundary between two pours... So far, the main block is behaving itself very well, which is a relief.
So.. clearances sorted out, it was time to get milling. The angle plate (which is needed later) is mounted & squared up first, then the block is mounted & squared on the angle plate. Thus:
In the pic, I'm about to locate my reference point (the top right-hand corner, as you look at the picture), from which all subsequent measurements and co-ordinates are taken. So, about an hour later (I was being cautious....):
They're milled 25mm deep, 75mm wide as required. The bits in between each pocket are where the bearing journals live, and will be left there for strength. So now it's time to mill out the first angled bit. Thus, it's time to brush off my old Trig knowledge, and get head scratching
Most of you will probably be immediately familiar with all of that. The only bit I'll explain (just in case, if by the remotest chance, my old school Maths teacher ever sees this: Thanks Mr Parry!) is SOHCAHTOA (pronounced "soccah toe ah"). It means, simply: Sine=Opposite over Hypotenuse, Cosine = Adjacent over Hypotenuse, Tangent = Opposite over Adjacent; I've always found it to be a dead handy aide memoire when messing around with triangles.
So, on with the show. 33.7 degrees the doctor called for, so we set up the angle plate:
The small spanner there is used to loosen & tighten the angle plate bolts. Did I mention I'm doing this in miniature? That spanner is just 4" long...
So, after a little while:
The actual cutting operation was done largely by look & feel; when I thought the remaining lip looked "about right", I stopped cutting. The coordinates have been noted, so when I come to do the real aluminium sump, I should just be able to crack right on into it, without worrying about where to start & stop cuts.
Last job for today was to flip the piece over and cut the other angle. About 40 minutes of the next hour were spent setting up:
- Reset angle plate to flat
- Turn piece around
- Dial in
- Find reference point & reset DRO
- Set angle
After that, the cut went on nice & easy. Because I used the same reference point, all my X-axis numbers were the same (with the sign reversed; so positive instead of negative); the Y-axis was also mirrored, but somewhat differently... In fact, I ended up with slightly different offsets; but I think I got the first ones in slightly the wrong place, as there's more of a lip on the first cuts compared to the second.
So, as it stands now:
Next job: Figure out where the channels for each main oil drain (the holes cut yesterday) are going to go, and how deep they need to go to pick up the main oil channels. And, speaking of which, the time draws ever closer when I'm going to have to break out that big drill.......
Watch this space
