mills 1.3cc diesel mikes-models

2nd January 2008 - session 1 – Making the crankcase

Well today I started the build by getting the main body machined to size.
Firstly I converted the measurements from fractions to decimals. I then
squared up my block of aluminium on the milling machine. I found that the
width was about 2 thousands undersize. Whilst this doesn't seem much I
was disappointed because I wanted to get it a couple of thou oversize to
allow for cleaning up. I wasn't worried though because I believe it is none
critical.

I then set about laying out the marks as per the diagram on the plan. I used
layout blue at first but decided to go back to the thick black permanent
marker. Since my 'Christmas' present of a digital height gauge (see photo 1
after it got here!) had not arrived I used my digital callipers' I set out the
lines. This ended my first disappointment with a scruffy looking, but
accurately marked block.

The next stage was to drill two 1/8th" (0.125") holes. However this brought
out my first problem. The way I read the article, the holes were to form the
slight curvature on the top sides of the lugs. When looking at the photo
though, the holes were on the same side. After looking at the plans and all
the photo's of the designer's build, I decided that the picture of the blank
was wrong. I would go with the written description which was backed up
by other photo's.

Now my floor standing pillar drill has yet to be 'adjusted' to run 'straight'
vertical holes. Since these two holes would go all the way through I decided
that I would use the milling machine and I would drill just over half way
through from both sides to ensure an as accurate result as possible. And
that's what I should have done! But in the real world it didn't happen. I had
to break off at this point and after a couple of hours when I went back I
picked up the blank and off to the pillar drill! Yes, you guessed it, I drilled
the holes and the run out on one meant the piece is ruined!

When looking at the exit for the holes though on the reverse side there
seems to be another issue. The holes as I marked them out came inside the
cavity at the back. So I must have gone wrong with my marking! What has
gone wrong I don't know yet as at this point I felt it was better to search for
'another' suitable piece of aluminium for a new crankcase, then leave it for
another day.

I have now decided that I will run the scrap first crankcase on and when I
am happy start on the new squared up blank (see photo 1). That way I will
see what other issues I will face and with the experience gained, hopefully
produce a better second attempt!.

Time spent so far (including roughing out the second blank) are 2 hours.