KIWI Mk2
I/C ENGINE BUILD
Part 12 By Vince Cutajar
KIWI Mk2
I/C ENGINE BUILD
Part 12 By Vince Cutajar
Next it’s the connecting rod. The plan was the best I could think of. There are no flat surfaces and nothing is parallel on this casting so I needed a flat surface to use as a reference.
Started out by roughly marking out the centre line of the beam of the con rod. Clamped the con rod on the mill table and shimmed the beam with feeler gauges to bring the centre line as much as possible to be parallel with the mill table (Photo 1 & 2).
I then slowly milled the big end and the small end to have a flat surface as a reference (the big end was about 1mm higher then the small end) (Photo 3).
With the con rod having two flat and parallel surfaces, I put it on the granite plate and marked out a centre line around the con rod. From this centre line I marked the big end and the small end for 0.5" width. Also marked the con rod beam for the correct width (Photo 4).
Used an angle plate on the granite plate. With a toolmaker’s clamp, held the con rod lightly to the angle plate and nudged it vertical using an engineer's square (photo 1). I then used a clamp on the small end (photo 2). Checked again it was still vertical and used another clamp to the big end (photo 3).
I then transferred the setup to the mill table and squared it up. I had previously marked the position of the holes on the con rod. Using the needle point of the wiggler I put the spindle over both holes and wrote down the X and Y readings for each hole. Using a 6mm slot drill I milled both flats where the bolts will rest. Then using the previously recorded coordinates I drilled and tapped for 3mm (photo 4).
Today decided that the setup was good enough but just to make sure that this does not move I applied a toolmakers clamp on each side of the parallels.
I did the cut with a 1.5mm slitting saw at 300 rpm and a depth of cut of 0.2mm. I was not taking any chances. Eventually (after 64 passes) I finished the cut.
Drilled the oil hole in the small end with a centre drill. I was going to clean up the the I-section of the beam but then I remembered that in commercial cast conrods that part is left rough so I left it as is (nice excuse). Just gave it a lick with a Dremel wire brush.
Trial fit in the crankshaft and it turns smoothly. Removed some material from the front crankcase (where the con rod had some interference) with a Dremel and problem fixed.