Member postings for David K

Then the outside is turned to shape

After turning the ends square I started to turn the inside to the dimensions shown
in the plans. These consist of shoulders and pockets for the bearings, ring gear and clearances
for the crankshaft.

To start the crankcase I cut a piece of alloy bar and mounted in the lathe.

I then transferred it to the mill and drilled the holes for mounting .

The crankcase has a timing gear fitted inside, this is one of the few items I need
to buy for the engine. It is an internal ring gear , 60 tooth , 48dp which I managed
to buy from HPC gears . The gear will need reducing in width and diameter so I
turned a boss on the end of some alloy bar. The gear was then tapped onto the boss and this was enough to hold it
in the lathe.

That's it , all cylinders done , crankcase next

The cylinder liners are made from seamless 4130 aircraft grade tubing. The tube will only
need a light hone ready for use.
I made an expandable reamer to hold the tubing while I cut the short lengths so I didn't
crush it. I turned a small chamfer on the inside edge to make it easier to fit the pistons.
These will be a push fit held in with Loctite

Finishing off the cylinders, I made a jig to cross drill the rocker posts and then
rounded the tops with a file

You can see from this picture were the drill breaks into the valve guide.

Next job is to drill the inlet / exhaust ports.
These are drilled from the centre at a slight angle to the valve guides.
The cylinders are nearly finished so each operation becomes more nervy ,
I would be gutted to mess up now.

The guides are screwed in with green permanent Loctite

the holes drilled in the cylinder head actually
came out in the correct place in the combustion chamber. I am happy to say the jig did its job.

cutting the seat

While I was making the guide I made a small collet to slide over my 90 degree
cutter to enable me to keep it square while I cut the seat for the guide.

finished guides

I then placed a bit of alloy in the lathe , tapped it m10 and screwed the guide into this
so I can reduce the top halve to form the guide. Two small holes are drilled either side
of the valve guide and a tool is made to insert into these which will allow me to screw the
guides in.

continued from above
This taper will be the seat for the guide when screwed into the cylinder.
A 3mm hole is then drilled and reamed through the centre, the front half is opened
out to 6.5 mm then a 45 degree valve seat is formed as in the pic below.

With the cylinders drilled and tapped I need to make the valve seats/guides.
These are made n one piece out of 660 phosphor bronze.
A piece of bronze is turned down and threaded m10 fine to match the Cylinder, then
the first 2mm is turned down to 8mm and the step is turned a 45 degree taper.

Here you can see the cylinders just needing the second slot finishing on the left
hand rocker posts

Remember the set up on the mill was turned 49 degrees , that is because the rocker posts are
fitted at a 49 degree angle from the valves.
So while centred over the valve guide I offset the table 0.344'' and drill / tap a m3 thread, a post is
screwed in with permanent Loctite and then a slot is milled to accept a rocker.