No flying again today...

...but you wait, tomorrow will be glorious when I'm back at work - 'hit happens, aaargh!

So, into the machine shop for some more exciting swarf making. This engine I'm building is my own design, and I'm drawing it up on AutoCad before making the parts. Occasionally I have to go back to the drawing board to make alterations to the drawings because in practice, sometimes things don't quite turn out as you'd expect. Its called research and development or R & D. The engine I've named, the Ketro KT120fst. is 1.2 cu.in., 20cc swept volume and about 22cc full capacity. Its a horizontally opposed twin cylinder four stroke engine also known as a "Boxer".

Centre drilling position for the crank pin.


Having drilled the hole its now ready for reamering.



Finished, and its a good fit.

All the bearings arrived this week, so now I'll be able to finish the diameters on the crankshaft parts, as I will use each bearing as a gauge to test the fit.

All the parts together, nearly finished. Just the counter balance to mill and the holes for the clamping screws.

And yet more engineering

It looks like this is going to be the norm for at least the rest of this month and probably well into December as the weather situation is leaving a lot to be desired. Even the long range forecast doesn't look promising. Anyway it gives me a chance to get on with the Winter project. I'm hoping to have this engine fitted, working and flying early next year. No pix today, (sorry) but I've started on the rear part of the crankshaft. After I'd nearly finished it, it didn't look right so I had to do some cross referencing with the other drawings, and indeed I found an error. Having now corrected the error I can proceed with the part. Luckily nothing was spoiled. The other thing is I've ordered all the bearings for the engine. Six in all, but one size was not available in britain (would you believe it?) so I had to get it from Hong Kong of all places. Then I had to buy ten and I only needed three. Hey ho!
Soon I'll order the cross helical gears for the gearbox. These come in mild steel and will need to be case hardened. The supplier could do that for me but the extra cost makes it more than prohibitive, so I'll do that myself. It was successful on the KT54fs I made earlier, so it should be OK for the KT120fst too.
More on Sunday 30th all being well.

Very bad weather all week-end - NO FLYING...AGAIN!

So more engineering. I've made a start on the crank shaft front part. All the diameters are turned and the M6.0 hole has been tapped. Its now ready for parting off. I'll do that with a hacksaw, and although this sounds a bit crude its my preference in this case as the part protrudes out of the chuck by a long way. Parting in the conventional way would be a bit risky.

Notice the DTI on the cross slide to assist with accuracy.

Turning the 10.0mm dia. Revolving centre for support and helps prevent chatter.

Ready for parting. Note the M6.0 thread has been cut.

Oh! yes, and I've cut the flats on the central web as seen in the log below.

More engineering today

Made the central crank web this afternoon, turned up a piece of mild steel to 29.5mm Ø, drilled a 6.0mm Ø tooling hole in the centre, and parted it off to 3.0mm thickness. Placed it in a 3 jaw chuck mounted vertically on the milling machine, and clocked the tooling hole to centre it on the machine. Drilled and reamered 2 holes through 6.0mm Ø in 'Y' +10.0mm position and 'Y'- 10.0mm position.

Then I cut off two pieces of 6.0mm Ø silver steel to 17mm length, and silver soldered them into the central web. I've not cut the 3.1mm wide flats yet, that'll be done the next time I work on it. Check out the pictures...

No flying today, poor weather conditions

The wind was blowing a hooley today, so I spent the day in the machine shop. Finished the finning on the cylinder heads, and now I'm thinking about the crank shaft design change. I have to enable the use of one piece conrods due to lack of clearance on the lower parts of the cylinders and the pistons. This will necessitate the design change from a one piece shaft to a three piece.