The internal surface finish is quite ok, but as you say I might be found out on the consistency of the internal diameter, I will find that out when I make the pistons. Following your experience I make my models without piston rings but if I have a id issue then I might use a larger clearance and O rings. Failing that then I would make new cylinders out of brass or aluminum as I don’t fancy my chances of skimming the copper tube.

Andrew

Some progress to show, I have made ties between the head and deck, supports and a centre bearing.

The crankshaft will be run on ball bearings and I next need to make a couple of bearing housings which will be fixed to each support. These will allow some alignment adjustment with the centre bearing. In truth I don’t think a centre bearing is needed but I think it would look a bit odd without. I have a separate shell for the bearing which is yet to be split and I hope it will also position the crankshaft axially.

The head is a bit blocky at the moment, may try some shaping later on.

Andrew

Thanks for the comment.

Bearing housings are made, next will be the connecting rods and pistons, you will notice I am leaving the challenging rotary valve to last !

There might be a brief hiatus in progress. What started off as having new smart meters installed has resulted in our gas supply being cut off, condemned as the service pressure is too low at c. 15mbar. The theory is the new plastic liner fitted 12 months ago in the pipe from the street to the meter has kinked or collapsed. We might get away with a new section of pipe, worst case is all new piping and a new meter position which means big disruption in my workshop where the meter is.

Andrew

I managed to solve my clearance issue by making a recess for the big end cap bolts and using socket head screws. The centre bearing is assembled and this sets the crank axial location and it turns over without any binding which is pleasing. I have fitted a flywheel and made a wooden base.

Next will be the rotary valve, I have in mind a valve turning at half engine speed but want to mock it up before cutting any metal. Still contemplating sculpturing the cylinder head, possibly simple channels to pick out 4 raised squares on each side.

Andrew

I haven’t inspected the pistons since it started running but performance wise I have not noticed anything. AI tells me it is a very poor material pairing for running together but hopefully ok for light model running.

You can just see in the video on the top of the head there are 5 blanking screws for oiling points positioned between the valve cutaways and oil  reaches the cylinders from the valve chamber.

I have attached a picture of the valve, very simple but lots of agonizing before I made the cuts  to ensure the correct orientation for the ‘firing’ order.

Andrew