The Steamboating Forum

Hi,

... Spotting the bearing housing flange against the crankcase:

how do you fix the housing while doing the job?

----
Dietrich

p.s. It is possible to show three picture in one post.

Hi Dieter,

Two small spots of superglue on the flange. After drilling I knocked them apart. Superglue has poor shock resistance if the glue area is small.

Here is the bearing housing and crankcase together:

Cylinder ported and lapped:



Piston cast, turned, bored, cutting ring groove:

I remember porting the exhaust passages on two stroke Go-Kart engines many years ago. Engines generally had circular exhaust ports, and we would try to make them into square ports for better engine breathing. A common problem if the ports were re-shaped to actually approach exhaust ports with horizontal surfaces, the ports would hang up on the piston rings, and destroy the engine. Do I see those horizontal port openings on your uniflow ports?

Perhaps with some file work the port openings could be reshaped so the piston ring will not have to cross over a horizontal opening, but rather the ring would be forced to stay compressed while traversing the ring traverse of the port opening.

My uniflow engine has 18 ports, all circular, and the rings are not pinned, so the ring gaps may traverse a port opening. To guard against a ring gap hanging uo on a port the ring gap edges are slightly ground so as to not present a sharp edge to the port opening, Some engines have pinned rings, so the ring gap will never cross over a port opening, another method of protection against ring "hang-ups"

Thanks Fred, very good points, and I have been giving a lot of thought to that. The ring will definitely be pinned with a stainless steel pin to keep the gap away from the ports. I've thought about easing edges, but not totally convinced that's going to be a positive.

The engine follows very closely the design of two successful similar size flash steam model racing boat engines. No guarantees this won't self destruct at first try since I can't know what special fitting nuances they might have taken when building, but the ports rings and piston are the same size, number shape and placement. I see this as an experimental engine to find out what it can do. Might be just one rotation, but at least I'll know the reason, and work on it for the next one.

Side note...I've been told that rings don't need pins if horizontal ports are under 25 degrees in arc, and okay with pins to 60 degrees. Mine are 43 degrees and will be pinned.

I do truly appreciate your commenting. I was starting to think this wasn't of much interest here.

Cylinder lapping

Lap made:




Compound:




Lapping:




Finish was cross hatched, but too fine to see. Cylinder finished out to 0.999" :

Piston lapping:

Lap made:




Lapping the piston:




Measuring, the piston was lapped to 0.996" for a 3 thou clearance.




Piston cleaned up:

Elver1 stated:
"I was starting to think this wasn't of much interest here."

I can state that I remain very interested in your design and fabrication, and I read all of your posts, as do others here.
I just don't post responses because I don't have anything useful to add! I will post, if and when...
Pease keep designing, building, and posting.
Thank you.
RussN

Your rings may well be OK, for a small bore the rings are relatively more rigid than skinny rings on a much larger bore. Not something that is covered in my textbooks. I would however recommend a very slight edge treatment where the lapped bore surface mates at 90 degrees with the exhaust port passage. Just enough emery dressing to make that edge not a sharp edge.

Thank you Fred, and RNoe. Just catching up here.

Parting a ring off after sizing the blank, and using a form tool to form the dyke ring "L" shape:




Splitting the ring using a Morse taper dead center as a wedge: