Having just finished an ED Baby, which with its tininess meant it wasn't that pleasant to build, especially when it ran but not well, I needed something I could enjoy building just for the fun of it.
So I set myself a challenge - build an engine in under a week and under 40 hours.
Well it went from blocks of round alloy for the crankcase and a piece of spring steel for the crankshaft (offcuts from auto swaybars wonderful steel but oh so hard to drill) to an engine that fired and ran in my hand on the 7th night, yes I will resist comparisons .... Took 35 hours by the way.
Today ran it in the test jig and it ran 9200 on a 9x4 wood, some 600 better than my original Owen Mate, and its still very tight so suspect it will pick up another 3-400 in time, so very happy with that. Bit of a contrast to the ED Baby !
The design simply splits the crankcase at the vertical line from the cylinder at the front and has a bolt on nose with a 19mm ball bearing at the conrod end and a plain bush the prop end. Almost the same as the Inline Twin I made.
David Owen always wanted to do something along these lines so I am calling it the Owen Mate MkII - and I think it is quite a handsome engine.
It handles beautifully, easy to start and responds well to compression, I haven't tried leaning it yet left it at 2.5 turns out.
One thing I was impressed with on the ED Baby was the use of a slitting saw to create the ports for inlet and exhaust, so used this method to make the exhausts. Having not done this except off a plan before - almost cut the top off the cylinder and the ports would cover over 300 degrees of arc compared to maybe 150 degrees in the original, so I hope the top doesn't break off in time. What happened was I kept looking to see the breakthrough but - the metal that was broken through didn't cutaway looking like it hadn't happened, thankfully I realised this at a point 2.9mm deep - 3mm and it would definitely have left it too weak. Having done one port this way made the others 2.8 deep but still its not much meat - and to make matters weaker the transfer port is in the middle of the inside - so time will tell.
As I said earlier ran it on the 8th day - well this morning and it behaved as good as I hoped.
here's a few pics and I'll try a short video.
[ame]https://www.youtube.com/watch?v=nCE0_zQuH_I&list=UUubyGt1AITy-eOwBAFBBvig[/ame]
Ed
The last photo added after posting - shows the small meat between exhaust ports ... at least the 4 caphead bolts help hold it together ( I hope) !
So I set myself a challenge - build an engine in under a week and under 40 hours.
Well it went from blocks of round alloy for the crankcase and a piece of spring steel for the crankshaft (offcuts from auto swaybars wonderful steel but oh so hard to drill) to an engine that fired and ran in my hand on the 7th night, yes I will resist comparisons .... Took 35 hours by the way.
Today ran it in the test jig and it ran 9200 on a 9x4 wood, some 600 better than my original Owen Mate, and its still very tight so suspect it will pick up another 3-400 in time, so very happy with that. Bit of a contrast to the ED Baby !
The design simply splits the crankcase at the vertical line from the cylinder at the front and has a bolt on nose with a 19mm ball bearing at the conrod end and a plain bush the prop end. Almost the same as the Inline Twin I made.
David Owen always wanted to do something along these lines so I am calling it the Owen Mate MkII - and I think it is quite a handsome engine.
It handles beautifully, easy to start and responds well to compression, I haven't tried leaning it yet left it at 2.5 turns out.
One thing I was impressed with on the ED Baby was the use of a slitting saw to create the ports for inlet and exhaust, so used this method to make the exhausts. Having not done this except off a plan before - almost cut the top off the cylinder and the ports would cover over 300 degrees of arc compared to maybe 150 degrees in the original, so I hope the top doesn't break off in time. What happened was I kept looking to see the breakthrough but - the metal that was broken through didn't cutaway looking like it hadn't happened, thankfully I realised this at a point 2.9mm deep - 3mm and it would definitely have left it too weak. Having done one port this way made the others 2.8 deep but still its not much meat - and to make matters weaker the transfer port is in the middle of the inside - so time will tell.
As I said earlier ran it on the 8th day - well this morning and it behaved as good as I hoped.
here's a few pics and I'll try a short video.
[ame]https://www.youtube.com/watch?v=nCE0_zQuH_I&list=UUubyGt1AITy-eOwBAFBBvig[/ame]
Ed
The last photo added after posting - shows the small meat between exhaust ports ... at least the 4 caphead bolts help hold it together ( I hope) !
