Vertical Single 4-stroke IC Engine

[cfellows]

A fellow on another forum offered me an explanation of why model IC engines are difficult to make them idle nicely.  What he said made a lot of sense.  Basically, the problem is this.  To get a small engine with no load to idle slowly, you have to pretty much completely close the throttle.  This means that at the bottom of the intake stroke, there will still be a pretty strong partial vacuum in the cylinder.  This effectively lowers the compression ratio since you are starting the compression stroke at a negative pressure.  The solution it seems, and I have pretty much already verified this, is to slow the engine with a load so you can keep the throttle opened far enough to allow near normal pressure in the cylinder at the bottom of the intake stroke.

So, I spent the day today working on a small generator.  I started with a small DC motor and a 2.5" x 2.5" x 1.5" block of aluminum.



I bored the center hole in my lathe, then whittled away the outside on my CNC milling machine using a simple g-code program I wrote myself.  I milled the profile half way through one end then flipped the piece over and milled the other end.  The rounded profile on the edges was done with my router and I smoothed it up some with 400 grit sandpaper. 



And here's an idea of what it will look like on the engine.



Tomorrow I'll get it installed on the engine base.

Chuck

[NickG]

Good idea Chuck, will be nice to see it driving something.

[Roger B]

That's a neat housing   

I did a similar thing for my horizontal engine. My next challenge is to make voltage regulator to charge the battery for the ignition system and make it self supporting.

[Brian Rupnow]

Chuck--I never actually realized before this week, how much simpler an overhead valve engine is to fabricate when compared to a side valve. I would have vigorously argued with that because of the added complexity of pushrods, rocker arms, etcetera, until I started trying to come up with a side valve engine that lends itself to easy fabrication.---Brian

[cfellows]

Chuck--I never actually realized before this week, how much simpler an overhead valve engine is to fabricate when compared to a side valve. I would have vigorously argued with that because of the added complexity of pushrods, rocker arms, etcetera, until I started trying to come up with a side valve engine that lends itself to easy fabrication.---Brian

I'm sort of in the same camp.  I always figured flathead engines were less complex, but it turns out the devil is in the details...

Chuck

[Roger B]

OHV allows you to separate most of the difficult bits into separate jobs. My neighbour keeps asking me why I didn't start with a 2 stroke engine as it is simpler, but I would rather make a simple cylinder and liner, then a cylinder head, then some valve gear, then a camshaft and gears. Each bit is on it's own and can be remade as desired. Once you have made a 2 stroke port too big you start again with a new liner 

[cfellows]

OHV allows you to separate most of the difficult bits into separate jobs. My neighbour keeps asking me why I didn't start with a 2 stroke engine as it is simpler, but I would rather make a simple cylinder and liner, then a cylinder head, then some valve gear, then a camshaft and gears. Each bit is on it's own and can be remade as desired. Once you have made a 2 stroke port too big you start again with a new liner 

Yeah, I have to agree.  I tend to do things in stages as well.  I like taking small bites at a time.

Chuck