Basher - A Super Simple Uniflow

[Jasonb]

I lik ethe sound of the 15psi one, the uniflows do sound good.

[PaulR]

I lik ethe sound of the 15psi one, the uniflows do sound good.

Hard to tell from the video but it's ear-splittingly loud!

I'm cooking up an idea for the next one while finishing off this one.

[Michael S.]

I think the sound of the exhaust is great! Many years ago, we deliberately drilled holes in our motorcycle exhausts to get a "fast" sound.

[Charles Lamont]

That seems to be working well. If you wanted to experiment a bit more with it, I would try reducing the valve lift even more. I will bet you £1 that it will run well with as little as 0.4mm lift. I think that would give you a more flexible (and probably quieter) runner.

[PaulR]

That seems to be working well. If you wanted to experiment a bit more with it, I would try reducing the valve lift even more. I will bet you £1 that it will run well with as little as 0.4mm lift. I think that would give you a more flexible (and probably quieter) runner.

Wager accepted!  I haven't made any extra exhaust ports yet, do you think it would benefit from another small hole between each of the existing ones (almost making a slot)?

[PaulR]

Shaved a bit more of the rod, it's now around 1mm and I would say it's made a very small improvement so I might try a bit more.

One thing I did try: putting the engine in different orientations. With the valve at the bottom it oscillates and seems disinclined to run, horizontally it runs as shown, with the valve at the top it runs better (well, about the same but with less pressure). All of which seem to match what one would expect!

[PaulR]

Finished this by rounding off the end of the con rod, making a little oil hole for the shaft and a simple wooden base. It seems to run quite nicely but definitely doesn't want to run slowly (or quietly!).

<a href="https://www.youtube.com/watch?v=CALFSwZKzbU" target="_blank">http://www.youtube.com/watch?v=CALFSwZKzbU</a>

[Michael S.]

  nice

[Sanjay F]

Another nice engine, well done 

[crueby]

Runs very nicely! 

You mention it does not like to run slowly, I wonder if a heavier/larger diameter flywheel would have an effect on that? Enough mass to let it carry around the return stroke, and also not accelerate as quickly on the power stroke? Could be some interesting experiments to see.
 

[PaulR]

Runs very nicely! 

You mention it does not like to run slowly, I wonder if a heavier/larger diameter flywheel would have an effect on that? Enough mass to let it carry around the return stroke, and also not accelerate as quickly on the power stroke? Could be some interesting experiments to see.
 

Yes I did think about that to begin with but I went with materials on hand and there's now a cutout in the frame/base which only just clears the existing diameter. I could stick something on the back surface of the flywheel near the rim I guess...

[astroud]

Hello Paul
I came across this comment on piston operated air valves and you being an experimenter thought you may like to give it a go.
Andrew

[PaulR]

Hello Paul
I came across this comment on piston operated air valves and you being an experimenter thought you may like to give it a go.
Andrew

Thanks, that's an interesting idea, I've been trying to come up with something along the same lines (but never considered springs!).

I foresee some issues with this idea though...

How could the inlet spring be held in place? Maybe a 'washer' soldered at the top to stop it falling into the cylinder but it might not seat very well. Ditto how to stop the exhaust passage spring flying out. Maybe a screw-in tube? I think the main problem is it would need lots of empirical testing to get the right spring and the right length and there's no way to adjust things other than shortening the springs.