Horizontal Air Cooled Engine

[brian Rupnow]

This video, made 17-Feb 2022 shows my most recently designed and built single cylinder horizontal engine running with a home made sparkplug. I had issues with the cylinder head, mainly because I messed up the 1/4"-32 threads for a standard sparkplug, so had to redrill and tap to a 5/16" fine thread. I had Steve Huck make me a "special" sparkplug with a 5/16" fine thread, but could never get it to work consistently. Then I made a sparkplug, but my design was a bit fishy, with a 0.060" spark gap. It would spark to get the engine running, but as soon as it warmed up, the spark would jump across the outside of the sparkplug to ground and the engine would stall. Finally, a redesign of the sparkplug with an 0.025" spark gap worked successfully, and the fact that the sparkplug is 3/8" longer than the first home made sparkplug keeps it from arcing to ground on the outside of the sparkplug. I am happy, the engine runs fine, and now I can put this project to bed. If you want to buy a complete set of plans to build this engine, contact me at [email protected]---Brian https://www.youtube.com/watch?v=gTnwDFAI-MU

[Richard P Wilson]

Traditionally, horizontal engines had a drip feed oiler feeding the cylinder through a hole in the top of the cylinder liner, and then the piston had a hole in the top to (hopefully) let the occasional drop of oil fall onto the little end bearing. Crude, yes, but it seemed to work for tens of thousands of open crank engines.

[PStechPaul]

At what point do you think the valve timing slipped?

It might be an interesting and worthwhile challenge to design and build an engine with some sort of lubrication system.

[aostling]

. . . That seems to keep the cylinder oiled enough for short runs.

For short runs you might not need the fan. As an experiment you could disconnect it, and keep a finger on the cylinder fins until it seems too hot.

[brian Rupnow]

In order to oil the top end of the con rod, oil gets squirted into the cylinder from the crankshaft side. That seems to keep the cylinder oiled enough for short runs. if I was going to run it for an 8 hour shift, then you're right--I would mix some oil with the gas like a two stroke requires.

[Sparky_NY]

Today I'm going to call this engine "finished". It is doing everything I set out to accomplish, and is running with cast iron rings. There is a bit of a write up with the video. Thank you all for watching the build and for the helpful hints and suggestions. ---Brian
https://www.youtube.com/watch?v=2j1gQ2O3dDs

I read the video description. As far as I can tell, there is no lubrication for the cylinder walls ! All engines need this. I would suggest a bit of oil mixed in with the fuel. You don't want to score up the cylinder walls !

(Video description says its running on Coleman fuel with NO oil added. Only the conrod gets oiled manually)

[brian Rupnow]

Today I'm going to call this engine "finished". It is doing everything I set out to accomplish, and is running with cast iron rings. There is a bit of a write up with the video. Thank you all for watching the build and for the helpful hints and suggestions. ---Brian

https://www.youtube.com/watch?v=2j1gQ2O3dDs

[olf20]

It's the little things that usually bit you! BTDT
Great job!
olf20 / Bob

[Sparky_NY]

Glad you got everything sorted out.

[Ringo]

That is Great
Good job

[Cuttings]

Sounds and looks good.

[brian Rupnow]

After more trials and tribulations than you want to hear about, this is my 7/8" horizontal engine running with cast iron rings. This was much more of a struggle than I anticipated, but the fault was mostly that the grub screws holding the bottom timing gear had slipped enough that the engine was out of "correct valve timing". To me, this is wonderful. This is the first 7/8" bore engine that I have installed cast iron rings in. In this video my engine is running on Coleman fuel.---Brian

https://www.youtube.com/watch?v=WifDJa8tBZ4

[brian Rupnow]

Nothing really new going on. There will be an update to this thread, but I'm not sure when. I have something else going on right now and will get back to this thread later.---Brian

[Sparky_NY]

Any updates? Its been 4 days since the last one. This is usually not a good sign.

[aostling]

I am disappointed that the plan to lap a snug diametral clearance of 0.0002" did not materialize. I was hoping to learn if thermal expansion of the piston relative to the thermal expansion of the cylinder would be catastrophic. I visualize the engine starting up easily, then slowing down and seizing solid after a minute or so when the cold engine heated up.

This scenario would not require a large temperature differential -- as described in reply #467 the 0.0002" will close up when the average piston temperature exceeds than the average temperature of the fin-cooled cylinder by only about 30 Fº. This assertion would be more valid for aluminum (which has higher thermal conductivity, so that thermal gradients in the solid can be ignored), but it is a good starting point for a rough calculation for cast iron.

During much of my engineering career I was a thermal modeler, analytically predicting temperatures in spacecraft. If I still had access to SINDA I could model this situation rather simply, needing only to make some conservative approximations of the convection heat transfer in the diametral gap. The convection heat transfer from the fan-cooled cylinder fins would be straightforward.

Ah well, it will be nice to see the engine running, soon.