Rupnow Ovehead Cam Air Cooled

[Brian Rupnow]

The engine is finished mechanically. The last thing I had to do was cut a keyway in the crankshaft, and that is done and the completed flywheel is mounted. I have to pick up a set of ignition points and a condenser for it (I have an old set of points on it right now that I use for "set-up" purposes). If I don't run into any unforeseen issues, I MIGHT have a runner in the next few days.

 

[Ghosty]

Brian,
It is really starting to come together. It's looking good too. Could you use a smaller timing gear setup?

Cheers
Andrew

 

[Brian Rupnow]

Ghosty--there is a factor called "minimum wrap diameter" that deals with how small the crankshaft pulley can be. This differs between manufacturers of belting, but the bottom line is that if the pulley becomes too small in diameter, the belt has to flex so much to accommodate the smaller pulley that the belt fails very soon. I don't really know how much smaller I could go, but I don't mind the proportions the engine has now. ---Brian

 

[Johno1958]

I like this engine a lot Brian,can't wait to see she runs
Cheers
John

 

[Brian Rupnow]

Thanks Johno--I like this engine a lot myself. I just put the new points and condenser on it, and set the ignition timing and valve timing. I have looked a little closer at the brass bit I have attached to the carburetor and decided that it is more hindrance than help. Not all of my ideas pan out as well as I had originally hoped for them. I will take that brass bit off tomorrow and craft a better throttle lever.---Brian

 

[Brian Rupnow]

And so, boys and girls, Mr Rupnow must have done something right in a previous life, because the engine started this morning as soon as everything was hooked up. I made a wild grab for my video camera and made a video of the first run, but there was so much movement that a person would have gotten sea-sick trying to watch it. After things calmed down a little bit, I made a second video of the engine running with everything a little calmer. I originally had some brass fittings on the carburetor to control the free swing of the throttle arm, but it didn't work out terribly well so I removed it and just attached an aluminum extension handle to the small throttle lever that came on the purchased Traxxas carb. In this video you will see my low-tech rubber band holding the throttle closed because without it the damned throttle arm wants to swing into the wide open position and my engine revs so high it almost scares me to death. I am extremely pleased with how well this thing runs, and how little screwing around was required to get it running this well. somebody please let me know if the video shows up alright.---Brian Rupnow
[ame]https://www.youtube.com/watch?v=N7_klnlI3Ak[/ame]

 

[dnalot]

Well done, I love the slow idle. I'm going to miss reading your frequent posts. So whats next?

Mark T

 

[DavidLloyd2]

Brian
Video shows up good this end,

DavidLloyd

 

[Johno1958]

Brian
You must be pleased as punch. A very nice runner.
Cheers
John

 

[Ghosty]

Brian,
Congrats, great work as usual. And yes the video is good.

Cheers
Andrew

 

[Herbiev]

Another great engine Brian. Well done and thanks for sharing.

 

[Brian Rupnow]

Thank you, gentlemen. This build got me thru the coldest, darkest part of the winter, and overall it went very well, with no do-overs except for the ill fated gas tank. I am always greatly gratified when an engine fires right up and runs first try. When I look back at my first i.c. engine attempts like the Webster and the Kerzel, and all the horrible issues I had with non sealing valves, it makes me give my head a shake. I don't do very much different now than I did five years ago when I first started building i.c. engines, but we must learn by our mistakes, because I seem to have a lot fewer problems now. It's been a fun ride, and I thank all of you who followed along during the build.---Brian

 

[Brian Rupnow]

And just to show that I'm not a total barbarian, I dug around in my box of tension springs and found one that will act as a throttle return spring so I can get rid of the rubber band!! It is going to attach to that head bolt nearest to the other end of the spring, but first I have to buy a longer #6 shcs to replace the one that is in there already.

 

[rac37]

Very nice Brian, Will be interesting to see what is next.
Bob

 

[Cogsy]

Congrats Brian, another great runner. It seems from the video that it sounds very different to the Rupnow Vertical and I can only guess it's because the intake valve is not atmospheric? It almost makes me want to build another vertical with a cam operated intake valve just for comparisons' sake, but I just don't have the time.

 

[Brian Rupnow]

Cogsy--that is something that I have noticed as well. All of my engines have a distinctive sound, and all of the engines with two cam driven valves sound different than the ones with atmospheric intake valves.---Brian

 

[Brian Rupnow]

With the completion of this engine I have now built just about every version of the internal combustion engine. I have built flathead engines, overhead valve engines, overhead cam engines, two cycle engines with no valves, hit and miss engines, and both atmospheric valves and cam operated valves. I know there are more "strange one of" versions of the i.c. engine out there, but I have just about covered all of the popular styles. I have not, and probably will not build a radial i.c. engine, although I have built a 5 cylinder radial "steam engine".

 

[Cogsy]

I have not, and probably will not build a radial i.c. engine, although I have built a 5 cylinder radial "steam engine".

What about a single cylinder, stationary crankshaft engine where the cylinder revolves around the crank? That sounds like a design challenge you could sink your teeth into!

 

[Brian Rupnow]

What about a single cylinder, stationary crankshaft engine where the cylinder revolves around the crank? That sounds like a design challenge you could sink your teeth into!

A bit too dangerous for me Al. I damned near lost a finger to an engine like that when I was about 13 years old. I had an old single cylinder washing machine engine that you started by wrapping a pull cord around the flywheel pulley and giving it a yank. Being 13 years old, I only had half a brain yet, so didn't have the engine bolted down to anything. The engine immediately started, flipped over onto it's flywheel, and then proceeded to spin around like a whirling dervish between my feet. In a panic I made a grab for the sparkplug wire and something metal hit the knuckle on my right index finger, almost tearing it off. The motor eventually quit on it's own, but I still carry the scars from that event on my knuckle. I don't want to go for a repeat.---Brian

 

[Brian Rupnow]

We've reached the end of the trail, partner. This engine is done like dinner. The only thing left is a video of it doing a bit of honest work, and I made that about half an hour ago. I have no idea of what I may do next, but it won't be for a while. I love these builds, but when I have finished one, I don't want to machine anything for a little while.----Brian
[ame]https://www.youtube.com/watch?v=A8aKoDtPxc0&feature=em-upload_owner[/ame]