Horizontal Air Cooled Engine

[Brian Rupnow]

I had a stroke of good luck this morning. After tapping something like 20 holes, and assembling things, I discovered a length of 01 steel with two cams cut on it. The last time I set up to cut cams I decided to cut over-length while I was in the set-up for use on a potential future engine. The future has arrived!!!

 

[Jasonb]

Ken, the fan bracket does look a bit heavy to my eyes too but I think its all part of Brian's style of building that differs to mine but at the end of the day he does seem to get a good running engine and anyone building one of his designs can always add their own touch so long as the critical sizes remain the same.

I suspect Brian will be cutting the finned cylinder from Aluminium so not too easy to join to and as it won't be painted you can't hide JBWeld. One option you might want to think about Brian is not cutting one of the fin grooves which would leave you with a thick fin of about 3/8". Id you then set up the cylinder on the rotary table you could use a 1/8" cutter to form the missing grove but don't go full circle, leave a bit so you can drill & tap for a stud to mount the fan on.

 

[Brian Rupnow]

Jasonb----I like your idea. I'm not sure I will use it, but I do like it.---Brian

 

[Brian Rupnow]

--I picked up my cast iron today to make the cylinder. The only material that my supplier had in stock was 2.1" diameter ($25 for 4"). I haven't made the cylinder yet, but this gave me an idea. Without changing anything, I can make it look like this if I want to. This shape harkens back to some of the early model two cycle airplane engines that were made in the 1930's to 1950's. I kind of like it.

 

[Steamchick]

Hi Brian,
This barrel shape (for 2-strokes) was to keep the "top-of-the-stroke" Hot, for better combustion, but cooling where the exhaust gases heat the lower part of the barrel during the exhaust port open phase. - Or anyway, that's what I understood.
4-stroke engines e.g. motorcycles, that were without fans and housings) always had a taper so the bottom of the cylinder wasn't cooled too much, but the top was cooled MUCH more 3~5 times more fin area? (The taper can be a curve - like a half barrel?).
Cheers!
Love the work,
K2

 

[Steamchick]

I like the simplicity of the cam drive and push-rods.... But I would have a cover (maybe even clear acrylic?) over the rockers. - Just personal preference...
K2

 

[Steamchick]

I also noticed the "levitation" facility - as shown on the CAD drawing. How does that work? I'm fascinated....
K2

 

[Donnyo65]

Hi Brian, I'm fairly new to all this and i am currently building the Nemmet 15cc four stroke engine. Just a question from your earlier post, you mentioned cutting part in aluminium on a band saw. What type of bandsaw do you use? i have a portable (ish) metal bandsaw that I have used to cut up to 5" En8 steel but it won't work in vertical mode and has no fitting for a table even if I could get it vertical. Is yours a dedicated metal saw or just a wood saw with a metal cutting blade? Im after a wood cutting bandsaw anyway and if this can be used successfully for metal that would be great.

 

[Jasonb]

Same as a Mirror, if you stand an item on a mirror it is not the top of the glass that the reflection is in but the silvered backing which will be some distance from the top surface depending on thickness of glass

 

[Thommo]

Hey Brian, I had to laugh. A couple of weeks ago you were saying that you were over building engines for awhile. Haha so much for that. Once the bug has you, it won’t let go in a hurry. Love the new engine btw.

 

[Brian Rupnow]

Up until very recently. I used an upright wood cutting bandsaw, to which I had added a second shaft and pulley set, to get the blade speed down to 175 foot per minute, which works well on steel or aluminum. I used this for ten or twelve years and just last month I bought a huge industrial metal cutting bandsaw from a used industrial equipment seller.

 

[Gordon]

I have converted a few wood band saws to cut metal and always used a gear reducer which eliminated the belt slip. Used gear reducers can be rather cheap, at least in my area.

 

[Brian Rupnow]

This morning I made up the main baseplate. This plate has an interesting feature in it. In order to keep everything small, a scallop was cut from the baseplate to clear the 40 tooth cam gear.

 

[Brian Rupnow]

This afternoon I machined a cast iron cylinder. I like that shape a lot. I've got a temporary clamp on there right now, because I haven't drilled any bolt holes yet. I'll do that tomorrow.

 

[Ghosty]

Brian,
Looks like the top cap head screw needs to go a bit deeper in the case. Still following your work.
Cheers
Andrew

 

[Brian Rupnow]

Since I have to build a complete cylinder head, I may as well get crazy and make a finned cylinder head. It isn't a lot more work to do this. It just means the overall height of the cylinder head increases by 1/4". The valves get 1/4" longer, and the blue rocker arm support gets 1/4" taller, and the pushrods get 1/4" longer.

 

[Richard-Vanderpol]

it looks like a hit and miss engine

 

[Robsmith]

Hi Brian,
This barrel shape (for 2-strokes) was to keep the "top-of-the-stroke" Hot, for better combustion, but cooling where the exhaust gases heat the lower part of the barrel during the exhaust port open phase. - Or anyway, that's what I understood.
4-stroke engines e.g. motorcycles, that were without fans and housings) always had a taper so the bottom of the cylinder wasn't cooled too much, but the top was cooled MUCH more 3~5 times more fin area? (The taper can be a curve - like a half barrel?).
Cheers!
Love the work,
K2

Two stroke engines were also cooled by the fuel.

 

[Steamchick]

Two stroke engines were also cooled by the fuel.

Hi Rob, yes I heard that about some Kawasakis, etc in the 1970s... I.E. A rich mixture "to avoid overheating". But from my and friends' experience, as long as the ignition timing is Not too far advanced, the mixture Stoichiometric, and the engine properly set-up, the rich mixture was just a myth for helping the engine.... soot developed in the wrong places that caused pre-ignition and consequential overheating failures. My last 2-stroke was a prod, racer LC350 with stage 3 tuning... needed 105 octane fuel, but correct mixture... I also knew a reliable Prod racer Kawasaki 500 triple in the 70s. Mixture critical, it had to be right, not rich. As did all the winning Yamahas when I used to Marshall at race meetings.
Myth proven by reality in my book....
K2

 

[Zeb]

Aircraft engines (fuel injected) are often run "lean of peak" using change in exhaust gas temperatures (EGTs) to conserve fuel. Carbureted engines have uneven mixture distribution between cylinders, but I guess if you ran just one it wouldn't matter. I've had to change out a few cooked jugs from aggressive leaning. Would be neat to see the all the nice looking engines on this forum react to mixture and cooling under a FLIR camera.
Gradient eye candy!