• Welcome aboard HomebuiltAirplanes.com, your destination for connecting with a thriving community of more than 10,000 active members, all passionate about home-built aviation. Dive into our comprehensive repository of knowledge, exchange technical insights, arrange get-togethers, and trade aircrafts/parts with like-minded enthusiasts. Unearth a wide-ranging collection of general and kit plane aviation subjects, enriched with engaging imagery, in-depth technical manuals, and rare archives.

    For a nominal fee of $99.99/year or $12.99/month, you can immerse yourself in this dynamic community and unparalleled treasure-trove of aviation knowledge.

    Embark on your journey now!

    Click Here to Become a Premium Member and Experience Homebuilt Airplanes to the Fullest!

Engine design/comments/thoughts

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

DLrocket89

Well-Known Member
Joined
Aug 10, 2009
Messages
249
Location
Janesville, Wi
Disclaimer: I am a metallurgical engineer. If you want me to tell you what to make parts out of the engine out of, what type of lubrication materials you should use, how to heat treat your various parts, I’m your guy. My mechanical design experience is exactly zero…all I know is what I have experience with wrenching on, namely 1970’s motorcycles, tractors from the 1930s, and my ’97 Chevy S10. That and I have a crazy gearhead friend who designed, fabricated, and built his own functional internal combustion engine “because he got bored”…he talks, I listen.

So, I’ve been thinking about the things that make aircraft engines what they are (thinking along the lines of a Lyc/Cont/Jab here), ie air cooled, flat, simple. Above all, they are intended to be reliable. That got me thinking about a potential new design.

My friend’s engine design uses an input valve actuation method that I can only presume is a technique used way back when…the intake valve has no mechanical actuation. It’s held up by a low-rate spring…on the intake stroke, the vacuum pulls the valve open. The compression stroke closes it. The firing stroke keeps it closed with the pressure in the chamber, ditto with the exhaust stroke. Very simple, only practical at low RPMs. Exhaust valve was pushrod/rocker arm like anything else.

If the intention was a low-RPM airplane engine, say with a redline in the 2000-2200 RPM range, could something like that work? Obviously a lot of testing would be needed....

What I’m thinking here is a flat 8 or even a flat 10, small bores, low compression, looong stroke, redline 2000-2200 like I said.

You could ditch the weight of one whole valve train, use lighter rods because of lower stresses, etc etc. Decent chance of making it light…granted, the displacement is going to be high compared to other engine technologies for the same horsepower, but one might be able to keep the weight low enough to make the HP/weight ratio reasonable.

It’d put a crank bearing between each cylinder like a Jabiru. Use needle bearings on the crank, on the rod bearings, maybe the camshaft, etc…goal would be something like a 4000 hour TBO because things on the bottom would be moving slow and have good bearings. It might need new pistons and a cylinder hone more often because (depending on the stroke) as the piston might actually be moving relatively fast.

The goals are stone-cold reliability, long TBO (bottom end at least), and reasonable weight. I haven’t run a single number about anything, wouldn’t know where to start if I did. Does anyone have comments on the design concept? I might have to brush off my CAD skills and mess around with this.

On a related note, does anyone have any good books on internal combustion engine design? I’d be interested in reading up. (-:

Thanks for any replies. Please don’t fry the noob.
 
Back
Top