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Tillotson 212cc and 225cc on efficient ultralights?

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patrickrio

Well-Known Member
Joined
Aug 15, 2020
Messages
365
I had been looking at the least expensive 4 stroke engine options that might be used in high efficiency ultralights and had identified the Tillotson 1 cylinder 4 strokes as very likely options. They are promising enough that I think they should have their own thread. There is not a good place to put this in the Engine section, and since they really are not likely to be useful anywhere but on an ultralight I have put the post here.

Even the $200 base model comes shipped with crank and valve mods normally done to handle aircraft use, and it also comes with a mechanical fuel injection option which is interesting. And the weight is not too bad either, at 42lbs shipped with a likelihood of reaching mid 30s pounds in weight in the most lightened aircraft versions....

For flying aircraft, they might be a great option for cheaply replacing the dual motors on a Lazair???

Can an ultralight be designed that is light and efficient enough to fly right around 55 knots top speed while retaining a 500ft/min climb for takeoff and downdraft safety, all on the 9+HP of a single Tillotson 212cc? Seems like a worthy challenge.....

And it seems that there is already a member testing. REVAN, who I believe is the son of Jedi Has been doing this:

My Tillotson 212cc test engine has the electric starter and the steel fuel tank on top. It is stock, with the only modification being a prop flange and propeller attached to the engine shaft. On the test stand, I've got about 40 hours on the engine so far. The test engine as it stands weighs in at 42 pounds with oil.

I'm intending to just use recoil start on my ultralight (at least in the beginning). Dropping the starter, steel fuel tank and oil from the engine's empty weight should get it down below 39 pounds. Then if I want to shed more weight, I'll replace the iron fly wheel with an aluminum one. That will cost about $100, and should bring the engine+propeller weight down into the 35 to 36 pound range. Cost for the engine with aluminum flywheel and propeller will be around $500 for about 10 Hp, or $50/Hp.

If it is too underpowered, one option is to upgrade to the 225cc engine. I figure I can prop it to de-rate the 17.5 Hp engine down to about 14 or 15 Hp and still direct drive the propeller. This will provide more margin on heat rejection than running it at 17 Hp. The downside is the 225cc engine is more expensive and drinks premium fuel instead of regular. I'll be looking at more like $1000 for engine+propeller, or about $70/Hp. So, for about double the installed cost and also more noise and more expensive fuel, I can get about 40% to 50% more power.

In any case, I think these engines need their own post so information on them can be grouped in one place.....
 
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