What a surprize!

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What a surprize!

Postby ama1437 » Wed Jan 21, 2015 8:31 am

I've always heard that the OS FS-20 is the world's smallest four stroke engine made in mass production. I'm selling one on eBay right now and as I was doing the pictures, I noticed that it is actually .217 cu. in. Says so right on the box!!!

So I checked the bore and stroke and did the calculations on that AND did the same for the HP VT 21 and guess what? The HP VT 21 is actually the smallest, NOT the OS!!!

Here are the numbers:

HP VT 21 = .21163406 cu. in.
OS FS.20 = .21753722 cu. in.

I'm sure I'm not the first to notice this, but I've never seen it said before.

I have always preferred the HP to the OS and now even more. I have one in a 2 meter motor glider from about nineteen eighty something. I set it up for cross country flying. Has a Graupner 24.7 oz tank. I have no idea how long it would actually fly. I always pumped a BUNCH of fuel out after flying. Back then, I was limited by Tx and Rx batteries. Think it's time to pull it out, clean it up and fly it again.
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