Ryobi vs Zenoah

Back in November 2004, Walt asked the question of the cost of conversion of
a Ryobi 31 cc. For my part, I have done this conversion and I have a great
engine for less than $150.00 (less than half than comparable "model
airplane" gas engines). With that said, I just read a review of the Zenoah
G26 in the latest issue of Fly RC mag. Guess what? My weed cutter Ryobi
conversion turns a 16x10 prop at a higher RPM (8,100 vs. 7,260) and idles
lower (1,400 vs. 1,860) than the G26. And my tests are at 5,500 ft altitude
with 15% thinner altitude, which knocks the crap out of engine horsepower.
As for weight my Ryobi is almost 1/2 pound lighter (51.1 vs. 58.3 oz.). I
should add that I added a homebuilt electronic ignition and dumped the stock
one pound flywheel/coil assembly.
Granted my $150 total cost doesn't include some of my labor and my friends
machining (I owe him a lunch) and my 31cc is 22% larger displacement that
the G26 @ 25.4cc.
Therefore my observation is that the engine conversions are at least
comparable to other gas engines in their displacement class and cost less.
What's wrong with this logic?
How much does it cost to convert the engine to airplane mounting and
> stuff. I have the engine,but don't have a clue what to put it on.I'd
> like to use the standard servos that I already have,radio also.Engine is
> still in the weedeater,so I have to start from scratch.
> Any sugguestions??
> Thanx
> WAlt
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Good point that should be factored into the equation ... durability/quality. I do own a Ryobi weed-eater/brush cutter. It has given me good service for one season. And when you own 35 acres it gets a good workout. Right now my airplane Ryobi has about three gallons of gas run through it and it only seems to get stronger. Wear-out may be an issue, but my local small engine repair shop assures that he can get any part and do any service required. Since we are talking about rural America his rates are quite reasonable.
Another good point about the altitude effect power absorption. There is a very noticeable effect of power drop off with altitude, moving to Colorado from sea level. Since I studied propeller design and aircraft power plants I should know this answer. Maybe I should take a drive up to the top of Pikes Peak (12,200') and give my Ryobi a test run. What is the top end RPM? In the early days of aviation planes couldn't fly more than 8 to 10,000' so they trucked aircraft engines up to the top of Pikes Peak and did a lot of pioneering engines tests.
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The equipment of choice for commercial purposes seems to be Shindawa (sp?) I have been told it is robust by more than one contractor.
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