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Old Jan 21, 2013, 05:47 PM
no no no, a music gig
Chophop's Avatar
Pleasant Valley Modelport
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Found, 50.5 CC Poulan !

I stumbled onto a 50.5cc Poulan chainsaw engine today. It was used for parts at a local outlets store. The motor is left intact and the compression is very strong, but not quite like a Stihl.
Now I can't find any horse power rating on it, it is from a Poulan Pro 5020AV.
I have the tools to convert it, but I do wonder what prop it will turn. I expect 8000 rpm and hope to run something like a 20x10 on an 80 inch scratch cessna type plane. I'm guessing it has to have at least 3 to 3.5hp.

Any ideas of what I can do with this engine ? Maybe even a stretch 90 nitro to gas conversion. I am told a 90 heli can still fly with a 15 lb payload so for sport/scale, this motor may work and be about a pound or two heavy.
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Last edited by Chophop; Jan 21, 2013 at 07:21 PM.
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Old Jan 21, 2013, 07:01 PM
The Prez....... again
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United States, IA, Rockwell
Joined Jul 2011
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It's funny Poulan won't publish any specs (HP) on it's saws.
FWIW, Poulan is considered a "throwaway" saw. For model use it will probably last long enough. It won't get the abuse like being used in a chainsaw. I'm guessing it is right at 3 HP. A Stihl 50cc saw runs from 3.5 to 3.75 HP. I doubt the Poulan will top those numbers.
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Old Jan 21, 2013, 07:02 PM
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not sure what prop it would swing, but 50cc for a 90 size heli is in my opinion way to big. I have a Bergen intrepid with a 23cc engine swinging 800mm blades and it has plenty of power. Bergen does have a 52cc industrial twin heli. you can check them out to get a idea of how stout 5ye heli has to be.
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Old Jan 21, 2013, 07:25 PM
no no no, a music gig
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Pleasant Valley Modelport
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From what I'm finding, the 50cc motors are only a few ounces heavier than the 30's and have about 2.5 to 3x the hp. I'll need to strip it then get the weight. My 25cc Homelite is about 3.5 lbs. They say it powers a 1.20 just fine , like a Four Star 120. At a few more ounces the 50cc will power it just finer.
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Old Jan 21, 2013, 07:38 PM
no no no, a music gig
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Pleasant Valley Modelport
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BTW this one has a two barrel carb. The 2nd barrel opens at 1/2 throttle. Never saw that on such a small engine. I wonder if that carb would perk a smaller engine up ? They all say put a larger carb on it.
I'd really rather have an RC engine but it fell into my hands. So maybe make a scratch build for it.
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Old Jan 21, 2013, 08:47 PM
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I TOBOR's Avatar
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The engine is likely timed to turn 9,000 to 10,000 rpm, so when limiting it to, say, 8,000 to 9,000 a larger carb could very well be a detriment.
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Old Jan 21, 2013, 09:43 PM
no no no, a music gig
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I'm good at getting a bad one to run but squeezing performance is something I need to learn. Maybe a good point for electronic ignition. If it runs a 18x10 at 9000 rpm I'll be happy. Not so easy to find as with electric motors.

18x10 looks like a realistic possibility.
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Old Jan 23, 2013, 03:04 PM
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Looks like it will be ok for the job :



Extreme Flight Yak-54 (2 min 2 sec)
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Old Jan 23, 2013, 06:57 PM
The Prez....... again
kenh3497's Avatar
United States, IA, Rockwell
Joined Jul 2011
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Quote:
Originally Posted by Chophop View Post
BTW this one has a two barrel carb. The 2nd barrel opens at 1/2 throttle. Never saw that on such a small engine. I wonder if that carb would perk a smaller engine up ? They all say put a larger carb on it.
I'd really rather have an RC engine but it fell into my hands. So maybe make a scratch build for it.
The second barrel does not introduce any fuel to the engine. Stihl would call this engine a "Stratified Charge" engine. Several companies use this design. It uses fresh air to purge the engine of exhaust gas before the fresh charge makes it to the cylinder. It does work and it reduces emissions and increases fuel economy to boot.

That saw engine is designed to run at about 10,000 RPM so try to prop it in that range to get everything to work correctly. The Strat charge needs designed RPM to work.

A you tube video of it in action.
Strato Animation 460 XTORQ (1 min 35 sec)


Ken
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Old Jan 23, 2013, 07:06 PM
no no no, a music gig
Chophop's Avatar
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I don't know everything but at least I know one more thing. Thanks. It's in good hands.
So anyone have an idea how much HP this Poulan 50.5cc motor makes ? Still, my best guess is about 3.5 hp. And yes, a dedicated RC motor would be a better bet.
I'm getting hyped on the NGH 9CC for a .40 airplane also. Full climb power all through the flight sounds good to me.
I'm sorry but I just can't see $35+/gallon of fuel. And although the glow fuel smells good, it also gets all through the house. And on the funny side, a guy could run into some pretty mean women by slapping a little glow fuel on for aftershave.

Stack this on top of it all, I can go out and fly my little E-Starter and still have plenty of fun. So light and spritely.
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Old Jan 30, 2013, 05:50 PM
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Pleasant Valley Modelport
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Here's the kicker. After stripping all the chainsaw stuff off, it weighs between 4.6 to 5 lbs. My Tanita digital scales go in .5 lb increments so that's bad news. An RCGF 50cc is just under 3.5 lbs.
So now I'm back to the merit of this 50cc unfinished conversion vs my Homelite 25cc already to put on a plane. that one is just over 3 lbs. An RCGF 26cc is 2.5 lbs when pulling an airplane up in the wild blue yonder.

That tells me this conversion stuff just isn't such a good idea. I stumbled onto them for a very low price, and the 50cc motor isn't even broken in yet. So I still juggle over what to do.
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Old Feb 01, 2013, 07:50 AM
Two left thumbs
Muncie, IN
Joined Sep 2006
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Chainsaw engines are inherently heavier than the old "throw away" Homelite and IDC/Ryobi string trimmer engines because they have double conterweighted crankshafts. The cheapo trimmer engines have crankshafts built like a typical small glow engine, without the second counterweight/shaft/bearing a saw needs.

Although Jason is right that the typical big box store engines, with the exception of Echo, are built as cheaply as possible, they are much more suitable for conversion than the better quality stuff. So, if you want a light weight engine, look for one that has the starter at the front, not the back. That's a dead giveaway that the crankshaft's a single counterweight type - and light weight.

Geoff the other small engine mechanic
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Old Feb 01, 2013, 08:18 AM
no no no, a music gig
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I think I might just use this for a surface vehicle. A mini dune buggy maybe.
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