Glow Engines Discuss RC glow engines

OS 50sx prop size

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Old 05-11-2005, 09:46 PM
  #1
kf6gub
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Default OS 50sx prop size

I was advised that an APC 12.25x3.75 prop would be appropriate on my Katana GS 40 powered by an OS 50sx. The engine tacks at 11500 rpm, but the engine itself has less than half a gallon through it. Is 11500 rpm enough for this prop? thx. Jim
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Old 05-11-2005, 09:49 PM
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Default RE: OS 50sx prop size

This is a very common combination.

I havn't tached one lately but I was thinking they went faster than that? Do you have your engine mixture set correctly?

12,600 is the usual rpm with this prop.

Enjoy,

Jim
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Old 05-12-2005, 05:05 PM
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Default RE: OS 50sx prop size

That's way too low. With stock muffler, you should get at least 13000 rpm with this prop. With tuned muffler, like Tower 46 muffler or Rossi 46 black tuned muffler, people are getting 14k.
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Old 05-12-2005, 05:55 PM
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delman
 
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Default RE: OS 50sx prop size

His ringed 50sx may not be broken in yet as well as an apc 12x4 for will turn a few more rpm's.
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Old 05-12-2005, 10:22 PM
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Default RE: OS 50sx prop size

I am looking for a good .50. What is the difference in the sx over fx. and what is the sx?
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Old 05-12-2005, 10:40 PM
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w8ye
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Default RE: OS 50sx prop size

The SX engines are their higher performance engines
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Old 05-22-2005, 03:27 PM
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Default RE: OS 50sx prop size

I have a 40 size MOJO which is VERY close to your katana. They should weigh about the same and are intended for no holds-bared 3D. On my mojo I run 3 props depending on what I can get.

I prefer APC prop because I hit the ground a lot and even when the get shorter I just keep flying for the day.

My favorite APC's are
1. 12 x 4
2. 12.25 x 3.75
3. 11 x 4

If they spool up a little slower than you would like try a master airsrew or preferably a wood prop like a 12 x 4. The wood props spin up MUCH faster although they give a little less thrust in the end I think, from flexing.

Hope it helps,
Dave

Hey try the tower hobbies .46 muffler, its a gem for 15.00 bucks
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Old 05-26-2006, 09:49 PM
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Default RE: OS 50sx prop size

I get 13,100 with a 12.25x3.74 APC on my 50SX
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Old 05-26-2006, 10:25 PM
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Default RE: OS 50sx prop size

Get yourself a Tower muffler and APC 12X4 prop and adjust the needles.
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Old 05-26-2006, 11:54 PM
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Harry Lagman
 
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Default RE: OS 50sx prop size

Quote:
ORIGINAL: kf6gub

I was advised that an APC 12.25x3.75 prop would be appropriate on my Katana GS 40 powered by an OS 50sx. The engine tacks at 11500 rpm, but the engine itself has less than half a gallon through it. Is 11500 rpm enough for this prop? thx. Jim

Jim, that's a little lower than it should be. Like the guys are saying, 13k+ is more the norm for that engine/prop combo. Does the muffler still have the baffle installed? Install a Tower muffler - this should be worth at least 500 rpm on its own. The .50 SX also responds well to a little nitro, with good gains in power up to about 15%.

Good luck and report back on progress.
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Old 05-26-2006, 11:55 PM
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Default RE: OS 50sx prop size

deleted duplicate post
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Old 05-28-2006, 05:30 PM
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Default RE: OS 50sx prop size

I build a moosecan for a friend of mine for his OS.50SX he was getting 15,000 with a 12x4. It would pull a 5lb profile out of sight. It has so much power the whole fuselage would flutter on full power uplines. and yes the prop was balanced.
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Old 05-28-2006, 05:48 PM
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Default RE: OS 50sx prop size

If the engine has less then a half gallon through it I would give it some time most engines need a couple gallons before the really wake up
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Old 05-28-2006, 06:32 PM
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Default RE: OS 50sx prop size

As some have pointed out, this is a ringed engine. It's just not broken in yet. Less than 1/2gal is not even half way through the break-in process for ringed engines. Run it slightly rich for no less than a full gallon of fuel. Don't try and get max rpm until you do that. Then, very gradually lean it during your second gallon of fuel. It will get there.
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Old 05-28-2006, 08:06 PM
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Default RE: OS 50sx prop size

Oh, my 13,100 tach reading is still within the first gallon of fuel. I am still running it rich, about 1.8 - 1.9 revolutions on the needle.
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