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RE: O.S. 55AX thread - 6/6/2008 4:12:11 PM   
MarvinE255


 

Posts: 146
Joined: 3/24/2002
From: Boynton Beach, FL, USA
Status: offline 		I have this engine in a world models mustang using a pitts muffler(slimline). I tried a 12x6 prop and the rpm was poor. Went to 11x7 and got 12,000. I have not tried a 10x7 but think it will work better. I think the pitts is somewhat restrictive on the exhaust. I was using 15% omega fuel and APC props. Doc

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DOC

(in reply to bgee)
       Post #: 51

RE: O.S. 55AX thread - 6/17/2008 3:27:37 AM   
AstroDad


 

Posts: 117
Joined: 5/26/2008
From: , PA, USA
Status: offline 		Will this engine run well on 5% nitro?

(in reply to MarvinE255)
       Post #: 52

RE: O.S. 55AX thread - 6/17/2008 4:08:07 AM   
Mr. Mugen



Posts: 5512
Joined: 3/24/2006
From: Ishpeming, MI, USA
Status: offline 		I ran mine with a 11x7.5 on my 40 size sukhoi and dont care for it. I wrote down the rpm....but lost it. I will recheck before changing it. I think a 10x8 is next.

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       Post #: 53

RE: O.S. 55AX thread - 6/17/2008 5:21:03 AM   
DarZeelon



Posts: 7082
Joined: 4/9/2003
From: Rosh-Ha'Ayin, ISRAEL
Status: online
quote:

ORIGINAL: AstroDad

Will this engine run well on 5% nitro?


Yes, AstroDad.

It will even run pretty well on FAI fuel (20/80 castor/methanol).

Power will be down ~150-300 RPM at the very top (compared to 15% nitro) and fuel-consumption will also become noticeably lower.


You can remove the head shim (replace with one fabricated from thin aluminium foil for a seal), to get some performance...





< Message edited by DarZeelon -- 6/17/2008 5:54:29 AM >

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       Post #: 54

RE: O.S. 55AX thread - 6/17/2008 1:22:06 PM   
AstroDad


 

Posts: 117
Joined: 5/26/2008
From: , PA, USA
Status: offline 		I have this engine on my Arrow 40 trainer and love the power. It climbs like crazy, and also does not go so fast that I worry about the airframe failing.

In this thread I see a lot of discussion about props smaller than what is recomended in the manual. Are you guys using the smaller props just to improve top speed performance?

for my trainer I have been using a 12X7 and do not really want any more top speed, but if possible, I would be happy to improve my flight time, by cruising around longer while burning less fuel. Should I consider a different size prop? I have not tried 5% nitro, so I suppose that would be my next step, would 0% be even better?

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       Post #: 55

RE: O.S. 55AX thread - 6/17/2008 1:53:14 PM   
DarZeelon



Posts: 7082
Joined: 4/9/2003
From: Rosh-Ha'Ayin, ISRAEL
Status: online 		AstroDad,


A 12x7 prop is HUGE for this engine.

Using a 12x6 will free more RPM from the engine, but actual flight speed will be reduced still.


Additional speed management can be done by managing the throttle...

Your trainer will easily fly at 1/3 throttle... It will even climb at this setting.


Your engine will idle more reliably on 5% nitro than on 0%, but make sure the fuel you use contains a good measure of castor oil.
This is what OS have to say about it (ABL engines are also ABN).

Don't use Cool Power green, which is all synthetic, for example. Don't care what others do (they will eventually pay for this 'violation', with internal failures).

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       Post #: 56

RE: O.S. 55AX thread - 6/17/2008 5:35:30 PM   
jeffk464


 

Posts: 1241
Joined: 10/31/2004
From: cerritos, CA, USA
Status: offline 		I switched from a 12x7 to a 12x6 and didn't really notice a big difference. My rpm jumped 500rpm or so, but a 12x6 need to turn faster then a 12x7 to pull the same rpm. I think its a toss up, but the engine runs fine on either prop.

Marvin - This engine is designed to spin a larger prop at a lower rpm like a 4 stroke, there is no real need to try to up the rpm.

< Message edited by jeffk464 -- 6/17/2008 5:40:07 PM >

(in reply to DarZeelon)
       Post #: 57

RE: O.S. 55AX thread - 6/17/2008 7:53:01 PM   
jeffie8696



Posts: 1137
Joined: 5/10/2007
From: coralville, IA, USA
Status: offline 		I would love to see the tach numbers posted in the tachometer readings section. http://www.rcuniverse.com/forum/tt.asp?forumid=173

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       Post #: 58

RE: O.S. 55AX thread - 6/17/2008 8:02:22 PM   
liquid_TR



Posts: 501
Joined: 4/8/2007
From: ISTANBUL, TURKEY
Status: offline
quote:

ORIGINAL: jeffk464
Marvin - This engine is designed to spin a larger prop at a lower rpm like a 4 stroke, there is no real need to try to up the rpm.



I dont think so.. Im was running mine with APC 9x9 at 15200 rpm... singing quiet happily.

then with the ultrathrust muffler I switched to APC 10x9 running at 14300 rpm static - unloads really good in the air as well.

There is no reason to believe that this engine was designed to be loaded with .75 size propellers.. with those huge props, this engine cannot produce any reasonable power..

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RE: O.S. 55AX thread - 6/17/2008 10:25:30 PM   
DarZeelon



Posts: 7082
Joined: 4/9/2003
From: Rosh-Ha'Ayin, ISRAEL
Status: online
quote:

ORIGINAL: jeffk464

...but a 12x6 need to turn faster then a 12x7 to pull the same RPM.



Jeff,


You mean, to attain the same flight-speed... RPM is how fast the engine and the prop are turning.
Yes, a 6" pitch prop needs to spin 1/6th faster than a 7" pitch prop. That is nearly 17% more, or ~2,000 RPM where your engine is running.


And as to speed; if you want your plane to fly more slowly than it does, exercise throttle management...
You really don't need to fly that trainer at light-speed, so full-throttle should be avoided in most flight circumstances.

Reduce the throttle until you are comfortable with the speed (but not too close to stall-speed... ).

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       Post #: 60

RE: O.S. 55AX thread - 6/17/2008 11:38:14 PM   
jeffk464


 

Posts: 1241
Joined: 10/31/2004
From: cerritos, CA, USA
Status: offline 		Oops, I meant to say to pull the same amount air(thrust) not rpm.

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       Post #: 61

RE: O.S. 55AX thread - 6/18/2008 5:05:58 AM   
Oly


 

Posts: 180
Joined: 7/23/2003
From: Missoula, MT, USA
Status: online 		Hi DarZeelon,
I really appreciate your advice and input on these forums, you certainly know your stuff. As per a few posts ago, I run Cool Power in my two stroke engines and have found they do well on this fuel. I do make every effort to not run them too lean/hot as this can damage/ruin them.

Because of my experience running this fuel, I guess I'm not convinced that castor oil is essential.

Again, thanks for your input.

Oly

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       Post #: 62

RE: O.S. 55AX thread - 6/18/2008 5:28:21 AM   
DarZeelon



Posts: 7082
Joined: 4/9/2003
From: Rosh-Ha'Ayin, ISRAEL
Status: online 		Oly,


Thank you for appreciating my efforts ...

As to 'Cruel Power'... Morgan Fuels themselves (the CP manufacturer) recommend only their own Omega™ and NOT this fuel, for ABC/ABN engines. But CP should initially be OK for ringed, ball bearing engines. ...And even then you are much more likely to encounter bearing problems with this no-castor fuel. Just search this forum on OS bearings...

Since neither Morgan, nor OS recommend this fuel for ABC/ABN engines, I believe there is very good reason for you to limit its use to your engines that do not have a tapered cylinder bore.

As to older style meehanite-steel engines (iron piston) and bushing-bearing engines; CP is like hydrochloric acid... Keep away from it! Only very high castor fuels (not even Omega™) should be used in them.


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       Post #: 63

RE: O.S. 55AX thread - 6/18/2008 6:48:31 AM   
XJet


 

Posts: 3451
Joined: 3/31/2003
From: Tokoroa, NEW ZEALAND
Status: offline 		Dar speaks the truth - ignore his sage advice at your peril :-)

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RE: O.S. 55AX thread - 6/18/2008 9:47:28 AM   
bgee


 

Posts: 20
Joined: 9/5/2005
From: camperdown, VT, AUSTRALIA
Status: offline 		Would a OS 50sx Bisson pitts muffler work ok with a 55ax?

(in reply to XJet)
       Post #: 65

RE: O.S. 55AX thread - 6/18/2008 10:19:49 AM