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Jan 18, 2020, 08:49 AM
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Help!

OS 55AX Prop Size


Guys: In the manual the recommended prop sizes are 12 x 7-8; 13 x 6-7. It just seems to me that those are big props for a 55 sized engines. What have some of you guys used that you like? Thanks
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Jan 18, 2020, 09:11 AM
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I've had many OS engines through the years. Currently have an OS .55AX on a nice Avistar trainer that I used to teach my two grandsons to fly with. I broke it in with an 11 X 6 for about 4 tanks. I then switched to 11 X 7 using both Top Flight and Master Airscrew wood props with excellent results. I of course balance all my props carefully. I use Cool Power 15% synthetic fuel, OS #8 plug. Great idle, crisp / smooth transition, with MORE that enough top end power for this plane. Good Luck !
Jan 18, 2020, 10:39 AM
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Depends on the plane and what you want from it? On my pattern plane I used a 11x8 and turned good rpm.
Jan 18, 2020, 11:13 AM
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Don't run these engines lean. Tach them on the ground to peak, then back off 800 RPM, fly and slowly adjust if needed. Keep them rich and they'll last a long time. I have two of them, superb engines in a "40" size case.
10x8-11x8 for hi speed, depending on air frame. Bigger Diameter with less pitch for scale or 3D, Just a suggestion to start with.
Jan 18, 2020, 11:17 AM
A man with too many toys
I would use 11x6 or 11x7 for first flight and experiment after the engine is broken in, probably a couple of gallons.

.
Jan 18, 2020, 11:24 AM
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Hi Bill,
I agree with all the comments above. I ran one in a Kyosho Osmose with an APC 13x7 (which has pretty narrow, thin blades) and got great performance from the engine. I have been very impressed with the 'AX' series of engines. I've run the 95AX and the 120AX extensively with pipes and pumps and they produce great power with reliability and durability typical of OS. Plus I never liked the remote needle in the 'FX' series (though I love the 140RX and the 160FX!!!).
-Will
Jan 18, 2020, 04:18 PM
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Thread OP
HI Guys: Thanks for all the informed responses. Soooo the consensus seems to be a prop in the 11" range and one in the 12" range. I am going to put it on my Phoenix Typhoon and will run 15% nitro. I will do some experimenting.

LongTime I actually had this in a trainer for my grandsons but swapped it for the Typhoon. I have an OS 46 in the trainer now.
Jan 18, 2020, 09:01 PM
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The Typhoon has a very narrow fuse, I think the 11" will work well for overall performance. Of course try and see what works best.
Jan 19, 2020, 05:58 AM
A man with too many toys
Quote:
Originally Posted by Sam Ehab
The Typhoon has a very narrow fuse, I think the 11" will work well for overall performance. Of course try and see what works best.
I agree. I would bot use anything larger on that airplane.

Also larger props can cause overheating - especially when the engine is new and not yet broken in.

.
Last edited by RC Man; Jan 19, 2020 at 09:24 AM.
Jan 19, 2020, 08:55 AM
AMA 477098, - Jimmy Russell
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I believe the reason OS recommends such large prop sizes is because of noise. The AX series has more cooling area and performs well within a wide rpm range. In a big trainer the 55 would probably do well with a 13x6 and be fairly quiet, but it won't spin it at 13k. For a classic I agree with others 11x7 or 11x8 to let it get more into the power band 12k+ is the ticket.
Jan 19, 2020, 12:14 PM
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Mr - Punk , do you have pink hair??!!, very inciteful. I appreciate the info. I am going to start with an 11 x 8 and see what I get. I want the r's meaning speed for the classic schedules I like to fly, Thanks to all again. Bill
Jan 19, 2020, 01:00 PM
AMA 477098, - Jimmy Russell
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Hehe, not pink. Although when I was teen in a band it was neon orange for a bit. Now it's just brown and grey. 11" prop set slightly rich of peak and have fun.

Jimmy
Jan 19, 2020, 03:25 PM
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Bill, lots of good advice here on the .55. The Typhoon thread has gotten long enough that it's a chore to go through it all. Back at the beginning of that thread, some of us were experimenting with the .55 AX and had good luck with it. I settled on a Xoar 11x6 with the Jett muffler sold by Horizon for the small case Evolution .60. That combination got me in the 15k range recommended for the muffler. Horizon no longer offers it but you can get the muffler direct from Dub Jett. I recently considered joining a club with more strict noise limits than I had been used to. The stock OS Powerbox muffler with an APC 11x8 got me where I needed to be and still flew the Typhoon well though I prefer the 11x 6 setup. Guys flying 3D on smaller profile models like the .55 AX with large diameter low pitch props and mufflers like the old Mac's black tube type. I really like the .55, probably my favorite OS since the old FSR series, just wish it had a true AAC or ABC piston/sleeve.
Jan 19, 2020, 10:59 PM
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Quote:
Originally Posted by gltruett
Bill, lots of good advice here on the .55. The Typhoon thread has gotten long enough that it's a chore to go through it all. Back at the beginning of that thread, some of us were experimenting with the .55 AX and had good luck with it. I settled on a Xoar 11x6 with the Jett muffler sold by Horizon for the small case Evolution .60. That combination got me in the 15k range recommended for the muffler. Horizon no longer offers it but you can get the muffler direct from Dub Jett. I recently considered joining a club with more strict noise limits than I had been used to. The stock OS Powerbox muffler with an APC 11x8 got me where I needed to be and still flew the Typhoon well though I prefer the 11x 6 setup. Guys flying 3D on smaller profile models like the .55 AX with large diameter low pitch props and mufflers like the old Mac's black tube type. I really like the .55, probably my favorite OS since the old FSR series, just wish it had a true AAC or ABC piston/sleeve.
Do you have pix of your 55 in the Typhoon? I was thinking to do the same, but the cowl is so small it will get hacked quite a bit. What RPM where you getting on what fuel and which prop? I was going to use APC 11x7 for overall performance.
Jan 20, 2020, 12:16 AM
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Sam I am almost done with the install. I misplaced some connecters, what a dunce, so I am waiting on some replacements from Dubro. As soon as I am finished I will post some pics. Should be a few days., The cowl did need some extra hacking where the needle valve assembly was. I am sure it will be worth it as the 55 seems to be the power of choice. I will take a picture of that. I am going to go with 15% Cool Power and an 11 x 7 prop to start on the stock Power Box muffler.


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