OS .75AX users please post prop sizes

OS .75AX users please post prop sizes
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OS .75AX users please post prop sizes - 10/8/2007 3:27:07 AM

summerwind

Posts: 1242
Joined: 2/16/2007
From: fresno, CA, USA
Status: offline

i've given up on the Tower .75 (read my thread if you like)........................i should have bought the OS.75AX to start with.
i need an engine that isn't a "dead stick queen"................and the OS is it.
question is, through the search i see people using all sorts of props for this engine.
Bax says that OS recommends prop sizes based on noise rules in Japan.
the list shows 14x6 thru 15x7............but i'm thinking around 13x6.
i will NOT use APC for reasons i've witnessed, so my choices will lie in the wood prop selections.

thx
-mike

Post #: 1

RE: OS .75AX users please post prop sizes - 10/8/2007 4:46:03 AM

Flyboy Dave

Posts: 13448
Joined: 3/20/2002
From: San Bernardino County, CA, USA
Status: offline

....throwing in the towel already ???

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A mechanic says..."Oh yeah, watch this".
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(in reply to summerwind)

Post #: 2

RE: OS .75AX users please post prop sizes - 10/8/2007 5:41:57 AM

summerwind

Posts: 1242
Joined: 2/16/2007
From: fresno, CA, USA
Status: offline

yep..............although, i have an email into the nice lady i deal with at Hobbico...............let's say i will give anything a chance..................after that it's the 'ol paperwieght box..

(in reply to Flyboy Dave)

Post #: 3

RE: OS .75AX users please post prop sizes - 10/8/2007 5:50:25 AM

MOTORMAN37

Posts: 2088
Joined: 10/26/2002
From: CLINTONVILLE, WI, USA
Status: offline

Please send it to me, I need a another engine.

(in reply to summerwind)

Post #: 4

RE: OS .75AX users please post prop sizes - 10/8/2007 8:11:06 AM

alan0899

Posts: 2022
Joined: 4/17/2006
From: Cundletown, NSW, AUSTRALIA
Status: offline

G'day Mike,
I ran my 75AX in on an APC 13x7, in a 60 size Diabolo, it spins it like a toothpick, now I'm running an APC 14x8, the engine handles it easily, & flys the plane beautifully, remember it's ported for larger props.
Depending on what plane you put it on, it would easily swing up to a 15x7.

_____________________________

Good Flyin Mate. Keep Thyne Airspeed up, lest the ground arise & smite thee, Allan.

(in reply to summerwind)

Post #: 5

RE: OS .75AX users please post prop sizes - 10/8/2007 9:12:57 AM

speedster 1919

Posts: 1467
Joined: 12/17/2004
From: Martinsville, IN, USA
Status: offline

15x7 on a 75 is got to be a joke. A fast prop on a 75 would be a MAS 12x7 and 13x6 is a 91 size. I would try the 13x6.........Sometimes OS way over prop recomends and the Japan noise rule would explain this.

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Hey Buddy -That was the most spectacular crash I've ever seen , That rolling cart wheel with parts slinging out was cool...

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Post #: 6

RE: OS .75AX users please post prop sizes - 10/8/2007 11:32:30 AM

alan0899

Posts: 2022
Joined: 4/17/2006
From: Cundletown, NSW, AUSTRALIA
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G'day Mate,
Or is it possible that, to you, unless it does a zillion revs, it can't be running right.

_____________________________

Good Flyin Mate. Keep Thyne Airspeed up, lest the ground arise & smite thee, Allan.

(in reply to speedster 1919)

Post #: 7

RE: OS .75AX users please post prop sizes - 10/9/2007 12:44:03 AM

CustomPC

Posts: 349
Joined: 4/19/2004
From: SydneyNSW, AUSTRALIA
Status: offline

Allan, did you ever tach it with those props?

I have a bunch of props here to try on mine. APC 13x6, 13x7, 13x8, 14x4W, 14x5N & 14x6 plus Bolly's in 13.5x6 & 13.5x8.

I'm sure i'll find the best match out of that lot

(in reply to alan0899)

Post #: 8

RE: OS .75AX users please post prop sizes - 10/9/2007 1:33:01 AM

tailskid

Posts: 5509
Joined: 11/30/2001
From: Tolleson, AZ, USA
Status: offline

I'm using a MA 14-6 on mine and is pulling my CG Skylark 70 around with authority! I believe I've richen it to 8900 rpm's. Topped out at 10,400 w/ MA 14-6! Idled about 2900....

Jerry

< Message edited by tailskid -- 10/9/2007 5:33:24 AM >

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Post #: 9

RE: OS .75AX users please post prop sizes - 10/9/2007 5:14:16 AM

alan0899

Posts: 2022
Joined: 4/17/2006
From: Cundletown, NSW, AUSTRALIA
Status: offline

quote:

ORIGINAL: CustomPC

Allan, did you ever tach it with those props?

I have a bunch of props here to try on mine. APC 13x6, 13x7, 13x8, 14x4W, 14x5N & 14x6 plus Bolly's in 13.5x6 & 13.5x8.

I'm sure i'll find the best match out of that lot

G'day Mate,
Yeah I did tach it when I put the 14x8 on it, I think it was around 8,600, but I really can't remember, & I don't care anyway, it flew the Diabolo beautifully, but so did the 13x7.
I will be flying it this weekend, I flew my Katana last weekend, & I'm sure the 75AX will get better with some more flight time.

_____________________________

Good Flyin Mate. Keep Thyne Airspeed up, lest the ground arise & smite thee, Allan.

(in reply to CustomPC)

Post #: 10

RE: OS .75AX users please post prop sizes - 10/9/2007 9:53:35 AM

speedster 1919

Posts: 1467
Joined: 12/17/2004
From: Martinsville, IN, USA
Status: offline

quote:

I'm using a MA 14-6 on mine and is pulling my CG Skylark 70 around with authority! I believe I've richen it to 8900 rpm's. Topped out at 10,400 w/ MA 14-6! Idled about 2900....

Tailskid I see a problem if you don't-- first 10400 to 8900 says your richened by 1500 RPM and not the norm 300-500 (running to hot otherwise) and 2900 RPM is way to high to brag about.

_____________________________

Hey Buddy -That was the most spectacular crash I've ever seen , That rolling cart wheel with parts slinging out was cool...

(in reply to tailskid)

Post #: 11

RE: OS .75AX users please post prop sizes - 10/9/2007 10:40:07 AM

CustomPC

Posts: 349
Joined: 4/19/2004
From: SydneyNSW, AUSTRALIA
Status: offline

How is the spool up and throttle response with a 14x6?

Those numbers are the same as (if not slightly behind) most 4-stroke .91's which have the torque to deliver decent throttle response. I'm worried that 14x6 is over propping the 75AX.

(in reply to speedster 1919)

Post #: 12

RE: OS .75AX users please post prop sizes - 10/9/2007 10:44:20 AM

alan0899

Posts: 2022
Joined: 4/17/2006
From: Cundletown, NSW, AUSTRALIA
Status: offline

quote:

ORIGINAL: CustomPC

How is the spool up and throttle response with a 14x6?

Those numbers are the same as (if not slightly behind) most 4-stroke .91's which have the torque to deliver decent throttle response. I'm worried that 14x6 is over propping the 75AX.

G'day Mate,
A 14x6 is not overpropping the 75AX, remember some fellas think that engines must be revving at very high revs to run properly, but not the 75AX, it is designed to run slower with larger props, like a 15x6 or 14x6, 7 or 8.

_____________________________

Good Flyin Mate. Keep Thyne Airspeed up, lest the ground arise & smite thee, Allan.

(in reply to CustomPC)

Post #: 13

RE: OS .75AX users please post prop sizes - 10/9/2007 11:28:02 AM

speedster 1919

Posts: 1467
Joined: 12/17/2004
From: Martinsville, IN, USA
Status: offline

OK MATE On the OS web site the OS75 is 2.4 HP at 15,000 RPM and your going to prop for 9,000 and under. OS states the break in prop for a .61 is 11x7 and a .75 does 15x6. FS 70 is 11x9 for break in and the .75 does 15x6 (remember the 4 strokes swing a much bigger prop ) and to top it off an FS 120 break in prop is 14x9. This will be linked to the likes of OS and the .91-2 stroke big prop recommendations. The fix to OS 91 problems is 2 fold. Redisgned HS needles and going down to a smaller prop than recommended.
I don't believe 4 stroke will swing much bigger props. Prove it to yourself. Look up size for size and the 4 stroke will probably go up 1 pitch. Remember size for size not a .46 2 stroke to a .82 saito 4 stroke. 91 to 91 120 to 120

< Message edited by speedster 1919 -- 10/9/2007 11:29:44 AM >

_____________________________

Hey Buddy -That was the most spectacular crash I've ever seen , That rolling cart wheel with parts slinging out was cool...

(in reply to alan0899)

Post #: 14

RE: OS .75AX users please post prop sizes - 10/9/2007 1:27:55 PM

Cyclic Hardover

Posts: 7218
Joined: 5/7/2002
From: New Mexico, USA
Status: offline

quote:

ORIGINAL: summerwind

i've given up on the Tower .75 (read my thread if you like)........................i should have bought the OS.75AX to start with.
i need an engine that isn't a "dead stick queen"................and the OS is it.
question is, through the search i see people using all sorts of props for this engine.
Bax says that OS recommends prop sizes based on noise rules in Japan.
the list shows 14x6 thru 15x7............but i'm thinking around 13x6.
i will NOT use APC for reasons i've witnessed, so my choices will lie in the wood prop selections.

thx
-mike

Need to know what size and type plane for an answer to be of any value. Are you going to 3d or what?

_____________________________

Retired Army Aviator - Excuse Me! You sold me a hair with a cake around it!

(in reply to summerwind)

Post #: 15

RE: OS .75AX users please post prop sizes - 10/9/2007 1:35:46 PM

summerwind

Posts: 1242
Joined: 2/16/2007
From: fresno, CA, USA
Status: offline

quote:

ORIGINAL: Cyclic Hardover

quote:

ORIGINAL: summerwind

thx
-mike

Need to know what size and type plane for an answer to be of any value. Are you going to 3d or what?

yes that would be heplful eh?
the plane is a GP Big Stik.........1,000sq in wing...............right now with the TH75 mounted, the plane wieghs 6.25lbs.

(in reply to Cyclic Hardover)