Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

a8.5x7.25 on a OS 46 story in magazine

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Old 01-29-2007, 01:01 PM
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suzonka
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Default a8.5x7.25 on a OS 46 story in magazine

this article about the shriek in the modlers magazine this month from AMA has a point abput useing an apc 8.5x7.25 in which I looked up and they dont make that size, well it was on a shreik with a regular OS BB 46 an it was an APC pylon Racing prop , is this possible without burning up the motor??
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Old 01-29-2007, 01:15 PM
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Default RE: a8.5x7.25 on a OS 46 story in magazine

Yes, it is an APC prop.

The 8.5x7 and 8.5x7.25 are D-1 series Q-500 props.
LP08570 8.5X7.0
LP085725 8.5X7.25
LP08575 8.5X7.5

Although you may be correct .... APC may have discontinued the 7.25 version (per the website)

They are not AMA428 racing legal, but they were very popular for SEMPRA and CAPS racing using the Jett SS-40 sport racing engine.

On this engine, they typically tached around 19,500-20,000 rpm for launch.

The OS engine is quite capable, and very durable. No reason it should not be able to turn upward of 18,000 or so without a problem.

On the stock muffler, the 8.5x7.25 or 8.5x7.5 might reach up toward 17,000 on the ground.

With a pipe or jett-stream or ultra-thrust muffler, you might see a little better.

The engine will take it.
Although most of my experience has been with the OS46FX (and with the Thunder Tiger .46 Pro). Others may chime in here as to the capability of the .46AX.

My understanding of the .46AX is that it likes bigger props, tends not to like to run as well much over 15,000 rpm

DaveN ..... perhaps you can better comment on the AX ?

Bob
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Old 01-29-2007, 01:21 PM
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Default RE: a8.5x7.25 on a OS 46 story in magazine

The AX just doesn't go any faster at 16,000 as it does at 14,500.

Anything over about 14,500 is wasted from my use of this engine.
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Old 01-29-2007, 01:49 PM
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Default RE: a8.5x7.25 on a OS 46 story in magazine

ORIGINAL: daven

The AX just doesn't go any faster at 16,000 as it does at 14,500.

Anything over about 14,500 is wasted from my use of this engine.
Isn't the horsepower peak of the AX with stock muffler just about on the torque peak at 13k or way down there somewhere? I thought that's what the review I read a while ago determined. If so, it is certainly a different engine altogether than the FX.
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Old 01-29-2007, 01:53 PM
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Default RE: a8.5x7.25 on a OS 46 story in magazine


ORIGINAL: daven

The AX just doesn't go any faster at 16,000 as it does at 14,500.

Anything over about 14,500 is wasted from my use of this engine.
Thanks Dave.....

I've only run one of these so far, and I know you had some experience with it ....

your info is about the same as what I see with the AX.
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Old 01-29-2007, 03:21 PM
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Default RE: a8.5x7.25 on a OS 46 story in magazine

The article I had read listed the torque peak in the low 14,000' (I think it was 14,200). A 10x7 APC prop on most AX engines will peak right about there. A well broken in AX with head shim and baffle removed will peak closer to 14,500.
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Old 01-29-2007, 03:41 PM
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Default RE: a8.5x7.25 on a OS 46 story in magazine

ORIGINAL: daven

The article I had read listed the torque peak in the low 14,000' (I think it was 14,200). A 10x7 APC prop on most AX engines will peak right about there. A well broken in AX with head shim and baffle removed will peak closer to 14,500.
Gotcha, thanks. Good to know. I must find the review I read to see where I got those numbers.

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Old 01-29-2007, 06:00 PM
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Default RE: a8.5x7.25 on a OS 46 story in magazine


ORIGINAL: bob27s

Yes, it is an APC prop.

The 8.5x7 and 8.5x7.25 are D-1 series Q-500 props.
LP08570 8.5X7.0
LP085725 8.5X7.25
LP08575 8.5X7.5

Although you may be correct .... APC may have discontinued the 7.25 version (per the website)

They are not AMA428 racing legal, but they were very popular for SEMPRA and CAPS racing using the Jett SS-40 sport racing engine.

On this engine, they typically tached around 19,500-20,000 rpm for launch.

The OS engine is quite capable, and very durable. No reason it should not be able to turn upward of 18,000 or so without a problem.

On the stock muffler, the 8.5x7.25 or 8.5x7.5 might reach up toward 17,000 on the ground.

With a pipe or jett-stream or ultra-thrust muffler, you might see a little better.

The engine will take it.
Although most of my experience has been with the OS46FX (and with the Thunder Tiger .46 Pro). Others may chime in here as to the capability of the .46AX.

My understanding of the .46AX is that it likes bigger props, tends not to like to run as well much over 15,000 rpm

DaveN ..... perhaps you can better comment on the AX ?

Bob
Its a good thing I wrote this thread , what about a 46 magnum BB,will it handle a LP085725 8.5X7.25

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Old 01-30-2007, 09:38 AM
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Default RE: a8.5x7.25 on a OS 46 story in magazine

Idunno...

Id imagine so.

If anything is going to let go, it will be the rod.

In any case here..... we are talking about a Shrike. Its quick, but it is a bit draggy. That 8.5"x7 size is not the best prop selection in that application (not guessing here, from experience).

Needs prefereably a 9x6, 9x7, 9x8 standard blade, or one of the bigger D-1 seriese props like a 8.75x8 or 8.8x8.5 for any of the engines you mentioned.

Take the OS46FX, Mag46, or any compariable clone - with the stock muffler - target the peak ground rpm between 15,500 and 16,000 rpm with your prop selection. On an OS AX, target 14,500 peak ground rpm. If you choose to upgrade to a tuned muffler, target the same rpm range - you will just be able to go up in pitch a bit.

Bob
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