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

OS 75 - anyone play with one yet?

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Old 10-19-2007, 01:04 PM
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bob27s
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Default OS 75 - anyone play with one yet?

Hi folks......

Anyone have one of the OS 75 engines yet?

I was reading this RCU review
http://www.rcuniverse.com/magazine/a...article_id=920

Wanted to know if anyone could share similar data and experience to correlate.

Article notes very respectible rpm with a crud load of prop ---- and on the stock p-box muffler.

I have a lot of time working with the OS91 for speed applications and some good data, but nothing with the new engine yet. So some data from my revver buddies here will help from any who can provide it.

Bob
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Old 10-24-2007, 04:09 PM
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Default RE: OS 75 - anyone play with one yet?

Bump.

I'll be interested to see if this one makes it or not. Although it fits the same bolt pattern as the .61 FX, it is physically larger in the pictures, which means the .91 FX will fit in the same space. With the .91 an already proven engine with greater power, displacement, and .1 oz less weight, the .75 AX leaves me wondering what purpose it holds in the current market place.

It has occured to me, however, that OS may very well be phasing out all of the FX line one engine at a time, and with a .46, .55, .75, and a 1.20 AX and the .46 FX ancient history, the .61 and .91 might be soon dropped with the .75 and 1.20 respectively as their "replacements"?

Just an opinion, really, but I don't think the .75AX will sell too well here in the US unless OS stops production of the .91FX. I even doubt that stopping production of the .61 would make a noticeable difference in .75 sales.
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Old 10-25-2007, 09:21 AM
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Default RE: OS 75 - anyone play with one yet?

I may have read the magazine article wrong along the way.... thought I saw some other rpm figures. My aging eyes.

The OS specs on the engine are a good example of why that data has to be taken with a grain of salt.

They noted 2.4 HP at 15,000 rpm, practicle range up to 16K rpm.
Then recommend "9,000" rpm props. ???
Just does not make sense at all.
Have to wonder, why "rev-limit" the engine [sm=confused.gif]


Threads elsewhere on RCU seem to indicate it is a good running engine.... does run with the big props well. That is good to see.

My thought was more along the lines.... if it is hitting peak HP at 15,000 ..... what prop does it take to get to 13,500 or 14,000 rpm so it can approach that peak? No doubt the tuned muffler would help too.
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Old 10-25-2007, 11:53 PM
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Default RE: OS 75 - anyone play with one yet?

All the new OS engines are going to lower RPM and torque. They are trying to get the prop noise down, and the over all noise of the engine. This may be due to the noise regulations in Europe or maybe something here in the US? 3D flying ?

Fine by me! those motors have their applications, but I will stick with high revving motors for speed.
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Old 10-26-2007, 08:12 AM
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Default RE: OS 75 - anyone play with one yet?


ORIGINAL: Julian537

All the new OS engines are going to lower RPM and torque. They are trying to get the prop noise down, and the over all noise of the engine. This may be due to the noise regulations in Europe or maybe something here in the US? 3D flying ?

Fine by me! those motors have their applications, but I will stick with high revving motors for speed.
They are definately taking the right approach... the market out there is for quiet engines. Here in the US just as much as anywhere else.

If you want quiet.... you need lower rpm and a good exhaust system that is properly matched to the engine.
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