Pipes: Am I doin' it right?

Stuka Stunt Main Forum · 3 of 3 known posts recovered

Ion · Jul 28, 2003 11:53 AM

Yesterday I put the OS.25VF (I can say it’s practically broken in) on the bench and burned some five 4 oz. tanks. With the pipe at 16.25” or so from plug to baffle.

It starts on the first flip, and seems to dislike running rich.

It just don't sound "happy"...

I kept closing the needle, and all of a sudden it “jumped” to 12,000 rpm, sounding really happy.

I tightened the needle a little more, but it stayed at 12,000, so I opened it again until he sounded “crancky” again.

I then closed it just a little bit and it stays as if “locked” at 12G.

I figure it has been ran some 35 – 40 minutes.

I’m still takin’ it easy. I let it run fast for a couple of minutes, then ease it up to 8,000 rpm (he doesn’t seem to like it), let it cool a little and the back to 12,000.

Hope I’m doin’ the right thing.

Am I?

In Christ,

Ion

Brett Buck · Jul 28, 2003 03:51 PM

#1 source

>Yesterday I put the OS.25VF (I can say it’s practically
>broken in) on the bench and burned some five 4 oz. tanks.
>With the pipe at 16.25” or so from plug to baffle.
>
>It starts on the first flip, and seems to dislike running
>rich.
>
>It just don't sound "happy"...
>
>I kept closing the needle, and all of a sudden it “jumped”
>to 12,000 rpm, sounding really happy.
>
>I tightened the needle a little more, but it stayed at
>12,000, so I opened it again until he sounded “crancky”
>again.
>
>I then closed it just a little bit and it stays as if
>“locked” at 12G.
>
>I figure it has been ran some 35 – 40 minutes.
>
>I’m still takin’ it easy. I let it run fast for a couple of
>minutes, then ease it up to 8,000 rpm (he doesn’t seem to
>like it), let it cool a little and the back to 12,000.
>
>Hope I’m doin’ the right thing.
>
>Am I?

Depends on what you want. I would guess it's been broken in *plenty* by now, so I presume you want a good setting. The phenomenon you are seeing sounds like the engine is coming "on" the pipe. If you want it to run at the same "locked" type of run, but at lower revs, lengthen the pipe. For 11,000, move it to about 17.25". I would imagine, however, that 12000 is in the ballpark for flight with a maybe, 10.5-3.5 Bolly 2-blade.

Bear in mind, I have limited experience with the 25VF, but I'm pretty sure this what you are experiencing.

Brett

Thanks, Brett! · Jul 28, 2003 03:57 PM

#2 source

> Depends on what you want. I would guess it's been broken
>in *plenty* by now, so I presume you want a good setting.
>The phenomenon you are seeing sounds like the engine is
>coming "on" the pipe. If you want it to run at the same
>"locked" type of run, but at lower revs, lengthen the pipe.
>For 11,000, move it to about 17.25". I would imagine,
>however, that 12000 is in the ballpark for flight with a
>maybe, 10.5-3.5 Bolly 2-blade.
>
> Bear in mind, I have limited experience with the 25VF,
>but I'm pretty sure this what you are experiencing.
>
> Brett

Thank you once more, Brett!

I really want 12,000 rpm on an APC 10-3 prop, so I figure all's fine.

I had the feeling I was doing the right thing but it's always good to hear it from the guys that know what the heck they're talkin' about...

In Christ,

Ion