[NSRCA-discussion] Pipe Length

[Jerry Budd]

Dave, et all,

The measurement you're looking for is 24.25-25" measured straight 
line from the plug to the first baffle on an ES pipe.  My OS140's ran 
between 8200-8400 rpm with this setting with an APC 17x12 using 
Magnum #1 fuel.  Switching to Magnum 15% gave me ~ 200 rpm less (the 
rpm's quoted are takeoff settings not peak rpm).

If you are running in the low 7k range you are either too long on the 
pipe, have too much prop (not likely with a 16.5x12W), or you may 
have the needle backed too far out.  The OS140 likes to run in the 
high 7k's to low 8k's.  You can prop it to run at a lower rpm (the 
major benefit is it's quieter when run that way) but it's also more 
difficult to do so.  Dave Lockhart had good success doing so but he's 
got a lot of experience setting up motors too.

If you set the pipe length to around 24.5" you should be seeing 
7800-8k rpm with that prop (which is quiet enough for most anybody 
except maybe FAI at the Nats) and vertical performance shouldn't be a 
problem with any airplane weighing under 11 lbs.

As always, YMMV.

Thx, Jerry


>Thanks Mike.  I ran this prop for a few flights on the same pipe 
>setting as I used for a 16x12.5 wide APC,and 15% Cool Power. It 
>would turn about 7400,but I backed off the needle so that it barely 
>touched 7200.  It pulled a 10.75 lb.
>Brio surprisingly well but certainly not well enough on verticals.
>My mistake in misnaming the fuel I intend to use.
>
>Thanks again         
>
>Dave
>
>----- Original Message -----
>From: <mailto:drmikedds at sbcglobal.net>Dr. Mike Harrison
>To: <mailto:nsrca-discussion at lists.nsrca.org>NSRCA Mailing List
>Sent: Tuesday, November 28, 2006 5:38 PM
>Subject: Re: [NSRCA-discussion] Pipe Length
>
>One more thing, the Cool Power is 20% Problend.
>Mike
>
>----- Original Message -----
>From: <mailto:davidsmith at ns.sympatico.ca>Dave Smith
>To: <mailto:nsrca-discussion at lists.nsrca.org>NSRCA Mailing List
>Sent: Tuesday, November 28, 2006 2:46 PM
>Subject: [NSRCA-discussion] Pipe Length
>
>What would be a good starting point to set an ES tuned pipe,Model 2C 
>140MU on an OS 140 RX,(w/extra head shim and OS "F" plug),running on 
>Cool Power 20/20?
>
>Prop is APC 18.1x10.1W.
>
>Thans,Dave  NSRCA  #943
>
>
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-- 
___________
Jerry Budd
Budd Engineering
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