[NSRCA-discussion] Pipe Length

[Dave Smith]

Jerry:   My question yesterday was not worded very well.   The RPM I was 
referring to was with the 18.1x10.1W.
The 16.5 x 12 was in the 8000 to 8100 range.   To have lengthened  the pipe 
for the bigger prop would have been not worth the effort. Quite a bit of 
cutting and hacking involved.

Thanks,,,,,,,,,,Dave


----- Original Message ----- 
From: "Jerry Budd" <jerry at buddengineering.com>
To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
Sent: Wednesday, November 29, 2006 2:59 PM
Subject: Re: [NSRCA-discussion] Pipe Length


> 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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> -- 
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> Jerry Budd
> Budd Engineering
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