Further thought – The prop load
curve will vary, depending on whether it is static runup, climb, cruise . .
A typical load curve for SL cruise for
my NA 20B might look something like the attached.
Al G
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Al Gietzen
Sent: Wednesday, October 28, 2009
8:57 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Prop
Loads
Greg;
I
had the same dilemma when running my engine on the dyno.
The
primary reason I wanted to simulate a prop load so I could do tuning of the EC2
on the dyno. But that never happened. I generated an approximate
prop load curve but could never follow it – IIRC, it was because you
can’t set the load, and there is more than one RPM/MAP combination for a
given load. Dyno work is basically about generating WOT HP and torque
curves. You set the mixture according to the A/F ratio. And you always
learn some other things along the way – flow rates, EGTs, fuel burn, etc.
And
Gary, I don’t think prop load varies as the square of the rpm –
does it? I think some aspects, like thrust, go as the square; but the
drag goes more like the cube. I generated one both ways, and neither is
the real world.
Al G
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Greg Ward
Sent: Tuesday, October 27, 2009
6:43 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Prop Loads
Finally in the
dyno room building the mount plate to begin testing. Tracy says that the
engine should be tested with the prop on, and this is kind of hard in a dyno
room. We are mounting the engine without the PSRU, so that we don't tear
it up in testing, and instead hooking directly to the shaft which is loaded by
means of a water brake. We can put any load on it that we want, problem
is, how to calculate that prop load in foot-pounds, at different settings.
Talked to Craig Cato, and he is leaving for Europe, so doesn't have time to run
the calcs, and I am just a dumb high country nail-banger. Any thoughts?
Lancair 20B
N178RG in progress