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