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Date: Wed, 28 Oct 2009 10:06:39 -0400
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Message-ID: <1b4b137c0910280706s52e45d7bo31b91e749774bea6@mail.gmail.com>
Subject: Re: [FlyRotary] Prop Loads
From: Tracy Crook <tracy@rotaryaviation.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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I don't understand the problem.  Why do you care what the prop load is?  A
dyno is used to measure the engine torque at various rpms so a dyno run is
typically done by setting WOT (after warmup at idle of course), starting
with enough load to hold engine at minimum rpm of interest then gradually
reducing load to allow rpm to rise to maximum rpm of interest.   The whole
run takes only seconds if all is running well.

Your dyno operator will know this (or should).

You can calculate prop torque later by multiplying engine torque times
redrige ratio.

Tracy

On Tue, Oct 27, 2009 at 10:43 PM, Greg Ward <gregw@onestopdesign.biz> wrote:

>  Hey Troops;
> 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?
> Greg Ward
> Lancair 20B N178RG in progress
>

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I don&#39;t understand the problem.=A0 Why do you care what the prop load i=
s?=A0 A dyno is used to measure the engine torque at various rpms so a dyno=
 run is typically done by setting WOT (after warmup at idle of course), sta=
rting with enough load to hold engine at minimum rpm of interest then gradu=
ally reducing load to allow rpm to rise to maximum rpm of interest.=A0=A0 T=
he whole run takes only seconds if all is running well.<br>
<br>Your dyno operator will know this (or should).<br><br>You can calculate=
 prop torque later by multiplying engine torque times redrige ratio.<br><br=
>Tracy <br><br><div class=3D"gmail_quote">On Tue, Oct 27, 2009 at 10:43 PM,=
 Greg Ward <span dir=3D"ltr">&lt;<a href=3D"mailto:gregw@onestopdesign.biz"=
>gregw@onestopdesign.biz</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"border-left: 1px solid rgb(204, =
204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">





<div bgcolor=3D"#ffffff">
<div><font color=3D"#000080">Hey Troops;</font></div>
<div><font color=3D"#000080">Finally in the dyno room building the mount pl=
ate to=20
begin testing.=A0 Tracy says that the engine should be tested with the prop=
=20
on, and this is kind of hard in a dyno room.=A0 We are mounting the engine=
=20
without the PSRU, so that we don&#39;t tear it up in testing, and instead h=
ooking=20
directly to the shaft which is loaded by means of a water brake.=A0 We can=
=20
put any load on it that we want, problem is, how to calculate that prop loa=
d in=20
foot-pounds, at different settings.=A0 Talked to Craig Cato, and he is=20
leaving for Europe, so doesn&#39;t have time to run the calcs, and I am jus=
t a dumb=20
high country nail-banger.=A0 Any thoughts?</font></div>
<div><font color=3D"#000080">Greg Ward</font></div><font color=3D"#888888">
<div><font color=3D"#000080">Lancair 20B N178RG in=20
progress</font></div></font></div>
</blockquote></div><br>

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