From: "Tracy" <flyrotary@lancaironline.net>
Received-SPF: pass
 receiver=logan.com; client-ip=209.85.223.175; envelope-from=rwstracy@gmail.com
Subject: Re: [FlyRotary] 20B with RD-1C Prop Options
References: <list-8113330@logan.com>
Content-Type: text/plain;
	charset=utf-8
In-Reply-To: <list-8113330@logan.com>
Message-Id: <B2153CB5-FCE3-4A1E-AC2A-B231712A4D15@gmail.com>
Date: Thu, 29 Oct 2015 21:32:00 -0400
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Content-Transfer-Encoding: quoted-printable
Mime-Version: 1.0 (1.0)

Hi James,
   HP targets sound doable, but those rpm numbers are probably off.  Remembe=
r that with a fixed pitch prop, hp varies as the CUBE of rpm.  Would recomme=
nd propping for a max power at top speed rpm of about 7000.  That will give y=
ou a static rpm of around 6000.

Will get those instruction manuals you asked about to you next time I'm in t=
he office.

Tracy

Sent from my iPad

> On Oct 29, 2015, at 16:22, James R. Osborn <flyrotary@lancaironline.net> w=
rote:
>=20
> Hi guys,
>=20
> So I am going to be building an RV-10.  I sourced Bobby=E2=80=99s spare 20=
B / RD-1C combo and my plan is to work on the motor first, kind of bass-ackw=
ard but that is what I am doing.  My plan is to build a motor/mount test sta=
nd and work everything out on the ground before I ever put it in an airframe=
.  I plan to set it up NA using the existing side port configuration.  I don=
=E2=80=99t know if it is ported - I am going to attempt to determine this by=
 inspection without cracking it open and doing a dynamic compression test to=
 evaluate the health of the motor.  If it is necessary to entirely rebuild t=
he motor, I would probably go PP.  So I am thinking the target HP as it is w=
ould be in the 275 HP range and probably 325 HP if it ends up being a PP.  H=
ow do these numbers sound to you all?
>=20
> I will be looking for a way to dyno it, hopefully borrow one to get some d=
ata.  But I was also thinking about just getting an appropriate fixed pitch p=
rop and working through the bugs based on static run ups.  I like the idea o=
f a three blade prop.  I like the idea of optimizing for cruise at 75%, say 5=
800 rpm which would put full throttle at 7733 rpm on the 20B.  At 5800 rpm, t=
he prop would be spinning 2035 rpm and at full throttle 2713 rpm (using the 2=
.85 ratio RD-1C PSRU).  Do all these numbers sound about right?
>=20
> If so, then how do I choose a prop that will result in 2713 rpm static run=
 up at full throttle, but be tuned for efficiency at 2035 rpm cruise?  I am a=
ssuming at these reasonable RPMs that it will be a larger swing and the thre=
e blade makes sense - what do you think?  Is there a convenient way to find p=
rops out there that will work at the target full throttle HP of 275 or 325? =
 Also if you guys have any good resources to learn about how to figure these=
 things out (books, web pages, online calculators, etc.) that would be great=
!
>=20
> Another option might be to go with something like the IVOPROP Magnum, eith=
er ground adjustable or electric inflight adjustable.  What do you guys thin=
k of these?  Would the adjustability really help me adapt to however my powe=
r plant turns out?  Would the extra complexity be worth it?  For the ground a=
djustable one, I am thinking the process would be:  1. select the =E2=80=9Cc=
orrect=E2=80=9D swing (how?) and go for three blades, 2) use ground adjustab=
ility and work up to THE pitch while I tune the motor until I achieve full t=
hrottle static run up around 7700 RPM.  Will this result in a reasonably eff=
icient setting for 75% cruise?  Am I thinking about this clearly?  All opini=
ons are welcome.
>=20
> There=E2=80=99s a lot for you to chew on!
>=20
> =E2=80=94 James
>=20
>=20
> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/List=
.html