From: "James R. Osborn" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] 20B with RD-1C Prop Options
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Date: Thu, 19 Nov 2015 09:36:56 -0800
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References: <list-8174631@logan.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>

Hi Jeff,

Yes no time pressure at all.  This will be a test stand development.

We don=E2=80=99t know the full providence of this motor.  It appears =
that it has been rebuilt and there is rumor that Bruce Turrentine was =
involved with that.  He has a reputation, but I don=E2=80=99t know if it =
true he rebuilt it or wishful thinking.  And I don=E2=80=99t know what =
kind of porting was done - it looks more like just cleanup than porting =
from the outside inspection, but I wouldn=E2=80=99t know for sure until =
and if I take it apart.

I am not too afraid of rebuilding it as I have plenty of 13B experience. =
 But if the numbers seemed acceptable, I was thinking I would try avoid =
it.  Peak HP considerations aside (as Bobby mentioned), I am inclined to =
go PP if I tear it apart - I always wanted one!  This would eliminate =
unknown factors about porting altogether too.

=E2=80=94 James

> On Nov 19, 2015, at 5:03 AM, Jeff Whaley <flyrotary@lancaironline.net> =
wrote:
>=20
> My gut feeling is if you are confident in the engine's history then =
run the engine for several hours and retest the compression numbers.
> Don't know where your engine came from, how long it has been sitting, =
or what preservation treatment it received. In general terms it is =
always best to overhaul an automotive engine prior to installation in an =
aircraft. My guess is if you are building an RV10, you are still a long =
way from actually flying? - If that is true you will have plenty of time =
to perform an overhaul - it takes about 1-2 weeks real time.
> Jeff
>=20
> -----Original Message-----
> From: James R. Osborn [mailto:flyrotary@lancaironline.net]
> Sent: Wednesday, November 18, 2015 9:05 PM
> Subject: Re: 20B with RD-1C Prop Options
>=20
> So I finally got a dynamic pressure test done on this 20B.  Here is =
what I got:
>=20
> Front: 105-125-105
> Center: 105-101-87
> Rear: 130-125-120
>=20
> This is in PSI and was done with all spark plugs out except the rotor =
being tested.  That one got one spark plug and the compression fitting =
with pressure transducer attached in the other.  I used the RD-1C =
installed, but not engaged - I bolted up the flex plate without the =
adapter and bolted up the RD-1C with a starter to be able to crank it =
over.  So the redrive was not slowing things down when I cranked it =
over.  Then I recorded the pressure wave on a laptop and looked at three =
bumps in a row.  I did this a few times for each rotor with a pause in =
between and took the highest readings of any three successive peaks to =
estimate the health of the three faces on each rotor.
>=20
> My understanding is that higher numbers are better and the same =
numbers across all faces in the motor is better.  I am unclear what an =
unacceptable low number might be.  The actual values you get are =
dependent on a number of factors including how fast you are cranking =
(how well charged your battery is, how beefy the cables are, what kind =
of porting, other losses like the PSRU if it were engaged, etc.) and if =
the motor is broken in or not.  I don=E2=80=99t know if this motor was =
broken in, or if any seals were replaced.  It looks clean inside and =
there is evidence of porting, but I don=E2=80=99t know exactly what =
(this is a side port configuration motor).
>=20
> When I lost a side seal on my 13B REW in my RX-7, I got something like =
118-120-50 on the rotor that had the problem.  So that was clearly not =
good.  When I rebuilt that motor that time, I had the plates ground as =
they were beyond the wear limit and I used all new side and corner seals =
and springs.  After that rebuild, I got uniformly 120 to 130 on all =
faces which I think is very good.
>=20
> So, what do you guys think of my 20B numbers?  Is that low face on the =
Center rotor bad enough to warrant tearing the motor completely apart?  =
If I decide to do that, I might very well go PP.  Though Bobby at least =
thinks that is a bad idea due to noise and tuning difficulties with the =
PP.  Or I could just live with it with these numbers, go side port, and =
break it in and start checking this periodically to see if there is any =
improvement or further deterioration.
>=20
> Thoughts or opinions?
>=20
> =E2=80=94 James
>=20
>> On Oct 29, 2015, at 1:22 PM, James R. Osborn <rxcited@gmail.com> =
wrote:
>>=20
>> Hi guys,
>>=20
>> So I am going to be building an RV-10.  I sourced Bobby=E2=80=99s =
spare 20B / RD-1C combo and my plan is to work on the motor first, kind =
of bass-ackward but that is what I am doing.  My plan is to build a =
motor/mount test stand 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 the motor, I would =
probably go PP.  So I am thinking the target HP as it is would be in the =
275 HP range and probably 325 HP if it ends up being a PP.  How do these =
numbers sound to you all?
>>=20
>> I will be looking for a way to dyno it, hopefully borrow one to get =
some data.  But I was also thinking about just getting an appropriate =
fixed pitch prop and working through the bugs based on static run ups.  =
I like the idea of a three blade prop.  I like the idea of optimizing =
for cruise at 75%, say 5800 rpm which would put full throttle at 7733 =
rpm on the 20B.  At 5800 rpm, the 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 assuming at these reasonable RPMs that it will be a larger =
swing and the three blade makes sense - what do you think?  Is there a =
convenient way to find props 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, =
either ground adjustable or electric inflight adjustable.  What do you =
guys think of these?  Would the adjustability really help me adapt to =
however my power plant turns out?  Would the extra complexity be worth =
it?  For the ground adjustable one, I am thinking the process would be:  =
1. select the =E2=80=9Ccorrect=E2=80=9D swing (how?) and go for three =
blades, 2) use ground adjustability and work up to THE pitch while I =
tune the motor until I achieve full throttle static run up around 7700 =
RPM.  Will this result in a reasonably efficient setting for 75% cruise? =
 Am I thinking about this clearly?  All opinions are welcome.
>>=20
>> There=E2=80=99s a lot for you to chew on!
>>=20
>> =E2=80=94 James
>>=20
>=20
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>=20
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