--------------------------------------------------------------------------
Your following message has been delivered to the 163 members of
the list
murphy-rebel@dcsol.com at 13:03:09 on 1 Nov 2000.
--------------------------------------------------------------------------
Bruce, Walter and All,
I measured the distances early this morning, by using a tape measure off the
door post and "eyeballing" with a carpenters square to the starter ring.
Four (4) Rebels on site(all with standard firewall positions), 2 Conicals
(O-320-C2A and an O-320) and 2 dynafocals (O-320-E2D and an O-235-L2C) and
all are within a 1/4" (at the most).
While I was at it another <GREAT> thing hit me about the older "nose bowl
and doors" style cowling, besides the obvious ease of engine maintenance
compared to the speed cowling! With the older cowling you can mount the prop
without a prop spacer if using a 10 to 11" spinner. Doing as I am doing
right now and mounting a 13" (speed cowling) spinner on C- FOKM, I had to
space it out only 3/4" to clear the starter bump on the nose bowl (if
building new you could get rid of the bump by building the cowling assembly
out 3/4" further and have less spinner gap at the top). With the speed
cowling MAM spells out that you should use a 2 inch propellor spacer for
proper cowling fit (Although it can be done with an 1 1/2 spacer
successfully).
Therefore the old cowling, versus the newer speed cowling, can move that
propellor weight aft as much as 2 inches for you and that is a big C of G
difference, especially when swinging a 40 pound Sensenich propellor. (I know
Bob, you wish I had of thought of that before I put a speed cowling on XWI!)
YES Dynafocals are supposed to be smoother (less vibration) in the cockpit.
BUT, to do this the engine is allowed to shake like hell up front, in
comparison to the conical mount, so you need to take this in to
consideration when fitting everything and allow for the extra movement. As
an eye opening example (for me anyways), Howard was complaining that his
engine ran on after he pulled the mixture after returning from Oshkosh. Just
as it would almost stop, at the shake it would restart and do this about 4
times before stopping. Everyone gave him their opinions as to what could
cause it, but he had the plane up at the lake so we didn't get a chance to
actually look at it, and Howard never pulled his cowling to investigate! I
pulled his cowling yesterday to start his annual (now that he is gone south
for the winter). I found that even though all 4 bolts are still safetied
with the tab washers on his carburetor, that hold the top section to the
bowl assembly, there is well over a 1/16 of an inch clearance between the
mating halves and you can rotate the bowl assembly back and forth at least
3/16 of an inch.Every time the engine shook, it was throwing fuel from the
bowl, past the gasket and into the venture (I presume) to make it run again
until the fuel got low enough to stop. I suspect this was caused by the
engines extra movement with the dynafocal mount and possible the air filter
assembly hitting the sides of the intake scoop. None the less, Howard is
lucky he didn't become a fireball somewhere in his travels, so make sure you
have extra clearance to everything if using the dynafocal mount!
Regards,
Wayne G. O'Shea
www.irishfield.on.ca
----- Original Message -----
From: "Walter Klatt" <
Walter.Klatt@home.com>
To: " (Murphy Rebel Builders List)" <
murphy-rebel@dcsol.com>
Sent: Wednesday, November 01, 2000 9:13 AM
Subject: Re: 0 320 engine mounts
Bruce, I believe the conical mounts and dynafocal mounts are the same
distance (propellor
to firewall) for Rebels. However, I have never measured it, so can't say
for sure. You
might want want to check that with MAM. Wayne O. could probably tell you,
too. My
reference was more to Cessnas and Pipers which I was more familiar with.
In my case, and
probably yours, too, my model O320 has the carb mounted more to the rear
of the oil pan,
which makes it extra tight for throttle and mixture cable mounting. So,
no, I would say
being close to the firewall does not compensate for not cutting back the
firewall. I am
sure all this was taken into consideration by MAM. However, if I get a
chance this
weekend, I will do some measurements on mine against some other Rebels at
my airport that
have the dynafocal mounts, just for curiosity.
As for smoothness, by design, the dynafocal should be better. However,
again, I have
found my engine/propeller combination to be very smooth. I have flown in
other Rebels
with metal 2 blades and dynafocals, and really can't tell the difference.
I use a Warp
drive 3 blade, which may help with the smoothness.
Legeorgen@cs.com wrote:
Walter,
Does the conical engine mount for your 0 320A set closer to the firewall
than
the dynafocal mount? Does it compensate for not cutting back the fire
wall
and if so, how much? I was told the conical mount was not as smooth as a
dynafocal. Do you notice a difference?
Bruce G 357R
*---------------------------------------------------------------------------
--------*
*---------------------------------------------------------------------------
--------*
*---------------------------------------------------------------------------
--------*
*---------------------------------------------------------------------------
--------*
*-----------------------------------------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*-----------------------------------------------------------------------------------*
-----------------------------------------------------------------
List archives located at:
https://mail.dcsol.com/login
username "rebel" password "builder"
Unsubscribe:
rebel-builders-unsubscribe@dcsol.com
List administrator:
mike.davis@dcsol.com
-----------------------------------------------------------------
