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That's actually a dynafocal mount.
'Conical' is the nonsensical term for all four mount surfaces
being parallel to each other. Think small Continental 4cyls, and
early Lycs (and their helicopter engines).
https://s28490.pcdn.co/wp-content/uploads/2019/05/mount-lycoming-types.jpg
Dynafocal on left; conical on right. Perhaps the 'conical' term
originates with the rubber components. the rubber parts of a
dynafocal are basically flattened donuts, while the rubber parts
of a conical mount really are cone shaped. the 'focal' in
dynafocal refers to the extended lines of the four mount bolts
converging to a single focal point inside the engine mass. When
configured properly (rare occurrence these days), the focal point
is at the CG of the engine/prop package. Hence 'type 1' &
'type 2' mounts; type 2 has a shallower angle and was used in some
twins that used extended hub c/s props, which shifted the CG of
the engine forward.
The pics that came through do look like Mistral stuff, but Kelly
is a lot more familiar than I am.
I think that the total message size is limited to around 200KB, so
image size somewhere under 130K usually makes it through. Depends
on how much other stuff is in the body of the email.
Charlie
On 7/9/2020 12:38 PM, Marc Wiese cardmarc@charter.net wrote:
Great stuff. I saw and read that
Kitplanes article with great interest back when.
Here’s some conical
mounting back plate pictures I found on my hard drive, I
believe they are all Mistral, but don’t know where they came
from originally (perhaps Paul Lamar’s group) One is a 13B named
‘Steve’.
Hopefully these pics get thru-there is a picture limit on
this list that makes it difficult to send larger files, so I
didn’t send all of them I have just of the
backplate, what is the MB/KB limit here?
Marc
From: Rotary motors in aircraft
Sent: Thursday, July 09, 2020 1:28 AM
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: Aviation Specific 13B/20B
Mazda Front Side Housing
Le Roux,
Thanks for digging this up as it
will answer a lot of questions from the
group..........This was the final iteration of
"Mistrals" alloy side housing / accessory drive
that was headed for US & European
certification.........It incorporated the "30
Degree/#1 Dyna Mount Ears" for the Lycoming O/IO
540 engine mount..........This is
what this thread is all
about..........My friend is attempting to come up with a
less expensive version of this plate but without all the
accessory drives and using the
stock RX 8 front cover with stock
water pump and ignition pickup (electric
airplanes)............Photos are worth a thousand
words..........
Kelly : Just saw this on the
archive on our group thread you post in April 2011
Only the early "Mistral"
13B/20B based engines used the bolt on front
cover/accessory drive alloy cover that had mount
points that used the Lycoming O/IO 320-360
"Dynafocal Type 1" mount ring.........I know
this
as fact as I am the proud
owner of one of these alloy housings.........I
have all the housings and parts to build a
bastardized part alloy "P port" 13BREW
engine.........I retained the cast iron front
(Rear in tractor A/C)
side housing because I was
not comfortable having my engine hang on its
mounts from a housing attached only by several 6
mm bolts threaded into a cast alloy "Racing
Beat" front side housing.........All the other
housings (Center & Rear)
are alloy "Racing Beat"..........The earliest
"Mistral" 20B engines also used this alloy front
cover but also had mount points at the redrive
end of the engine (Essentially a Bed type Mount)
and
only used the bottom two
mount points on the accessory end of the
engine.........At that point in "Mistral's"
engine development the engines they sold to
experimenters were basically "Mazda" engines and
all their parts
were directly adaptable to a
stock "Mazda" engine (such as my
engine)............The last iteration of their
engines were designed to be certifiable so they
had to have a verifiable manufacturing
trail..........So they made
engineering changes in their
parts to eliminate things about the stock
"Mazda" parts that were not needed or were
improvements for aircraft use..........Most of
the last versions of their engines had parts
that were not
adaptable to the stock
"Mazda" engines...........Long winded but
perhaps will enlighten some about the "Mistral"
series of engines..........
Yes Charlie the
accessory "iron" side housing is what
would be replaced with an aluminum housing
with built in mount points that replicate
the Lycoming O/IO 540 mount ears and
locate the Mazda eccentric
shaft centerline in the
same place as the Lycoming crankshaft
centerline and make the Mazda a bolt in to
any aircraft using the O/IO 540 30 degree
"Dyna1" mount system.............
Mark I am well
aware of the different opinions on using
the rear dyna focal mount on the
Mazda.........Bill is correct about the
need for .500 in/12.5mm studs and a
stiffening plate and/or rigid oil sump to
further resistance to
torsional twisting..........But remember
that the O/IO 540 family of engines with
firewall forward weights of 400+ to over
500 lbs for some turbo models are all
using this mount system and
that an all alloy 13B
or 20B (even with reduction drive) will be
much lighter..........I do not believe
that the "Mistral" 13B or 20B used alloy
housings for other than the front
accessory housing and I have never
heard if they used the
oversize .550 inch/12.5 mm studs in any of
their engines..........This is probably a
question that will have to be proven one
way or another in actual use..........IMHO
Wonder why Mistral
used dynafocal type mounting on their
13b and 20b designs?
M
Kelly,
The
"dynafocal" type mount has
been tried on the rotary but
has not worked out well..One
of the obvious rotary traits
is that it has a hot and
cold side. Various methods
have been used to limit this
but there is no way to
eliminate it completely.
Because of this the engine
tends to "work" and move
around on the studs. Using
the engine as a stressed
member is not recommended
with the rotary. If you
were to do this anyway I
wouldn't do it without a
stud kit. You will have
better results using a bed
mount. YMMV
I
am in contact with a
person with the design
and manufacturing capability
to produce an Aviation
Specific 13B/20B Mazda
Front Side Housing
machined from 7075-T6 with
mount points
that would allow these
engines
to be a bolt in to
the engine mount ring
(30 degree number 1
Dyna) as used by the
"Vans" RV-10 and other
aircraft that use the
Lycoming O/IO 540
engine..........This
side plate is in the
preliminary design
stage and at this
point I am a go
between to see if
there would be any
interest in this
product if and when it
is produced...........I personally am interested this side
plate........As we on
this forum know both
the 13B / 20B are
capable of truly
amazing power levels
both naturally
aspirated and turbo
boosted.........The
20B would make the
Van's RV-10 , Glasair
3 or Lancair's that
use the Lycoming O/IO
540 an easy 300+ hp
almost bolt in
engine...........
The "Reno" Sport Class
"Glasairs" and
Lancairs" are
producing almost 400
mph speeds using dual
turbo Lycoming IO-550
engines that are
virtual hand grenades
pulling over 700
hp...........There are
turbo 20B's pulling
1200 hp out in the
auto racing world with
good
reliability..........A
20B boosted to 700+ hp
is not even breathing
hard.........IMHO
Would like to hear
what interest there
may be in this product
if and when it may be
produced............Or
any comments pro or
con..............
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