Scott Gettings wrote:
>
> Paul & group:
>
> A while ago you graciously answered some early questions about
13B mounts in a Glass Goose. To recap, the Goose is a pusher with a
cutout in
the upper wing
> for the engine and mounts, and a very narrow rear pylon. The
summary of the previous thread was to have a front mount (water pump end)
as wide as
possible
> using a 12A front cover, and some type of rear, Schertz beam.
>
> I've obtained a 12A front cover, a 6061x1/2" plate for the
front mount main beam, and a RWS motor mount plate (thanks, Bob White!). I
have some
crude wood
> mockups of some front mount options to present.
>
> The Goose upper wing cutout is 22" wide at its narrow point,
which will just allow 20" between the front mounts. The first pix on this
message
show a
> "horizontal tab" mount mockup, based on Paul's front mount
layout.
>
> One problem with this version is that it forces the engine
about an inch aft - not good. Another is the wood/composite mount
support will
interfere with
> the aluminum main beam, because the composite structure will
need a vertical box underneath to support its horizontal part. If the
horizontal
aluminum tab
> can only cantilever out 1", then it isn't quite long enough to
allow the Barry/bolts/washers to fit within the composite structure. If the
aluminum
> horizontal can handle the load with the bolt hole being about
1 1/2" out from the end of the vertical metal, then it would just fit.
>
> Perhaps a better option might be to allow the engine to move
as far forward as possible, and use a piece of angle bolted on the aft
surface of the
primary
> beam to hold the Barry mount. This would place the Barry
mount behind the beam (see pic) and help the CG issue. Since an angle
could be bolted
with its
> surface below the primary beam, there would be no interference
with the composite structure underneath.
>
> Another solution might be to place the Barry mounts vertically
(see pic), but this would place all the torque on the mount's radial axis --
probably no good
> (but easy to build the mount).
>
> My specific questions on this front mount are:
> 2. Is a 6061 angle bolted to the back of a 6061 1/2" main beam
a reasonable way to accept these loads? (this would be much easier to
build and
better for my
> CG) If so, will a 3/8" thick 6061 90 degree angle be heavy
enough? Or do I need to go with 1/2"? I'm assuming that four AN-4 bolts
on each end
will be more
> than enough for these shear loads -- or, are AN-3 sufficient?
No need for this if you just use 3" by 3" by 1/4 inch thick
angle.
You can buy this stuff at Industrial Metals Supply in San
Fernando Calif.
> 3. What is the smallest vertical dimension for the 6061, 1/2"
thick main beam in order to support the front mounts at 20"? This will
need to
handle some
> twisting loads if an angle is used. The beam I have is 6"
high, so I'll need to cut it down to the appropriate dimension.
Twisting loads will be minimal with the 22001 rubbers and 3 x 3
angle and not worth worrying about.
Paul Lamar
Scott, I too have a small cowl to deal with in the RV-4. See
the attached picture for my solution. Note that Paul has since come up
with a P-51
type mount that I like better, but I'm not planning to rebuild
this mount. I also used a 12A front cover and Paul (and the other
engineering types
(thanks guys)) was uneasy about putting the loads into the
aluminum front cover; in response to this concern I ran tubing from the
lower mount to
the engine so that the front cover sees very low loads.
Ken Powell
The 12A front cover is plenty strong enough as that is how they mount
the
whole 12A engine in the first gen RX7 and some other early Mazda cars.
The third mount in
these cars is at the back of the transmission.
This is not really applicable to the Glass Goose as the Goose is a bed
mount.
Bed mounts are ideal for the rotary.
Paul Lamar
Thanks very much for the information and advice on the front mounts. One
issue I still have to deal with is the CG. The engine needs to be as far
forward as
possible in order to avoid adding weight in the nose to stay in W&B. A
3" (or 2") 90-degree angle in front of the engine will space it a little
farther aft
than ideal.
Scott Gettings
Well you can always use a Schertz beam under the front (car) end housing.
Not the front cover. The front end housing.
That will move it well forward. What about the prop location and cowl?
Will that still fit with the engine moved one inch aft? If you move it
two or three inches forward will it still fit?
BTW with the engine moved one inch aft of a point... that is a moment of
300 inch pounds.
That can be balanced CG wise by having ten pounds 30 inches forward of that
point. In other words it all depends on what type of shoes you are wearing
and the shoe size you wear :) Hiking boots might move the CG too far
forward :)
Sorry about the lame attempt at humor. If it is 50 inches forward of that
point
it only requires six pounds to balance. Where is the battery?
We still need to talk about the rear mounts.
BTW here is the way Rino Lacomb did it. I have a lot more pictures if you
need
them.
Paul Lamar
Thanks again Paul. No problems with the prop location or cowling within
these few inches.
We discussed Rino's installation in the past - we communicate regularly.
HIs method requires 2 bridges (extra weight and complexity), special engine
center mounts, and only has about 14" of inter-mount width at the very
most. Another Goose builder had to add 12 lbs of ballast in the nose to
compensate for his 13B that was mounted 4" behind the wing cutout! The
battery is already in the nose. The Goose is unfortunately an aft-CG prone
plane, which is why no one is using an 0-360 instead of the slightly
lighter 0-320. So the CG issue is fairly important.
Thanks for the front end housing mounting idea -- that might work. Perhaps
I also could use a longer 1/4" angle (4x3") turned around so the horizontal
part was facing aft, yet was low enough to clear the front housing? This
option might place the mounting plane too low on the wing cutout, however.
I'll check it out.
If none of these options are working, is a flat plate on the 12A front
cover with bolted-on, rear-facing angles a viable possibility at all? I
realize that the 1/2" plate is overly heavy, but are there other reasons
this won't work? This option would handle the CG issue and allow the
composite mounts to be placed in an ideal spot because the location of the
angles would not be fixed. It this might work, and 1/2" is overkill, would
a 1/4" or 3/8" x 3" flat plate be more appropriate instead? I will
certainly static load whatever I end up with.
Thanks again,
Scott Gettings
