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
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