Hi Paul, what info do you need, to construct a cad model of a rotary
engine mount for a tango XR? In broad terms the firewall dimensions
are 42" wide x 26 3/8" at the widest points, the thrust line is
approximately 11" below the top of the firewall. More accurate thrust
line measurement to follow soon but11" is pretty close
Also I have been chatting to Milo with the RV8 FWF for sale, there's
obviously a lot of changes to make that fit, what we thought of doing
was superimposing the rv8 mount over the tango XR mount to get an idea
of what sticks out the cowling and would have to be moved, would you be
able to help with this?
Alex
The firewall dimensions. You can take a perpendicular picture of the
firewall looking back at it and then tell me the max width. From that
I can scale the dimensions that I need.
Also i need the point on the firewall that represents the thrust line.
A
piece of tape will mark that point. This way I can do a cowl drawing to
make sure everything fits. If you have a cowl we can use that. I need
the
lenght and the size of the spinner. If no cowl I suggest using an 18"
spinner as the rotary engine is roughly round and that gives more room
in
the cowl.
Paul Lamar
Hi Paul sorry for the delay I just got back to my project today, a
perpendicular picture of the firewall as well as cowling photos are
attached. The accurate dimensions are:
Firewall:
The thrustline is 10 7/8" down (from the top centre of the firewall) and
marked by an X, also marked as the line on the top edge of the tape.
Maximum firewall width is 42 7/16"
Maximum firewall height top to bottom along the vertical line is 26
5/16"
Firewall width running through thrust line marked by X on firewall is 42
3/8"
I still need to incorporate a 1.25 degree offset from the X point, (as
is
required by the plans for the lycoming install) or can this be done with
computer modeling? I would prefer to offset the rear of the engine from
the
X mark to achieve the required 1.25 degree offset, because the cowling i
have already has the offset built into it.
Cowling:
Length 36 3/4" (as measured along the top)
Spinner diameter 14"
Spinner 1 length 14.5" (same spinner as in the photo)
(Optional spinner 2) length 19"
Additional cowl info, lower cowl circular inlet is 2.5" inner diameter,
both forward air intakes are 2.5" wide and approximately 6.75" long
I'm planning on using Tracy's 2:85 reduction so thrust line offset would
be
to the right as viewed from the cockpit and I was hoping to incorporate
an
exhaust augmenter setup to help with cooling,
I forgot to mention, my pre drilled engine mount holes on the firewall
are
both 37 15/16" apart from each other in width, and vertically 19 13/16"
apart, all measured from centre to centre. These holes are already
hardpointed to take the mount,
Alex Molteno
Good work Alex. I'll see what I can come up with.
Unless you want to put something under the fuse there will not be enough
room for a proper exhaust augmenter. If the cooling diffusers are done
right there will be no need.
Paul Lamar
Hi Paul
I hadn't firmed up my ideas entirely regarding the lower cowl setup. I
thought i might need to hang a spintech muffler underneath the cowl if
i
need to quiet the beast downwhich would negate using an augmenter.
i also wanted to go with a sub cowl design like Ed Vettermans (or
better
yet the one that was posted a couple of days ago on the newsletter) to
clean up the cooling drag for any air exiting the bottom cowl. i know
there
is a bit of reverse flow going on there because where oil pools up on
another completed tango next to mine, it doesn't streak and run
backward
in
flight like usual, so I need to do something there anyway to clean it
up.
The current firewall design makes cowling air turn through an abrupt
90degree bend on the bottom of the firewall, and after the bend no
attempt
is made at accelerating the cooling air back to free stream flow
What I liked most about the augmenter idea was that with the pumping
gains
from the exhaust I could ditch the thermostat, cooling air flow through
heat exchangers would be automatically regulated (more or less) by the
amount of power I've set. Having such a wide range of hp my aircraft
will
be flying at, also helps keep the inlets from having to be oversize or
undersize in order to be able to keep within limits.
Alex
It is not a good idea (I think) to use any commercail muffler. I am
afraid
you wil Hi Paul,
I assume you have the C of G for a generic rotary install (not sure if
this
changes much with individual installations such as heat exchanger
placement, etc) I have the old style horizontal stab which is 10 lbs
heavier than stabs on newer tango's nowadays, plus I think I could be
lighter with Milo's rotary FWF than a standard lycoming for this aircraft,
and I moved the rear bulkhead backward 3,5" aft for space to put a child
seat. Additionally, all tangos so far have a 45-60lb aero composites prop
or hartzell. This is all trending towards an aft cof g, so I want to try
and put the rotary as far forward as I can (as well as mount 2 batteries
on
the cool side of the firewall instead of behind the rear bulkhead.
On the standard lycoming install as measured off a plane next to mine in
the hangar is 33" from the firewall to the front plate of the flywheel for
the lycoming, I can go to 36.5" on the rotary then I only need a small
prop
spacer to clear the spinner against the cowl rather than a prop extension.
I could, at a stretch, sand down the back of the spinner but this will
also
reduce spinner diameter and it won't be a flush fit.
Is it possible to move the rotary further forward?
With this in mind, regarding the engine mount, is it possible to move the
front of the rotary to 36.5" from the firewall. The standard
I have forward and aft fuel tanks on the wing. If the C of G turns out to
be slightly fwd then I can keep fuel in the aft tanks to compensate, but
rather fwd than aft I think.
33" from the firewall to the front plate of the flywheel
36.5" max 39 3/4
2 7/8 inches
Alex
The standard is 37 inches + or - 2 inches from prop flange to firewall. If
the cowl is done it is best to use the stock cowl as it is a lot of work
to
make a new cowl.
I'll do a 3D shortly.
Paul Lamar
Paul
I'm happy to keep with the stock cowl if its less work for me, the spinner
backplate is 2 3/4" deep so we can probably take it from 37" anywhere up to
39" from prop flange to firewall.
The lycoming prop flange to firewall is 36.5" (including extension)
Alex
Alex, check these dimension. Use MS paint to fill in the correct dims with
red
text and send it back.
Paul Lamar
----------------------------------------------
There is plenty of room in the stock cowl.
Paul Lamar
Hi Paul, corrected dimensions are attached, i took the firewall width
through point X on the firewall as it gave me a known quantity from where
to measure the width, then i know we are measuring width at the same point,
best regards
Alex
Use the lower right mm hard point (from the pilots P of V) as a reference point.
Get one of Jeffs plates to make a MM jig.
The easiest thing is get a steel tube about three to six inches in
diameter and with a length from the firewall to the motor plate. Weld a 10" by 10"
square steel flange on both ends. Bolt it the firewall or thick particle board in the
right place and one of Jeff's motor plates on the forward end. That's it. Jig is done.
If you want down or side thrust use a protractor and shim it with washers.
I have a guy in Ventura CA that will tig weld a MM for you. I am here and can watch
over it for free. http://doritefab.com/ I have one of Jeff's plates that he can use
to make the jig.
Paul Lamar
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