It looks like we have a new project !
This enormous radio control Pilatus
Turbo Porter. You might recognize
this famous aircraft from the films
James Bond
Goldeneye and Air America.
In the James Bond film, the plane is made
famous because it does a very steep,
controlled, almost vertical dive
and in Air America it's famous because
of its short field takeoff and landing
performance.
Both of these qualities will be
really useful in this type
for our project. You remember me
saying a while back
that our electric tow plane is a little
bit small for some of our bigger
glider models - well this could be the
answer !
I purchased this almost ready to fly kit
in the sales, although I don't care much
for the paint scheme.
We're going to put this together -
together, and make
some modifications as we go, including;
adding a variable pitch
constant speed propeller, modifying the
tail to make it removable for transport,
and adding a glider tow hook.
I have this motor and speed controller
left over from a previous project
and this speed controller has a governor
mode on it which is important
for this constant speed propeller
project. We will need to replace
this solid metal shaft though from the
motor with this one which is hollow
from a T-rex 500 helicopter.
Once again, my friend Mark to the
rescue with his metalwork lathe and
milling machine. From this sketch that we
arrived at,
we came up with this solution. This hub
is machined from aluminium,
and on the edges are 3mm
holes around which
a T-rex 450 blade grip will rotate
and these will hold our propeller blades.
Then, the second, smaller disc will be
fastened to a rod
which moves in and out inside the motor
shaft
and that will control the blade pitch.
Let's start by disassembling the motor
in order to replace the shaft.
I found one grub screw that was really
difficult to remove
as it been done up really tight and
secured with permanent red thread lock.
In the end I had to drill it out !
I really hope that all this effort will
be worth it, but remember
the full size is powered by a PT-6
turboprop - that's a jet engine that
turns a large variable pitch propeller -
and that's what gives the aircraft this
amazing performance.
Hopefully this large brushless motor
running at constant rpm on a governor
will sound quite realistic too.
These three bolts that I'm undoing pass
through the radial bearings
in each of the T-rex 450 blade grips.
They thread right through the hub boss
and tighten down onto the motor shaft
securing the propeller in position.
Here we have the new hollow motor
shaft installed,
ready to fit the motor into the aeroplane.
To do this I'm going to make our own
mount and I am
starting with this drawing I'm doing in
inkscape
using simple shapes.
I'm making good use of the align and
distribute tools
and also the path add and subtract
functions
to get to our final shape.
Welcome back to my workshop please
excuse the mess as
usual there's lots of jobs going on all
at once.
Here are cut parts - quite flexible in
this thin plywood -
but we're going to now laminate all four
of these parts together with slow curing
epoxy
which will make them super tough and
we will also laminate them with carbon
fiber while we're at it.
I took the trouble while I was laser
cutting these parts to cut one out of
clear acrylic as a template so we can
accurately mark
the firewall, and I'll have to carefully
position
the template so that we avoid the
stringers on the inside for the claw
nuts.
I glued together and laid all these bits
up between two
sheets of glass with weights on top
while the epoxy cures overnight.
Now let's drill some holes in the
firewall and fit some claw nuts for our
standoffs.
I'm using a bolt and washer to draw the
teeth
of the claw nuts into the back of the
firewall.
I'm making some standoffs for the
mounting plate
from this M6 steel threaded rod and some
aluminium tubing.
These standoff components are glued
together using
JB-Weld, which is a special epoxy for
gluing
metals.
We must clean out the excess from the
threads with a rag
soaked in isopropyl alcohol.
The propeller pitch servo will fit in
this bay
and it will move a bearing and collet
assembly on this rod.
With the motor and propeller assembly
all installed
I figured we could use some more access
into the motor bay,
so I've decided to take the cowl and cut
it like this
so it comes off in two bits, and in fact
I'll put a little bit of wood or
something in here for a rebate to the
top to fit against
and a further block and two screws and
perhaps two screws so it's nice and
secure.
But now we have access to the back of
that propeller boss
that the spinner can fasten to and
obviously all this has to come apart yet
and be reassembled with thread lock when
we're ready, but at least it gives us an
idea.
Finally, I've decided to make
something with a bearing in that
supports
this motor shaft back here.
This shot should clearly demonstrate why
we're choosing to make the tailplane
removable
as now we've added the motor and
cowling, it's getting quite long
although it is very light for its size.
Of course we're going to need some
propeller blades,
and so I used this diagram that I
downloaded to draw out some ideas in
google sketchup.
I don't yet know whether I will 3D print
the propeller blades directly,
or whether to 3D prints and molds to
make some carbon fiber blades.
I'm going to run some test parts off our
cr-10 Max
3d printer.
That's all we have time for in this
episode. Please like
and subscribe to support the channel.
We'll try our very best to put the
updates of this project
out every Saturday but we might just
need to intersperse the project with
some of our other videos,
just to let the build catch up. Catch you
next time.