Hello, and welcome back to Scale Me Down,
and to another episode all about this
Pilatus PC-6 Turbo Porter with variable
pitch propeller.
In the last episode we decided we needed
some new propeller blades with reduced
pitch,
so here we are, I've 3D printed a brand
new set of 3 in PLA+, all sleeved
and balanced, ready to go.
Just a reminder of how we got here
though, and before that, before we fit
them, remember to like and subscribe to
support the channel.
I redesigned the blades with five
degrees less pitch
and then reprinted them one at a time in
tougher PLA+.
I roughened and cut some new brass sleeves,
grinding them all to the same length
before fitting them with JB-Weld epoxy.
So, three new blades fitted - let's see if
they work !
Let's start with some taxiing.
It looks as though we've solved that
vibration problem we found in the last
episode.
Ground speed is now completely
controllable using propeller pitch in
ground mode.
These new propeller blades seem much
better -
in fact good enough to try a maiden
flight !
The propeller slipped on the shaft again,
so we stripped it down and re-tightened
everything before trying again, this time
without the upper cowling and spinner.
However, once again the propeller slipped
on the motor shaft although the
acceleration at maximum pitch was very
impressive.
We were running out of daylight really,
so after re-tightening everything, I
reduced the maximum propeller pitch to
prevent it from keep slipping - just to
see if this thing would ever fly.
I gently coaxed our plane around one
circuit, being as gentle as I could on
the pitch lever just to get an initial
idea for the trims, center of gravity, and
control throws, I've got to say the
handling and control harmony was very
nice.
My first impressions of the tail
surfaces that we scratched built in
episode 2
are that the section and incidence seem
appropriate and the plane seems quite
stable in flight.
On landing, I accidentally touched the
propeller on the ground.
That looked a lot worse than it actually
was ! I just touched the propeller just on
the ground, and the blade grip failed,
as you would expect but other than that
let's get it back to the workshop and
have a look at it.
Now we're back in the workshop, it really
isn't that bad.
Obviously, we're going to need to replace
the blade grips, and whilst we're at it
we'll strip the motor and propeller unit
down, and I'm going to ask my friend, Mark
to put a grub screw in this boss right
here and a flat on the motor shaft to
prevent the propeller from slipping on
the motor shaft.
Actually, most of the damage occurred on
the ground at the end of the landing
roll, and was caused by the vibration
when one of the blades came off.
The good thing is it didn't shake itself
to bits, however we do need to print a
new tailwheel bracket - that's no big deal
but the most disappointing bit were the
wing struts. Now come on VQ Models. As
supplied with the kit these have little
tin plate ends and the metal is very
thin and it fatigued with the vibration
and broke, so we'll put some proper ends
on these. Let's make a start on the
repairs.
But first, over to Mark's workshop to
make some modifications to the propeller
boss.
Here he is setting up his milling machine
using an edge finder so he can drill a
centered hole right across the hub.
This was then tapped for an M4 grub
screw, which when tightened against a
milled flat on the motor shaft, should
prevent the propeller boss from slipping
once and for all.
Then I could refit the motor including
the shims to ensure that all the
bearings lined up for the pitch change
rod.
And then refit the propeller hub,
tightening the set screw we just fitted.
I've reassembled and refitted some new
blade grips,
and then I had to make and refit a new
pitch change rod assembly.
All working smoothly again, so I could
refit all the cowlings.
And then refit the propeller blades.
When I removed the covering from the
damaged struts, all I had to do was drill
out this rivet to remove the ends.
I replaced the ends with bent 1/8"
aluminium, which I epoxied into position
and secured with bamboo cross dowels.
Now let's move on to the landing gear,
and let's 3D print a new tail wheel
bracket to replace the damaged one.
As before, this was reassembled with 2mm
threaded rod dowels and C.A.
glue.
I think we need to improve the clearance
between the propeller and the ground, and
to do that I've drawn and 3D printed
some new wheels.
These are more true to scale like
the tundra wheels and tires often fitted
to this type.
What we need to do now, is make some
tyres to fit them,
and hopefully the improved clearance
will prevent further prop strikes.
I started by cutting out some tyre
blanks on our laser from this scrap
packaging EVA foam.
I had to cut it in 3 low power
passes to get a good cut and avoid
melting the foam.
2 thicknesses were required, and
contact glue was used to bond the layers
together.
I used a nut and bolt to chuck the
wheels up in my drill in order to carve
the tyre profile using a Perma-Grit
block.
This revealed some of the open cell foam
structure, so to seal it back up, I
brushed on two coats of this foam armor
from Deluxe Materials.
Whilst that dries, let's press the
3/16" bearings into the hubs.
Once the foam armour was dry, I gave the
tyres two coats of this rubberized truck
bed liner paint.
UHU-POR secures the tyres to the
rims.
Here we are with our new wheels fitted,
and you can see there's much improved
ground clearance.
The wheels look super blingy and
scale-like and free-running on their
radial bearings.
Hopefully that should avoid further
prop strikes.
I am really looking forward to trying
again next time as we're nearly there,
although we're running out of time in
this episode, but if we are more
successful on the next flight, we're
going to fit some more scale features
such as these modified cargo/camera pods
and we've mounted our RunCams to these
and they mount underneath the wings in
the scale positions so we should get a
better look of the mechanism in flight.
As ever, thanks for watching. Stay tuned,
and we'll see you next time in the next
episode.