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JUAN RIVERA HELICYCLE BUILDER LOG #2
TAIL ROTOR SCISSORS
www.Helicycles.Org May 23, 2014 Page 1
Well, there goes my baby, N750G, to its new home is San Diego. I immediately purchaed another kit so
I’ll have something to do. As with the first one, I’ll be jumping around and not necessarily following the
order of the video’s. That’s because some components are not here yet, and any work done is progress,
so the main thing is to stay busy. Most of the time it pays to proceed in the order suggested, but many
of the smaller subassemblies can be done in any order. With this kit I plan to use all the lessons learned
from building the first kit, and incorporate a number of modifications and enhancements that were not
practical to retrofit to my first Helicycle. Here’s a list:
Bigger skids because they look cool and I think the ship will look more substantial
Instrumentation I customized with UMA where I am now a dealer – Most indicators now have
alarm settins that are available on the rear connector as well as colored silk screened arcs that
are tailored to the Helicycle. All the alarms go to the Annunciator circuit (see below.)
A two-probe fuel quantity totalizer so the indicator reads accurately
A main rotor torque telemetry system
A master warning annunciator system that will monitor 16 paramters automatically
A bigger windsheld for greatly improved visibility
Nav/Position/Strobe LED lighting, LED landing lights, and instrument lighting
My 55-Amp alternator modification to power all the goodies metioned above
JUAN RIVERA HELICYCLE BUILDER LOG #2
TAIL ROTOR SCISSORS
www.Helicycles.Org May 23, 2014 Page 2
All projects have to start somewhere and I decided to machine my tail rotor scissors. I always try to do
the best job I know how, and not rush. As a result it took me two days to fabricate these two pieces.
I created an AutoCAD drawing from the factory sketch. The top view is rotated so that the horizontal
axis is the bottom edge of the part instead of the center line of the bolt holes. This saved me the effort
of milling one long side. That meant that each bolt was at a slightly different elevation, but with a mill
this is not a problem.
The factory sketch calls for a 3⁰ offset in the axis of the slotted hole at the top of the drawings. After
reaming the bottom end of the hole (labeled ‘Pivot Point’ in the bottom drawing) I can achieve that 3
degree axis offset by rotating the pieces around that hole until the far right edge moved 0.419 inches
down. This is one of the great strengths of a CAD program – you can figure these sorts of things out. So
I simply made a stop that distance away, loosened the clamps, rotated the parts till the end touched the
stop, and then clamped them in the new position. At that point I could move my mill table up the
vertical axis 0.250 and ream the upper end of the slot. Then it was a simple matter to clean up the area
in the middle and I was done with that slot.
JUAN RIVERA HELICYCLE BUILDER LOG #2
TAIL ROTOR SCISSORS
www.Helicycles.Org May 23, 2014 Page 3
I wish I had a metal-cutting band saw, but I
don’t, so I either have to get out my hack
saw or mill straight cuts by making many
multiple passes until I get through the
material, and then slowly closing in on the
edge. In this picture you can see the
scribe line I made and my progress as I
sneak up to it. I align the material by eye
using an edge finder. Once I get where I’m
going I can clean up the edge with my
deburring wheel and/or a file.
I drilled and reamed the three bolt holes first and then pinned the two pieces together with AN-3 bolts.
This insured that the two pieces will be identical.
JUAN RIVERA HELICYCLE BUILDER LOG #2
TAIL ROTOR SCISSORS
www.Helicycles.Org May 23, 2014 Page 4
In this picture I’ve reamed the bottom end of the 3/8” slot (left arrow) and I’m going to reposition the
material to align the vertical axis of my parts 3 degrees off axis (per the factory drawing) by rotating the
material around the reamer until the right hand edge has moved 0.419” and contacted the block I have
positioned for the purpose (right arrows.)
I reamed that big ¾” hole as I got into that area and it will serve as the inner radius on the arms once I
remove the excess material.
JUAN RIVERA HELICYCLE BUILDER LOG #2
TAIL ROTOR SCISSORS
www.Helicycles.Org May 23, 2014 Page 5
Once all the parts were cut
to shape the next step was
to round the ends. I wanted
to make an accurate radius
and insure that the holes
were in the center.
I clamped a bolt into my mill
vice and offset the two
pieces with a stack of
washers. Then I fired up the
mill with this burr installed
and manually swept the
work from side to side while
slowly moving closer to the
burr until I had the radius I
wanted. Then I touched up
the edges on my deburring
wheel.
JUAN RIVERA HELICYCLE BUILDER LOG #2
TAIL ROTOR SCISSORS
www.Helicycles.Org May 23, 2014 Page 6
Here you can see the 3
degree offset slot and the
finished end.
Here are the two finished
pieces ready for bending. I
have no good way to bend
them other than clamping
them in a vice and giving
them a thump with a
mallet. I’ve got way too
much time invested in
these to mess this up so I’ll
hold off for a while until I
think of a better way.
JUAN RIVERA HELICYCLE BUILDER LOG #2
TAIL ROTOR SCISSORS
www.Helicycles.Org May 23, 2014 Page 7
All modern digital printers are extremely accurate dimensionally. Here you can see that the center
marks for the holes in the drawing line up exactly with the actual part. I take advantage of that often
and cut out parts in paper to fit check them prior to actually fabricating the part.
If you’re wondering why the dimensions don’t match the factory drawing it’s because I rotated the part
to make the bottom match the mill’s horizontal axis instead of the holes. In this orientation the middle
hole is 0.050 higher than the right hand hole and the left hole is 0.075 higher than the middle hole.
JUAN RIVERA HELICYCLE BUILDER LOG #2
TAIL ROTOR SCISSORS
www.Helicycles.Org May 23, 2014 Page 8
I don’t have a break so I have
to do my bending using my
mill vise the old fashion way.
I stuck a thin piece of
aluminum sheet at the bend
axis to help radius the bend
and then bent the part by
thumping it with a leather-
covered piece of wood and a
mallet.
I can check progress with this
really useful digital
protractor that I picked up
used on eBay. It reads out in
tenths of a degree.
JUAN RIVERA HELICYCLE BUILDER LOG #2
TAIL ROTOR SCISSORS
www.Helicycles.Org May 23, 2014 Page 9
I checked my work with this protractor and worked cautiously to avoid overshooting.
JUAN RIVERA HELICYCLE BUILDER LOG #2
TAIL ROTOR SCISSORS
www.Helicycles.Org May 23, 2014 Page 10
After making the first
bends I stopped to
examine my work. So
far, so good…
The next step worried
me because the exact
point where I clamped
the pieces in the vise
would determine if I
came out where I
needed to be, and
trying to determine
how the thickness of
the material would
affect the outcome
was something that I
wasn’t comfortable
with. I had to trust the
CAD dimensions I
came up with and
press on.
JUAN RIVERA HELICYCLE BUILDER LOG #2
TAIL ROTOR SCISSORS
www.Helicycles.Org May 23, 2014 Page 11
After clamping the
pieces on the vice
at the location
determined in my
drawing all I could
do was to make
the second bend
equal to the first
so that the end
was vertical and
hope I had the
correct offset.
You see my wood
scrap and the
leather glove I
used to protect
the metal from
dents. The digital
protractor says
this one is as good
as I can make it. I
hope this works…
JUAN RIVERA HELICYCLE BUILDER LOG #2
TAIL ROTOR SCISSORS
www.Helicycles.Org May 23, 2014 Page 12
The bends all worked out very well. I may need
to tweak them just a bit to account for the
washers later.
But I’ve run into a slight problem - the Slider
Assembly has two flats machined where the
scissors mate up, but they’re too small.
I’m either missing something here, or those flats
are too small. I also seem to be missing the
bushings that should fit inside the slotted holes
to account for the difference in the outside
dimension of the AN4 bolts (0.250) and the
inside dimension of the slots (0.375) so I’ll have
to stop and wait for some clarification.
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