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TO - Replace
the boom on a Belt CP
pilots who are just learning too fly have the problem of the boom
getting bent in a crash, and have no idea how to replace it. So
here is the easiest way to do it. These instructions are aimed at
the plastic tail, but will work equally well for CNC tails
1 - Remove
the two screws that hold the vertical fin (king pin) to the tail
2 - Remove
the three small screws at the very back end of the tail drive
3 - Remove
the screw(s) that hold the silver tensioner pulley into the tail casing.
4 - Unclip
the plastic link on the tail control rod from the control ball on the
tail control rod.
Carefully pull the left hand side of the tail casing away from the right
Carefully pull the right hand side away from the boom, and then release
the toothed belt from the drive gear.
7 - On the
inside end of the main drive shaft in the assembly you have just removed
from the right hand side there is a small plastic belt holder that can
and will slide of the shaft, so remove it now before it gets lost by
sliding it of the shaft. - NOTE the way it
goes on, with the flange in towards the gear itself.
8 - Put all
those parts to one side carefully.
9 - Undo the
two screws the hold the horizontal tail stabilizer and remove it from
the top of the boom.
10 - Remove
the two screws on the side of the bracket that held the horizontal
stabilizer, and slide that bracket of the back end of the boom (or wait
till you can do so from the front of the boom if the bend is behind it.)
11 - Unclip
the tail control rod from the small clamp it slips into halfway along
the boom. then disconnect it carefully from the servo and lay it to one
side. Loosen, but DO NOT REMOVE the screws that hold the servo
mount to the boom (not the servo to the mount screws) so that it can be
slipped off the front of the boom when we are ready.
12 - Pull
the small plastic strip that tightens that bracket on the boom, and then
slide it off the boom if possible
13 - Move
the very back of the main frame, where the boom goes into it, and you
will see 4 screws, one in each corner, that trap the boom in place
Loosen (don't remove) all 4 of those screws.
14 - Pull
the boom backwards out of the frame. You may need to wriggle it
around a little, but don't twist it too much as there is a slot in the
boom that slides over a plastic ridge to stop it rotating. The
drive belt will also pull down and out of the boom. If the damage
is to much to let the belt pull out, use a small screwdriver or similar
to lift it off the drive pulley just behind the mainshaft, and pull the
boom off with the belt in it. You can then cut the boom as
necessary to remove the belt afterwards.
couldn't slide the brackets off before, slide them of the front
end. If the boom is bent on both sides of them, use a hacksaw to
cut it so that you can remove them more easily.
boom is now fully removed from the aircraft
new boom is basically a reversal of the above procedure, with a few
other things you need to do, such as feeding the belt into the boom
carefully so that it doesn't get twisted, and setting the belt tension.
1 - Pull the
belt through the new boom. The best way to do this is to use a bit of
old piano wire or similar. Make sure that it does NOT get twisted
as you pull it down.
2 - Pull it
out of the back of the boom only far enough to let you tape the belt to
the boom using some electrical tape or similar. This will stop it
twisting at the back.
3 - Slide
the servo mounting bracket and servo over the front of the boom,
ensuring it is refitted the correct way around.
4 - Pull all
the rest of the belt out of the front of the boom, and push it into the
hole the boom is going to push into as far as possible.
5 - Slowly
push the boom into the hole. Make sure that the slot in the new
boom is on the left hand side at 9 o'clock so that it will engage with
its guide. Push it in as far as it will go, ensuring it fits on
the guide. Lightly pinch all 4 securing bolts/screws
6 - The belt
should now be visible, so use a pair of swan nosed pliers or similar to
lift it and drop it over the tail driven gear. Make sure you don't
twist it any more.
7 - Before
we go any further, slide the control rod hanger and then the horizontal
stabilizer bracket over the boom from the back.
Then complete following steps 10 onward (in reverse)