15
Propellers
22)
Now, propellers! Notice that these have black adhesive tape attached to some blades. The purpose of
this tape is to balance the propellers. It is very important that the propellers are well balanced, as out-
of-balance propellers will vibrate and cause unsteady flight. In extreme cases the motors or their
mountings may be damaged. Therefore, please observe the following cautions:
Do not disturb the tape on the blades.
Do not loosen the propeller from its spinner adapter. The propeller + spinner is balanced as a
unit, and will not remain balanced if disturbed.
Note that the propeller is assembled onto the spinner with the grub screw aligned 180º opposite
the “blank” blade (the other two blades have text embossed on them). If the propeller should
become loose in a crash for instance, it will usually remain quite well balanced if it is re-
tightened in this same orientation.
It is a good idea to check the aircraft for vibration before a flight, by holding it from underneath
and revving it up. Get used to the way it feels and sounds when it is running smoothly, and if it
doesn’t feel right, look for the problem.
A common cause of vibration after a crash is poor blade “tracking”. A propeller’s three blades
should all run level with each other when viewed edge-on. If one blade is bent slightly upwards
or downwards, it will cause vibration. Poor tracking is easily spotted if the propeller is gently
spun up whilst the aircraft is viewed from the side in front of a white surface (Photos 20 and 21).
Blades can get bent if knocked in a crash, but they can often be straightened again. However if
there is any sign of cracking of the plastic at the blade root then the propeller should be replaced.
DO NOT FLY UNBALANCED OR DAMAGED PROPELLERS
23)
Each propeller carries a red or yellow sticker, to indicate whether it should run
clockwise
or
anticlockwise
. Fit the propellers onto the motor shafts, in the locations indicated in Figure 1
(Note that
the positions are opposite to those on the original QuadPod!)
Ensure that each propeller is oriented so
that its grub screw (set screw) bears onto the flat area of the motor shaft (Photo 22), then tighten the
grub screw with the Allen key (hex key) provided. Take care not to over-tighten the grub screws - it is
possible to strip the aluminium threads with extreme force.
22
20
21
