Recipe for cheap lightweight swivelling eyeball vents:
Bore a hole in the front and back of a ping-pong ball (or table tennis ball
if you prefer) and redux-in a short length of close-fitting tube, flush at
the 'rear' and protruding as much as desired at the 'front' of the ball.
The holes in the ball can be snipped out with scissors, but finish with a
cone-shaped grindstone, which melts the edges slightly and prevents splits.
It the tube is centred off diametric axis, then the vent will have a greater
range of angular adjustment.
The socket depends on what you are attaching to. In my case it was a 1" pipe
(the air exit end of the NACA duct molding). So the socket was laid-up over
a male mold comprising a 1" stub of blue foam (cut with a cork borer) glued
to another ping-pong ball, which is later scrapped as the lay-up is
subsequently cut off.
The socket is axially slit into two halves. These two halves are then held
together onto the 'pipe' at the rear of the NACA duct by two O-rings; add
more or smaller O-rings if a stiffer rotation is needed.
The advantage of this arrangement is that the whole assembly will knock off
in an accident; safety is further allowed for by a ring of PVC foam bonded
to the front edge of the protruding tube; so that it doesn't core-out your
knee caps in a shunt.
The vents are turned on and off by means of the adjustable flap on the NACA
duct; however, the screw adjustment on mine only closes the NACA flap and
won't open it; a spring or similar is needed. But if both are turned off
then the cockpit windows steam up! Alternately, the vents can be turned to
deflect the blast of air up the side of the cockpit.
The blast from the 1" tube is a bit too vigorous and I am now trying a 3/4"
tube, which also allows a greater angular range of adjustment.
Duncan McF.
>
> >make your own out of a
> >ping-pong ball and a bit of the 1" tube left over from the aileron push
rod.
> >Mine weigh 12 grammes each
>
> Duncan - more info, please! Do yours swivel, and if so how did you
> make the bearing for the table-tennis ball? Do yours turn off & on,
> and if so, how?
> regards
> Rowland
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