ELECTRIC FLIGHT U.K. - British Electric Flight Association

large diameter meant severe butchery of the front of the cowl to clear it.
I have two other models this size with Model Motors AXi 4120/14 motors, which
are inexpensive and give a superb performance. I decided to buy another one, and
this time take advantage of the radial mounting option made possible by the third
bearing fitted to the latest versions of the motors. Puffin Models were able to
supply the motor and adaptor kit.
The radial mounting kit (see photo) contains a cruciform mounting spider, together
with a threaded propeller adaptor which screws onto the "back" end of the motor.
In addition to the necessary screws, a large collet is supplied, which fits over the
normal shaft. At first, I was puzzled by this, then the penny dropped.
Used normally, the shaft is retained in the stator housing by a small, thin circlip.
Propeller thrust tends to pull the shaft out of the motor, unloading the circlip.
However, used with the radial mount, this little circlip would have to take all the
propeller thrust, and might not be "man" enough for the job. The collet is attached
by a thread-locked grub-screw hard up against the circlip to back it up solidly
against thrust loads.
The mounting spider and propeller adaptors were then attached using thread-lock
on the screws, and the motor was ready to mount.
All the models I have seen so far with the radial-mounted AXi motors have a
spacer box built-up to stand the motor the correct distance off the firewall. Peter
Nicholson's big Corsair is a case in point. My original intention was to do this too,
but I came up with a simple and more adjustable idea.
Rather than have four screws to attach the motor to the box, then four more to fix
the box to the firewall, I decided to mount the motor on four lengths of 2BA studding
(see photo). "Penny" washers spread the load into the rather soft ply "firewall",
and pairs of nuts are locked up tight at each end to attach the studding to that and
the motor.
I had to drill out the end holes
in the motor spider to clear
the studding, but that was
the only complication, and I
had the motor mounted in
about half an hour.
I was easily able to adjust the
motor thrust line to give
sidethrust and a little
upthrust as well - this is a
low-wing model after all.
The weight of the mounting
The AXi motor on the radial mount
arrangement was probably
32 E.F.-U.K.