One cable can go slack in the Europa. Operationally is could be that this
will never happen with feet on the pedals, but if you are of the "can happen,
will happen" school then read on. The consequence of a slack cable have been
seen on the ground by more than one builder when ground testing the gear, and
the consequences in the air would be serious. I have already had an instance
of tufnol guide block breakage this way. The springs intended to take up the
slack would need to be much stronger to remove the slack, as they need to
overcome friction in the plain bearing of the pedals and rubbing of the cable
on retaining guides and/or tubes if fitted, the latter being one way of
ensuring that the cable cannot in fact snag on the gear. However they
themselves contribute to the difficulty taking up the slack as there must
always be exposed cable near the crank.
The problem could not arise if the cable were a continuous U from tail to
front and back again, but this is not possible with the engine sitting
between the cranks. Several solutions are possible of varying complexity.
1) Lock a pair of gears on the pedal link tubes centrally where they cross
betweeb the firewalls. Tidy but difficult to fit retrospecively unless you
cut one into two halves and make a suitable bolt-through attachment.
2) Fit cranks on these tubes, one up one down and link across. Unfortunately
not enough
space to link directly betwen the shafts, so the coupling has to be a U
shape.
3) Cable-link the uprights of one pedal set, round pulleys and across the
fore end of the footwell
Finally, be revolutionary in the spirit of the monowheel and throw out all
the footpedal mechanism entirely. Make the cable system a "closed U",
returning it across the tunnel round pulleys at the side of the tunnel, just
behind the wheel. Fit a pivoting operating lever through a transverse slot
in the tunnel top. Hand operation is probably quite adequate for anything but
aerobatics, or you could fit a servo assist Might need a side throttle if
you like to keep a hand on the thottle while taxying.
Well, who's going to be first ?
Graham C.
|