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Ed de Chazal wrote:
The problem of a bent cylinder rod as Scott reports may or may not have
anything
to do with bottoming out the cylinder internally. What would bend that (very
strong) rod? How would the forces be applied to accomplish this?
After reading the several replies to my original question and having spent
several hours a few days ago getting the main gear cylinders setup, I think
I can shed a little light on the situation.
If you look at how the system performs in each direction it becomes pretty
obvious that if you don't allow the cylinder to bottom out on the down
stroke, when the o/c links stop the gear from any additional outboard
motion, something is going to have to give. I see 3 possible scenarios if
there's still piston travel left when the downlocks snap into place. First
possibility, nothing happens... the hydraulic pressure will just force the
o/c links into a more tightly locked position and the system will become
static at that point. Second possibility, the actuator attachment arms on
the o/c link fail allowing the cylinder to reach the end of its travel...
highly unlikely considering the geometry and materials being used, although
I suppose the attachment fittings could fail over time if the bolt holes
became elongated and the assembly started to move with every cycle. Third
possibility, the gear locks down, the o/c links stop their motion and the
actuating rod flexes to allow the piston to bottom out in the cylinder.
Also highly unlikely, given the current thickness of the piston rod, but
the most likely eventuality of the three. The obvious solution to
precluding any of the former things from happening is to have the actuator
reach the end of its travel at the same time the o/c links snap into place.
I personally don't see a way to bend the piston rod in the retraction
phase, as when the gear-up pressure is applied to the actuator that piston
rod is in tension, and there's no force that could be applied to it by the
actuator that would impose a bending moment on it anywhere through its
travel. Needless to say (but I'll say it anyway) there needs to be a means
to stop the inward stroke to keep the wheel from pressing itself through
the upper wing skin. Naturally, if you can adjust the inboard mounting
position to a location where the final location of the gear coincides with
the bottoming of the piston in the cylinder you've solved the problem and
everything is hunky-dorey. Prudence would recommend, however, that you
provide some means for adjusting the upstroke to allow for expansion of the
tire with altitude, or to be able to fine tune the upstroke should you
change tires and need to make allowances for a different tire width. The
stop sleeve which is supplied with the LC20 kit is the obvious answer. I
will likely have to have longer sleeves fabricated as I want to be able to
have stop nuts at both the rod end and behind the sleeve. Until I'm ready
for final assembly, however, and I make that last adjustment of the up
travel, I'll be using a pair of washers between the stop sleeve and the end
of the actuator... a dab of super glue will keep them temporarily attached
to the sleeve until I arrive at its final required length. My plan is to
have the stop sleeve, its locknut, whatever spacer is required, the locknut
against the rod end, and the rod end itself all in intimate contact so
there's no possibility of anything moving after everything is adjusted. I
may even just fabricate a single locknut which is the exact length required
to create that solid piece between the sop sleeve and the rod end. Time
will tell.
Sorry for the long-winded dissertation, but I felt that additional
clarification of this matter was called for. Thanks to everyone who
responded to my original question, you laid out the road map to my
understanding of exactly how all that hardware in the gear well relates.
<Marv>
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