>The 1/4" holes in the bottom of the stick have no effect on the
>strength of the stick, as it is at the position of the holes
>socketed in to the lower fitting (CS01), which is of much greater
>diameter and with much greater wall thickness.
>
>The steel stick is stronger than the alloy stick. In particular, the
>cranked and welded alloy sticks have virtually no strength, because
>welding removes most of the strength of the 2024 heat-treated alloy
>from which the stick is made.
>
>The greatest forces on the stick will be in the for-aft direction
>e.g either in the situation of a jammed elevator control and
>feet-on-panel to get a decent 'pull', or as a matter of design
>requirement (i.e CS-VLA). That means that any hole in the stick
>should be drilled on the neutral axis in this situation (i.e. on the
>side of the stick) and as far above the point at which the stick
>enters CS01 as is possible.
>
>As regards the size of hole, you could calculate that from the
>proportion of material removed from the, say, a quarter of the
>circumference of the tube. So if you remove half of the
>quarter-of-circumference, then the hole would need to be half way up
>the stick, for no significant effect on strength of the stick. Or
>calculate from CS-VLA what strength you actually need and how much
>material you can remove!
>
>Anyway, why must you insist on a full grommet, when careful
>attention to radiusing of the hole and some extra heatshrink on the
>wires at that point should suffice.
Duncan - thanks for that very full explanation.
My original intention to fit a grommet was simply good electronic
engineering practice. As I said in a reply to Peter Rees, if the hole
edges can be radiused and smoothed, then securing of the wire against
movement both inside and outside would be as good and perhaps even
more satisfactory than a grommet - I just hadn't thought of doing
that!
One thing that might be difficult is ensuring that the inside edge of
the hole is free of sharp edges, particularly if it has to be distant
---From the ends of the stick.
As to the position of the hole, it's beginning to sound as though
it's hardly worth considering drilling the CS16, and that a hole
through the CS01 would be safer. From your opening para, I assume
there would be less concern about adding weakness by drilling CS01 -
is that correct?
I'm copying this reply back to the list as Duncan's reply came only
to me (instead of to the list), and I think the points he raises are
worth publicising.
regards
Rowland
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