I'm about to make an argument for stops at the surface only. I think I've
got a good argument here.
I've had wire cables fail two ways for me. One way, is where the
crimp/soldered end/etc tears off the end of the cable. I think I've had
that happen three or four times over my lifetime. The other failure I've
had is midpoint wire breakages.
As we all know, wire rope doesn't stretch beyond taking it's initial set.
Three times I've had wires start stretching on me. Two were brake cables,
and the third was a throttle cable. In all three situations I was able to
stop the bike, and control the bike, in spite of the control cable
lengthening due to available over travel in the control. eg: brake levers
that had more travel before they hit the bar, and a throttle tube that
could turn another 1/4 turn beyond full throttle.
If there were stops built into the brake lever, or throttle tube, instead
of stops on the calipers and carburetors, I'd have been left with no
brakes, or stranded on the highway.
This is the same reason the throttle spring on your carburetor is at the
carb, instead of the control cable. If the control fails, the system is
safe without it. If your rudder doesn't have stops at the control surface,
if something happens to the control wire, you could end up with rudder
interference with the elevator, or other damage.
Okey, so lets try something else. Lets say your fairlead fails, or a cable
hops off a guide bearing, and your control wire now has 3" more length in
it. If you have your stops at the control, you now have sufficient slop in
your system that you have no control over those surfaces. If you don't
have stops, there's some chance that by going to the extremes of your
control range that you could still have some authority on which way those
surfaces go.
That's my argument for not having stops at the control itself.
... I didn't actually have a serious opinion on this until I thought about
it last night. Definitely stops at the surface. Not at the control.
On Tue, Jun 9, 2015 at 8:12 AM, Flesner via KRnet
wrote:
>
>
>> "Hey Guys, Looks like I'll be doing Rudder stops as an afterthought.
>> What's the best place and method for this ?"
>>
>
> +
>
> When it comes to stress loads on the control systems in my KR, I'm
> convinced the greatest source would be if the control surfaces are stopped
> and the input end is capable of additional input, especially the rudder
> system. My rudder pedals are spring loaded to the firewall to center /
> tension the cables. My rudder does no flop back and forth on the ground as
> a Cessna or RV would do as their cables go slack without the pilot's feet
> on the rudder pedals. If the wind is moving the ailerons or elevator on
> the ground, it seldom does, I can lock them with the seat belt to the
> stick. There is no way to eliminate air loads on the system in flight but
> they are very light and have nothing to do with system stops as the
> surfaces only move a few degrees in normal flight mode. I can't imagine a
> flight condition where the air loads on the surfaces will overpower pilot
> input and the surface would contact a stop at the control surface. The
> only time control stops are an issue is at maximum deflection which is
> seldom. Where are the system loads originating from at that point, the
> control surface or the input end?
>
> Consider your system setup and put the stops where you think best. I'm
> convinced the pilot is capable of stressing the system more than any flight
> loads so my stops are on the input end. As always, your results may vary.
> :-)
>
> Larry Flesner
>
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