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Force on flap & elevator pushrods.

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Tim Wescott:
Anyone got an idea of the amount of force it takes on a flap horn to make it deflect?  Or how much torque there is at the hinge line?

Based on control geometry and the fact that I can maintain control, I'm guessing that in normal flight, my Atlantis is presenting no more than 16 pounds at the bellcrank's horn -- probably less, because I can maintain reasonable control when it's overhead.

I'm thinking about a design improvement on Paul Walker-style screw-adjustable flaps, but it involves selecting just the right belville washer.  I'm wondering if anyone knows better than my vague musings.

Howard Rush:
As Gary Letsinger said, maybe quoting somebody else, "Hinge moment calculations are easy to do, but hard to believe. "  I'd like to do some experimental measurements. 

Tim Wescott:

--- Quote from: Howard Rush on September 10, 2018, 02:43:22 PM ---As Gary Letsinger said, maybe quoting somebody else, "Hinge moment calculations are easy to do, but hard to believe. "  I'd like to do some experimental measurements.

--- End quote ---

Heh.  I can believe that.  Although I do think you get a valid maximum by (over) estimating the force on the lines and calculating the maximum the surface could be resisting that from the control system geometry.

Howard Rush:
One way to measure hinge moment is to measure differential line tension at the handle and use my control geometry program to figure mechanical advantage.  I have some of those little strain-gauge luggage scales that I intend to instrument for differential line tension, but I'd welcome a better idea.

You could overestimate by using the amount it takes to break a line and subtract .5mV2/R from it.

Tim Wescott:

--- Quote from: Howard Rush on September 10, 2018, 06:45:06 PM ---You could overestimate by using the amount it takes to break a line and subtract .5mV2/R from it.

--- End quote ---

I think just assuming 2 - 4g would be safe enough.  Line-breaking tension would be upward of 10g, and I don't think my plane has ever pulled 40 pounds, even yesterday with the tank problems plus winding up in the wind.

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