Servo Bracket Material Questions

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farmrjohn

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Apr 29, 2020
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Which alloy and thickness would be appropriate for creating an aileron servo mounting bracket (Trio Gold Standard Servo Servo )?
 

wsimpso1

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You did not even tell us what the base airplane is made of. Then the shape and dimensions of the bracket matter a bunch too. If this thing is only a inch off the fuselage floor, that is one thing, if it has to be attached to something 18" away, that is quite different. All that stuff matters a lot as to making the servo stay put, not rip out of the base airplane, etc. To design a decent part, you will have to figure out how it is to be mounted, what the loads are, etc. And if you are not qualified to design such a part, whoever you hand it off to will be asking these questions too.

We usually build the rest of sheet metal airplanes out of 2024 or 6061, that might be a good place to start.

As to thickness, you are designing an airplane part. It has to support the mass of the item at the g limits of the airplane and with max servo holding force, all with FOS of 1.5. You can start doing the engineering or hope that somebody comes along and gives you a design. I don't have the background to just look at it and tell you what stock and how many rivets of what size will work, and guessing is bad.

Billski
 

Jay Kempf

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What a completely incomplete question. What is the nearest structure where you intend to mount it? What is the span between the mountings? What direction is it mounted? If in between a couple ribs you might need to pan the edges of the sheet metal for stiffness and then a bunch of fabrication details so you don't introduce cracks at the bends. Fasteners, aero loads, pushrod length, load in the pushrod (gearing), etc... are all considerations of deflection of the bracket that needs to be designed. Or you can just prototype something and load up the surface and test. Won't be the lightest unless you isolate the loads and do the optimization. How thick? As thin as you can get away with and not deflect permanently under the highest load applied...
 

farmrjohn

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Aluminum. Location will be existing tray riveted between two fuselage frame bulkheads that formerly housed an elt. Main purpose of the bracket would be to change the servo arm orientation from vertical to horizontal.
 

Geraldc

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The servo website has mounting information for RV's so start there.
 

Jay Kempf

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Sheet metal is best used as shear webs. Bending flanges strengthens an edge and gives and opportunity for attachment. So if you are taking a flat bolted attachment and standing it up best to fold the thin metal to make triangular brackets on the ends of the plate and to flange around for stiffness. Thickness depends on load applied and controlling how much deflection results.

You can calculate like crazy or you can create a test for the load in the pushrod and apply to your new bracket to assess deflection. Create a bench mockup and test your design until you are comfortable that you have enough stiffness.

Much more complete question, thank you.
 

farmrjohn

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Apr 29, 2020
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The servo website has mounting information for RV's so start there.
Thanks. I've reviewed their RV mounting instructions as well as looked at Dynon, GRT, and Garmin. They don't have information on type or thickness. I am thinking more along the lines of the GRT or Dynon mount to change the servo's orientation.servo1.jpg servo2.jpg
 
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