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Spec for patrol springs

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  • Spec for patrol springs

    Does anyone have a spec or measurements or description for the flap handle button compression spring and the rudder return springs? I’m using dual pedals on my Patrol if that makes a difference (probably not). Thanks

  • #2
    Here is a thread where we talk about Rudder Springs.

    In my notes I have written down that the Flap Thumb Button Spring is from the Hardware store and is .750 DIA x 1 to 1.25” long. I do not have anything that shows the diameter of the wire that the spring is fabricated from. Make sure its diameter is large enough so that it cant migrate between the plunger that moves the taper pin and the wall of the tubing. For some reason it seems to me like a builder I know who is flying had that happen to him.

    Screen Shot 2020-10-08 at 3.47.48 PM.png
    Brooks Cone
    Southeast Michigan
    Patrol #303, Kit build


    • #3
      I have dozens of 3/4" diam springs that people in Oz / NZ / RSA etc can have for free (fit Model A four-place handle, not sure about the other types). The springs have hooks and are designed to be used in tension, but I cut the hooks off, pulled to stretch the spring out, and bent the wire ends flat so that it pushed against the plungers.

      I'm not sure how much resistance you're meant to have with the flap handle, but I just put it in and tested it with my thumb, and if it was too soft, stretched it some more. Looks like it will work!

      I'm initially thinking of using the same springs for the rudder pedal return springs, but they might be a bit soft. Very hard to find the 1" diam springs here in Australian hardware shops.

      Last edited by James; 10-09-2020, 01:03 AM.
      The Barrows Bearhawk: Who knew my wife could get jealous of a plane?


      • #4
        I measured the ID of the flap handle at .680" and the OD as .750 I used a 5/8" diameter spring, an inch long with a wire gage of .040." Hopefully that is the actual spring I used. I have an assembly manual for the fuselage flap system as well as an isometric drawing of all the hardware for the fuselage flap rigging if you are interested.


        • #5
          That info should help a lot. Most of the compression springs I have access to in that diameter are 3” long and require 1 lb of pressure. I cold cut them down of course, but that seems soft. Cut down for length and then stretch for a firmer button action maybe.


          • #6
            Found what I think is the perfect spring for the Patrol flap handle. Sold by the Hillmangroup and carried by my local store. Item #540464. 3/4” diameter, 2-3/16” long, .062” gage.


            • #7
              The timing on this thread is interesting as I had a similar opportunity at work dealing with springs. Several spring manufacturers have really slick websites that you can put in the specs of the spring (diameter, wire diameter, overall length, material) and the "tool" will allow you to pick force on the spring. The "tool" will also give you recommendations. After reading Mark Goldbergs post on Bob wanting builders to learn about made me think about the manufacturers websites. I may not be a spring engineer but I now understand how to spec one...or reverse engineer the specs on one.

              Just one of many examples: Compression Springs - WB Jones (