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Bensen rotor blade fasteners

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  • Bensen rotor blade fasteners

    The Bensen manual specifies MS20002-6 washers ONLY for hub bar to blade fasteners, can anyone provide a supplier or acceptable substitute?

  • #2
    One source
    http://www.aircraftspruce.com/catalo...lickkey=112073
    PRA member 41204
    PRA Chapter 16

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    • #3
      I'll be damned. Never noticed that language in the instructions for my Bensen blades.

      It makes sense, though. The holes in the pitch blocks for the 8 horizontal bolts are oversize, to allow you to swivel the blocks to adjust pitch. The washers therefore are bridging over air. We don't want them to cave in under the couple tons of centrifugal force caused by the blades' rotation.

      My (1973-ish) Bensen blades have steel plates that bridge over the oversize holes, and the washers then bear on those plates, not directly over the holes. The plates that go under the HEADS of the bolts (inboard) even are thicker than those under the NUTS (outboard). These plates may make the hardened washers unnecessary, but I don't know that for sure.

      The MS washer spec calls for steel, heat-treated to 125,000 PSI instead of the regular mild steel (62,000 PSI) used in AN 960 washers. It should be possible to locate some 125,000 PSI steel washers on the 'Net.

      Worst case, there are heat-treating shops around that can bring up the strength of AN 960's to 125,000 PSI (destroying the plating in the process, though). I use to have steel axles for the Gyrobee heat-treated at a nearby shop that did work for the local Vermont granite-cutting industry. It wasn't very expensive.

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      • #4
        Aircraft Spruce part number 05-14015

        http://www.aircraftspruce.com/catalo...clickkey=37605
        PRA member 41204
        PRA Chapter 16

        Comment


        • #5
          Aircraft Spruce part number 05-14015
          PRA member 41204
          PRA Chapter 16

          Comment


          • #6
            That's the info I needed! Thanks guys, be back in the air soon

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            • #7
              My Bensen blades do not have the plates but my plan says that they are required. Does anyone know wherte I can get them?

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              • #8
                I would be interested in the plates too. Aircraft Spruce showed only 1 washer in stock at over $5 ea. , I found these at Spencer Aircraft for $ .27 : http://spenceraircraft.com/hardware/...um-plated.html

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                • #9
                  I ordered AN washers but now I am having second thoughts. I also replaced 4 of the tension bolts with an AN conversion from the original BA bolt. I think that I will do a little more research on British Airforce bolts compared to US Army Navy bolts.

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                  • #10
                    I mean Airforce Navy bolts

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                    • #11
                      I have read a lot of material on bolts. I found that BA stands for British associates and that these fasteners were used on early autos for starters distributers etc. I think that when it comes to bolts I am going to go with the AN.

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                      • #12
                        It might be that "BA" stands for Bensen Aircraft.
                        PRA member 41204
                        PRA Chapter 16

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                        • #13
                          So I tested these Bensen/Brock blades today, after I got them tracking together I had to spin them up to 360 rrpm before I lifted off. Its a 22'disc, my 23' DWs would lift off at 290

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