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Konny Gearcase

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  • Konny Gearcase

    8 heats of racing and minimal test time. What would cause this and is it repairable. Sheared a 1/4" aircraft pin the 1st time it was used and used 5mm pins after, with no problem. Any help would be greatly appreciated. Thank you

  • #2
    How did the hole get big enough to accept a .25" shear pin? Or are they manufactured that way now?


    • #3
      Your shaft is hardened. That makes it strong. It should be harder on the exterior than the core. That makes it tuff. I prefer shafts that have the end drawn back, or have had the hardness releived in the last inch or so. That lessens the possibility of the fracture that your shaft experienced. If you were using a bushing in your prop, that could have displaced the shear area away from the shaft, and caused the pin to bend slightly. That would allow the pin to overcome the champfered area. In my opnion, your shaft is too far compromised to be reliable in the future. The chipped out area is a stress riser, and will probably continue to crack until the shaft fails completely. I would suggest that when you replace the shaft, you carefullu polish the shear pin champfer area to prevent any future. stress riser failures. R.T.


      • #4
        Thank you doc. Looks like it will get torn down. I did have a prop shim and I mistyped the original pin size. I believe it was 3/16