6643 wrote: ↑Mon Jun 05, 2023 1:59 pm
wingspinner wrote: ↑Sun Jun 04, 2023 12:04 am it’s not clear why there would be more shear stress on the bolt since it’s only supported at one end anyhow.
Just to (try to) clarify:
The rubber bushing doesn't concentrate the shearing force at the ends of the bushing. Also, there isn't "more stress" with the AN5 bolt over the AN6, just less bolt to take that stress. Since there have been reports of sheared AN5 bolts I'm saying, to others who may be reading this, that switching to the steel bushing should be restricted to the AN6 bolt only.
Ok, understand. You are just being thorough.Good on ya!
I would tend to agree with your interpretation of shearing action except the bolt is only secured to the airframe at the top end of the bolt indicating that ALL stressors, shear or otherwise, are always focused on that point. Not a good design in my opinion and obviously Cessna thought it needed some improvements so they improved it slightly on the 140A with a larger bolt and steel bushing, also a slight improvement for the 170A which is nearly identical to the 140A except for a more hefty bottom retainer, and significantly on the L19 by larger bolt, steel bushing and also by bolting the bottom retainer to the airframe so the main bolt is supported at both ends . Anyhow, the 140 is a small, relatively light airplane and the tailwheel attach has been "good enough" for a lot of years so little to be concerned about in my mind.
Regarding putting a steel bushing on a 140 with an AN5 bolt. My earlier reaction to that was simply because I didn't recall discussing that at all and since there is no AN5 version of the correct bushing from Cessna nor the PMA version from Univair anyway, it didn't occur to me as an option so it kind of hit me a coming from "left field". I apologize if my writing came across with any sort of attitude attached - wasn't my intent - but you know how emails and forum posts can "sound" like as if having attitude sometimes even though unintentionally. The point is rather moot though unless someone chooses to fabricate a bushing themselves and install it without any sort of approval in order to log test pilot time.
Anyhow, thanks for your notes. I've put this issue to bed as my focus right now is verifying the correct gas caps, making sure the 4-way fuel valve is working correctly, and installing a 50 amp alternator to replace my woefully inadequate 12 amp generator! Best regards - Ron
