Tail wheel Bolt

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Tail wheel Bolt

Postby MoonlightVFR » Wed Mar 15, 2017 2:06 am

I am reading in the IPC issued Sept 1, 1956. Chartreuse / Black cover imprint.

Am I correct in understanding that the tail wheel bolt can sometimes fail?

Page 155 Fig. 94- 5 Bolt AN7-20A.

My question to the forum is concerning an improved stronger bolt availability.

70 years later can we source a better stronger bolt? Aviation grade obviously.
gradyb, '54 B N2890C
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Re: Tail wheel Bolt

Postby gahorn » Mon Mar 20, 2017 7:57 am

The AN bolt specified is an aviation grade part. Yes, even aircraft parts sometimes fail. :wink:

Many have replaced that bolt with the L-19 part, an eyebolt, PN-062105, which accommodates a tie down rope.
'53 B-model N146YS SN:25713
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Re: Tail wheel Bolt

Postby Bruce Fenstermacher » Mon Mar 20, 2017 11:33 am

Answer #1, yes the bolts fail.

Answer #2, no there is nothing stronger readily available and legal to install.

The L-19 Cessna part George mentioned is a modified AN7 bolt. Presumably, it has at least the same strength as an unmodified AN7. I wouldn't think it is stronger than a standard AN7.
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Re: Tail wheel Bolt

Postby gahorn » Tue Mar 21, 2017 5:20 am

I suppose one might find a NAS bolt with higher tensile strength than the average AN bolt (typically 160,000 psi vs 125,000), but tensile failure is not the typical failure mode. Usually the failure is due to a stress riser created in shear due to marking of the bolt. The best answer is to inspect and replace on a regular basis, especially if you find the bolt is marked or scratched by the assembly.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight.
An originality nut (mostly) for the right reasons. ;)
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Re: Tail wheel Bolt

Postby c170b53 » Tue Mar 21, 2017 5:53 am

Crazy I guess George and I can't sleep tonight and crazy we are both replying to this question at the same time. Here's my take;
I would think that you could use a NAS bolt which would have a higher tensile/shear strength than an AN bolt. Con; the higher cost and the NAS bolt may not be as malleable as the AN bolt, which might lead to other problems if neglected.
Then again, any neglected item will come back to be a pain. If the bolts are changed when the spring is changed and the install is checked at annual, there should be no surprises. Just did mine.
Jim McIntosh
1953 C170B S/N 25656
1979 172XP. S/N R1723135
02 K1200RS
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