Axle bolt sizes

[dickc]

I've got a small collection of gear legs and axles and a 140.
Looking at the parts manual, SNs and a few planes I'm finding bigger or different bolts. But it all looks factory? Is there service literature on this?

dickc

[6643]

As far as I know, all 120s and 140s came from the factory with NAS144 (1/4-28) socket head bolts. There are different lengths depending on which brakes and shims were fitted. There is a chart on page 50 of the illustrated parts catalog.

Landing gear extenders and crosswind landing gear are a whole other story.

The original nuts are an off-the-shelf high strength nut, 22FL428. As far as I know, the exact part is not available today. Years go I tracked down the manufacturer (SPS Technologies), but couldn't find an equivalent part. NAS1804-4 nuts match the strength of the original fasteners (Which have been superseded by MS20004 bolts.)

[brandon7766]

From my understanding, the 140s/120s can either have 1/4" or 5/16" bolt holes depending on when the aircraft was produced. A Neil write article titled "Landing Gear Legs and Extenders for the Cessna 120/140/140A Planes" (found under the "Landing Gear, Extenders, and Changes" archive) states that the switch from 1/4" bolts to 5/16" bolts happened around serial number 13400 (Mid 1947).

Talking with a seasoned 140 mechanic, he said that Cessna likely ran out of a cheap source of the NAS144 high strength bolts (that they were supposedly buying by the barrel after WW2) so they switched to cheaper AN 5/16" bolts.

My 1946 140 had 5/16" bolts so at some point, likely when the wheel extenders were installed, the gear leg hole was enlarged. I honestly would not be too surprised if you found 2 3/8" bolts installed if an axle was changed out and the correct axle bolt configuration could not be found.