The International Cessna^® 170 Association

Good afternoon,

Upon re-installation of the chain guard, how tight should the AN4 bolt be? If torqued to AC43.13 Table 7-1 the aluminum spring shackle legs will be bent significantly. Right now it's tightened until the chain guard won't move, but not so tight as to squeeze the shackle. However, the shackle and chain guard rattle around. Any input/guidance sure would be appreciated!

Thanks so much in advance.

All my best,
Rob

It would be helpful to know what chain, guard, and shackle you are discussing.

My apologies, George!

You're so right. The tailspring shackle. Boy do I feel silly...sorry about that.
Thank you for the help.

All my best,
Rob

Rob,
As you write that the spring shackle (fig. 29-15, p/n 0542108) is aluminum I wonder if yours is an owner-produced part. The original is steel. Does yours have the locating pin? We discussed that here. Because of the similar part number for the L-19 shackle -- 0642108 -- I bought this one. (Often, but not always, an 06XXXXX on an L-19 part is identical to a 04XXXXX or 05XXXXX in the C-170B IPC). The tailwheel steering chain guard (fig. 29-16, p/n 0442125) is .020" aluminum.Regarding the torque, I'd go with a German torque -- gut en tite. Here George recommends adding a rubber hose/tubing over the bolt shank to prevent it from chaffing the lower leaf spring. On my old one there was only a 0.032” gap between the bolt and the bottom of the lower spring so it would take a very thin wall hose. If instead you used a section of 0.035” wall aluminum tubing as a bushing over the bolt shank I think it would allow a higher torque value on the bolt/nut without bending the shackle arm and, with an interference fit, prevent the shackle from rattling.

The L-19 shackle, p/n 0642108, is identical to the C-170 shackle, p/n 0542108, except that the holes are larger. They fit an AN5 bolt rather than an AN4 bolt. This is odd because the L-19 IPC calls for an AN4 bolt. With an AN5 bolt there is no clearance between the bolt shank and the bottom of the lower leaf spring.