Cessna 120-140 Association

I have a C140A and found a crack in the tail wheel mount during annual. I have the new mount clecoed in place, …and then went to Oshkosh. I looked at as many 140 tail wheel mount installations as I could find. I saw two that used #8 machine screws; another used #10 bolts instead of rivets. I asked my AI about using bolts vs rivets as I do need to go oversize in several holes, and installation would be easier. He suggested asking the Club membership if there was any paper trail out there to justify the use of bolts vs rivets for this installation. Has anyone used screws/bolts when installing a tail wheel mount, and if so what if any paperwork was done?
Thx
Bill

Bill, do you have the new (steel) mount from Lowe Aviation? If so, David will likely have best method info. for installation. No doubt there'll be other answers here but -- as you've indicated -- I've seen both screws and rivets used. The parts manual doesn't appear (to me) to specify, but the drawing suggests rivets. Again, I'm confident that there'll be more dependable experience/expertise sharing to come -- stay tuned. sorry I can't offer more. FWIW, here's a link to an install video: https://youtu.be/KfaV18KGQwU Mac

The factory used rivets. Rivets have the advantage of giving you a zero clearance fit. I've seen people use bolts, but I've never seen any justification. Personally, I'd avoid it if at all possible.

Thank-you for the replies. I bought the aluminum bracket from Univair, didn't know about the steel unit.
Thanks,
Bill

8218 wrote: ↑Thu Aug 22, 2019 10:18 am Thank-you for the replies. I bought the aluminum bracket from Univair, didn't know about the steel unit.
Thanks,
Bill

That'll work well -- Cessna engineered & made it well. Univair's is the same. While I haven't talked to David about his, I understand that he has an approved "repair" that basically "converts" your damaged bracket to steel. In any event, if at all possible, it sure seems best (and, "legal") to heed John's advice on using rivets vs. bolts for mounting. Keep us posted. Mac

At a past convention that I was fortunate to attend, David talked about seeing several airplanes at the convention that had bolts installed in the subject part instead of rivets. David definitely pointed out during the maintenance forum that he was against utilizing bolts and stressed that the part in discussion should be riveted as my fellow moderator John, and good friend Mac have pointed out. I think I would opt for using rivets. John makes a good point that rivets are designed to provide zero clearance in the drilled holes. Steel AN bolts don't compress and expand in a hole as a rivet does. Just my 2 cents.

I believe that Lorraine also once answered that question in a older thread, and that it was not approved to put bolts, only rivets are accepted.

I’m curious on where the bolt substitution came from. Is there something that was misinterpreted to allow the substitution, or rather lack of factory guidance specifying only rivets are approved?

It seems widespread enough that it isn’t the work of just one rogue mechanic.

Bill, there is no steel replacement bracket there all alum. David Lowe will "Refurbish" yours and use your existing "steel" tabs or mounting parts theirs 2 of them. Would highly recommend rivets not bolting as mentioned for the tightest and zero Torrance. Its not a bad job helps to have 2 people on some of those rear rivets. Good time to replace all mounting hardware (including rubber mounts at tail wheel) lube cable wheels and service trim jack screw.

8451 wrote: ↑Fri Aug 23, 2019 9:21 am I’m curious on where the bolt substitution came from. Is there something that was misinterpreted to allow the substitution, or rather lack of factory guidance specifying only rivets are approved?

It seems widespread enough that it isn’t the work of just one rogue mechanic.

I suspect it's rooted in laziness. There really isn't any guidance to misinterpret. I doubt you'll find any thing published that says either "bolts may be substituted" or "only rivets are approved".

So, does that make it the work of many rogue mechanics?