Anyone have experience tightening or replacing the large rivets at the top of the lift strut connecting it to the bracket that bolts to the wing? I have one new strut, but the old one on my '59 continues to weep from these rivets. Makes me worried that they are working some and I think they are kinda important....

Yep, replaced a number of them several years ago. I forget where I got the rivets though, I think they were DD's.. I dumped them with a hydraulic press and shaved them. Sorry not much help!

onefitty wrote:
I forget where I got the rivets though, I think they were DD's..

WHOA THERE ! This might accidentally kill someone who does not spot this typographic error.

DD rivets are the SOFTEST of all aviation rivets, essentially 1100 series aluminum. I'm guessing you mean "AD" rivets, which are 2117 alloy if memory serves, which are the far stronger standard airframe rivet. However, I might also be wrong, the Cessna specification may call for a special alloy or special rivet other than AD (or DD). With something that is this flight-critical, you simply must check the Cessna manual and find out what they are calling for.

Further, if you have loose rivets on any of the four strut fittings, safety and sanity demand that you remove the fitting and check for cracks or worn holes in the machined fitting and the strut tube.

There are real live engineers on this forum (I'm not), and on behalf of all of us I sincerely ask that they chime in here and make any corrections to what I've said. I also believe that wearing out those huge rivets means that someone has been dangerously abusing an airframe, and that a lot of other things should be looked into. If the Cessna manual actually calls for DD rivets, then I'm scared shitless right about now.

EZFlap wrote:

onefitty wrote:
I forget where I got the rivets though, I think they were DD's..

WHOA THERE ! This might accidentally kill someone who does not spot this typographic error.

DD rivets are the SOFTEST of all aviation rivets, essentially 1100 series aluminum. I'm guessing you mean "AD" rivets, which are 2117 alloy if memory serves, which are the far stronger standard airframe rivet. However, I might also be wrong, the Cessna specification may call for a special alloy or special rivet other than AD (or DD). With something that is this flight-critical, you simply must check the Cessna manual and find out what they are calling for.

Further, if you have loose rivets on any of the four strut fittings, safety and sanity demand that you remove the fitting and check for cracks or worn holes in the machined fitting and the strut tube.

There are real live engineers on this forum (I'm not), and on behalf of all of us I sincerely ask that they chime in here and make any corrections to what I've said. I also believe that wearing out those huge rivets means that someone has been dangerously abusing an airframe, and that a lot of other things should be looked into. If the Cessna manual actually calls for DD rivets, then I'm scared shitless right about now.

Actualy, DD rivets are almost the strongest solid shank rivets available. If youre planning on a repair, do your homework with the manufacturer. Forum advice is often missleading. Good luck!

Don't have experience changing out those rivets as mine are tight but thought I would add to the discussion about rivets:

"A" rivets are the 1100 alloy and are considered "soft" at 15 ksi. "DD's" are 2024 which are 35 ksi rivets... until the 7050 "E" rivets came along the DD's were the strongest out there. "AD" Rivets are 2117 alloy which are 27 ksi.

"Soft" and "hard" can be misleading characteristics in fastener materials. AN and NAS hardware for instance is spec'd because of its elasticity, not because of its hardness. I'm not sure if that applies to rivets or not.

30 thousand foot view...

When owning and maintaining a Cessna I purchased the part and service manuals, they are on CD now. Also, AC 43.13 will help in a general way too.

I would not do anything until having approved data to log the entry.

EZFlap wrote:

onefitty wrote:
I forget where I got the rivets though, I think they were DD's..

WHOA THERE ! This might accidentally kill someone who does not spot this typographic error.

DD rivets are the SOFTEST of all aviation rivets, essentially 1100 series aluminum. I'm guessing you mean "AD" rivets, which are 2117 alloy if memory serves, which are the far stronger standard airframe rivet. However, I might also be wrong, the Cessna specification may call for a special alloy or special rivet other than AD (or DD). With something that is this flight-critical, you simply must check the Cessna manual and find out what they are calling for.

Further, if you have loose rivets on any of the four strut fittings, safety and sanity demand that you remove the fitting and check for cracks or worn holes in the machined fitting and the strut tube.

There are real live engineers on this forum (I'm not), and on behalf of all of us I sincerely ask that they chime in here and make any corrections to what I've said. I also believe that wearing out those huge rivets means that someone has been dangerously abusing an airframe, and that a lot of other things should be looked into. If the Cessna manual actually calls for DD rivets, then I'm scared shitless right about now.

Ok, being a real live engineer I'll chime in and correct you! You're thinking of soft 'A' rivets. DD shear strength is considerably higher than AD rivets, in fact they require heat treatment prior to driving due to the material strength. Sooooo.... You're doing major mods to aircraft and not really aware of the differences in fasteners... Just joking, no offense meant! I would like to think an owner wouldn't attempt to replace the rivets in the strut fittings and I would like to think an engineer would confirm the material type as well. A vague reference on a forum is not considered acceptable technical data!!

Thanks for the replies. I think it goes without saying that all work will be done by or under the direct supervision of an IA. And yes, we have all of the parts and maintenance manuals....

However, sometimes little nuggets of wisdom can be gleaned from the wealth of knowledge on these forums. Don't worry, I'm not going to go out and buy whatever hardwear someone recommends from the local NAPA and drill the things out in my basement. But even my very experienced IA doesn't have all the answers. Pressing with a hydraulic press instead of trying to pound them - good idea.

onefitty wrote:A vague reference on a forum is not considered acceptable technical data!!

+ ∞ (but that's impossible...)
The real PROBLEM is, the new generation of "handymen" seem to think that forums can be used as stand-alone technical guidance. They are a fantastic source of both true and false information, which you can learn from and cross-reference before using

Back on topic, the OP is right in thinking those rivets are kinda important
Probably the second-most nerve racking holes I've drilled, second to the spars. Oh - and 'squashing' the Cessna 182 wing strut to fit, now that was tense...
If DD rivets are 2024, then I would think carefully about the best way to drive them without risking damage to the strut, those don't come cheap and any big enough dent/scratch/nick (like from a rivetting gun) is cause to consider scrapping the part. I have good days and bad days with the rivet gun, I'm sure IA's do too.

I stand corrected... I was indeed mistakenly thinking about the soft A rivets, and I had confused it. My bad. I get 40 electronic lashes. Wouldn't be the first time or the last.

onefitty wrote:
Sooooo.... You're doing major mods to aircraft and not really aware of the differences in fasteners... Just joking, no offense meant!

Well, fortunately on any of my major structural mod projects I have the good fortune to have an old English stress engineer from deHavilland running all the calculations and fastener loads. A man whose resume' none of us here are physically strong enough to lift

Battson, the DD's must be cooked (correctly!) to soften them sufficiently prior to driving. They're then quite soft and drive easier than an AD, almost as easy as an A. They can't be driven in their natural state and will crack. They work harden as you drive them and then age harden a little more over a period of time. I use buckets of them when re-sparing Partenavia's. Not because of a strength issue, we simply can't drive an AD rivet of the required length without damaging the spar straps.

A retired dehavilland engineer eh..? Does that mean every bolt must have a drilled and lockwired (with copper) head, a retainer riveted over the head, a copper tab washer under the head, a cotter-pinned castellated fibre lock nut and then finally peen the whitworth thread...? I look after a few British planes... The Americans can build a decent robust plane from 25 separate parts, the poms will take a similar design and find a way to build it from 250,000 parts, none of which can be removed or repaired without first removing the engine or wing. And not one of those 250,000 parts will fit another airframe even 1 serial number away... I'M JOKING!

I look after a Percival Provost with an Alvis Leonides engine. Nice plane and nice engine but the only thing it does better than a 150 is guzzle oil and gas. The manual has a procedure for refitting the prop, "offer the propeller up to the crankshaft, spin the nut down by hand then give it two sharp blows with a rawhide mallet" I'm not sure where to get a rawhide mallet let alone calibrate one!

What does any of this have to do with rivets in strut's..?? I forget now.. Sorry for thread creep

How come nobody will purchase a British Car?

onefitty wrote:Not because of a strength issue, we simply can't drive an AD rivet of the required length without damaging the spar straps.

Well, funny you should say that.
Putting in the 5th last AD rivet in our second wing (the last of many thousand), it was a slightly longer one through 5 2024 T3 0.032 sheets (dimpled). Sure, it's not that long by standards, but AD4 so quite long compared to diameter, and needed a good prolonged hard hit...
We had a bucking bar jump and dent the capstrip (spar strap). We were both aghast. Thankfully the dent is only millimetres in length and a tiny faction of 1mm deep, but deep enough it can't be polished out without deminishing the cap strip. Still umming and ahhhing about the greater evil of those two. You would have to disassemble the entire (solid rivetted) wing to change the capstrip.
But either way we have a lifetime inspection item, lucky it's in the fuel tank bay and easily accessible on each annual.

onefitty wrote:
Does that mean every bolt must have a drilled and lockwired (with copper) head, a retainer riveted over the head, a copper tab washer under the head, a cotter-pinned castellated fibre lock nut and then finally peen the whitworth thread...? I look after a few British planes...

I owned an Auster once, and I'm very !(#$*$ familiar with trying to un-do 50 year old peened bolts and staked nuts. And yes I had to go to a !)$*%$ British motorcycle shop and buy a set of !($*% Whitworth wrenches to take the wings off!

By the way, my retired old gray haired DH engineer is working with one of your blokes down under... they're building an entirely new scratchbuilt 1940 Heston racer (!!!) Since there were no parts, plans or detailed documents that survived the war, my friend is simply reverse engineering the entire aircraft from a handful of photos. A brand new Heston racer (my God, just the thought of that) is about the only thing that could top that stunning Mosquito they just rebuilt down there, eh?

Now it's me who is sorry about the thread creep

FWIW my C150 parts cataloog calls out the following p/n's for those rivets:
upper end quantity four p/n 0723600-6 ,
lower end quantity four p/n 0723600-6, and quantity one p/n MS20470AD10-28.
The non-MS p/n must be a Cessna number.