cessna170bdriver wrote:How would YOU set a rivet like this?
On a part like a strut I'd be tempted to try a giant rivet squeezer -- a hydraulic press.
cessna170bdriver wrote:They are a bit on the uncommon side in that they have an 82-degree head angle rather than 100.
I've never heard of a 426 rivet being anything other than 100-degrees. Quite astute for Del to notice the difference. Not to be nit-picky but based on figure 2 of this restricted wartime report I think the hole for the rivet might be 82 degrees while the rivet is 78 degrees. What I found most interesting in this report was that the tightest joint was made by driving a round head rivet from the opposite side so that the shop head filled the countersink.
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Metal Master wrote:
bagarre wrote:
Both my '52s have hi-locks.
Hi-locs are threaded fasteners. The original fasteners were Hi-shear rivets with a driven collar.
From the 1996 and on Single Engine Models 172, 182, … Maintenance Manual, Chap. 51 4.C.(1) "It is permissible to replace Hi-Shear rivets with Hi-Lok bolts of the same material, diameter and grip length."
cessna170bdriver wrote:How would YOU set a rivet like this?
On a part like a strut I'd be tempted to try a giant rivet squeezer -- a hydraulic press.
cessna170bdriver wrote:They are a bit on the uncommon side in that they have an 82-degree head angle rather than 100.
I've never heard of a 426 rivet being anything other than 100-degrees. Quite astute for Del to notice the difference. Not to be nit-picky but based on figure 2 of this restricted wartime report I think the hole for the rivet might be 82 degrees while the rivet is 78 degrees. What I found most interesting in this report was that the tightest joint was made by driving a round head rivet from the opposite side so that the shop head filled the countersink.
Report.jpg
Metal Master wrote:
bagarre wrote:
Both my '52s have hi-locks.
Hi-locs are threaded fasteners. The original fasteners were Hi-shear rivets with a driven collar.
From the 1996 and on Single Engine Models 172, 182, … Maintenance Manual, Chap. 51 4.C.(1) "It is permissible to replace Hi-Shear rivets with Hi-Lok bolts of the same material, diameter and grip length."
You are correct. The rivets are are the standard MS20426D (100 degree), but the countersink in the lift strut is 82 degree. So, we are removing the head of the rivet, and allowing enough of the rivet shank to protrude equally from both sides as we squeeze them down into the 82 degree countersink. I've only done one test sample, which I have yet to complete a destructive test. I'll drill off the "head" and measure the force required to press the compressed rivet shank out. This will then be compared to a Cessna installed rivet on damage lift strut.
Gary, the report you linked is great. This is exactly what we are doing. The rivet, before squeezing, is left long enough so that after it is squeezed tightly down into the countersink, it still protrudes about an 1/8". We will microshave to be flush
c170b53 wrote:Would (maybe obvious to some) you shave the two ends afterwards, for the finish?
Jim,
Yes, the manufactured 100 degree head is removed prior to insertion in the hole. It's length is cut to allow ample protrusion on both sides so that after the rivet is squeezed tight throughout the length of the hole and into the the countersinks on both sides. Then we use a rivet shaver to mill it smooth.
I've to make a couple special tools for the press so I can do some destructive testing. After I'm confident with our process I'll post some more info and pictures.
Aryana wrote:Miles, we need something in that photo for scale reference! Those flush rivets in the strut are huge and I always wondered how they bucked them...
They are 5/16" diameter and 2 inches long. It's been 27 years since I've worked with rivets this size. It was on a Twin Otter wing spar. They had corrosion and were replacing the spar caps. They had 5/16" DD "icebox" rivets. We tried the 2 rivet guns idea, but learned that did not expand the shank of the rivet throughout the full length of the rivet hole. We built a hydraulic press frame with a 60 ton hydraulic jack, which dangled from an "A" frame hoist, to squeeze those rivets. Sorry, no pictures of that operation, but I wish I had some
wingnut wrote:Yes, the manufactured 100 degree head is removed prior to insertion in the hole. It's length is cut to allow ample protrusion on both sides so that after the rivet is squeezed tight throughout the length of the hole and into the the countersinks on both sides. Then we use a rivet shaver to mill it smooth.
Wouldn't it be easier to use AN425AD10 rivets? I'd never heard of them before today but see that they are 78-degree countersink rivets. I'm looking forward to your pictures of driving/squeezing those suckers. Do you have a large enough rivet squeezer for that operation or are you going to have to use a press? If it doesn't work as planned there are always struts, 0523606-12 and -13, for sale online. Wing struts might be one item that one would rather not have off of a wrecked aircraft though.
c170b53 wrote:Most excellent Gary, Hi-shear replacement; that was going to be my next question to Jim ( Not in the third person).
Jim, I ran across this after I found that Hi-Shear rivets were replaced by AN bolts in my landing gear box. There is a wealth of information in the Structural Repair section of the 1996 and on Single Engine Maintenance Manual.
John Hess
Past President 2018-2021 President 2016-2018, TIC170A Vice President 2014-2016, TIC170A Director 2005-2014, TIC170A N3833V Flying for Fun '67 XLH 900 Harley Sportster EAA Chapter 390 Pres since 2006 K3KNT
wingnut wrote:Yes, the manufactured 100 degree head is removed prior to insertion in the hole. It's length is cut to allow ample protrusion on both sides so that after the rivet is squeezed tight throughout the length of the hole and into the the countersinks on both sides. Then we use a rivet shaver to mill it smooth.
Wouldn't it be easier to use AN425AD10 rivets? I'd never heard of them before today but see that they are 78-degree countersink rivets. I'm looking forward to your pictures of driving/squeezing those suckers. Do you have a large enough rivet squeezer for that operation or are you going to have to use a press? If it doesn't work as planned there are always struts, 0523606-12 and -13, for sale online. Wing struts might be one item that one would rather not have off of a wrecked aircraft though.
Because the hole is approx. 1.5" deep, I want to squeeze the rivet into the countersinks on each side, using equal force on both sides. If I used a flush rivet that was already flush on the manufactured head side, I worry that the rivet would get tight first on the shop 'head' side and would not be equally tight throughout the entire depth of the hole and/or the in the countersink area of the manufactured head side. Hope this makes sense.
So, it matters not if I use a 425, 426 or even a 470 button head rivet. I'm cutting the rivets to length anyway
No, I'm not making anything. I'm proving (or not) a process. If I'm satisfied with my process, then I'll be installing serviceable fittings into a serviceable lift strut tube. If I'm not satisfied, then I'll buy a serviceable assembly.
What I found most interesting in this report was that the tightest joint was made by driving a round head rivet from the opposite side so that the shop head filled the countersink.
. Thanks everyone !