Re-riveting the Elevator Bellcrank Bulkhead

How to keep the Cessna 170 flying and airworthy.

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cessna170bdriver
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Re: Re-riveting the Elevator Bellcrank Bulkhead

Post by cessna170bdriver »

gobrien wrote:I was thinking of something like https://www.aircraftspruce.com/catalog/ ... 9-1-05.php suitably sized, this specific one is likely too big. This is a pan-head screw with a shank (used for seat belt harness attachment). While I understand that the rivet fills the hole my concern is that the parts are pulling apart, and the previous attempt resulted in a shop head forming between the parts which I've had happen. If you can get the holes close to appropriately reamed, the clamping action of the screw as it is driven closed will tend to pull the parts together, this would seem a better option to riveting those 2 holes, even with blind rivets.

This may not be permitted with a certified plane; which was more where I was headed. How much discretion does one have to do such things?
I think a repair such as you describe might be doable, but would probably require special dispensation from either Cessna or a DER. In fact, the screws you reference are the ones that McFarlane has approved as an alternate way to fasten replacement seat rails. However, with a wood block as a fulcrum I can use a small prybar to make the flange lay down against the skin, but I just can’t get a bucking bar alongside to buck a rivet while it’s being held. So, we’re going to install the Cherry Max rivets while I’m on the inside holding the flange against the skin. When it’s all done, the bulkhead flanges will be held tight against the skin and all the holes will have either solid AD or Cherry Max rivets in place.
Miles

“I envy no man that knows more than myself, but pity them that know less.”
— Thomas Browne
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c170b53
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Re: Re-riveting the Elevator Bellcrank Bulkhead

Post by c170b53 »

I think, everyone here is promoting a perfect world which I believe few live in, Cessna certainly was not perfect. There’s nothing wrong in striving for perfection but I always suggest there’s good, better and best when it comes to mx approaches. So if you’re using (SP) a one in ten rule of thumb for defective rivets, your at best. In this (Miles) case the structure held together even with defects. Now it appears the structural defects have been corrected and I would not hesitate to use an equal to or stronger fastener. As for reaming the holes, thats the norm for structural repairs in a pressurized vessel for removing the cutting groove and provide a perfect hole but for our planes filling the hole will suffice.
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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GAHorn
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Re: Re-riveting the Elevator Bellcrank Bulkhead

Post by GAHorn »

c170b53 wrote: ..... Cessna certainly was not perfect....
8O 8O 8O

It’s taken almost two decades ...but you have finally earned ONE DEMERIT in the forum-oberkommando blaspheme-rule-book. Beware! (99 more will get you one FULL asterisk placed beside your username to your eternal shame.).

:P
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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