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Date: Sun, 21 Mar 2010 17:58:37 -0500
From: Charlie England <ceengland@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Fwd: Question on RD2-C
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There have been engineering tests on 'dry' riveted sheets vs. riveted 
sheets with 'proseal' sealant between the sheets, & the 
prosealed/riveted combo was measurably weaker, due to the increased 
bending loads (instead of pure shear) on the rivets. IIRC, selection of 
proper bonding formula chemicals instead of sealant increased the 
strength of the joint. Sealants like proseal don't have much shear 
strength, compared to true bonding formulations.

Charlie

On 3/21/2010 1:03 PM, Bill Bradburry wrote:
>
> I agree that steel rivets would be better than the bolts. I am not 
> certain of the difficulty in squeezing them, but they would provide a 
> “press fit” where the bolts would not. The strength would be similar 
> in shear which is where most of the forces would be. They would also 
> be a lighter, important in a rotating mass. The idea of putting 
> something like “Proseal” in before assembly makes sense as well. The 
> combination should ensure that shear forces would never move it. In 
> the current situation it must be moving else the rivets could not 
> loosen???
>
> Bill B
>
> ------------------------------------------------------------------------
>
> *From:* Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] 
> *On Behalf Of *Al Gietzen
> *Sent:* Sunday, March 21, 2010 11:53 AM
> *To:* Rotary motors in aircraft
> *Subject:* [FlyRotary] Re: Fwd: Question on RD2-C
>
> The rivets are aluminum.
>
> I find this surprising, as well as disappointing.
>
> I checked the rivets on my RD2-C damper assembly and was able to 
> confirm that they were in fact beginning to loosen as evidenced by the 
> radial streaks on the damper plate. I picked four rivets at random, 
> approx. 90 degrees apart, and grabbed the shop heads with vice grips 
> and tried to spin them. All four would spin with little effort, thus 
> confirming that they were beginning to loosen. After a phone call to 
> Tracy, we decided to replace the ring of rivets with AN3 bolts, which 
> I've now done.
>
> One advantage to rivets is that they fill the holes to zero tolerance. 
> The bolts will be MUCH stronger, but I’m wondering about the potential 
> for some very small amount of ‘play’ to begin with, which would not be 
> a good thing. I don’t know much about steel rivets, but maybe that’s 
> the way to go.
>
> Mark; what nominal length and grip length on the bolts? Are you using 
> standard AN bolts or are there ‘true’ diameter or ‘close tolerance’ 
> bolts available.
>
> Al
>
> Hum-m-m; I just decided I could change schedules in order to fly to 
> the Jean, NV gathering next week. Now I’m wondering whether to fly 
> anywhere before changing out the rivets. I’m thinking that since I see 
> no movement between flange and plate after 180 hours, it should be 
> good for at least a few more hours.
>