Looks to me the spacer is only there to prevent the rod end from sliding out of position. It is the bolt (AN3 or 4 presumably) which carries the vast majority of the load...
I don't believe that is necessarily correct.
For one thing, cantilevering out 3/4" or so on a 1/4" shaft and expecting it to repeatedly react flap extension loads gives me way more shivers than what is shown. I'm not an engineer, but I regularly use formulas from standard references such as
Machinery's Handbook to design mechanisms and structures to react bending. Assuming that an AN4 bolt is good for 125ksi, it looks to me like that bolt will start bending at an applied moment of about 125 in-lbs. So a 3/4" long bolt would bend at an applied force of about 167 lbs. I don't know how much force multiplication there is in the manual flap lever, but I have to believe that it is at least 3:1. So a handle force of only 55 lbs would cause the bolt to bend. That may sound like a lot, but it's not. Applying the flaps at the top of the white arc probably takes half again that much force.
Here's the engineering test that Steve Smith taught me to apply: visualize that AN4 bolt sticking 3/4" out of the side of a tree or maybe out of the granite half way up El Capitan. Would you place your whole body weight on its bolt head and trust your life to it?
Historical note: The early ascents of El Cap all relied heavily on 1/4" steel rivets hammered into hand-drilled holes in the granite. However, these rivets were hammered all the way in against steel hangers to which rope and webbing was attached, so they were loaded primarily in shear, not bending. A fresh 1/4" steel rivet is good for around 2000 lbs of shear. Less fresh rivets are a different matter; I've seen rusty 1/4" rivets broken under body weight.
Regardless, in the situation at hand there has to be some clamping force between the bolt and the spacer in order to transmit bending. Otherwise the bolt will just wallow over in the shallow hole in the plate on the flap. That would make a mess of that plate in short order. This situation is similar to that of the rod ends used for elevator and rudder hinges; the jam nuts at their bases must be snug in order for them to react bending effectively into their attachments on the stabilizer spars.
Anyhow, the extended bolt and spacer look scary enough, but I think that the real problem is that the bending applied by the bolt and spacer has to be reacted into the relatively thin aluminum plate on the end of the flap. That plate and its attachments were probably designed to be loaded primarily in shear, not with the kind of bending moment applied when you move the rod end inboard substantially. Loading it in bending will drastically increase the rate at which it fatigues.
As a final note, the reason I take this kind of thing pretty seriously is that asymmetrical flap deployment is often a killer situation. At altitude there is often time to get things sorted out, reduce the symmetry to the degree practical, and limp in to a landing. However, flaps are often applied during landing where there just isn't that kind of margin.
Thanks, Bob K.
Thank God, Van over designed that mechanism.
