[Healeys] Shock Bolts

[J. Armour]

Further to Larry and Michaels input maybe I should further discuss 'high
strength friction grip' bolted joints. By the way this is how hot riveting
works, when the rivet cools and shrinks in length it clamps the hell out of
the jointed items. I once did a hot rivet repair on a 90 foot high and 25
foot dia. pressure vessel that was jointed with rivets only and in some
joints it had 4 overlapping layers of steel plate all fixed with one through
rivet.
Friction grip joints require very clean surfaces and this means no paint or
oil etc. The mating faces should be flat and parallel preferably with a
little texture ie. fine grit blasted.  Then as previously listed high
quality fine threaded bolts, large dia. and hardened washers, lubricated
threads to eliminate friction and use a good torque wrench to stretch the
bolts or snug tighten and then turn say another one flat to stretch the
bolt. This way the bolts are a clamping mechanism and the resistance to
rotation of the body is from the friction between the mating faces. If the
mating area and friction levels are high enough the bolts do not restrain
the rotation of the shock body and do not see shear loads which then hammer
out the holes in the thin mounting plate. The tighter the fit of the bolt
shank, don¹t have threads in contact with the mounting plate of shock, helps
avoid excess movement when the bolts do loosen.
Healey design does not have much in its favour, thin mounting plate, soft
shock bodies ( melted down Spitfire parts) only two bolts that are difficult
to access and tighten.

A modification to consider is locating snugs each side of the shock body.
Maybe a second mounting plate with formed up edges, welded to the original.
This modification would not be very obvious to the average originality
obsessed inspector.

I will sign off with a relavant comment from one of the Sydney AH club early
members

" always keep your tools clean and your nuts tight"
Joe


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