Subject: [Healeys] Shock Bolts

From: "J. Armour" <[email-masked]>
Date: Tue, 5 Jan 2016 19:43:09 +1100

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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 throug=
h
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, don=B9t have threads in contact with the mounting plate of shock, help=
s
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 difficul=
t
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 earl=
y
members

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

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<html><head></head><body style=3D"word-wrap: break-word; -webkit-nbsp-mode: s=
pace; -webkit-line-break: after-white-space; color: rgb(0, 0, 0); font-size:=
 14px; font-family: Calibri, sans-serif; "><div>Further to Larry and Michael=
s 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.</div><div>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. &nbsp;Then as previously listed high quality fine threaded bol=
ts, large dia. and hardened washers, lubricated threads to eliminate frictio=
n 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 cla=
mping mechanism and the resistance to rotation of the body is from the frict=
ion between the mating faces. If the mating area and friction levels are hig=
h 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, don&#8217;t have threads in contact =
with the mounting plate of shock, helps avoid excess movement when the bolts=
 do loosen.</div><div>Healey design does not have much in its favour, thin m=
ounting plate, soft shock bodies ( melted down Spitfire parts) only two bolt=
s that are difficult to access and tighten.</div><div><br></div><div>A modif=
ication to consider is locating snugs each side of the shock body. Maybe a s=
econd mounting plate with formed up edges, welded to the original. This modi=
fication would not be very obvious to the average originality obsessed inspe=
ctor.</div><div><br></div><div>I will sign off with a relavant comment from =
one of the Sydney AH club early members</div><div><br></div><div>" always ke=
ep your tools clean and your nuts tight"</div><div>Joe</div></body></html>

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