the frame in the engine compartment.
The some of the spot welds on reinforcement plate had
broken which lead to cracks in the body.
A shot of a crack emanating from a spot weld fatigue
failure. A hole was drilled to stop any further migration
of the crack.
It was decided to reinforce the reinforcement plate. First a
jig was made of cardboard, then the two above plates were
fabricated using .10 inch thick 4130 chrome moly (yes it is
overkill). The one on top already has a 90 degree bend at
the top. This increases the rigidity markedly.
The reinforcement bracket treated with rust killer after
carefully removing as much of the rust and debris from
underneath it as possible. The small hole center picture
was intended to be a drain hole, it didn't. The hole went
only through the plate, not the body. The larger hole just
to the right is the lone body mount bolt hole. My TR-3 has
two bolt holes here, a much stronger design as stress is
spread over a much larger area.
The reinforcement plate going in. The first hole is already
drilled and a cleco installed, the right way to do this job.
A second hole was drilled at the other end and another
cleco installed. Now the rest of these holes could be drilled.
Note the drill being used, an Atlas Copco right angle air drill.
Very power but easy to get into tight spaces. This is just one
of a huge assortment of air tools collected by my partner.
All of the holes have now been drilled in the original
reinforcement plate and the new piece. Since they were
both drilled together all the holes will line up perfectly
and are tightly toleranced.
Since several of the spot welds attaching the reinforcement
plate to the body had failed, it had to be firmly re-attached.
We decided to use an aircraft technique: carefully
toleranced holes, the correct hardware and lots of it. The
hardware used was 1) NAS 6703-3 #10-32, 3/16" grip. This
is a structural bolt made from A-286 stainless steel, cadium
plated. Minimum 160K psi tensile, 95K psi shear.
2) MS21042, a flange nut or jet nut. 3) AU 960 washer. If
this seems a tad bit hardware wonkish, that's because it is!
It is, however, all critical to getting a permanent repair.
The grip length is very important, it must such that the
shank of the bolt passes just through both pieces. This
ensures that each joint is "pinned", these joints will never
get loose and are stronger than a spot weld.
Another shot, we made certain that all of the body panels
were well connected!
A shot from the inner fender side.
A final shot, it's finally done! Although we did end up
turning some of the bolts around. I know some people will
look at this and shake their heads, massive overkill! But
this repair made a huge difference in the stiffness of the
area and was well worth the time and effort.
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