Star Tech Journal

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STAR*TECH Journal
August 1993
FLIPPER LINK FAILURE SOLUTION
INSPECTION
&
RE-ASSEMBLY
Phil Stracke
Kapsalis Enterprises Limited
Scarborough,Ont., Canada
SUBJECT
SOLUTION
In response to Mr. Kingsley
Sime's article regarding flip-
per link failures (S,n'J June,
1993), I would like to offer a
solution I have had favorable
results from.
It is vitally important that this
edge not be installed through
thinking they were the reason
for link damage.
After a few more untimely fail-
ures, I even tried nylon crank
bushings until I lit upon the
roll pins. While several other
factors doubtless contribute to
the eventual failure of this as-
sembly, I haven't had any re-
peat business on this remedy.
Lip
PROBLEM
If one examines the flipper/
link assembly, you will note
that the spiral roll pin is of
critical importance. Examin-
ing many broken links I have
noted that 95% of them break
in the shaded area (see figure
1).
Figure 1: Flipper Link
CAUSE
This is a very strong portion of
the mold, thus the failure
must be due to unnatural
stress somewhere other than
the weak points (see arrows).
In the roll pin cross section,
(see figure 2), you will notice
the spiral construction, which
leaves an exposed, lightly
ground lip on one radial edge.
Figure 2: Roll Pin (side view)
r-,
the plunger in any position
other than the one indicated in
figure 3. Please also note that
there is a right/left: CCW/CW
orientation that is preferable.
You can determine this, and
using red/blue markers color
the upper and lower sides of
the plunger to make certain
they are properly installed.
Way back in Space Shuttle
days, I tried using external
return springs instead of the
original concentric springs,
Bottom View
Figure 3:
Correct Flipper Wrist Pin Assy
INSPECTION
Existing plunger/links can
easily be inspected and re-as-
sembled with a shim and cen-
ter punch on your bench vice.
Open vice 1/4 inch, lay the
plunger in the crack and insert
a metal shim between the top
of the link and bottom of the
upper fork on the plunger be-
fore driving the pin out or
plunger damage will result. I
have found that a very large
number of pre-assembled link/
plungers have this fault.
Right Hand CCW (red)
Crank Movement
----- Optimal Roll Pin
Edge Positions