Housing, spark slug cable complete, right hand 32000-42
Housing, spark slug cable complete, left hand 32001-42
After recreating the top-light brackets, Willem
had another challenge for me. Aparrently THE most difficult XA
part to find is the sparkplug cap. The spark plug caps are in
a highly visible location and one can immediately see if the wrong
kind have been used
The original parts were made from thin stamped steel
back in 1942 and aparently have all rusted away by now and Willem
had only 1 complete set, he needed 14 for his 7 XA's.
I studied the documentation and measured up the
set Willem had and made CAD drawings of all the parts, plus added
the original part numbers.
The reason these sparkplug caps are relatively
complex is that they are radio suppressed, this was something
fairly common on military (and police) vehicles. The radio suppression
is achieved by added an extra layer of metal outside the insulation
of all the parts. For this project I would be needing to make
steel stampings, bakelite insulators, folded edges, CNC machined
bits etcetera, sounded like fun!
Keep in mind that the original tooling would have
been quite expensive and intended for large production numbers,
whereas I intend to make 30 of these sets or so, so I would need
to get a bit creative.
Shield spark plug, lower, 32140-42
This part has 2 interesting features, first of all it has an
internal hex shape that would be tricky to machine and it has
4 very thin flaps at the bottom that clamp onto the body of the
sparkplug. After some experimenting and a few manual prototypes
I decided CNC machining plus wire erosion for the internal hex
was the best solution.
Speaking about the internal hex, the original XA spark plugs
had an unusual hex size and are no longer available anywhere,
so the design was slightly changed so it can be used with "normal"
sparkplugs such as the HD No.3 (part number 32303-47A). After
all the plan is to ride these things!
I made a special tool to bend the flaps, worked like a charm! After
all the machining was done I put the parts in a vibrating drum for
24 hours with polishing soap and little stainless steel balls, this
removed all the burrs and sharp edges and made the parts look and
feel less brand new.
Finally they were Zincplated, as an
alternative for the original Cadmium which is outlawed here in
Holland because it is very bad for your health apparently. The look
is very similar.
It occured to me when the first batch
was ready that maybe I should have made them in stainless steel and
then glassbeaded them, after all rust was the main reason they are
so hard to find now..