Lumbar bracket repair notes
- Inevitably, the chintzy plastic bracket setup used
the 700 series breaks. The Brickboard FAQ offers several
nice fixes that are well worth a look at, including
instructions on how to pull up the seat cover to get at the mechanism.
- Basically, there is a large while plastic 'bolt' with
a rectangular hollow base that houses a metal pin. The lumbar strap
mechanism operates through this pin. The black adjuster knob
you turn to adjust the lumbar support pulls this bolt/base affair .
The resulting stress on the plastic causes it to break at the
bolt base where it joins the rectangular base. The fixes on
the FAQ entail using some sort of metal bolt to reattach the plastic
bolt to the base. But if the plastic base is broken you need
a plan B.
- Plan B: make your own rectangular base and bolt it to
the plastic bolt. Construct a base out of some scrap metal
plate as per the image below. I used aluminum.
Note that the pin is an interference fit so drill the pin holes
on the small side. Work up to a hole such that the pin can be
tapped in place and is snug. Drill a hole in the base of the
plastic bolt and thread a
metal bolt through it and the rectangular base as shown. I
used a carriage bolt that had a thin head so that it did not interfere
with the pin. Cut the bolt to length so that it does not
interfere with the stroke of the black plastic adjuster knob (just
visible in the last image). You could reverse the direction
of the metal bolt as long as the head is small enough a diameter so it
does not interfere with the black plastic adjusting knob.
- As they say, assembly is just the reverse of disassembly.