the Pro from Dover wrote:
The
rack of the rack and pinion , ie the long ‘‘bar’’ that connects to the
tie rod assenblies on both sides, has a center. That center is located
by inserting a pin as described above. The pinion gear that connects
to the steering column , is just that, a gear. The pinion gear has a
notch machined in 1 place . The pinion gear can be meshed with the
rack in as many places as there are teeth on the gear. Only 1 place
will put the notch in the correct place relative to the steering
column. If all were perfect in the world, the rebuilders of the racks
would insert the pinion with the correct orientation. The fact is,
they don’t. Since you can only connect the rack and the lower column
in one place, the factory built in a way to correct the resulting
misalignment. I have changed hundreds of these racks, and almost
without exception , they required re - centering the column when the
rack was installed. I quote from the Factory manual, section 57 13’‘If
a replacement rack unit is to be fitted it may be necessary to detach
the lower column at the universal joint to obtain the correct
centralization’’
OK, lemme see if I have this straight. There’s the rack, which has a
splined shaft sticking out of the top of the tower, and this spline
has a missing tooth or two so it can only be reconnected to the
universal coupling one way – and this may be in the wrong place
because the nimnul rebuilding the rack didn’t do his job right. Then
there’s ANOTHER connection somewhere in there with splines that DON’T
have a missing tooth so you can put them together any which-a-way in
order to correct for the nimnul’s shoddy work? Where is this second
set of splines? Between the universal coupling and the lower end of
the steering column shaft?
If this is the case, I still stick with my contention, although it
must be clarified. The way to center the steering wheel is to insert
a dowel in the rack, and then center the steering wheel – by
disconnecting the universal joint from the lower steering column,
aligning the steering wheel, and reassembling, NOT by pulling the
steering wheel itself off and reinstalling. Once done, it’s done, no
need to readjust.
I hate it when designers provide a positive indexing feature for no
good reason. There was one heinous example at P&WA I remember, a
seal in the F100 turbine. On a jet engine, a seal is a metal ring
with a couple of knife edges around the OD. This ring pressed onto
one turbine disc, and then that turbine disc was installed on a
splined shaft. They put a missing spline on the seal to ensure that
it would be installed in a particular position – but it often was
not, it would be off a tooth or two, you couldn’t tell when it went
together because you couldn’t see it. The assembly tools were
powerful enough that they would simply crush that section of the
seal, and the turbine would go together and run fine. The only time
anyone would find out was at the next rebuild, when the seal would be
found damaged and would have to be replaced.
The seal ring was perfectly symmetrical EXCEPT for the missing
spline. I argued until I was blue in the face that the missing
spline should be deleted from the design so the seal could be
installed any which-a-way without damage. All fell on deaf ears; “We
must insure that seal is indexed properly when installed. We simply
must! End of discussion!”
Meanwhile, our competitors at GE were making similar parts without
any such indexing so they could be installed any which-a-way, and
they proceeded to take more and more business from us partly because
their engines required fewer replacement parts, less training, and
fewer special tools to rebuild.
We had a goodie with a bearing, too. There was a roller bearing in
the front of the F100 engine in which the outer race occasionally got
installed backwards. It would run fine, but there was only one
puller groove on the race for getting it out. Once installed
backwards, there was no way to get it out. I argued over and over to
simply install a puller groove on both sides so you could pull it out
whichever way it was installed. Everyone else thought I was nuts and
were working very hard on ways to make sure you couldn’t install the
race backwards, all of which were looking like they were going to
involve the redesign of the support assembly and a lot of expensive
machining and retooling.
– Kirbert
// please trim quoted text to context only