On 2/8/2011 5:45 AM, pc2a@pi4cc.nl wrote:
> Rroger (K8RI on TowerTalk) schreef:
>>>> Michael de W5NIG
>>>>
>>> We (PI4CC) has bas experience with this rotor. Within 5 years it hits
>>> the trash can.
>>>
>> Hopefully not. They use normally available automotive parts except for
>> the gears them selves. The bearings and seals are inexpensive automotive
>> parts. Although fairly easy to rebuild there are a few critical points
>> which are addressed in the rebuilding link above. It cost me less than
>> $30 for all new seals and bearings. The top and bottom of which are
>> very common wheel bearings.
>>
>> 73
>>
> Roger
>
> There was no way to to get the bearings of the as.
> We have used pulley's, heating, but is was so heavy rotten together
> there there was no other solution to trash it
That original top seal was a poor design, but it can be fixed.
I realize this one is gone and getting one apart when it has gotten this
bad can be a daunting challenge.
When they are that bad (mine was) it can take the services of a
machinist, or some home made tools and some experience working with
machine tools but they can be disassemble or carefully cut apart. I also
realize not every one has access to the tools, or background to make
them. Plus getting that inner shaft out can often be a challenge even
for an experienced mechanic or machinist if they are not familiar with
the construction of the PST-61. The inner shaft is keyed and held in
place with a snap ring. It's often more difficult to get out than the
bearings.
It must be removed before starting on the bearings.
As I mentioned in the tutorial, that brass worm gear is fragile,
expensive, and difficult to obtain so do not press against it. This is
not a job for everyone!
First we cleaned the shaft until it shined (see photo 4 on
http://www.rogerhalstead.com/Gears.htm ). Then soak the whole works in
PB Blaster or another *good* penetrating oil for 12 to 24 hours. Don't
use WD-40 as it's normally not sufficient. I cut a piece of steel to fit
(In a "U" shape) around the shaft so we could press against the little
edge of the bearings inner race.. When you look at photo 2 which is
upside down compared to photo #4 the space between the worm gear wheel
and the bearing is the only space available for a tool to press against
the inner race of the bearing. The brown area was the area that had to
be cleaned . The smooth area is where the inner race of the old bearing
was seated. There is not much of the inner race you can get at due to
the shoulder on the shaft. Ideally you can make the "U" or forked
shaped tool to fit snugly around this shaft using a milling machine. I
used a hacksaw and rat tailed file so it can be done by hand<:-)) IIRC
the one we made was a bit over 3/16" thick steel. A 1/4" to 3/8" would
be better, but then the inside has to be tapered to fit the shaft and
that adds more time. Although it is time consuming and requires a LOT
of patience. The tendency is to run out of patience and try to hurry
resulting in removing too much material. A machinist could make one in
a few minutes even by hand. Most of us might take up to an hour. When
sawing, leave a little extra metal and then file to fit. It may not be
pretty but the goal is something that will work, not a piece of art
work. I realize there are some out there who can get both. Mine...work.<:-))
When I say we, it took 3 of us to get the bearings off. One to hold the
shaft with gear and bearings from under the press, one to hold the tools
in place, and one to operate the press. I don't have a press that size
so we went to an automotive shop. We used the same press to press out
the inner shaft *before* starting on the bearings. There we used the
fork shaped tool along with a split inner race from the same make and
model bearing as support to press against. Here the inclination is to
press against that large gear, but it's not meant to take a side force
and can be easily broken.
IF and I emphasize the IF the outer race and rollers can be removed
(they can be cut off with a hand held abrasive cut off tool, which I do
have) a *long* gear puller can also be used. It takes one with a good
grip though as the initial pull only has about a 1/16" lip (0.0625")
about 1.58 mm to pull against. As soon as the bearing breaks loose you
get more room to work with.
An alternate method of removing the bearings would be to cut them off
using one of those hand held abrasive cut off tools or grinder. This
takes a lot of care not to cut onto the shaft. The easy part is cutting
through the outer race in two places. The parts and rollers will just
fall off once cut through.
I should emphasize that cutting the inner race like this is a risky
approach.
It will take two cuts on the inner race with one each on opposite sides
of the shaft. Don't cut all the way through, but as far as possible
without cutting into the shaft. Then a bit of tapping with a hammer and
cold chisel (at an angle to the shaft, not straight toward the shaft)
should snap the race into two pieces which will fall off. Hitting
straight toward the shaft can allow the chisel to hit the shaft (when
the race breaks) causing a dent with raised edges requiring some work to
smooth out so the new bearing will fit. That bearing race is HARD. The
shaft is not.
I do not recommend using a torch to cut them off as few have the skill
(including me) to cut the race off without ruining the shaft. My torch
skills are ... well...crude at best.
Unfortunately I don't have any photos of that part of the procedure.
73
Roger (K8RI)
> peter
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