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Well then RJ, I guess it's obvious that I'm not a EE
either.
As I said in my post, "A liberal coating of a good dielectric
grease on the contact disk and studs might be a good idea." And I
guess I should have added that I have not used that type of grease on one of
these disconnect switches.
Somewhere along the line, someone has led me to believe
that it would be a good application for stuff like this. But I'd
welcome someone addressing this issue and straightening me out.
Mike in KY
----- Original Message -----
Sent: Wednesday, November 12, 2008 5:15
PM
Subject: Re: (ET) power disconnect
switch
Yes increasing the
contact area is a plus.A final burnishing after assembly but before
installation with valve grinding compound makes for a dandy contact surface
both on the bolts and the disk. ( Clean thoroughly before using.
)
I must take issue with the use of
dielectric grease on the conductive surfaces.Why would you want to coat that
surface with a substance that inhibits current flow? {Bear in mind that I'm
not an EE, nor do I portray one on Television.}Would not conductive grease be
a more appropriate choice?
And
lastly, I've not heard of a source for replacement insulating bushings and
washers the replace those that have returned to the dust. :) I have several
Power Disconnects that have been robbed of those very items to repair
others.That situation was the impetus for the more carefree solution.I just
don't have nay more of them. :)
RJ
Mike Wallace wrote:
I've made this same repair/rebuild to several disconnect switches over the
years and agree with what Dwight is saying. I feel I've had good success and
the switch is probably as good if not maybe a little better than it was
originally. But if you'd rather take the easy way out and replace it with
one of the Pollack switches from guys like Jim Coats and maybe others, then
by all means go that way. I'm pretty sure that Jim's switch has already
been modified to have the third terminal not found on the standard Pollack
switch (no offense to you guys whose last name ends in 'ski', this name has
two 'l's and it's a company that makes the aftermarket switch best suited
for use in our ET's). The last Pollack switch I bought was around $25, so
Jim's modified and ready to install switch at around $50 is a good deal.
Now if you want to try and rebuild the OEM switch yourself, here's a couple
of things I've learned and would like to add to what Dwight has said:
Once you have removed the groove pin and found all the parts that went
flying across the floor, simply flipping the contact disk is the logical
approach for the first rebuild. Next time you can file or sand it smooth
and clean. I sure hope you took that picture Dwight mentioned or have
another disconnect laying around to use as a reassembly guide. There are
two springs and several washers/bushings (some metallic and some
non-metallic) that must be put back together in the proper order for the
disconnect to work properly.
I also have carefully filed a little material off the rounded heads of the
contact terminals (they are actually 1/4-20 copper alloy carriage bolts) to
achieve more contact area with the disk. Once the handle/shaft and related
parts are removed, filing the heads of the two contact studs is fairly easy.
Use care in doing this as the same amount of material should be removed from
both heads and those two surfaces must be in the same plane for optimum
contact with the disk once it's been reassembled. I think it's best to file
both of them at the same time while carefully holding the switch frame in a
vice.
I prefer to chemically clean all of the copper alloy parts before
reassembly. This involves removing most of the nuts & lock washers on all
three studs and the fusible link. Be sure to use two 7/16 wrenches when
loosening the nuts on either side of the fusible link's terminals. (The
inboard wrench is going to have to be kinda thin, something like a tappet
wrench or one of those cheap sheet metal wrenches you got with that
Christmas toy you had to assemble last year.)
I do not suggest removing the bottom nuts that hold the two contact studs
into the Bakelite body of the switch (learned that one the hard way).
Chemically cleaning the exposed face of those two nuts and the threads of
the studs with a Q-tip is sufficient. It's imperative that any and all
surfaces that are going to conduct electricity be as clean as possible, or
you could still have high resistance connections.
Pay close attention to the "tightness" of the crimped connections of the
terminals on the fusible link, as I've found those to loosen over time with
repeated heating and cooling cycles. Keep in mind that although some of us
have replaced power cables with something like say #4 welding cable, every
bit of power still goes through that little fusible link. So far I've not
had to replace one, but it just looks to me to be a 2 1/4" long piece of #12
copper wire. After cleaning the fusible link assembly, I always recrimp
those terminals to help insure a tight connection.
If I recall correctly, I've added a washer or two between the larger spring
and the groove pin to increase the compression load of the spring against
the disk and the two contact studs/terminals. When reassembling everything,
take care as to how tight you make the threaded connections. Just remember
that all of the threaded studs and nuts made of copper alloys and are rather
soft and can't be tightened as if they were steel nuts and bolts. A liberal
coating of a good dielectric grease on the contact disk and studs might be a
good idea.
Mike in KY
Side Note: I probably shouldn't say in this discussion group how I
chemically clean the copper alloy parts because I'm afraid David Roden will
turn me into the EPA or someone like that. Hell, I'm still getting
unannounced inspections from my local County Electrical Inspector trying to
see how I got my standby generator hooked up to the house. LOL
----- Original Message -----
From: "Hazen, Dwight L" <hazen indiana edu>
To: <elec-trak cosmos phy tufts edu>
Sent: Wednesday, November 12, 2008 8:49 AM
Subject: (ET) power disconnect switch
Not to spoil anyone's replacement disconnect business, I have had good
luck repairing the disconnect switch. Water and then corrosion cause the
spring loaded copper disk to hang on the shaft causing intermittent
operation.
You need to disassemble the switch (take a picture of it before you start)
and clean all the parts, make sure you get the springs right when you
reassemble (look at your picture). Lightly sand the disk, contacts and
shaft if needed "less sanding is better than more" turn the disk over and
use the other side if sanding will not work. A small amount of grease on
the shaft will help the disk to move, careful not to get any grease on the
disk or contacts. There is a little pin that rides on the cam that makes
the detents. If that pin is bent the switch will not work correctly,
straighten or replace.
There is a right way and wrong way to put it back in the tractor, make
sure when you are done the off position is down from the operator's
position with the handle toward you. In an emergency you what to just slap
the handle down to cut the power. Never force the handle that is how the
pin gets bent.
The switch is not a bad design and it seems to be made to take apart and
fix. Most devices today can not be repaired just replaced.
Try it you have nothing to lose.
Dwight
Dwight L. Hazen
Indiana University, UITS, Networks
Bloomington, In. 47408-7378
812-855-5367
Ham Radio wb9tlh arrl net http://wb9tlh.ampr.us
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