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Re: (ET) power disconnect switch



Mike you are right, "dieelectric grease" would work fine, it is the same stuff "we" electric types use to wire in heavy current pulling leads in a panel, very good if you have two unlike material..i.e. alum/steel...copper/steel, etc..
 
Jerry NW Ohio
----- Original Message -----
Sent: Wednesday, November 12, 2008 6:59 PM
Subject: Re: (ET) power disconnect switch

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 -----
From: RJ Kanary
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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