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Re: (ET) power disconnect switch

I would think adding grease to a connection that makes and breaks would be a bad idea due to the environment it is in.
The thought is the grease will collect dirt and could cause a poor connection over time, where a clean contact the dirt won't stick.


At 06:59 PM 11/12/2008, you wrote:
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
To: Mike Wallace
Cc: Hazen, Dwight L ; elec-trak cosmos phy tufts edu
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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