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
- _______________________________________________
- Elec-trak mailing list
- Elec-trak cosmos phy tufts edu
- https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak
- _______________________________________________
- Elec-trak mailing list
- Elec-trak cosmos phy tufts edu
- https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak
Elec-trak mailing list
Elec-trak cosmos phy tufts edu
https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak