LT35 Simple Set Travel Switch

[Rhodemont]

I considered posting this in MM thread on maintenance and repairs but decided to post new as this is something up my alley.  I recently posted in " did something dumb" that I caught my belt loop on the travel lever of my simple set and broke it.  The return worked but not properly.  I ordered a new lever and got around to installing it this morning.  The return did not work at all.  So, I had to open up Simple Set and see what was going on.  Having worked the majority of my engineering career on electrical contact materials and components the problem stood out immediately.

When I broke the switch lever I also bent the contact arm for the return on the switch as can be seen in the first pic.  The lever is connected to a shaft that has two contact arms and two neutrals on it. On each side of the shaft there are three spring loaded contacts.  The photo is of the lever not fully engaged in the return.  When you pull the lever for return the contact lever on the top should engage the two spring loaded contacts on top.  When you push the lever forward to travel the other arm on the bottom engages the two spring loaded contacts on the bottom.  The engagement of two contacts (and a neutral for each) completes the circuit and powers the motor. But, as you can see the arm is bent and will not engage the center contact.  Therefore circuit will not be completed and nothing happens.

So, with needle nose pliers I pulled the bent arm back into position.  As you can see in the second photo the arm will now engage both contacts to complete the circuit.  It works now.  Was it worth effort?  Well it saved $100 and yes it works but it is compromised so will need to be replaced eventually.

More thoughts.  The device is not a high reliability device.  The arms and contacts are silver plated copper.  Being 12volt the device is going to arc (12 volts is the potential when arcing will occur because the potential will arc just as the mating contacts are nearing each other.  Low amp will be less aggressive than higher amps that give a big spark).  Silver does not oxidize so it will protect a copper substrate form corroding and forming an insulating oxide layer that will prevent current flow between the contacts even when fully engaged.  But, silver does form a sulfide and a saw dust environment is loaded with sulfur so it can eventually form an insulating sulfide layer.  But, much worse, the arcing will burn through the silver plating in short time as seen in the photos.  This exposes the copper which will oxidize and continue burning away and it is all down hill from there.

If this was to be manufactured in a high reliability mode the mechanical design is just fine but it would require material change.,  The actual contact would be fine silver, the thickness would be defined by how long you want the device to work.  You want 10k cycles you make it X thick.  You want 100k cycles you increase the thickness to Y with added cost.  The current caring capacity of the arm is trivial in a low current short use device like this.  It is not going to get hot from long term high current.  A steel arm would more than suffice reducing copper cost to offset a little of the fine silver cost and provide a much more robust arm.  Unfortunately when silver jumped in price from $4/Z to $20/z the cost of contact , typically the most expensive single component in a device, cut into profit.  So, sales stepped in and said reduce the silver and to get cost down or we lose Home Depot and therefore the cycle life was reduced as well. Now your hot water heater, washing machine, water pump, etc will only run that 10k cycles instead of the previous 100k cycles.  Years ago before this cost cut you were more likely to have a repair man replace the electrical device or do it yourself.  But, sales stepped in again and said cut cost more so we keep Home Depot.  Now all the mechanical components are designed to last only as long as the electrical devices because labor to replace the device is so high and not many can do it themselves anymore.  Big win for sales to sell a new unit every 3 years rather than an electrical device every 10.

[WV Sawmiller]

   Yeah I have replaced mine at least once in the 8 or so years I've had mine and I keep a spare with me in my parts box. Same with the up/down drum switch on the other side. I thought they were both the same and interchangeable but they are not.

[Mr. Buck]

Would dielectric grease help reduce the arcing? 

[Rhodemont]

No, dielectric grease is non conductive and performs as environmental protection of a fixed connector such as a battery terminal.  The connection is made and the dielectric grease is applied to cover the connection and prevent moisture and corrosives from getting on the connection.  The name is quite confusing.  There are conductive graphite greases but they are not appropriate for an opening and closing switch. When a 12volt or higher switch closes or opens it is going to arc.  Conductive grease will not prevent arcing.  If applied to low current as this switch is it may prevent make of the contacts even though it is 'conductive'. What it will do when mechanically removed from the mating surfaces by opening and closing the device allowing contact and therefore arcing is to heat and spread around causing possible current flow to non desired areas and shorting.

[Rhodemont]

WV, I called WM to verify the part number of the lever when I broke it.  In the discussion the service tech said it is recommended to clean the switch at 600 hour and there would be a small tube of grease in the cabinet to apply at that time. Seeing the switch I agree that 600 hrs is time to clean the contact surfaces of the switch because of arcing  (I have 660 hrs). I did not find a small tube of what would likely be dielectric grease which would only be appropriate to apply to the shaft which rotates the arms, not to prevent further contact deterioration. 

[Magicman]

Properly greasing the contacts also prevents them from wearing down.  

My sawmill and it's drum switches are now 26 years old and there are some of the contacts that are worn through the silver and well into the brass.  Yes, there have been occasions when the proper switch maintenance (greasing) has not been done.     

[WV Sawmiller]

  I have heard about this little tube of grease that was supposed to be velcroed to the inside of the cover or such but I never got one with mine either and it not part of my normal pm servicing. It is not a checklist item on the service checklist in my manual.

[Mr. Buck]

Not sure if this is helpful, but I did see a youtube video on this topic and the grease came in a white plastic container with a snap on lid, not a tube, and the grease appeared to be a reddish color. 

Found it: https://m.youtube.com/watch?v=4n42MdVwxto

Hopefully this is useful to someone.

[Rhodemont]

Yes the video was helpful.  I was looking for a  tube of grease.  Went out, opened up the cover and there it is, the plastic container of grease.  There are even part numbers in the Drum Switch schematic for the container, decal, velcro pad, and high temp grease.  You can even see the container in the photos I posted. (Mariann must be correct "it is right in front of you")  I will plead that I was looking for a tube and the container, clearly marked 'grease', was unreadable because of the fine sawdust coving it (unlike the clean as can be interior of the video).  Going through my manual very carefully just now I agree with WV of finding no reference to doing this grease maintenance so I ask this be added to my defense.  Greasing has now been done and hand written into the maintenance checklist.  And yes MM, I can feel the action of the sliding contacts is now reduced by the grease when I move the lever which will reduce mechanical wear and corrosion.