OT- machining a relay contact

crossthread · Nov 7, 2021

This is sort of OT but it does pertain to machining somewhat. I have a Samsung dryer that would not start but would run when you gave the drum a push. Start winding, capacitor or something like that for sure. I pulled it apart and found a start switch mounted on the side of the motor which is activated by a centrifugal mechanism. Pulled the switch apart and the contact is gone but the beryllium strip is still intact with just a hole in it where the contact was. Samsung in all there eminent wisdom does not sell just the switch but requires that you buy the entire motor assembly for a couple of hundred dollars. I being old school who adheres to the premise that I can fix anything but a broken heart, want to replace the contact. My question is this: will copper work? I could turn one out of silver but that means I will need to come up with a small piece of silver bar stock. The hole in the strip looks just about as big as a piece of #12 solid copper wire. Easy to put in there and upset it on both sides. I did some looking around and it seems most contacts are either "fine" silver or some other exotic alloy. Will copper hold up? Thanks very much for any information.

rons · Nov 7, 2021

I would take apart an electrical relay and use a pair of contacts which are already installed on a strip of copper. In opinion it is better not to
removed the point but keep it on the strip and solder the strip to whatever was there.
Use a three pole relay and put the other two sets in a plastic bag and attach to inside of machine. You've got two spares and can go merrily on your way.

AHL2N SERIES ICE CUBE RELAY

crossthread · Nov 7, 2021

Rons, would you rivet the strip to the old strip or what?

DDoug · Nov 7, 2021

crossthread said:
Rons, would you rivet the strip to the old strip or what?

How was the OEM one held on ?

rons · Nov 7, 2021

crossthread said:
Rons, would you rivet the strip to the old strip or what?

A rivet requires a hole and may be moment arm is thin and that hole would weaken it.
From your information and my imagination ( :nutter:

) I would cut the existing strip square and solder the new strip with contact.

Display a picture and maybe a better answer will come your way.

kustomizer · Nov 7, 2021

crossthread said:
This is sort of OT but it does pertain to machining somewhat. I have a Samsung dryer that would not start but would run when you gave the drum a push. Start winding, capacitor or something like that for sure. I pulled it apart and found a start switch mounted on the side of the motor which is activated by a centrifugal mechanism. Pulled the switch apart and the contact is gone but the beryllium strip is still intact with just a hole in it where the contact was. Samsung in all there eminent wisdom does not sell just the switch but requires that you buy the entire motor assembly for a couple of hundred dollars. I being old school who adheres to the premise that I can fix anything but a broken heart, want to replace the contact. My question is this: will copper work? I could turn one out of silver but that means I will need to come up with a small piece of silver bar stock. The hole in the strip looks just about as big as a piece of #12 solid copper wire. Easy to put in there and upset it on both sides. I did some looking around and it seems most contacts are either "fine" silver or some other exotic alloy. Will copper hold up? Thanks very much for any information.

I have made them from coin silver found in a peace dollar, they work fine

crossthread · Nov 7, 2021

Spot welded Digger.

crossthread · Nov 7, 2021

This is what I am dealing with. Hole is about the same size as #12 solid wire.

jim rozen · Nov 7, 2021

Turn the silver contact to size to mate with the other contact, and have a boss on the backside that's a snug slip fit into the hole on the leaf. Make the height of the boss about 15 0r 20 thou taller than the leaf is thick.

Install the contact and gently peen the boss over to hold it in place.

crossthread · Nov 7, 2021

Jim, that would work exept this is a double contact. In other words the contact is on both sides of the strip. It makes contact in both directions if that makes sense. I wish it was just a contact on one side. That would make it much easier and I would do exactly as you suggested.

steve-l · Nov 7, 2021

One other tip. Make certain, no matter how you fasten the contacts, that the contact action is contact and wipe, not just contact. This greatly enhances durability. There also needs to be a slight crown shape for both contacts.

Tony Quiring · Nov 7, 2021

If it failed once it will again...

Maybe rewire is in order.

If you can get to the wires then re-route them to another relay or contactor.

Use this original mechanical device to control the better suited control.

Contractors and relays cheap, your time not so much.

Sent from my SM-G781V using Tapatalk

rons · Nov 7, 2021

crossthread said:
This is what I am dealing with. Hole is about the same size as #12 solid wire.

View attachment 333927

You got it made.

You can cut a line from the edge to the hole. Then part the copper slightly and drop in the new point. Solder cut section.
Assumes dimensions are similar. This would make it look like a new part.

Or solder the copper strip to the old one. A two sided contact would be in a DPDT or SPDT relay.

crossthread · Nov 7, 2021

That is a great idea Rons. I don't suppose the heat of making and breaking would melt the solder. I am going to go to the shop now and scrounge through my relay collection. Thanks.

rons · Nov 7, 2021

If you can make any solder job small then so much the better.

If the new point is secured to the previous copper arm because of a parting-type slot on the side of the point, then I would use it.
But I looked at a few relays and finding out would require you to damage a copper arm. Maybe if the relay was a three pole then no big deal.

I think you can make a neat solder job located far enough away. Or think of some mechanical way. In the relay collection I have the arms with
points are always in the middle of the contact assembly and have to be thin. A solder job is the only way. 2-56 screws?

Looking at the picture again, I would drill out the rivets and keep the old copper.
Get point on new arm in whatever way you like. I would try for a old relay arm that is longer and cut down the length. The use 2-56 screws to hold the copper.
If something gets fouled up you always attach the old arm again.

kustomizer · Nov 7, 2021

There should be a hole in the center of the contact, on the contact side not the peening side, it keeps one contact from making a peak that bridges the gap making contact all the time.

FredC · Nov 7, 2021

This thread made me think of 9100. He worked made relay contacts for the large relays in locomotives. It has been a few months since I have seen him comment here. Anyone seen or heard from him lately?

If I remember correctly the large relays he worked on used silver contacts.

crossthread · Nov 7, 2021

Feedback. The dryer is up and running guys. Wife thinks I am a trophy husband. I found a relay with some relay arms that were just the right width. I shortened them and cut off the ugly hole at the end of the one I was fixing. I overlapped the two arms and soldered them together. I had about a half inch of overlap so I think the solder will stay cool enough to hold. I thought about adding an insurance rivet but if it doesn't hold I know what to do now. Thanks for all the great replies.

rons · Nov 7, 2021

Would be interesting to get an IR temperature reading of the contact arm. My opinion is that you would see no change. The copper is a good conductor and any spikes of heat will draw out.

deltap · Nov 7, 2021

Motor contacts are made from coin silver(mostly copper). You could go the potential relay route and get rid of the centrifical switch. Don't know function of switch in other direction. A motor shop could be helpful.

OT- machining a relay contact

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