Can a sticky cutout be repaired? FOLLOWUP

[700rpm]

What causes a cutout to stick? And can a sticky cutout be repaired?

[Milton]

High amperage can weld the contact together. Sometimes, with luck, a sharp rap will unstick the contacts. Beyond this I have never had to disassemble a cutout. Tom Wesenberg is the man in this catagory.

[columbiA]

If the contacts are rough,run a strip of #320 sand paper thru them & it should be OK.

[awander]

Usually, what I have seen described as "sticking" is not a mechanical phenomenon(such as the contacts themselves actually getting welded together), but is electrical in nature.

You can test this by disconnecting the battery while the relay is "stuck". If the points open, then the relay is probably out of adjustment.

[Tom Wesenberg]

Cutouts aren't too bad to work on. I cut a hole in a block of wood to hold the cutout upside down. I use a very sharp thin chisel to split the spot welds, then the cover can be pried off. Once the cover is removed you can straighten the bent metal from using the chisel on it. Use compressed air to blow the metal specs off the top of the armature, where they like to collect due to the magnetism. File the contacts or sand them smooth, then set the open air gap to .020" and make sure when the contacts are closed that the top of the armature (magnetic coil) still has a thin air gap.

The cutout on the right and the bottom picture shows an original cutout and the quality it has over the left cheapo cutout.

The cover will fit tight and doesn't need to be soldered or spot welded to hold it in place.

[30ccpickup]

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This is how the cutout works.
http://modelabasics.com/Cutout.htm
I have included printably assembly drawings in a pdf format.

Paul

[700rpm]

Thanks Paul. I had an inkling about how it worked, but your link fills in the blank spots.

My trouble is momentary sticking; if I tap the cutout the points open. I recently replaced a broken 3rd brush on the generator with the only spare I had, which was thicker than the one that was on there. Would this affect the operation of the cutout? Would accumulated metal filings on the top of the armature cause the points to stick? Tom, I'll check the points and gap today.

[Purdy Swoft]

I've tapped on the cover with a screw driver handle or removed the cover and filed the points with some success. That was in the old days when that was the best that I could do. After the cut out starts acting up, I no longer trust it. Now that diodes are available for a few dollars, if I want to save the old cut out I just install a diode instead. You can't see any modification and there are no points to stick. My preferance is the Fun Projects voltage regulator. The regulator installs and looks like the cut out and it is not necessary to tear down the generator.

[Tom Wesenberg]

I think the problem with cutouts sticking closed is mostly caused by owner neglect, when the wire connections corrode or get loose and the unregulated generator puts out high voltage. I haven't touched my original cutout, nor generator since I rebuilt it about 15 years ago. I installed my EVR in the powerhouse, so the amps going through the cutout contacts is always as low as possible. You can see by the picture I wasn't exagerating when I said I haven't touched it. I don't even wipe the dust and dirt off.

[awander]

Originally Posted by 30ccpickup

This is how the cutout works.
http://modelabasics.com/Cutout.htm
I have included printably assembly drawings in a pdf format.

Paul

Good link, with a pretty good explanation of how the cutout works.

I would add to it the following:

-The fine-wire(inside) winding is just enough to get the points to close when the generator voltage rises above 6.2V or so.

-Once the points close, then the heavy-wire(outside) winding also begins to conduct, such that it;s magnetic field ADDS to that of the fine winding, firmly keeping the contacts closed.

-If the generator voltage drops below battery voltage, such that the battery begins to "charge" the generator ,instead of the other way around, the current in the heavy winding will be reversed, which means it's magnetic field will work AGAINST the fine winding, and cause the points to open.


Your symptom could be caused by too low a "cut-in" voltage, caused by too little spring tension.

[30ccpickup]

Originally Posted by awander

Good link, with a pretty good explanation of how the cutout works.

I would add to it the following:

-The fine-wire(inside) winding is just enough to get the points to close when the generator voltage rises above 6.2V or so.

-Once the points close, then the heavy-wire(outside) winding also begins to conduct, such that it;s magnetic field ADDS to that of the fine winding, firmly keeping the contacts closed.

-If the generator voltage drops below battery voltage, such that the battery begins to "charge" the generator ,instead of the other way around, the current in the heavy winding will be reversed, which means it's magnetic field will work AGAINST the fine winding, and cause the points to open.


Your symptom could be caused by too low a "cut-in" voltage, caused by too little spring tension.

Nice, thank you.
Paul

[30ccpickup]

700rpm,

I pretty much followed what Tom did above. The only difference was I used a wet stone instead of a file. No problems for the last two years. Big difference in quality of the original cutouts compared to the repro ones.

Paul

[awander]

...and yes, if it is an original cutout, it was made to be adjusted and rebuilt if necessary. If you can;t get it working, I could do it for you.

[700rpm]

Thanks everyone; I cleaned it up today and reinstalled and it worked fine the first time out. We'll see how it does over the next week (I drive the car every day).

[700rpm]

Followup: I filed the points on two different original cutouts. Both of them continue to stick closed. I think I'll try to convert one to a diode. Someone on another thread (that I can't find) mentioned which was the best diode to buy. Can anyone tell me what that one is?

[Tom Wesenberg]

Originally Posted by 700rpm

Followup: I filed the points on two different original cutouts. Both of them continue to stick closed. I think I'll try to convert one to a diode. Someone on another thread (that I can't find) mentioned which was the best diode to buy. Can anyone tell me what that one is?

A&L makes and sells an excellent diode cutout, and some of the other parts houses sell this same cutout. I wouldn't cut up an original cutout for a diode, as there are a lot of repro cutouts worthy of being cut up.

[700rpm]

Originally Posted by awander

...and yes, if it is an original cutout, it was made to be adjusted and rebuilt if necessary. If you can;t get it working, I could do it for you.

Please send me a PM with your contact info and how much you'd charge me to make one work.

Thanks.

[700rpm]

Originally Posted by Tom Wesenberg

A&L makes and sells an excellent diode cutout, and some of the other parts houses sell this same cutout. I wouldn't cut up an original cutout for a diode, as there are a lot of repro cutouts worthy of being cut up.

Right, Tom. I hate to alter or destroy or discard any original parts, even if they aren't working. You just never know what will be useful later on.

[Purdy Swoft]

I have mostly used the diodes from Brattons. They coime with instructions, cost around s6.95 part number 15600 . These fit the original style cutouts.

[Purdy Swoft]

Snyders has a diode on page A-141 of the new catalog for $2.95 This diode looks different from the one that Bratton sells but works just as well. I have used this type in the repro cut outs and will also fit the early 28 style. These are all easy to install. I've god several junk cutouts and don't think twice about installing one. If anybody wants the guts that I removed from junk cut outs, I saved them.