What does a cutout do?

[marty in Ohio]

I started a thread a couple weeks ago about burning out condensers. I got the good NAPA unit and everything seems OK now. When talking to our little Model A group (the A Team) the thought was that my generator was producing too many amps and it was burning out the 2 condensers that I put on this year. Most of these guys have alternators, with regulators built in, and say that their ammeters show charge when they first start out then drop back when the battery is satisfied. My ammeter always shows the same charge unless I turn on the lights of stop at a stop light. The guys say this is not normal and suggest that my cutout is not working properly. Should the ammeter drop back and just what does the cutout do? I've driven this car for over 20 years and sometimes I feel like a newbie.
Marty

[Rowdy]

The main thing the cutout does is prevent current from flowing back through the generator when the engine is not running. The current produced from the generator while running is adjusted by the third brush. The ammeter reads the difference from current produced and the load ( lights, horn, ignition etc.). Normally while running I set the third brush to about +3 amps and if running with the lights on I adjust the third brush to +3 with the lights on. I do think the internal EVR made by Tom W is a GREAT item and plan to install one in my powerhouse generator as I restore my delivery sedan. Rod

[30ccpickup]

Hope this helps. http://modelabasics.com/Cutout.htm

[Brianfrench65]

With my limited knowledge, the cut out disconnects the generator from the battery wire, when the generator is not charging (engine not running). With My limited knowledge, if the cut out is stuck closed, the generator will run like a motor, when the engine is not running, because power is being supplied to the output wire. If the cut out is not closing when the Engine is running, then you would not show charging on your amp meter.

The adjustable third brush inside the generator, is moved to increase or decrease the charging amps. I do not believe this adjustment changes the voltage.

I am not aware of any adjustments to raise or lower the generator voltage. I had the same problem, and was also burning out bulbs. I put one of the Powermaster alternators in my A. Painfully expensive, however no more problems or electrical issues. I did add a fuse at the same time, because the altenator does produce more amperage if the demand is needed.

[Kevin in NJ]

The cutout is a switch that knows when the voltage of the generator is greater then the voltage of the battery.

Then the magnetic coils on the cutout will close a switch connecting the generator to the battery.

The battery is the voltage regulator for the Model A. You as a user have to guess the charge rate by adjusting the third brush for your driving conditions.

If you want to be sure then getting a band voltage regulator will handle the charge automatically.

Next, understand that the ammeter is not always accurate. It should show movement. You know the cutout is working if you get a positive rate. You expect the needle to move lower as you add load (horn, lights, brakes). As long as it behaves that way then I would say you are pretty good to go.

The guys with alternators think they have a better system, but in reality it is no better then the generator. The truth is the generator, properly rebuilt, will put out as much power and last much longer then an alternator. Go up to the guys with alternators and use a finger to push the fins on the alt. If you can move it then it is too loose and refer them to the shop manuals from the 60's V-belt cars on the proper tension. You will find it has to be way tighter then you would expect.

[Brianfrench65]

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"Go up to the guys with alternators and use a finger to push the fins on the alt. If you can move it then it is too loose and refer them to the shop manuals from the 60's V-belt cars on the proper tension. You will find it has to be way tighter then you would expect."

Would that much tension effect the water pump bearing?

[marc hildebrant]

The advantage of the alternator over the original Model A system is that :

1. The alternators can produce more power than the generators.

2. The alternators produce a constant voltage whereas the generators produce a constant current. The Model A generator has many compromises in its design to make it work "O.K." without a regulator.

Thus, the alternators shouldn't overcharge the battery and they should be able to provide brighter headlights.

Now, the alternators are not perfect and many people can claim that original Model A headlights with good reflectors are just as bright as halogens. Also, some alternators have a voltage much too high...but in principal the alternators are a better choice.

Marc

[mrtexas]

The cutout is a relay.

[Patrick L.]

The cutout is nothing more than a switch, therefore it does no regulation.
As said, the amount of charge is set thru the third movable brush. Just remove the band and use a non-metal 'something' to move that brush until you get the charge rate you want. 2-4 amps without headlights is usually fine. If doing a lot of night driving then 10-12 amps [without the lights on] is OK. Don't adjust the rate for more than 14 amps, or, more than you really need unless you enjoy constantly filling the battery.
The regulator made by Tom W is a good addition.

[Kevin in NJ]

Originally Posted by marc hildebrant

The advantage of the alternator over the original Model A system is that :

1. The alternators can produce more power than the generators.


Marc

That is right the alt can produce more power.

BUT

It has some issues when installed on the A.

It take a certain amount of horsepower at the shaft of the alt to produce the power. To transfer the power you need to have a proper diameter pulley and the belt has to be properly tensioned.

I encourage everyone to look up on google the HP needed for a given Amp output. Then go find the specs on how large a pulley it takes to transfer that much horsepower. You will be in for a rude awakening. You have to remember the pulley has to be very tight and we can not do that on the A.

Then there is the derating of the alt when they get warm. I believe some go as far as half their rated power. Again, go look it up with google.

Alternators are not the solution that eveyone makes them out to be. The dealers make a lot of money off of them.

[mshmodela]

Originally Posted by marty in Ohio

I started a thread a couple weeks ago about burning out condensers. I got the good NAPA unit and everything seems OK now. When talking to our little Model A group (the A Team) the thought was that my generator was producing too many amps and it was burning out the 2 condensers that I put on this year. Most of these guys have alternators, with regulators built in, and say that their ammeters show charge when they first start out then drop back when the battery is satisfied. My ammeter always shows the same charge unless I turn on the lights of stop at a stop light. The guys say this is not normal and suggest that my cutout is not working properly. Should the ammeter drop back and just what does the cutout do? I've driven this car for over 20 years and sometimes I feel like a newbie.
Marty

Marty,

As newbie, I had an issue with my generator with old school cutoff charging +14AMP.... and discovered a metal spur on the ring that prevented me from lowering the output.

https://www.youtube.com/watch?v=yYlpy75GdA4

I run my now with ~7 AMPs and when I hit the brakes, yes the ammeter does drop from +7 AMPs to a little over +1 AMP (charging). If I turn my lights on, it would show less change applied and that's normal as the part of the generator output is feeding the lights instead of battery... I believe this is normal for a DC generator without a voltage regulator. My cutout will show little charge at low/ idle RPMs and as the RPM increase the cutout will permit the ammeter to show the normal +7AMP change which is normal as I set it.


The cutout permits charging of the battery when the engine is running and prevents the battery from discharging when not.

[marc hildebrant]

Kevin in NJ,

One horsepower is about 746 watts for 100 % efficiency.

With regards to the pulley size and belt , I use a belt that has over one inch of play and the alternator works fine. The pulley is smaller than the generator though.

Keep in mind that although my alternator can produce much power than the generator, I don't need that much. Thus, my belt is loose and I have a small load on the motor. Actually, I have a lighter load on the motor than if I was using a generator...during the day...since the alternator is more efficient and is regulated to put out just what the car needs.

Now, I would prefer that my car has an original generator on it, and original lights...but...it came with an alternator and halogen lights.

Marc

[mshmodela]

Marc,

I do not drive at night but here's my 6volt lights

low beam:
https://www.youtube.com/watch?v=HYnHNkVKn1U

hight beam:
https://www.youtube.com/watch?v=9N9T_VZRCYw

[marc hildebrant]

Mike in Cleveland,

What is the condition of your reflectors ?

Marc

[mshmodela]

Originally Posted by marc hildebrant

Mike in Cleveland,

What is the condition of your reflectors ?

Marc

Ugh, you've got mine on that one --too newbie.. In looking at the head lights, both forward most glass are reproductions but the stainless is original... Yet to open on of the lights.. but I would suspect if the outside glass is new, the insides are likely as well..

[Tom Endy]

The cut-out has a switch that is either open or closed. The purpose is to attach the generator output to the battery and electrical circuit when the engine is running and up to speed and the generator is putting out power. When the engine is stopped (or at idle) the switch opens to disconnect the generator from the battery and electrical circuit. If the generator remained attached when it is not putting out power It would act as a ground on the battery and soon discharge it.

The basic action of the cut-out is the opening and closing of the switch. How it does that involves some magnetic black magic to determine when.

Most reproduction cut-outs are poorly made with very little tungsten on the switch contacts. Over time with the arcing action that goes on they will weld together and remain in the closed position and discharge the battery when the car is parked.

It is best to try to find a serviceable original.

With an alternator a cut-out is not used. The disconnect is achieved with diodes in the alternator.

Tom Endy

[Mitch//pa]

i have good luck using the diode style cutouts.. no contacts to worry about...

[marty in Ohio]

WOW! You guys know it!
I read with interest what you all wrote - not sure I understand it all, but I feel better knowing that I don't think I have a problem. I've had my car for many years and I have the third brush adjusted to where I think it's best for my kind of driving. I'll stick with my generator just the way Henry built it.
Thanks so much for all your help.
Marty

[Tom Wesenberg]

Originally Posted by mshmodela

Marty,

As newbie, I had an issue with my generator with old school cutoff charging +14AMP.... and discovered a metal spur on the ring that prevented me from lowering the output.

https://www.youtube.com/watch?v=yYlpy75GdA4

I run my now with ~7 AMPs and when I hit the brakes, yes the ammeter does drop from +7 AMPs to a little over +1 AMP (charging). If I turn my lights on, it would show less change applied and that's normal as the part of the generator output is feeding the lights instead of battery... I believe this is normal for a DC generator without a voltage regulator. My cutout will show little charge at low/ idle RPMs and as the RPM increase the cutout will permit the ammeter to show the normal +7AMP change which is normal as I set it.


The cutout permits charging of the battery when the engine is running and prevents the battery from discharging when not.

Thanks Mike for posting that excellent schematic of the charging system. The cutout is a relay that should close when the generator output reaches about 6.0 volts, and open when the voltage falls below this level. The air gap of the open contacts should be about .020" and the spring tension can be adjusted so they pull closed at 6.0 to 6.3 volts. Original cutouts are by far the best, and some of the repro cutouts are only good for "show and tell" about junk parts.

Bert's in Denver sells restored original cutouts. 800-321-1931

As mentioned, the battery acts to control the voltage, so be sure every connection in the charging circuit is clean and tight.

[mshmodela]

Gee, I think I might be in the market, mine appears shorted ;(