Go Back   The Ford Barn > General Discussion > Early V8 (1932-53)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 09-05-2016, 05:14 PM   #41
Brian
Senior Member
 
Brian's Avatar
 
Join Date: May 2010
Location: Masterton, New Zealand
Posts: 3,816
Default Re: Generator Third brush Adjustment

Maybe your Dad didn't understand the concept either, same as all those people driving with their lights on to 'correct' an overcharge situation. Again, YOU regulate the output to suit the load requirements of the generator. You do this by moving the third brush and referring to the ammeter. After a while, it becomes so familiar, you'll just do it autocratically.
As I stated in an earlier post, just set the tension on the coverband sufficient to allow it to be slipped forward and backward and stay in place.
edit; sorry to repeat myself, it appears you've got it sorted.
__________________
Unfortunately, two half wits don't make a whole wit!
Brian is offline   Reply With Quote
Old 09-05-2016, 05:20 PM   #42
JSeery
Member Emeritus
 
JSeery's Avatar
 
Join Date: Nov 2012
Location: Wichita KS
Posts: 16,132
Default Re: Generator Third brush Adjustment

Quote:
Originally Posted by Capt Kirk View Post
I will go out and set it now. I incorrectly assumed that it was an automatic "on off" switch based on the batteries needs. Now I understand that I can set the third brush to put out a constant amperage based on my driving needs. I don't drive it at night and something has changed with the way it's charging over the years. I will report back in a bit after I make the change.
Just sent you a PM
JSeery is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 09-05-2016, 05:25 PM   #43
Bob C
Senior Member
 
Join Date: May 2010
Location: So Cal
Posts: 8,712
Default Re: Generator Third brush Adjustment

This might help explain how your generator works.

THREE BRUSH GENERATOR OPERATION:
The three brush generator design required removing the cover and adjusting the position of the third brush in order to change the charging rate.By moving the position of the third brush the voltage applied to the field windings was changed. This in turn changed the strength of the magnetic field applied to the rotating armature and thus set (or limited) the maximum charging rate, or current output, of the generator. The generator would continue to charge at this fixed current rate all the time, regardless if the battery was boiling over or dead, lights on or off, it didn’t matter. This was fine if the electrical load on the system remained constant, but loads usually do not. If the battery was low, or additional loads such as lights were turned on, the generator output remained the same. In short, the 3 brush generator cannot automatically compensate for any type of varying electrical loads.
The 3 brush generator did not have any type of voltage regulator built into it. Adjusting the 3rd brush only changed the current output of the generator. The battery essentially became the voltage regulator in the system. As a result, the generator consistently applied an excessively high voltage to the battery (on the order of 8 – 8.5 volts). In fact, as the battery reached a fully charged state, the generator current output actually increased slightly as did the battery voltage! Over prolonged periods, this would cause overcharging of the battery. Many batteries and fine paint jobs have suffered from this poor regulating system!
If for some reason the battery were to be dropped out of the circuit, the generator output voltage would now be unregulated. If allowed to run unregulated, the generator voltage would quickly rise and could easily get up to 40 or 50 volts. This would in turn burn out the light bulbs and other electrical equipment, such as ignition coils. Excessive heat would be generated internally and quickly damaged the generator as well.



Bob

Bob C is offline   Reply With Quote
Old 09-05-2016, 05:36 PM   #44
Capt Kirk
Senior Member
 
Capt Kirk's Avatar
 
Join Date: May 2015
Location: Clarkston MI
Posts: 830
Default Re: Generator Third brush Adjustment

This is the sound of someone eating crow! I offer my sincerest apologies for my doubting posts and humbly say that you were right!. The band was a little stuck since the paint kinda bonded together. The third brush moved easily...I moved it upward a bit and noticed a difference in the amp gauge...moved it some more and saw an additional decrease in amperage. My lights didn't work yesterday but thought I'd give it another try just now and they work (twilight zone stuff!). I now have it set with the needle a blond fuzz above the centerline at idle and it looks to be at about 3 or 4 amps with the engine spooled up. I turn my parking lights on and it's a hair on the discharge side and when I turn the headlights on at high RPM, it's showing like a 5 amp discharge. I don't plan on driving at night so the lights are irrelevant but if I need some extra amperage, I know where to get it now. Should I adjust it farther so the amp gauge is reading 0 when at high rpm? Again, sorry for my doubting posts...you guys are great!
__________________
35 Ford Cabriolet
56 Chevy Pickup
63 VW Bug
Empty wallet
Capt Kirk is offline   Reply With Quote
Old 09-05-2016, 05:38 PM   #45
Capt Kirk
Senior Member
 
Capt Kirk's Avatar
 
Join Date: May 2015
Location: Clarkston MI
Posts: 830
Default Re: Generator Third brush Adjustment

Jseery...didn't get yours either
__________________
35 Ford Cabriolet
56 Chevy Pickup
63 VW Bug
Empty wallet
Capt Kirk is offline   Reply With Quote
Old 09-05-2016, 05:39 PM   #46
JSeery
Member Emeritus
 
JSeery's Avatar
 
Join Date: Nov 2012
Location: Wichita KS
Posts: 16,132
Default Re: Generator Third brush Adjustment

Sponsored Links (Register now to hide all advertisements)
Just slightly above o on the charging side.
JSeery is offline   Reply With Quote
Old 09-05-2016, 05:40 PM   #47
JSeery
Member Emeritus
 
JSeery's Avatar
 
Join Date: Nov 2012
Location: Wichita KS
Posts: 16,132
Default Re: Generator Third brush Adjustment

Quote:
Originally Posted by Capt Kirk View Post
Jseery...didn't get yours either
I'll just post it here, PM doesn't seem to be working.

"Antique automotive electrical systems do not run on their battery, they run on their generator all the time. EXCEPT when the engine slows down to idle for a stop and then the cutout relay releases and the car runs on the battery. If the ammeter is going up to it's highest position the battery is taking that in as a charge. It should, and will, go away after a few miles as the battery charges up and the remaining amps showing will once again be what the car needs to run. It's like a "Y". The generator at the one end and the car's running load at the other end and the battery at the remaining end. The cutout is in series with the generator end. If it wasn't there then the generator would just keep pumping current into the other end, the battery and the car's load, as required and all would be fine. The only problem is when the engine slows down or is stopped altogether, the battery will try to put it's charged current right back into the generator's windings. Hence the full name of the cutout "Reverse Current Cut Out". It performs no other function but to stop the battery from "seeing" the generator as a dump to ground."

Last edited by JSeery; 09-05-2016 at 05:55 PM.
JSeery is offline   Reply With Quote
Old 09-05-2016, 05:48 PM   #48
Brian
Senior Member
 
Brian's Avatar
 
Join Date: May 2010
Location: Masterton, New Zealand
Posts: 3,816
Default Re: Generator Third brush Adjustment

Congratulations! Simple ain't it? You'll have no more troubles now you've got a grasp on it.
__________________
Unfortunately, two half wits don't make a whole wit!
Brian is offline   Reply With Quote
Old 09-05-2016, 05:52 PM   #49
Capt Kirk
Senior Member
 
Capt Kirk's Avatar
 
Join Date: May 2015
Location: Clarkston MI
Posts: 830
Default Re: Generator Third brush Adjustment

Brian...sorry for doubting you. My dad was a good mechanic and engineer working for Aerojet General in LA. It was the daily driver as he built the family. The fault in my posts was because I was still crapping green in my diapers during those days. This was a 5 minute fix...not counting a beer and engine warm-up.
__________________
35 Ford Cabriolet
56 Chevy Pickup
63 VW Bug
Empty wallet
Capt Kirk is offline   Reply With Quote
Old 09-05-2016, 07:43 PM   #50
koates
Senior Member
 
Join Date: May 2010
Location: Melbourne Australia.
Posts: 2,076
Default Re: Generator Third brush Adjustment

Capt Kirk, I am greatly relieved that, Brian, JSeery and Bob C have been able to finally educate you into the correct workings of the third brush generator system. Had some family health issues the last few days and therefore no time to post anything. You could read my posts # 4, 8 and 12 for earlier answers. The correct name for the generator cut out is a REVERSE CURRENT RELAY or RCR. Just another point, depending on your engine idle speed which would be approx. 500 RPM, at that speed the generator would have low voltage output and no output in amps and therefore the cut out contacts would still be open. Engine RPM may have to be 750 or more to enable the generator voltage to be high enough to close the cut out contacts and allow battery charging to be possible. Back in the day when these cars were used every day and most people did not understand the charging requirements one had to take their car to the dealership to have the third brush adjusted down or up to cover summer or winter conditions. The owners handbooks stated this. Good luck with your nice 1936 Ford V8. Regards, Kevin.
koates is offline   Reply With Quote
Old 10-08-2020, 10:45 AM   #51
Bob Carabbio
Junior Member
 
Join Date: May 2010
Posts: 1
Default Re: Generator Third brush Adjustment

Quote:
Originally Posted by Capt Kirk View Post
It seems to me that the cutout is designed to interrupt the generator when battery voltage is at whatever the voltage setting of the cutout is...correct?
Nope - the Cutout Couldn't care less about Battery voltage, or electrical system load. It simply Disconnects the generator completely when the generator OUTPUT voltage falls below the battery voltage, and reconnects the generator when the generator output voltage rises ABOVE about 6.2 volts, or so.

The Model "A" generator is "Third brush regulated" to deliver a "CONSTANT AMPERAGE" to the Electrical system of the car Regardless of what the battery voltage, or the generator speed happens to be. It does this because of the "Bending of the magnetic lines" is directly proportional to the rotational speed of the generator at the point where the field excitation is picked off by the "third brush".
When the generator speeds up, the Third brush delivers LESS power to the FIELD COILS. This automatically reduces the Field coil excitation, and keeps the AMPERAGE (not the voltage) delivered to the electrical system relatively constant. The Model "A" generator is only capable of about 10 amps constantly supplied, and will overheat and "throw solder" out of the commutator if you stress it higher.

A "Voltage regulator" is an entirely different breed of cat. It has a "Cutout relay" which functions exactly the same as an "A" cutout, but there are two additional relays which both control the Field Excitation,

The Second relay limits the VOLTAGE that the generator puts out, and is why the Charging rate after a startup will be HIGH, to replenish the energy used by the starter, and then fall to a low value as the battery voltage rises to avoid overcharging the Battery.

The third relay is a Current control, which won't let the generator exceed it's thermal capability, when current draw on the electrical system is high.
Bob Carabbio is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 05:27 PM.