Generator to Alternator Conversion

[Woodcarver]

My Oliver 880 has developed a problem in the charging circuit. The voltage regulator may be the source of the problem.  It hasn't worked just right for quite awhile.  I priced a new regulator.  Cheapest I could find was about $60.00. A rebuilt generator is around $70.00.

I'm think of replacing the regulator and generator with an alternator.  I can get an alternator and wire for a new wiring harness at a local salvage yard for $40.00 - $50.00. I'll have to switch the tractor from positive to negative ground, but that doesn't seem to be a big deal.

Anyone had experience with the switch from generator to alternator?  Anything in particular that I need to be mindful of?  Any and all advice will be appreciated. 

[sawguy21]

Mounting brackets and the pulley will probably be the biggest issues. The wiring will be straightforward as most alternators have the regulator built into them. You can use the old generator as a 12v motor, must need it for something.

[scsmith42]

Woodcarver, I've converted a lot of my equipment to the "one wire Delco alternators".  Around here, the local Carquest sells them for about $50.00, fully rebuilt and with warranty.  you don't need a harnes, you don't need a separate regulator - just hook up the charging wire that went to your old generator and you're set.  They are based on the 50 amp Delco model that was standard on GM vehicles from the late 60's up until the late 80's.

Just ask your local auto parts store if they can get your a "one wire" Delco alternator.

Ditto sawguy's comments about the brackets.

[leweee]

Ditto what Scott said. ;D

check out this tread:
LINK

[Slabs]

You didn't say if the "Ollie" was a gas or diesel.  Probably doesn't matter.  The coil on a gas will probably take whatever you give it.  The guages may need a little attention.  Leads on the ammeter(if got one) will need to be reversed.  That simple.  Fuel gauge-same.  Just keeps the needles moving the right way.  In the days of the imported Leyland (long) tractors the simple solution was to just turn the battery around.  The Smith guages("hot wire type") didn't care how you put the juice to them.  I think they would have been happy with A C if the rest of the system could take it.  The "one-wire" alternators are a boon but don't be afraid of the older two-wire modles.  The "other" wire was for voltage sensing remotely so as to not be influenced by the close proximity of the alternator output.  I've built test jugs to service alternators by connecting the sense terminal directly to the output terminal.  The "exciter" terminal would normally be on an ignition buss so as to preclude drain on the battery while the engine is not running.  I tested the excitation current on a two terminal unit but don't remember the figures other than I thought it was signifigant.  Also you might want to put a small 12 volt bulb in series with the exciter terminal to indicate alternator activity.  The old "IDIOT LIGHT" of the 50's and up.  It is really a good tool to indicate alternator activity and seems to get more attention than an ammeter.

Check out my gallery of pictures for the terminal locations on the older two-wire modles and a complete schematic of the units circa 1974.

Good luck

[Woodcarver]

The Ollie is gas.  It's a 12 volt system so the coil should be OK.  Will have to reverse the leads on it, too, I think.  I'll have a look at the pictures, Slabs.  Thanks for the input guys.     

[Slabs]

Hey Woodcarver

"DON'T" reverse the coil leads.  The lead that goes to the points is also the ground side of the secondary of the coil.  I've heard of reversed leads working but poorly but I've never seen it.  The coil really doesn't care which way the current flows through it as long as the correct parts are connected to each other.  The starter also isn't particular about polarity.

[Woodcarver]

I"m confused, Slabs (not at all unusual).  I've read a number of articles dealing with the change from positive to negative ground.  All of them, including the article that Leweee provided the link for, say that the coil wires should be switched.  ???

[sawguy21]

Actually, the starter cares a great deal about polarity, it is a DC motor and will run backwards if not hooked up correctly.

[PineNut]

There are two different types of DC motors. One has permanent magnets (usually very small motors) and they are polarity sensitive. The other type has electromagnetic fields and they are not polarity sensitive. In other words, they don't care which wire is positive and which wire is negative. A starter will fit into this category.

When I made a positive ground to negative ground conversion, I didn't do anything to the starter. The only changes I made were to change the generator to an alternator, change the battery leads and reversed the leads to the amp meter. Had no problems.
Changing to an alternator was the reason I made the change.

[Slabs]

Woodcarver

I'm at a loss to explain precisely my stand on the polarity thing but I'll give it a try.  The coil has  full primary and secondary sections.  The primary is the low of 12 volt section in this case.  The secondary is the high voltage section nominally 25000 volts.
The 25000 volt potential is a "dynamic discharge/field collapse" situation caused by the condenser charging upon the opening of the points.  While the points are closed, current is flowing from the 12 volt system through the coil primary and the points to the vehicle ground causing a field of magnetic flux to be generated about the core of the coil in "one specific" polatity.  The condenser is in parallel with the points.  As the points open the current form the system is interrupted and the field about the coil core begins to collapse toward the opposite polarity of that when the points were closed.  As the points are opened and the field starts to collapse the eneregy of the magnetic filed collapsing through begins to generate a potential opposite  of original potential caused by the original 12 volt application.  It is at this point that the condenser begins to absorb the energy created by the collapsing field and begins to charge up greatly enhancing the rate at which the field collapses causing a much greater potential in the secondary i.e. the resultant 25000 volts to fire the spark plugs.

The trick is that there are only three connections on the coil.  The high voltage output to the distributor cap, the primary system input and the point/condenser terminal.  The point/condenser terminal is common to both primary and secondary windings of the coil and conducts the "back" current of both windings to the condenser.  If the primary connections of the coil were reversed, the secondary winding would have to discharge through the primary winding on order to be absorbed by the condenser.  The coil really doesn't care which polarity it's energized as long as the secondary winding can discharge properly i.e. via the condenser.

I apoligize if this seems too complex but that's the best I can do without a full schematic.  I have heard the point-coil ignition called the "old Kettering ignition" but Charles Kettering's contribution was the electric starter (though he may have done some ignition work).

Yes the "excited field" D. C. motors will run in one direction regardless of polarity unless the armature excitation is changed 90 degrees as achieved by individually connected brushes and there are four brushes in excited field motors too.  The permanent field motors will reverse with reversal of applied polarity.