Delco Remy Generator Questions 6v or 12V?

The 6V system I currently have is just not up to the cranking task which is why I want to replace it. I do have the heavy duty 6V cable and ground strap installed and a fairly new battery. I have to jump start the tractor almost anytime for a hot start which is really aggravating. ///Gene Cockrell

If a 6 volt sytem dont crank satisfactory I first recommend the biggest heaviest highest rated battery that physically fits in the box and the use of 00 Gauge battery n starter n ground cables. Be sure n remove n clean n wire brush n reattach each n every battery n starter n ground n cable n switch/solenoid connection but if she still cranks slow you may have a starter/solenoid problem or finally the starter itself is bad. If the ground is to any thin wimpy or rusty sheet metal component, reattach it to a clean soild frame type bolt.

Dont forget any ignition modifications (ballast resistor or 12 volt coil) if you change to 12 volts and gauges n lights etc and ground polarity.

John T

1 - If generators are otherwise identical, the resistance of the field windings on a 12 volt generator should be about double that of a 6 volt. (Note: As field winding resistances are quite low in both cases you'll need an ohmmeter capable of reading to 0.1 ohm - ie. a digital voltmeter - to accurately measure winding resistance.)

2 - Generators ARE rotation sensitive. Brushes are positioned - and often also angled - for operation in only one direction (usually clockwise when looking at the drive pulley)

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Incidentally converting to 12 volts to deal with a slow cranking condition is only a temporary, "bandaid" fix. Your Allis should spin over just fine on 6 volts if everything is up to snuff. Requirements are good battery, suitably heavy battery cables (not the cheap "12 volt" cables like are sold in auto parts stores...), a good starter switch and of course a healthy starter.

BTW The starter on the tractor is fine, I have gone through this and it is in a good way. I have good cables (tractor cable) ground strap, connections, etc. I"m not cutting corners here.
When one hits the starter with 12V, the sucker spins. With 6V, unless it"s just off a battery charger you can"t get one complete revolution of the engine. Fortunately, the tractor if cold will always start by being bumped. I suspect this has to do with the engine. I rebuilt the thing a few years back and to get the head/block mating surface squared up, we had to machine almost 0.200" off. This has affected the compression ratio and I assume that this increased (from 5.7:1) compression combined with a marginal electrical system is the root of the problem. Like I say, when jumped with 12V, the starter cranks over like a BMW.

Shaft speed complicates things. Holding the same field excitation, simply turning the shaft twice as fast on a 6 volt generator makes 12 volts. Increasing the field current with shaft speed held constant increases the output voltage. That's limited by the magnetic saturation of the field cores along with the armature core.

The angle of wires leaving the commutator depends on which layer was put on last but it can affect the brush position.

The 6 volt starter worked for decades. If if won't crank with heavy duty (How heavy? 00 gauge is heavy, 2 isn't.) cables and battery, then there is need for starter attention. I believe in replacing bearings as well as brushes and solenoid and Bendix. Worn bearings (usually bronze bushings, simple sleeve bearings) let the armature drag on the pole pieces and that really kill shaft horsepower. When brushes are replaced they need to be sanded to the contour of the commutator and that commutator should have been turned and then the micas cut so they aren't touched by the brushes. Driving a worn out starter with 12 volts is like kicking a dead horse, doesn't make it work that much better for long.

Besides sturdy cables, the connections need to be clean through out the starting system.

Gerald J.