Wiring size question

In Bob M's schematic below, he calls for 10 and 14 gauge wire. Can any other gauges be substituted for a 12v system? A club member has some wire, but I don't know the gauges, and I'd rather not have to buy wire to get this H going again. (because I have a brand new wiring harness, but it's for a Mag, and I don't have a mag yet... so this wiring is only temp to get me going for a parade.)

Bob's is ok BUT when i do a rewire and when you throw in a 12 volt alt. The main wire off the alt i use 8 ga. and the 14 With a 12 volt system you can drop back as the amps are lower then on a 6 . But for the most part i do the 14 for most of the wiring and myself i use the correct colors . That way down the road someone can look in the book and know just where the wires are suppose to go by the color of the wire and the book . Hey it is just my thing as just try and chase down a problem when ya have all reds or what ever was on sale that day in a harness .

Mike,

There's nothing magical about any of the wire sizes. Any bigger size will always work, until you get to the point that its too big to fit on the connectors. A lot of times something smaller will work just as well.

12 volt lights draw less current than 6 volt ones, for the same brightness. However, 12 volt lights tend to be brighter (higher wattage) offsetting some of this difference.

For the ignition and field wiring, it only needs to carry a few amps, and just about anything sturdy enough to survive the vibration will work. I wouldn't go much small than about 18 guage just because it would be too easy to damage.

The wiring from the output of the generator to the battery has to be able to carry the output of the generator without overheating. For runs this short, the resistance of the wire itself can be reasonably ignored (resistance here will slightly affect how fast the battery charges, but won't keep in from charging completely). I probably wouldn't go much smaller than #12 for a 20 or 30 amp generator, although #14 would probably be OK for a temporary installtion.

Wiring to the lights should be a reasonable size, as extra resistance here will affect how bright the lights are. Again, for a temporary installation, just about anything of reasonable size would work, particularly if you're not concerned about how bright the lights are.

Bigger is better for starter cables.

Keith

Sure, Bobs wire sizes will work just fine HOWEVER NOTE it dont hurt much if a wire is bigger then necessary....For example if you had this big roll of No 12 wire I see no need to run out and buy some 14 gauge just to be in strict accordance with the diagrams. Still if you have to cheat, Id rather go with bigger then smaller wire which can reduce voltage drop and waste less energy in the form of heat losses (still negligible for the most part due to typical current and wire length)

For battery n ground cables I like at least 0 better yet 00 for 6 volt and on 12 volt I like No 1 or even 0, again no harm (even better for cold starting) in using bigger cables

FINE TUNING: On Ignition circuits like from ammeter to IGN switch and from switch to coil and from coil to distributor I use 12 instead of 14 just for general voltage drop considerations although 14 or heck less will get you by.......On charging systems like generators I use 12 from genny to VR and VR to ammeter and from ammeter to battery/starter and bump that up to 10 or even 8 on alternators......On many light circuits I use 14 or 12

I like stranded wire for its flexibility and vibration withstand and if you crimp and solder the terminals thats great.....

John T

The difference between the Mag wiring, and the coil wiring is only the method of using the wire going to the mag. All other wires should be identical to the coil wiring.
Use the mag wire as an ignition wire from the existing ignition hot when in the run position terminal, to the coil (or resistor if you have that type of coil).
Then when putting on the mag, you will change this wire from hot when on to a "mag kill switch" which is grounded when pushed in, and off when pulled out. It will then be attached to the mag Kill terminal. Do it in this order to prevent putting voltage to the mag, they do not like battery voltage at all. JimN
The 6v wires are just fine, and the job would be almost completely done if this method were used. JimN

As John T points out, the wire sizes given in my diagrams are only recommended minimums. There's no harm increasing wire size - other than the difficulty fishing/bending larger wiring.

Also as John T mentions using stranded wire is a MUST! The constant vibration that must be endured by tractor wiring can cause unsecured solid wire to fatigue and break - sometimes inside the insulation where the break cannot be seen.

Where ya been Robert?? What if Ol Jimbo or I get in trouble and youre not here to bail us out lol. Hey you gonna post the pics of our ugly mugs you took in New York?? DONT DO IT we will loose what little credibilty we have lol

RE Wire sizes, Ive never ran it through a calculatior but in the current ranges were talkin here (say 2 to 10 amps usually maybe 20 max in charging circuits) I bet if you compare the Voltage Drop for say a 3 to 6 ft run of 12 versus 14 gauge wire it wont amount to a hill of beans (even less, a small hill) difference STILL I just "feel better" when I use 12 for ignition and of course charging....

Ol John T

PS get your old moms in shape n retire so we can camp n visit some

Hey John - If you do the voltage drop calc’s, you'll find the modest current flows and short wiring runs on these old tractors make the losses in the minimum size wiring is pretty much inconsequential.

Bigger wires of course can’t hurt. But they don’t really gain you much either.

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Where have I been lately? The past several months have been kinda busy at my “day job”. Also I’ve been occupied the past 6 weekends helping at a friend’s fall festival/pumpkin patch. (Spent most of my time bouncing around on the farm’s various JD “A” tractors…makes me appreciate my Farmalls all the more!)

And I hear you on that retirement thing! I’m simply waiting for external_link to deliver my free health care and a generous bailout to cover my 401(k) losses. THEN I can afford to retire(!)

You telling us the AT's on the base can't cumshaw a littler wire? What's the Navy gone to?
Once I went to the Quartermaster and asked if I could get a piece of 3/4 inch manila line. He gave me a whole spool about 300 feet and said "bring back what you don't need." Turned out between my friends and I, we "needed" all of it

Gordo

You telling us the AT's on the base can't cumshaw a littler wire? What's the Navy gone to?

Click to expand...

I'm on leave, sir. I'm staying as far away from the base as I can for as long as I can.

Besides, I can drive 45 minutes one way to scrounge some wire, or I can drive a mile down the road to my buddy's house and scrounge his. Plus, I don't have to shave, get a haircut, and put on my uniform to do it! The math is simple.