D17 ALTERNATOR CONVERSION

You are correct as I stated in my post. "The more modern one wires excite at lower rpms to start the charging process sooner". (much easier on the older engines)  I was making a comparison between the old and new Alts. BUT, when you run a voltage sensing circuit on larger Tractors with more accessories, it allows the Alt to compensate for loads better where a one wire Alternator is charging just the Battery. When a load is put on the system, and a one wire is up front, the load is put on the Battery which can take the Battery out eventually before its time. Also, the more you turn on, and go beyond that one wires rating, you're really putting a strain on the system and the Battery. Big difference. The more loads, the tougher it is on the Battery as well as the system. If you have a one wire Alt on a Tractor equipped with a Magneto and just lights, there isn't any load on the system till the lights are turned on. With just lights, the Battery would have plenty of reserve to feed the Headlights. Its the only load on the system so it would be childs play for the Alt. The Battery should stay in service for a long time unless it sulfates and kills a cell or two from the Tractor sitting a lot. With early Tractors, like I described above, I don't remotely junction the voltage sensing circuit back at the dash, I just swing the voltage sensing circuit to the output terminal at the back of the Alt because early Tractors won't use any current because there's no accessories to draw on the system. Even if they're equipped with a Battery Ignition, there's plenty there to feed what's needed. Now, if there is an electric winch or something like that installed at the rear of the Tractor, then I would design the system to handle what that winch would need. I've designed quite a few of those systems to. Its comes down to whatever works for you...
Steve@B&B

One wire hysteria? I don't follow what that means, but there's nothing wrong with one wire Alternators, they just need to be installed on the right applications. The early 30's & 40's Tractors that were equipped with the 6V PG systems had engines in them that worked at lower rpms. In the earlier days of the one wire Alts, most one wires needed 1200-1400 rpm in order to excite the regulators to start the charging process. The only problem there was you had to rev the engine up into that rpm range to start the charging process.  The earlier older engines weren't designed to work up high in rpms, so it was a little tough on the engine revving it to get things charging. You had a choice. Either do a pulley change to spin the Alt faster, or just use the Alt as a three wire which after about 450 rpm, the Alt is charging and no revving was needed on the older engine. The more modern one wires excite at lower rpms to start the charging process sooner.  (much easier on the older engines)  Moving into the late 40's early 50's, engine design changed dramatically, and working in a much higher rpm range was no longer an issue, so the older one wires fit the bill fine if that's what you want. (like these D17's on up) Its just like an Automobile. When I build one of my 12V conversion systems, I always wire the Alts as three wire using one of the wires as a voltage sensing circuit. Doesn't matter what model Tractor it is. This will actually monitor the system better, and when things are turned on and the load is increased, the VR makes the adjustment and the Alt ramps up a little more to compensate. Pretty simple. There's only two more wires to connect. Not a big deal. On say like a "D" series Tractor, I'll run the voltage sense circuit up with the output circuit and junction both at the dash area being this is the busy area where current is being used and distributed throughout the Tractor. As I mentioned, as loads are increased turning accessories on, the VR gets the signals and the Alternator does its job to keep up with the loads and also to keep the Battery happy. Its even more important wiring the system that way if the Tractor is equipped with a cab were wipers, heater, extra lights etc are not uncommon.... HTH  
Steve@B&B

If you have a problem with the alternator cooling fan rubbing the PS pump belt, leave it off. There is enough fan blast from the radiator fan to keep the alt cool. I've done this DOZENS of times with Delco alts and never had a problem.

Thanks TramwayGuy and theropod for the answer!
I've seen some pretty good sales of odd ball alternators on ePay and now I can pick up one of them and it won't matter.  Hated to shell out $$$ for one and worried that it wouldn't spin the correct way.  Now I don't have to worry!  THANKS

jeickman01 wrote: Ted  There was an output test sheet included with the alternator but it doesn't state direction of rotation nor are there any markings on the alternator itself.  Never thought about it before but I wonder if an alternator can run in either direction.

Ted  There was an output test sheet included with the alternator but it doesn't state direction of rotation nor are there any markings on the alternator itself.  Never thought about it before but I wonder if an alternator can run in either direction.

I just took delivery of the DB alternator only to find that it's a plain-box-Made-In-China product.  However, the "fit and finish" appear to be good quality.  And even if I could find an American made version, it would probably have Chinese made bearings.  Was going to post something one time questioning whether the UAW was the downfall of Allis as well as International but then began to wonder if even though they were part of the problem they weren't all of it.  Deere survived the ag economic downturn that contributed to Allis' failure and they were also saddled with high UAW wages.  Sure miss the good old days of US industrial smokestack production.  A lot of thought goes into buying an alternator for an old D17.  

Generally the alternator is driven a lot faster than than the engine crankshaft by having a large pulley on the crankshaft and a small pulley on the alternator. A generator pulley will fit an alternator most of the time but is larger so it doesn't turn the alternator as fast as can be accomplished with the smallest available alternator pulley. The internal construction of an alternator withstands very high shaft speeds a lot better than a generator.

It takes more alternator current capability than the lighting, accessories, and ignition load. Because the battery needs serious charging after cranking. Starters draw a few hundred amps, as much as 400 amps for ten to 20 seconds, and a 20 amp charging current has to stay for 20 times as long as it took to crank, longer because the battery efficiency is not perfect. A 10 amp charging current takes 40 times as along as the cranking time.

Gerald J.

Charlie175 wrote: 35 amp is the max output, however that is at 6000 RPM At tractor RPM speeds, the output is much lower, however it is more than OK to charge the battery and run the lights. Starts charging at low RPM's also.

Also keep in mind this is a negative ground system so you do have to switch some wires around.

35 amp is the max output, however that is at 6000 RPM

Charlie 175, do you remember brand and model number of your mini alternator? Your setup is very neat.

Seems the next alternator beyond the 10SI is smaller and if you have access to that it's suppose to fit better .

You'll have to notch the upper bracket to clear the PS pump bracket and leave the cooling fan off of the alternator to clear the PS belt. Been there...dun that dozens of times.