Gear drive set up for later 6V-92 alternators vs 6-71 generators....

[zubzub]

Here is my dillema.  My bus lives in a used transit yard, there are lots of 6V-92s in there and I can get an alternator of one of them for cheap to next to nothing.  At first blush it seems like the gear drive part of the alts are not set up the same way as mine

this pic is on an angle but basically the gear (that inserts into the driven fiber plate(?)on the engine)  is in the center of the housing.  The alts I saw that had been pulled had the gear offset quite a bit and I'm pretty sure the housing was different.
 So here's my question, am I being thick?  Is the gear drive portion just bolted on to the end of the generator/alternator?  
Can I swap them out?
I know the answer to the 1st question depends on the day/week/month/year.  But how about the possible change ins.
I have sourced a gear drive/ pulley set up locally so that is a possibility, but I also like the idea(price/power) of a gear driven alt.  I don't like the idea of only being able to fit some weird old alt from the 60s as those are the kind of "modifications" I usually avoid. When I look at my old generator it seems like the gear is just bolted to the shaft of the generator and on the alts I saw the gear was offset (maybe there is a reduction gear in the housing?) plus the housing had a different bolt pattern/diameter.
  Thanks as always for your input, Patrick.

[TomC]

To me-your generator setup looks like it is just running at the same speed as the gear drive.  And if your generator is coming off the blower drive, that would make sense since the blower on the 6-71 runs at about 2 times the speed of the crankshaft. 
With most 50DN drives (at least what mine is) on the 8V-71, my power steering runs off the the blower drive, and my alternator runs off one of the accessory drives gears.  It is offset since the accessory gears runs at the same speed as the crankshaft, the alternator is geared to run at 2.75 times the crankshaft speed.  So like with my engine being red lined at 2400rpm, that means the alternator is turning around 6600rpm-which is a bit higher then the 6,000rpm it is rated at.  Luckily, I rarely get to that rpm.
I believe to switch to the 50DN you'd have to change out one of the accessory drive gears on the back of the engine.  If it were me-I'd just change one of the open spot accessory drives to a twin V belt drive and run a 200 amp Delco or LeeceNeville truck alternator with built in regulator.  Then if it goes out on the road, you just need to go to any truck dealer to exchange for a new one.  I know we were selling the 160amp for about $160.00 on sale. Good Luck, TomC

[luvrbus]

The 50D uses a single planetary drive gear you should be able to find one off a later model 8v71 that will work for

good luck

[RTS/Daytona]

from my notes - The gears may be different ??

 Most 6V92 / 8V92-->(2.94 (53/18) gears & 6 pulses per rev=17.66 pulses/rev)
 Most 24 volt - 8v71->(2.75 (55/20) gears & 6 pulses per rev=16.5  pulses/rev)
 Most 12 volt - 8V71>(2.29 (55/24) gears & 6 pulses per rev=13.75 pulses/rev) 

[zubzub]

I have a 6-71 and the generator runs off # 3  in the LA version of the gear train pictured below.



I agree that pulley drive probably makes the most sense.....it just there are so many alt  around, thanks for the note on the 8V-71 there is a scrapped buffalo right next to mine, it's from the sixties so I would probably get into a old stuff but maybe if the price is right....I know better but $$ is tight these days with work stoppages etc....the irony is  "less work = more time to work on bus but less work  = less $ to work on bus with"

[luvrbus]

Zubzub, there is a 1/2 spacers that you use also has 2 screws in it you set the backlash with.



good luck

[Hard Headed Ken]

If I remember correctly the updated version of that fiber drive was replaced with aluminum.

Ken