Sun Jul 27, 2008 11:13 pm
VW generator conversion for Chief: Let there be light!
With near 1000 miles on the ’46 Chief engine break-in I’ve come to realize that the “high output” generator with regulator isn’t putting out much more than my ’39 Chief generator with cut-out. I have a pair of driving lights which I can’t use or I’ll drain the battery. The only other extra electrical load on the ’46 Chief is a pair of rear marker lights. I figure total draw is about 20 amps and the generator is lucky to be putting out 15-18 amps. I remember hearing about a VW generator conversion which would double the output and so did a search and found very little to go on. I was able to obtain a VW generator and matching regulator rated at 7 volts, 45 amps, negative ground which I figured would do the trick. Cost: $20.00.
The VW generator’s dimensions were almost exactly the same as the Indian Autolite generator. The only real difference was the VW generator being slightly smaller in diameter (about 1/32nd”) but I knew it would fit into the generator holder even if I had to use a shim to make up the difference.
The main problem was going to be rotation of the armature for although both the Indian and VW generator show a clockwise rotation, you have to mount the VW generator “backwards” for it to fit in the Chief’s frame. Thus, the back end of the VW generator (normally with a large cooling fan attached and mounted inside the VW engine shroud) on which you have to mount the generator pulley would be rotating counterclockwise. I checked both generators by “motoring them” (attach positive lead to hot side of field, attach other field lead to armature lead and attach negative lead to generator body). Both motored in the opposite direction to their intended generating direction and in opposite directions to each other.
Since the flow of current in the field determines polarity, I figured that swapping the two ends of the field as they connect to the regulator would generate the right polarity with the VW running opposite its intended rotation. In essence this ran current backwards through the field to compensate for the armature running backwards in the generator. I had to solder on small wire extensions to the field leads so they could reach across to the other leads position on the regulator. I put it together and motored it again and….Bingo….it rotated just like the Chief generator.
Then it was just a matter of pulling out the armature, chucking it into my lathe and cutting the pulley shaft down to the same diameter as the Chief pulley. I also had to file down the key and slightly file open the key slot in the pulley so they would mate snugly. I then cut off the other end of the armature shaft…the end that would have normally been used on the VW for the generator pulley. I mounted the VW generator with the regulator pointing downwards: there isn’t sufficient room to mount it upright. I also had to insert a thin piece of brass shim (.015") about 1” wide and 5” long between the generator body and mounting bracket to ensure a snug fit.
The results were absolutely great! The battery charges to 7 volts regardless of the load and even with all the lights on there is still a slight maintenance charge. If the battery is run down, say at a traffic light, the generator charges it right back up and then goes back into a maintenance charge. With full load, the generator will charge at about 30 mph in 3rd gear. When riding with less than a full load (i.e. driving lights off) it will do even better. Even with all lights off, the current is regulated so you don’t have to worry about boiling off your battery.
I know it may seem sacrilege to use a VW generator on and Chief but I ride my bikes year round and performance and reliability are key. It also looks great too coming very close to the original Autolite in appearance! I guess I could have opted for a 12 volt upgrade to the Chief generator or even gone to an alternator. However, for $20.00 and a little bit of experimenting I have solved this common problem. I suspect that the Bosch electronics will be a lot more reliable as well. My biggest surprise was that Bosch was able to pack that much power into such a small package. I have a ’39 Plymouth with a 35 amp generator that has to be twice that size! VW also makes a 30 amp generator but I’d stick with the 45 amps: lots of reserve power means you can use higher output bulbs.
The VW generator’s dimensions were almost exactly the same as the Indian Autolite generator. The only real difference was the VW generator being slightly smaller in diameter (about 1/32nd”) but I knew it would fit into the generator holder even if I had to use a shim to make up the difference.
The main problem was going to be rotation of the armature for although both the Indian and VW generator show a clockwise rotation, you have to mount the VW generator “backwards” for it to fit in the Chief’s frame. Thus, the back end of the VW generator (normally with a large cooling fan attached and mounted inside the VW engine shroud) on which you have to mount the generator pulley would be rotating counterclockwise. I checked both generators by “motoring them” (attach positive lead to hot side of field, attach other field lead to armature lead and attach negative lead to generator body). Both motored in the opposite direction to their intended generating direction and in opposite directions to each other.
Since the flow of current in the field determines polarity, I figured that swapping the two ends of the field as they connect to the regulator would generate the right polarity with the VW running opposite its intended rotation. In essence this ran current backwards through the field to compensate for the armature running backwards in the generator. I had to solder on small wire extensions to the field leads so they could reach across to the other leads position on the regulator. I put it together and motored it again and….Bingo….it rotated just like the Chief generator.
Then it was just a matter of pulling out the armature, chucking it into my lathe and cutting the pulley shaft down to the same diameter as the Chief pulley. I also had to file down the key and slightly file open the key slot in the pulley so they would mate snugly. I then cut off the other end of the armature shaft…the end that would have normally been used on the VW for the generator pulley. I mounted the VW generator with the regulator pointing downwards: there isn’t sufficient room to mount it upright. I also had to insert a thin piece of brass shim (.015") about 1” wide and 5” long between the generator body and mounting bracket to ensure a snug fit.
The results were absolutely great! The battery charges to 7 volts regardless of the load and even with all the lights on there is still a slight maintenance charge. If the battery is run down, say at a traffic light, the generator charges it right back up and then goes back into a maintenance charge. With full load, the generator will charge at about 30 mph in 3rd gear. When riding with less than a full load (i.e. driving lights off) it will do even better. Even with all lights off, the current is regulated so you don’t have to worry about boiling off your battery.
I know it may seem sacrilege to use a VW generator on and Chief but I ride my bikes year round and performance and reliability are key. It also looks great too coming very close to the original Autolite in appearance! I guess I could have opted for a 12 volt upgrade to the Chief generator or even gone to an alternator. However, for $20.00 and a little bit of experimenting I have solved this common problem. I suspect that the Bosch electronics will be a lot more reliable as well. My biggest surprise was that Bosch was able to pack that much power into such a small package. I have a ’39 Plymouth with a 35 amp generator that has to be twice that size! VW also makes a 30 amp generator but I’d stick with the 45 amps: lots of reserve power means you can use higher output bulbs.
