Main Alternator Modifications August 13, 2003
I just got the mounting flange for the alternator back from the machine shop. The outer diameter was turned down to 3 inches to allow the alternator to resemble a Slick magneto. This is a 40 AMP Hitachi LR140-707 alternator that fits just above the starter in the magneto drive. The nominal RPM range of this alternator is 400 to 4000 RPM so it is perfectly suited to being driven from the end of a VW crankshaft. I'm waiting on new bearings for the alternator so that I can reassemble it and begin work on the drive coupling.
Update August 16, 2003
I manufactured the alternator hold down clamps from 0.125" x 4.0" aluminum stock. The first step was to mill .092" relief from the end of the bar stock to fit over the alternator mounting ring. This was accomplished with an X-Y table and a four fluted end mill in my drill press. Not very high precision, but acceptable for KR work.
The next step was simple cut, sand, file and drill to make two mounting tabs from the bar stock.
And here's a left and right side view of the installed alternator. It is a very tight fit for the mounting bolts under the alternator. The bolts must be put in place fully seated in the tabs and then taken up a turn at a time side by side to bring the alternator into the magneto mounting boss. It's one of those things that it fits but there's no extra room for bolt installation if the alternator is pushed all the way home before tightening the mounting bolts.
The alternator bearings arrived yesterday so today I'll install the armature and begin the task of fitting the alternator drive to the magneto drive on the end of the crankshaft.
November 30, 2003
The activities of life have kept me off track since my return from this year's KR-Gathering in September. New job, son's High School Football team made the State Championship Play-off, daughter's new horse ... I was determined to use the Thanksgiving holiday to get started again. I have completed the design work to modify the alternator drive to look like a magneto.
How do you make this 
Look like this 
?
The mounting flange has already been modified and it fits the engine. Next step is modify the drive hub of the alternator to allow the magneto drive hub to be welded to it.
October 5, 2006
My first attempt at fitting the magneto drive to the alternator turned out to be a big failure. After a couple of months getting my schedule to line up with a friend that had a lathe it turned out that the alternator drive hub was heat treated to a very high degree of hardness. We were successful in machining down a carbide tool on the lathe and the alternator hub had not taken off even .001"!
After some head scratching I was able to anneal the hub using my acetylene torch. It was a little tricky to get the whole hub to the right shade of dull cherry red. To facilitate the slow cooling of the part I used a two pound coffee can upside down on the welding table over the hub. I placed a huge pile of rags over the can to help insulate it and slow the cooling process. This same process was used to anneal the magneto drive hub so that it could be machined.
How do you make this
Look like this
The mounting flange had already been modified and it fits the engine.
The next step is to modify the drive hub of the alternator to allow the magneto
drive hub to be welded to it. 
The drawing can be found on sheet 3 at: alt0001.htm
To machine the hole in the center of the magneto drive hub I used a 25mm hole saw in the drill press. It took a couple of starts readjusting the clamp on the hub to get it centered but the result was quite good. The hole is .002" from centered. I'll chuck the hub in the lathe and clean it up to final fit. The hole is .005" undersized so it should be no problem getting it cleaned up to the final diminution of 1.100".
I also made a trip to the local auto-electric rebuilding shop and purchased a bad rotor for the alternator for $10. I took the commutater rings and fans off the rotor so that it can be used as a mounting tool to chuck the alternator hub in the lathe.
Hopefully this weekend I will have a complete alternator with magneto drive.
November 4, 2006
Today we successfully answered the question:
How do you make this
Look like this ?
The drawing can be found on sheet 3 at: alt0001.htm After two hours on the lathe the comment was made: "Hey, this thing is looking like the finished drawing!"
Next step is to reassemble the alternator and make a trial fit in the engine. If all is well the magneto drive will be welded to the alternator hub to complete the fabrication of the alternator drive. I plan to use four spot welds where the cross flanges are located to minimize any heat deformation of the finished piece.
November 6, 2006
Today I test fitted the alternator in the engine with the drive puck attached. I left the back half of the alternator case off so that I could spin the alternator by hand and determine the fit. All was well with the trial fit so I welded the magneto drive flange onto the alternator hub and test fitted the alternator in the engine with the drive puck. I could not find a good way to measure the drive puck engagement depth but it eye-balled at about .200". The puck depth is .250" so it seems ok for now. I now have a 40 amp alternator that looks to the engine like a magneto! Finally, it's only been two years working on this project.
Welding cast steel to mild steel was a little tricky but I went slow and got a relatively good looking weld. The cast steel wanted to melt at a lower temperature so torch control was critical. The cast steel seemed to have a lot of impurities in it that made it fizzle and spit if heated to much.
All that is left is to rebuild the alternator with new bearings and brushes a simple task compared to the 27 months of work to make an alternator look like a magneto to the engine! I will also be installing a thermocouple on the field windings so that I can monitor internal alternator temperature during the test flight period.
November 16, 2006
Today the hold down clamps were modified for the final assembly of the alternator to the engine. Once the alternator was torqued down in place there was a very slight clearance fit that allowed the alternator to be rotated. The hold down clamps were put on the belt sander and .006" was removed from the thickness of each clamp. They originally measured .245" thick and now they are both .239" thick. The alternator was reinstalled and torqued down and the fit was perfect. Originally the hold down bolts were 5/16" x 1/2" hex head bolts. When I got the drive coupling installed these bolts turned out to be very difficult to install. Because of the overhang of the alternator over the mounting flange you have to seat the drive coupling and then pull the alternator out aft enough to slide the hold down clamp in place and start the hold down bolt. Man just doesn't have enough fingers to make this happen. I got the idea to use a socket head screw with a ball end allen wrench to make installation easier. It took a few days to find the right size screw and then it turned out that the head was too high to fit. Now another trip to the hardware store to search for button head socket screws in 5/16" x 1/2". This made the installation workable. To make it easier I broke off two alternator cooling slot rails adjacent to the hold down screws to allow a shallower angle with the ball end allen wrench. The pictures below show the final result.
The picture on the right shows the very close proximity of the battery contactor to the alternator and starter. The B+ lead of the alternator will be connected directly to the starter with an ANL current limiter. From there it will ride on #2AWG cable to the battery contactor and on to the battery. Total length of the B+ wire path to the battery will be under 18". This combined with the linear B&C voltage regulator should provide a very quiet electrical system.