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external alternator BMW

Have any of you tried adapting an external automotive alternator to a airhead?? (motorcycle not babe)

Aftermarket upgrades are quite pricey and still limit power.

I have a plan but have not done it yet entirely. Just think, 80,100, 120 amps............pull a mardi gras float and light it too. ha. Wise cracks expected, of course. Yet still........
Jon

Hello

How do I send A photograph.

Regards

Barry

Jon,It's been done. I wish that I still had the link to an old photo. It appeared that the person who did it simply cut open the front cover with a band saw, bolted on an auto alternator using a conventional single mount and adjustable brace. The belt ran where you expected it to. No big deal. I believe that the one I saw was on a boxer that was being set up for some sort of world tour. Apparently it worked fine and eliminated a bunch of issues. It did look very unfinished and exposed.

Hello

Go to http://www.threewheels-uk.com gallery 18 there is a photo there, I have got a better one some where else and will look for it tomorrow.

Regards

Barry

Barry, read this thread

http://www.sidecar.com/megabbs/thread-view.asp?threadid=4470&posts=4

Thanks s-Uk, the pic is similar to my plan except on the other side of the frame. I plan to use the brakehose/horn tab for the top bracket and
the '78R100 crash bar clamp for the lower; they will be much smaller. It appears that it will all fit behind the Vetter IV lower. The alternator is very small, Nissan, Honda, Toyota, one wire built in regulator w/ sw and idiot light; wiring is simple and non destructive except for installing m/f bayonet connectors on ignition and charge light.

Send more pics to jcrow-t@bellsouth.net or send on to the forum for anybody else to see.

Questions that I have:

1.How much of an ill effect will come from the side stress of the belt on the crank bearing?
2. How did your example mount the pulley to the tapered crank and seal the timing cover? I plan to use a dead rotor for pulley mount, saving to good one w/ stator etc. to go back original if I want. Also have extra cover to cut.
3. How large was their drive pulley and what was their low rpm voltage?
My best measurement for the largest size possible to be 5 1/8 inches.
4. Did the rig affect the mileage very much? I get only 29+ mpg now.

More power!................hack heater or ac? Electric seat lift? (Becky is getting creaky.)

Thanks for the reply send more Jon

I too have done this mod and can recomend it. I have a different way of fixing mine than Barry in that my belt and pulley wheel are external. I had a steel extension made up same as the inside of a rotor. This then extended out of the timming chest where the pulley was fixed onto the extension (with a "woodruf key") so that it did'nt touch the timeing chest or the leading link fork's.
Then I mounted the alternator onto the right crashbar (it does'nt matter which side you mount it on, it will still work).
The critical thing is linning the alternator up with the pulley, as the engine tilt's backward's slightly. I welded an adjustable plate on the crashbar so I could use differant alternator's. At the moment I have a 75 amp on and it's been there for 12 yrs with no issues.
The main engerneering is in fabricating the extension from the crank, because the exteral diameter going into the timeing chest has to be exact as there is an oil seal there.
Sorry it's long winded, I guess a photo speak's more. I'll try and get one up. If you click on my profile you may just see it.
Safe riding Karl

Hello Jon

NOt sure of the detail, but I used to see the owner at most rallies around England so it must have been reliable.

Regards

Barry

look and ask on ratbike .org

Thanks for posotive comments. I am trying to locte a 5 inch pulley to mount on the dead rotor. I hab not thought of extending through the cover, a new idea.
I'll check out ratbike.org too, thanks.

My current plan is to mount the alternator, nippon denso small in physical size, on the left side, running the belt behind frame down tube.
I'll use the R100S crash bar clamp bolt to anchor the bottom where the tightening adjuster will be. The top has to be almost touching the gas tank. I plan to use both the horn bracket and voltage regulator bracket to locate the top stationary mount. Pieces of bed frame angle will do nicely, I think, which are easy to cut, grind, and weld, and will provide enough rigidity.
The 'one wire' alternator is simple to wire into the stock harness. I'll use bayonet connectors at the green ignition wire and the blue charge light wire where they go into the starter relay multiplug. The battery wire, which I already enlarged to #10 will be increased to the size of automotive starter wire. I'll remove and keep my good working stock components in case I want to go back original in the future.
The alternator will fit easily behind the Windjammer IV lowers panel.
I'll remove the stator and diode board.

I have a new unresolved question...........have any of you tried to disasemble a BMW rotor? Will the center machined part that fits the crank taper and timing cover seal press out of the windings part? If so,
fitting a belt pulley to the remaining outside shaft will be much simpler and a smaller pulley can be used.
Will the rotor shaft press out of the windings?

Whatcha got for me?................Jon

I found the answer ... here it is.
The rotor is 3 pieces, not counting the copper wire. To disassemble it, remove each end using short blows on alternating tips of the hex-fingers. The center will not press through and out because the part thatthe windings is wrapped onto is a larger diameter than the ends. The two hex-fingers will come off in opposite directions. The trick is to get them off without marring the end part that goes into the seal on the timing chain cover.
With the hex-fingers and windings removed, I can now have the center machined to fit pulley shaft hole.
After having found and read articles of successful auto alternator installations, I will change from the 5 inch pulley to a smaller one. With the machined rotor shaft, swapping pulley size will be simple. One article indicated that 1:1 ratio alternator to drive pulley worked best. I am wanting more output at lower rpm for town traffic, 4 brakelights and multiple headlights and a power inverter. I will try 3 inch or 3:2 ratio
pulley first hoping that at idle there will be no output change. Auot engines idle slower, but the pulley ratios are greater.
Maybe I'll figure out how to post pics so the modified rotor can be shared as well as the alternator brackets and final results . Wiring is the easiest part.

Yes, have done quite a few of these external alternator conversions. In almost every case they were BMW airheads, and I modified an old rotor, using the taper, to turn it into a pulley, and used a v-belt to drive an externally mounted alternator. The Denso alternators are very small and are very nice for this, providing about 600 watts. I have done a MUCH bigger alternator on occasion. You can contact me off-the-forum (I don't normally follow it....Joyce Canfield told me of your query) at:
snowbum (at) JPS.net
you know what to do with that address. Disregard any Earthlink notice that you need to be in my address book...I WILL get your message

Robert (Snowbum) Fleischer, Lake Tahoe, California, USA http://bmwmotorcycletech.info/emailimage.htm http://bmwmotorcycletech.info http://airheads.org ABC 1843; MOA Life 17058; AMA Charter Life 73254; USCA 6504….. ‹(•¿•)›

I'm sure that adding an auto-type alternator could be done. I'm not familiar with BMW's but I do know that several people have done this on the earlier Honda four-cylinder Goldwings. They were noted for poor alternator performance and it was necessary to remove the engine to change the alternator.

I looked on Google and found an article on a Goldwing conversion:

Here: http://www.icss.net/~squirts/stator.htm

I also looked at another article on Google where the writer talks about possibly overloading the belts with such a change. If a belt breaks, though, it's not a big deal, you could just change it.

FWIW, here is the other article: http://gl1200harness.tripod.com/belt.html

I like the idea of making changes like this. When I had my 1994 Goldwing a few years ago, the alternator really wasn't up to the job. I think it had something like 45 amps. I bought a Compufire alternator that was rated at 90 amps and it made quite a change. It fit like the original. The only negative thing about a larger alternator is that they do take a bit more power to turn and sometimes they can add vibration to your bike.

Good luck. Let us know how it turns out for you.