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Old 12-25-2011, 08:40 PM   #46
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sorry, Im nog addled this evening
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Old 12-25-2011, 08:46 PM   #47
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Actually there is no need to mount on the crash bar. Two points of the alternator need to be attached. The stationary mount point will be threaded into a stand off made in the timing chain cover. The movable mounting point is attached to arm that is also attached to timing cover. The rotor converted to a pulley and the V-belt passes thru reliefs cut into the points cover. The one shown with the alt hung on the crash bar was done with U-bolts and whatever scrap the guy had. It's OK, it works. But it wouldn't be hard to make it neater.

I don't think it would be ugly or unsightly. It's a very common complaint people make when ever any beloved machine is modified or something added on to improve function. I think I'd look at it and all I'd see is all the electrons zipping around.

Really the current after market alternators for our bikes are made of a size to fit under the points cover. These could be made a lot larger if the cover was modified. A bump in the cover and then it would all be back in the original position.

Charlie
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Old 12-25-2011, 09:15 PM   #48
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Originally Posted by Wirespokes View Post
I've got a one wire ND and it's about the smallest alternator available. Hot Rodders use them because they fit into very tight spaces. They are very small - someting like six inches long and wide. But even that is too large to fit behind the points cover.

And, Stage, I agree, mounting one on the crashbar is unsightly, but that's not the one we're talking about; mounted above the engine in front of the starter similar to the oilheads.

And I also agree that there's no patent on that design and doubt it could even be patented. Even if it was, there's no law against me building something like that for myself.
after thinking about Les' design ... the only possible place to reliably anchor an alternator is using the starter mounting bolts. which happens to be the only possible location deep enough. He used a Bosch alternator, there may be better choices.

found Greg's posting on MOA...

"You have to modify the timing cover, front cover and top engine cover. Total 20 minutes with a band saw. You have to drill and tap one hole in the engine case. 15 minutes. And it's so much easier with the engine out so if you're doing a rebuild, perfect time.

What you get rid of is the rotor, diode board, stator, and VR. What you get is an industrial strenght Bosche alternator mounted in a CNC aluminum casing complete with the drive pulley, brackets, and rectifier ready to mount."

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Old 12-25-2011, 10:00 PM   #49
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Originally Posted by _cy_ View Post
this design elegantly removes the fundamental weakness of airhead charging system. which is alternator cannot spin faster than engine rpm.
While I agree with the premise that most alternators are driven about three times faster than the crank rpm, it appears that the first pictured example does not use a significantly larger pulley on the crank to achieve this ratio advantage. Actual generating capacity of the pictured unit at idle would be compromised. Anybody have the voltage/amperage at idle for this alternator installation?
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Old 12-26-2011, 08:04 AM   #50
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The other thing to remember is that this power isn't free. It takes power to make power. You can put bigger and bigger pullies on your crank to spin the alternator faster and faster, but you're also killing power. The efficiency of a car alternator is about 60% at BEST. If you're making 800 watts with your alternator you're pulling 1600 out of your engine assuming an efficiency of 50% (and even 50% is on the optimistic side). That's about 2.15 horsepower you're robbing if you run the alternator at full output. Turn off all those lights and you'll actually feel your bike surge forward a bit.
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Old 12-26-2011, 08:20 AM   #51
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Quote:
Originally Posted by Airhead Wrangler View Post
The other thing to remember is that this power isn't free. It takes power to make power. You can put bigger and bigger pullies on your crank to spin the alternator faster and faster, but you're also killing power. The efficiency of a car alternator is about 60% at BEST. If you're making 800 watts with your alternator you're pulling 1600 out of your engine assuming an efficiency of 50% (and even 50% is on the optimistic side). That's about 2.15 horsepower you're robbing if you run the alternator at full output. Turn off all those lights and you'll actually feel your bike surge forward a bit.


2.15 would be somewhere around 10% on my /2. I'm not sure I'd be able to continue traversing in 3rd gear with such a massive loss of power.
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Old 12-26-2011, 10:24 AM   #52
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That's a good idea - produce a larger stator and rotor and then cut and re-weld a bump into the points cover. That could actually look pretty cool!

I LIKE that idea!

Maybe we can convince Motorrad Rick to do this for us.

As for the larger alternator dropping engine power - it'd only be when all the appliances are running.
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Old 12-26-2011, 10:43 AM   #53
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moving the cover always involved some problems with full wheel travel, but then again, if there's room for that pulley off the front...
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Old 12-26-2011, 10:50 AM   #54
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Could even make the cover in two parts to make fit and R&R easier.
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Old 12-26-2011, 11:10 AM   #55
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Originally Posted by Airhead Wrangler View Post
The other thing to remember is that this power isn't free. It takes power to make power. You can put bigger and bigger pullies on your crank to spin the alternator faster and faster, but you're also killing power. The efficiency of a car alternator is about 60% at BEST. If you're making 800 watts with your alternator you're pulling 1600 out of your engine assuming an efficiency of 50% (and even 50% is on the optimistic side). That's about 2.15 horsepower you're robbing if you run the alternator at full output. Turn off all those lights and you'll actually feel your bike surge forward a bit.
APU Auxiliary power unit is the real answer to this question that should have never been asked. The stock setup slightly modified works great IMO.
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Old 12-26-2011, 08:03 PM   #56
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Another idea I've toyed with is utilizing the wasted power of the exhaust. Instead of baffling the exhaust to slow it down, harness it with a turbine driving an alternator.
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Old 12-27-2011, 07:06 AM   #57
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Unless you're talking about software, you can use a patented idea/create a copy of a patented item for your own use. You might even get away with making a few copies, and giving them to some silent friends. BUT... making copies to sell, even a few, will be bring the lawyers out big-time.

Close, but no stogie.
Wrong. Where did you study patent law?
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Old 12-27-2011, 09:35 AM   #58
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Originally Posted by Wirespokes View Post
That's a good idea - produce a larger stator and rotor and then cut and re-weld a bump into the points cover. That could actually look pretty cool!

I LIKE that idea! Maybe we can convince Motorrad Rick to do this for us.
logic says if it was possible to easily exceed 450 watts for an alternator limited to size of airhead case and engine RPM. the aftermarket alternator folks would have already done it.

due to unsupported nature of airhead rotors, would not want to exceed OEM weight by much.
for higher output, either the stator/rotor has to be larger or RPM has to go up.

looking at the 800watt alternator design again... both pulleys are about the same size, which means new alternator is spinning same RPM at engine. so gains are from larger stator and rotor. not RPM increase.


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Old 12-27-2011, 03:50 PM   #59
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logic says if it was possible to easily exceed 450 watts for an alternator limited to size of airhead case and engine RPM. the aftermarket alternator folks would have already done it.
normally, I'd agree with that logic, but since airheads don't have the same market volume as say... ipod apps or honda civics...
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Old 12-27-2011, 04:03 PM   #60
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Same principle, different application = $50. Nowhere near as good looking, but hey 15 yrs of sterling work and not a part replaced.
And removable!
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