If I run a mag can't I spin the alternator off the driveshaft

Years ago in hot rod and I mean years ago they had a offy powered roadster pickup that was running the alt off of the drive shaft. On this banger I'm putting together what's stopping me from doing the same thing? I'm gonna run a magneto so that eases up the charging system no radio to fool with so your down to the ights and starter. Just run a deep cycle large cca battery right

 

Yes you can. the driveshaft should spin the alternator at a faster rate than the shaft turns...just like it does at the front of the engine (if you want the same charging ability).

If you can tolerate reduced output, you can spin it slower. The radio takes so little electricity, that its use will not have a big effect. If you can put it on a charger every day and not use the lights, you might even be able to get by with no alternator if you are using a magneto.

(I assume you will not have other things like a heater or electric radiator fan. )

 

I plan on running a electric fan so I will need an alt. That's about it other than lights and the starting circuit.

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I found a mount kit for the winters q/c on eBay I just need to figure out how fast to spin it. And do I run a big high amp alt or just a normal one

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Your electric fan will draw quite a lot of power so a larger alt would be my choice. Gary

 

And the alternator or course will not be turning while the car is sitting still.

 

And the times when the fan is really needed the alternator won't be spinning...

 

AND !! what is going to drive the water pump ???

 

It's common to get just the right size of belt to drive the w/p without a tensioner like an alternator.

 

Look for one that puts out high amps at idle, since it will always be run at a comparatively low rpm.

 

Or you could get one of these. Racemate combo water-pump/alternator.

 

Wow!, Except for the serpentine belt what a cool way to solve a common problem....never seen one of those!

 

I ran one off the driveshaft for years. Dont use a 1 wire since they have a higher excite rpm. Mine would start charging nearly right away, like 7 mph. My set up ran an electric fan, lights, dizzy, and never gave me a problem.

 

They have V-belt pulleys, doubles, even Gilmer-type. I don't know about serpentine aplications, but I bet that could be worked out too.

 

When you do run one off the drive shaft, where do you mount it? Everything's moving in and out and up and down back there.

 

here and
http://www.jalopyjournal.com/forum/showthread.php?t=89519&showall=1
picture of one way
there are more
http://www.specialstage.com/forums/showthread.php?44037-Toyota-MTEG-Stadium-Truck-Build/page11

 

They mount directly to the rear end.

 

I have a Joe Hunt, electric fan, electric water pump, and ran the alternator off the driveshaft.
Did it for about 5 years and always carried a jump box in the trunk.
I had to jump it numerous times.
Night time driving and long lines of heavy traffic were a killer for me.
I finally put a mini alternator on the engine and never needed a jump again.
Yes it looked trick, always drew comments, but it was stupid.