Thread: Direct Drive Alternator

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I would like to drive the alternator off the front of the crankshaft on a 427FE. Direct drive. No belts. Has anyone done this?

If you intend on any type of racing or high rpm's, you'll be over revving the alternator. I guess I'm really trying to figure out... why? You'll still need some mounting of the case and then a coupler between crank and alternator. So, why?? It could be cool I guess, just can't figure out if it's worth the bother. My 2 cents..

I'm with 34 on this one with the Why? But I've done some really different stuff just to do it, so I think I understand.

Problems are with the speed of the alternator. Driving it direct from the crank is going to be way to fast. Not a problem that can't be addressed but you will need some kind of a reduction to make this work. Second is coming up with a gear drive, good machine shop can do this if you can come up with some drawings of a system that works. Next your going to have to mount the alternator right next to the crank, so A workable mount needs to be designed as well.

Your question in the end is "Has anyone done this?" Man there's not much in the Hot Rodding field that hasn't been done, so yes it PROBABLY has been done. but it must not have been too succesful as you don't seem to see them around. Plan on this being a "One Off" kind of deal. Sharpen your pencil's and set down and design a system that may actually work. Then bounce the idea around some.

Roland

Without going into the why, think about it for a second and look a the size of a normal alternator pulley compared to the size of the crank pulley it's driven off of. The alternator would be being driven SLOWER on a direct drive setup.

Many motorcycles have "direct drive".

They turn them up to 15K RPM and I have never seen one come apart yet. The weak link seems to be rectifier and regulators, not the stator exploding due to high RPM. The motorcycles use the same Nippendenso "mini size" alternators like you see at the auto swap meets with just a different drive. In fact you might even take a look at one from a late model Triumph so you could adapt the driver instead of converting over from an automotive pulley style. Near as I can tell they look identical.

Originally Posted by Mike P

Without going into the why, think about it for a second and look a the size of a normal alternator pulley compared to the size of the crank pulley it's driven off of. The alternator would be being driven SLOWER on a direct drive setup.

Yup, about 1/3 to 1/2 speed.

Theres some Toyota van that drives an alternator from a mid engine to the frontal area

however, engine speed is too slow for normal operationnas usually an alternator has a very small pulley with a large( 8 in) pulley on the crank for around 4-1 ratio???

I have considered driving off the tailshaft coming out of rear of trans with a gilmer belt set up of around 3-1

Originally Posted by Mike P

Without going into the why, think about it for a second and look a the size of a normal alternator pulley compared to the size of the crank pulley it's driven off of. The alternator would be being driven SLOWER on a direct drive setup.

Correct!

If you mounted it direct you would need a flexible coupling between the crank shaft and alternator shaft, and of course a custom mounting bracket for the alt. As far as speed goes you need to know what minimum speed the alt will produce 14.5 V at. Direct drive that might not occur until ~2000 rpm?

Kitz