Crank Mounted Alternator Question

Has anybody mounted an alternator directly to the crank. A mate is looking into doing this on a current project.

Anyone see any dramas with doing this?

 

only problem I see is that it would turn about one third to one half as fast as it's designed to turn, so it won't charge until you get going pretty good.

 

Have thought about that - apparently the alternator he sourced starts charging around 1700-1800 rpm.

 

The other thing is that if it is connected nose to nose, it will turn in the wrong dirrection. I dont have any idea if it matters what dirrection an alternator spins. good luck.

 

Doesn't work when you are sitting still.

 

am I missing something ?

 

I've run GM 1 wire alts in reverse with no problems

 

Alternators dont care which way they turn. But like stated earlier it wont turn fast enough at idle.

 

alternators generate AC, and use diodes to turn it into DC, so direction does not matter.

 

Alternator=AC (alternating current)=it don't matter which direction

 

I believe you're thinking about an alternator running off the driveshaft

 

I know they rectify AC to make DC so from that standpoint it doesnt make a difference which way they spin. But if the brushes are off set as they can be in non reversable motors and some generators they will wear the brushes out real fast when turned the wrong dirrection.

 

But the brushes in an alternator contact slip rings....there is no comutator like there is in a DC generator or motor. I woldn't worry about the brushes wearing out.

 

Yep...

 

it could be made to spin faster with a rubber pulley pressed against the inside of a ring bolted to the balancer.

 

You don't say which engine but Mercrioser built alternators into dampeners. My Merc 224 had one that fit a 289 snout but wouuld need balance added. Low output, but if you don't have EFI etc and don't plan to drive all night would work. Also someone had one for SBC water pump pulley.

 

I tried to do this once, by driving one off the end of the crank, but it just wasn't turning fast enough to work. If you look at the stock pulley ratio you can see that they are usually spinning 3 or even 4 times crank rpm. When the engine is ticking over at idle, the alternator may be going 2-3000 rpm already and might hit 15,000 rpm when you rev the thing! but that's the way they work and an alternator that's direct drive from the crank with no step up in speed might not put out enough power.

 

Thanks mustangsix. That's been our main concern. Did it put out any charge at all? This won't be a daily driver and odds are it will end up being rarely driven knowing who it's being built for. So would a crank drive have enough output to keep things running over a weekend jaunt?