Crankshaft sheave change on 6/1

[veggie]

My crankshaft currently has a ~5" sheave mounted between the flywheel and the engine block.
I am considering changing the sheave to a 15" single groove model to drive an alternator.
The mounting hub of the new sheave may be 50% wider than the current unit.
This would mean mounting the flywheel about 1" to 1.5" further away from the engine.
I have not yet removed the flywheel so my question is twofold.

A] Is it even possible to locate the flywheel in different locations?
B] Is it ok to move the flywheel 1" to 2" from it's current location to accept a wider sheave hub?

picture below....

cheers,
veggie

[mobile_bob]

its possible to locate the flywheel pretty much anywhere you want it, but
why add stress from having it further outboard, especially when you can have the
pulley mounted outboard more easily.

i would place the flywheel in as far as necessary, and put the pulley on the outside
it will make belt servicing easier anyway?

bob g

[veggie]

i would place the flywheel in as far as necessary, and put the pulley on the outside
it will make belt servicing easier anyway?

bob g

The problem with mounting an outboard sheave is that it forces me to mount the driven component (alternator) quite far off the base and hanging in mid-air.
If possible, I'd like to keep the accessories within the area of the engine base.

veggie

[Ronmar]

The problem with moving the flywheels outward is crankshaft flex.  Those wheels are heavy, and the diesel torque pulse is massive.  The image that comes to mind is of the cross bar bending as an olympic power lifter jerks several hundred pounds of iron weight into the air...

What is wrong with driving the alternator off the flywheel face?  A 4" alternator pully would give you a 6:1 ratio or 3900 alt RPM for a 650 engine RPM...  A little less than 4" would probably be about right.  Most alternator charts I have seen show peak alternator output typically above 4000 RPM.

[veggie]

What is wrong with driving the alternator off the flywheel face?  A 4" alternator pully would give you a 6:1 ratio or 3900 alt RPM for a 650 engine RPM...  A little less than 4" would probably be about right.  Most alternator charts I have seen show peak alternator output typically above 4000 RPM.

Currently my obstacle is space and an adequate mounting location.(other things in the way)
The nice thing about being able to use the inboard sheave location is that it lines up with the adjustable water pump mount that came with the engine. The idea was to mount the alternator where the water pump would normally reside.
My plan was originally to drive from the flywheel OD, but this unused water pump mount looked interesting.

With regards to speed, the OD of the flywheel is definately a better choice.
My ratios are a bit different than what you stated, but I get your point.
In my case I will be running the engine at 650rpm when making AC power with the ST5.
But when charging the battery bank, the engine will be slowed to 420 (using a governor linkage with two detent set points) and the alternator would be switched on.
Engine speed = 420
Flywheel dia. = 23"
Alternator dia. 2.3"
Ratio = 10:1
Engine rpm of 420 = Alternator rpm of 4200. Just right  

cheers,
veggie

[Crofter]

Are you using the reduced rpm for sound level issues?

[veggie]

Are you using the reduced rpm for sound level issues?

Three reasons...

1] keep the engine loaded when the alternator is putting out full power of 960 watts.
2] Very low noise level
3] Nothing sounds better that a lister(oid) at 400-450 rpm    Sweeeeet,

No need to run it faster if the alternator can't put out any more amps (heat) and the small battery bank can't take much more juice.

Every setup has a sweet spot and after playing with various speeds, I found that 420 rpm is where my mount system and engine are very happy. Minimal vibration, minimal thumping, very low noise level, and enough speed to keep good lubrication.
So, 650 rpm for AC power and 420 rpm for 12 volt dc charging.

Have a look...

http://www.youtube.com/watch?v=sAzi588I9Ro

veggie