building a generator

[Halfcrazy]

Ok I am thinking of embarking on a new project. I have a 305 chevy v8 engine that runs super. I would like to mate it with a 12-15kw generator head to run my welder and my air compressor where I am off grid these 2 items are a problem for me.

My thoughts where to belt drive the head with 2 belts of the crank pulley on the 305. I also did not think I would mess with a Governor as I believe the v8 will carry either one of my loads no problem with a fixed rpm. My questions would be what are your thoughts on the 2 belts will it work ok? or does someone know of an off the shelf way to connect the st head to the flywheel? It seems like an awful good way to run these 2 items without any hardship and good use of a v8 engine I have laying around.

[bschwartz]

I think you've gone from halfcrazy to fullcrazy 

[Halfcrazy]

yeah but I am on a tight budget right now and looking for a cheep way to run these 2 items. I figure once I get the spare change I could buy a small diesel from surplus center and the st head would still be good for that purpose? so really it would not cost me anything to use the v8 I have tons of parts and radiators and everything for the v8.

[mobile_bob]

i would have to look it up to be sure, but i believe two "BX" belts from a good manufacture will carry
15kwatts without a problem, provided they have 5-6 inch pulleys to drive on.

if you are thinking of driving off the oem stamped steel pulley on the front of the crank, forget that.
find a standard trans flywheel and mate a steel two or more groove pulley to it, or have a stub shaft
fabricated and turned by a machinist to fit to the drive end of the crank and sandwich the flexplate between
it and the crankshaft.

you could go with a 4 groove, use two to drive the generator on one side, and the other two to drive
the compressor on the other side, and that way you balance the side loads pretty well.

sounds like a useful project to me.

bob g

[mobile_bob]

one more thing if i may

because you want to drive a compressor and an st head to power a welder, you need for very accurate 60hz
is not really required, but you will likely need some form of governor, so i would suggest this

if the engine is carburated
find a "ported" vacuum port, it is a port that connects to the venturi and develops vacuum as the engine speed raises
by way of the vacuum increasing with engine speed.

using a dashpot, attached to the carb throttle linkage, you can bias a throttle spring setup to bring the engine speed down
to a level you want, as the load starts to slow the engine the vacuum will drop and thus allow the spring to pull more throttle.

it works very well, and with a little tweaking you can get pretty stable and decent speed regulation.

you can also do it with manifold vacuum, but it is not as accurate in practice in my opinion.

also ford made many different little vacuum limiters, they came in different colors to indicate the timing or delay they operated at.
very useful little buggers in my opinion to tailor the operation of such a setup if slowing the action is required.

this would allow the engine to idle when no power is needed, or when the compressor cycled and then raise its speed to your set limit
when the compressor kicked on or when you flip a switch for welding.

bob g

[Halfcrazy]

Good points Bob the air compressor draws 21 amps at 240 volts running and the welder draws up to around 20 amps at 240 as well so the loads will not be that hard I know the engine is overkill but hey I own it I will put some thought to the Governor idea

[bschwartz]

How about something like this?

http://cgi.ebay.com/ebaymotors/Audiovox-CCS-100-Universal-Cruise-Control-System-Kit_W0QQcmdZViewItemQQhashZitem414defd03eQQitemZ280480436286QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories#ht_846wt_960

You could hook the sensor to any of your pulleys or shafts.

[Ronmar]

Welding and air compressors have huge load shifts.  You will need a governor to deal with these load shifts.  A cruise control typically has some lag and does not typically have full throttle authority.  But since you are only needing 30HP or so, it might work pretty well.  I think the vac control would also probably work well.

I would skip the belt and direct couple.  Cut a round plate to fit the flywheel and drill the mount holes.  Spin the engine with plate attached and mark the center of the plate.  Carefully weld a keyed stub shaft to this plate, preferably the same size shaft as the generator uses.  Join the shafts using a shaft coupling...  You will spend as much time cobbeling together a pully setup IMO, and still have side load issues to deal with...

[veggie]

I second what Ronmar said on the speed control issue.
I don't think the engine could hold speed when the welder strikes an arc.
When the load is applied, the rpm will drop until a balance is found, but until the load is released, the rpm's will not recover. A proper governor is probably in order.

veggie

[mobile_bob]

when  i suggested the vacuum controlled governor system, my thinking was you would be running a belt drive
compressor,

i know the system i outlined will work adequately well for a belt driven compressor and a generator to power a welder
where frequency shift of +/- 3 or so hz is not a big deal.

the vacuum governor is so easy to put together using junk yard parts and little cost, i don't know why more folks haven't
explored its use.

failing all that,

go to a farm equipment scrapyard, and look for a belt driven woodward governor, they can be mounted and belt driven easily
on the front of the engine, and take control of the throttle, their resolution/response and stability is very good, certainly as good
as any lister ever wanted to be.

and a good used one is pretty cheap used, just be sure to get a belt drive unit, not a gear driven one that needs engine oil to
lube itself, the belt driven ones have a self contained lube system.

i had my dad pickup one for me out of a yard back in kansas and i think he got it for 10bucks or less.

myself, i would not consider a cruise control for a governor, their resolution is just too poor in practice at higher loads, but maybe
quite adequate for 30hp out of a 180-200hp 305chevy. in any case an electric cruise control would be my last choice.

bob g

[XYZER]

....direct drive would be my choice....If you are near hay and farming country alot of the older swathers and such have nice govenors that are belt driven.