Hi
I'm thinking about doing away with a separate alternator, and working on a method of having the starter permanently engaged for use as a generator once the engine has fired up. I'm handy with the electricals so no fear there
Has anyone done this before?
Cheers
Never mind the size of your alternator Sumo - you should see the size of my starter!!!
Anyway it should be possible as I have used Lucas type generators (as fitted to old fords) as motors in the past.
I was thinking of wiring the starter switch through a relay - Press to connect batery to starter - once started and the button released the relay switches over to power the field coils and routes the armature ciols to the battery or vice versa (through a diode of course) and the thing runs as a generator. I am worried about the speed at which it will run though. On my lombardini single the starter gear on the flywheel is huge and the starter motors is tiny so that will have a huge rpm!!!!!
The good thing is that the output should be dc so no rectifier needed. combining starter and generator must save quite a bit of weight!
Cheers
If you gear the starter to the engine with a low enough ratio so the starter has enough torque to actually turn the engine over compression, the starter motor would turn way too high rpm at running rpm.
Smaller turbine engines (such as the PT6) frequently use a starter generator combo. The starter/generator is geared with a ratio that gives max starter generator rpm at max gas generator rpm. It is practical in these situations because the initial torque to start spooling up a gas generator is very low.
If you had a starter motor big enough to provide the torque needed to crank a piston engine, especially a diesel, at a gear ratio that wouldn't overspeed the starter at high engine rpm, the thing would be massive, much larger than your existing starter and generator combined.
Hi there!
Overspinning the starter is one thing.....I can control voltage and current by weakening the stator field/electronic regulation.
Do you think that the overspin would do mechanical damage to the starter?, It will be under less load from the electromagnetic stator field as this will be weakened as the rpm increases.
What do you think?
One would also need to consider the bearings involved. I'm not familiar with the particular starter in question however many starters use bronze bushings in lieu of bearings. My brother had the experience of having the bendix fail to disengage in the starter on one of his Hondas. The starter made it about 8 miles before it seized tight in the bushings and subsequently locked up the rear wheel at 70 MPH. What followed wasn't pretty. Clearly, bronze bushings were never designed to provide an adequate bearing surface for a sustained period of time at those RPM's.
Hmmm,
Damn shame - I suppose a special combined unit would need to be constructed with all the machining that such an enterprise demands, I still love the idea though. If I could I'd use a starter, put propper bearings in, and use something like a selector fork and a servo to keep it engaged once the engine had fired up - my starter is enormous, but it does run on plain bearings, electrically fine, mechanically not I guess - ah well cheers for the input guys!
Don't give up so quickly. Your proposal has been routinely used here in the states on many lawn and garden tractors. In fact, Ebay here in the states has currently 80 listings for starter generators, many of which were used on engines such as the 14HP Kohler. They would be easy to adapt given that they are belt driven. Additionally, while they might appear a bit on the light side for starting a diesel, one could modify the reduction by changing pulleys, as you would be more interested in lower RPM touque for a diesel as opposed to spinning up the RPM's to fire the poorly tuned petrol engine. They are indeed large and heavy.
Dont know about the electrical side but mecanicaly it seems to many problems to overcome, bearings not rated for permanent use, starter ring gear not lubricated and would be very noisy. not counted the teeth on both but a guess would be 12 to 1 then my starter on the ruggerini is geared perhaps 3 to 1 so at 3600rpm, starter would have to run at 129,600rpm, sounds a lot to me.
Hey there!
The best way round the continous rating for the bearings is to use the lucas style generator as I mentioned earlier, this was actually built to run constantly and has a pulley wheel on it. My Lombardini also has a pulley wheel on the flywheel as well as a toothed ring. On my Kawasaki GPz 550 the starter is a straight electric motor driving through a starter clutch. Maybe a combonation of Lucas generator + starterclutch + belt drive maybe the way to go?
Cheers
Hmm how do these image things work?
Anyway if they work you will see lucas generator and flywheel, the engine had a pull start option (I've never tried it though) so maybe I'm in with a chance.
pietenpol2002 wrote:In fact, Ebay here in the states has currently 80 listings for starter generators, many of which were used on engines such as the 14HP Kohler.
Would the horizontal version of a Kohler be suitable to mount in an Enfield frame? I wonder about the bulkiness. What I like about the engine, is that supposedly may be better quality than Chinese imports.
I'm contemplating a CH730.
'92 Enfield + Hatz 1B40: street legal, weld up stainless exhaust, check engine rpm and change final drive sprocket.
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