As promised...pictures of my mowernator...or rather tractornator
12 hp Briggs I/C (iron sleeved), 28 ci, model 287017
Old Crapsman tractor
GM "1-wire" 10SI alternator, BBB/Lester p/n 7127-1W
~70 amps output @ 1200 RPM motor speed, fuel consumption of about .5 gl/hr
This project started out as an old Crapsman lawn tractor. My father had acquired it secondhand to mow at his office for $200 about 15 years ago. 10 years ago I got it for free when they upgraded. I mowed with it at the house for probably 2 years. Then the deck just plain wore out and it wasn't cost effective to replace all the parts. I removed the deck and used it as a pseudo go-kart for the summer. In the winter I turned it into a halftrack. I built track frames using wood (I was young...welding wasn't an option yet) and made tracks using old carpet strips cleated with riveted wood strips and bolts for studs. It worked amazingly well. But all good things come to an end. The Peerless transaxle gave up the ghost and wasn't worth the replacement cost. The tractor sat for several years with a great motor. I couldn't get rid of it, but what do you do with a 12 horsepower vertical shaft motor?
Now I have my bus and the need has arisen for generating power for longer term boondocking. I do not like running the bus engine because a 6.6 liter diesel DOES suck some fuel down plus I don't want to damage a mission critical component like the bus' alternator in the middle of nowhere.
What's a guy to do? Well...I had an old lawn tractor, a 63 amp 10SI 3-wire alternator, and a queen size bedframe worth of angle iron. It was time to get to work and I ended up with what you see here. The original alternator I had a bad front bearing that turned on the shaft so replacing the $2 bearing wasn't an option. The regulator also had a diode that was malfunctioning in that it was drawing power even with the unit supposedly deenergized. I ended up putting on the alternator listed above and reconfiguring for 1-wire operation. I think I have since then toasted that alternator due to heat but lifetime warranties are great. The replacement will be a 7127-1W105 which is the 105 amp version of the alternator and is actually cheaper ($41) but was not on the shelf when I was doing this. I will put the correct reverse rotation cooling fan on it and may even put an aux. 12 volt fan on driven off the stator output of the Briggs.
So here it is. The rack on top holds a 6 gallon boat style tank which lasts a surprisingly long time. The chassis is the forward half of the tractor. I welded the draglink to the tierod to lock the steering and recycled the old deck lift handle as the carrying handle.
These are the controls. The throttle is the original from the tractor. All the way up is choke. I typically run this thing right around 1200 RPM or just above idle. It smooths out the performance but keeps the volume and fuel consumption as a surprisingly reasonable level. With my pulley ratio (using the original deck drive pulley) the alternator is spinning well above 4500 RPM at that engine speed so it is at full rated power. Anything above that and you hit diminishing returns.
The red switch grounds the ignition coil of the tractor. It will be interesting to see how long it lasts. Even in the open position the light will illuminate. This means that the spark energy is jumping the gap to ground. This has no ill-effects on engine performance, but the arcing can't be good for the switch. Still, it gives me an indicator light when the engine is running. I guess that's good if I ever lose my hearing.
The push button switch is for the electric starter. The tractor had no provisions for manual pull starting and converting wasn't feasible. This means you must have a battery with a decent charge remaining to start the rig. This never turned out to be a problem since it takes so little to kick over a Briggs. A person also could start it off a car and haul it over to the bus if they wanted.
You can also see the Ford solenoid in the picture. This serves as a common terminal as well as the solenoid to start the engine. The hot feed from the alternator attaches here as well as the cable going to the battery. This is also my take-off for the starter switch. All the wiring is 4 gauge with crimped and soldered connections.
Underneath you can see just how simple it is. There is an F-shaped bracket welded to the chassis that serves as the mount for the alternator. It pivots on this point so that the turnbuckle seen can be used to properly set belt tension. I mocked it up using a 15345 automotive belt (fan belt for a 22re
) so I figured a 35 inch A-belt would be about the right length. When I replace it I will go with a 34 inch to allow more adjustment if the need arises. The A-belt is a perfect fit on the tractor pulley and works ok on the alternator. It is far more robust than an automotive V-belt and was only like $5.
So how do you operate this beast? It's actually pretty simple. Obviously you need to put the fuel tank on and squeeze the bulb to get a prime to the carb. There is no fuel pump so this is important. You then hook up the ground and hot "jumper cables" to their appropriate places. This will backfeed to start it. A few revolutions on the choke followed by a few on a lower throttle position and it jumps to life. The switch light illuminates and the "jumper cables" now feed power to the battery as the alternator self energizes.
What are my overall thoughts? This thing is BIG and HEAVY. It is a pain to lug around. But with that comes reliability. All my parts are common and the 12 horsepower has no issues turning the alternator over at all. It is hardly even working which is nice. The stock muffler has also turned out to be surprisingly quiet. The best part is the fuel pinching nature of the 28 cubic inch Briggs single. I expected to put a lot of fuel through this thing for very little return in electrical energy, but that wasn't the case. Sure, I could turn a WAY bigger alternator which would alleviate some of my heat concerns, but for $41 I can't go wrong with the alternator I'm using. The engine also has another pulley on it. I've considered using this to turn an old power steering pump. With some quick connects this could serve to feed a log splitter or any other number of implements.