Exectutive Summary:
Inspired by an article in QST, and my interest in power generation in general, I built the above pictured lawnmower engine-powered alternator genset.  I determined somewhere around halfway through construction that it's not worth it, at least in terms of effort, cost and amount of potential energy possible from this unit.  But once having gone that far, I wanted to complete the unit since I had no portable source of emergency power generation, I had a bunch of money tied up in parts, and following through to completion would also serve to prove unequivocally that it wasn't worth it.  :-)

The mower that made the ultimate sacrifice.	Orphan GM alternator that has sat idle for nearly 10 years.

It all started with the acquisition of a defunct lawnmower.  I already had a GM alternator languishing in the garage, an orphan of having turned my S-10 pickup into an electric vehicle.  So I had most of what I needed already, or so I thought.  After it was all said and done I ended up with about $150 tied up in steel, welding supplies, wiring, hardware and a marine battery.  Not to mention the number of hours it took to cut and weld the steel, fit the pieces and complete it to it's finished state.  If that hasn't dissuaded you by now, read on...

This is the 12V Pup as outlined in the June 1999 issue of QST.	This photo of a 12V genset built by NS8O served as my inspiration to build my own genset as an 'over-under' rather than 'side-by-side'.

The spider coupler as provided by The EpiCenter.  The engine side is standard 7/8" with 3/16" key.  The alternator side is custom drilled and tapped to fit the shaft and threads of GM 10 and 12 series alternators.	The humble beginnings of the frame.

I thought it'd be easier to transport and use a genset that was a bit taller than the QST version which is long and flat.  Once the physical configuration was decided upon, I set about fabricating the frame.  I'm not fond of the nut and bolt method used in the QST article so welding was my method of choice.  I had some steel on hand, and decided I would focus on sturdiness before weight.  Well, I got my wish.  I used 1-1/2" square, 1/8" thick stock.  With the dimensions I ended up with this frame could easily support a two-ton automobile, much less a 20lb engine and 8lb alternator.  But it's no more work to use this material, so that's what I ended up with.  Once the engine, alternator and battery placement were determined, it was a relatively basic exercise to cut and weld the pieces together.  The only critical parameter was keeping the motor shaft true to the alternator shaft, but even that is mitigated somewhat by use of the flexible spider coupler.  The coupler itself was already drilled and tapped for a GM alternator shaft.  This made mating the engine and alternator quick and foolproof, compared to having to use pulleys with sheaves,  taper-lock couplers and belts, which require some method of tensioning adjustment.

Completed frame after painting. Color: Chevrolet Orange (since the alternator came out of a Chevy).	With gas, oil, and battery the Lawnernator tipped the scale at 115lbs!

How it works
After reviewing GM alternator specifications at various RPM's, as well as lawnmower engine specifications, I estimate the Lawnernator's output to be somewhere around 300-400W @14VDC.  Not enough to do much more than run a few lights and radios by itself, but with the deep cycle battery attached as a load leveler, it is capable of several times that amount during peaks.  Another nice feature of the deep cycle battery is you don't need to run the engine all the time, just enough to keep the battery charged.  Operating the unit in this manner is actually very efficient, since the alternator will be at full load while the engine is running, instead of just partial load were the unit running at less than peak load.  By connecting a 14VDC to 120VAC inverter, your peak power and AC current quality is limited to the what the inverter is capable of, which can be considered additional flexibility over an AC-only genset.

If you make lawnmower sounds, this photo could be a video.  The evidence that it's running is the DVM is showing 14.4VDC.	In a pinch,  the Lawnernator can be run off of propane.  No special fittings, just stick the hose in the carb and fiddle with the gas flow until it starts and runs under load.

• Chrysler Alt/Briggs 3.5hp Setup
• Using Induction Motors as AC Generators

• The EpiCienter- nSource of GM-ready spider couplers.
• Spider Coupler Data Sheet
• Nice GM 10/12 Series Alternator Info
• Briggs and Stratton Small Engine Parts
• June 1999 QST, The 12V Pup: A DC Generator You Can Build
• Another Lawnmower-Generator Site 
  



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