How to assemble a belt or direct drive generator.  The information that follows will show you how to build your own generator at home in the garage or shop.  There are a few basic things you should know before starting a project like this.  It requires about two horsepower for every kilowatt of power you generate.  A kilowatt is 1000 watts.  If you assemble a 5000 watt generator you will need at least a ten horsepower engine to turn your generator to full output.   There are two pole generators that operate at 3600 rpm and four pole generators that operate at 1800 rpm to provide the same 60hz frequency.  Things last longer when they turn slower so we choose to use the four pole generator.   The next thing to consider is the type of engine you will use to turn your generator.  I like diesel engines because they last longer and require no tune-ups and use less fuel than a gasoline engine.  Most diesel engines operate at a slower rpm than gasoline engines.  They also have more power at lower rpm's than a gas engine.   I will be using single cylinder water cooled horizontal diesel engine for this project.  It is a Chinese brand and is rated at 19.75 horsepower at 2200 rpm. It weighs about 450 pounds. When it is direct coupled to a generator it will turn at 1800 rpm and it may only produce 17 - 18 horsepower.  It will be turning a 10,000 watt ST10 generator head. The ST10 head weighs in at about 265 pounds. The generator head can also be turned with a belt instead of coupled directly to the engine.  This will allow the engine to turn at a higher rpm and produce more horsepower while the generator still turns at 1800 rpm when the proper size pulley is used on the generator.  I have decided to build a generator set that can be belt driven or direct driven to see what works best and which one I like.  Lets begin by taking a look at the engine and generator head I will be using.  I'm a John Deere Fan and so my project will be painted John Deere green and yellow.  The components for a belt drive and direct drive are also shown.

After we have chosen the engine and generator head we will use, its time to construct a rigid frame to support the head and engine.  They are both heavy pieces and need a good sturdy platform to set on.  The frame must be made of heavy enough material so that there is no twisting ,sag or distortion between the head and engine when it is operating  This is critical when using a direct coupler.  If using a small single cylinder diesel like mine and a 10 kw head the weight is already about 715 pounds,  add the frame at about 130 pounds and now its 845 pounds.  When completed it will be nearly 1000 lbs.  Use material heavy enough to support all this weight plus the twisting effect of the engine and vibrations.  I will use four inch I beam and 3/8 x 2 inch flat bar stock for the frame.   It will require about 12.5 feet of each for the frame which is about 45 X 20 inches.  The frame I will be constructing will allow me to set the engine and head up for a belt or a direct couple.  I will determine which way I will operate the generator set,  belt drive or directly coupled to the engine.  Yes it takes more time and work to construct a dual drive system but I will then know what works best.  As you follow along you will notice in the pictures that the generator head has both a pulley and lovejoy coupler half attached to its shaft.  Also notice that there are eight bolt holes and two notches in the frame,  only four holes are needed to mount the engine.  The other four holes are used when the engine is rotated.  The small notches cut into the frame are for clearance of the flywheel starter ring gear.  The slotted 3/8" flat bar stock for mounting the head have a 9/16" spacing between them to allow for 1/2" bolts to pass through and give a little wiggle room for adjustment.  You will have to determine the measurements and spacing of your frame according to the specific engine and head you will use.  I will be constructing the belt drive setup first.     

A belt driven generator head will require that there be a way to adjust belt tension and pulley alignment.  This means you should have a way to adjust the head in and out towards the engine and also left and right for proper alignment of the pulleys.  Belt life will be severely shortened if the pulleys are not properly aligned.   I will use 3/8 X 2 inch flat bar stock to make a pair of adjustable mounting brackets that will bolt to the generator head.  They are made of two identical pieces of flat stock with five inch long bolts with the heads cut off and welded in between the the two pieces of flat stock  The bolts are 1/2 inch in diameter but spacing between the two pieces of flat stock is 9/16 inches.  This 9/16 inch space between the two pieces of flat stock will allow 1/2 inch bolts to slide back and forth for adjustments. This is the same spacing between the flat stock pieces as was used on the frame.  I had the flat stock laying around here so that is what I used,  you may want to use something different.