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The Emergency Preparedness
Tip o'da Week

Build a Generator from a Lawn Edger Motor

The material presented on this page is intended to start you thinking about what you can do today that might someday save your life. If nothing else, our "Tip o' da Week" might just make your life a bit easier when a disaster strikes. We do not present topics that cost a lot of money (like structure reinforcement.) These are "do it yourself" projects and are relatively inexpensive.


FireBox stove in use with fire powered pan charger - Hatsuden Nabe

Introducing the Hatsuden Nabe

The Fire-Powered USB Thermoelectric Generator and the Firebox Folding Stove

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Building Your Own Generator (on the cheap)

-- See More Tips --


This tip is a visitor submission from David Hooper from Vancouver, BC 
(with additions from the crew at TheEpicenter.com)

About this T.O.W. submission:

In 1996 we ran a Tip o' Da week submitted by David Hooper from Vancouver, BC, which discussed building a generator from an old lawn mower and a GM alternator.  We recently received another set of comments from David on the subject and wanted to share them with you. We looked at David's idea and loved it!   We think we have improved upon his idea though, presenting our version in addition to David's input!

About David Hooper

David says, "I am a Canadian Civil Servant, with the Department of Indian Affairs and Northern Development, in the British Columbia Region.  Part of my job responsibilities involve Emergency Preparedness for First Nations Communities."


Home Brew Power!

Building your own generator (on the cheap).

This Tip o'da Week is intended for educational purposes only.  No guarantees are expressed or implied as to the accuracy of information presented here!  Consult with an automotive wiring expert before attempting to carry out any wiring.

A lawn mowerThe project in David's own words:

"My stand by battery charger for drag strip / RV use is now a "one wire" Marine alternator of 75 amp rating on a board (a 2 x 8) with a 3 hp horizontal shaft Tecumseh running the pulley.  My first one, since sold, was a 3.5 hp Briggs & Stratton from a vertical shaft mower.  I cut a slot in the front of the mower deck (but in retrospect, if I had to do it over, I would cut it in the back); then I added brackets made from old 1.5" angle iron for the pivot and an old (from the junkyard) slotted alternator bracket for the adjuster.  By re-using the mower deck, I had a place to mount the entire works, on wheels with an easily attached (and detached) handle. If I had been even remotely bright at the time, I would have cut into the back of the deck, so that the alternator and mounts were under the handle, instead of sticking out the front which made the entire rig about a foot longer than it needed to be. Oh well.... (Live & Learn!)"

"I actually used old bed frame rails for the angle iron to make the brackets.  (My neighbor was tossing out an old bed, so the steel was free!)"

"It isn't difficult to make this work. If you are after a system to charge a battery between rounds so you can run the race car without an alternator, it works great! As a standby power source, the most expensive thing is the inverter.  It has the advantage that you can run it to charge batteries, and subsequently run the inverter off the batteries for some light and silence!  In an emergency, there is a battery in your car, one in your spouse's car, one in your neighbors car, etc. so there is no shortage of ability to store some power.  Deep cycle (marine/RV) type batteries are greatly to be preferred, but if you don't have a boat or RV already, you are not likely to have them around, and the object of this project is to keep costs down while still avoiding "being powerless".  If you are only after some light, use 12 V light fittings and bulbs, and save the cost of the inverter.  Or use an inverter to run the heat recovery fan in your furnace/fireplace, and cycle it with the refrigerator / freezer to minimize the size of the inverter required and still use the 12 V lights."


We looked at David's idea and loved it!
We think we have improved upon his idea though - here's our version:

A completed generatorWe will discuss how to build your own generator that looks something like this.

This generator was built using a 3 horse power Briggs and Stratton horizontal shaft motor, a GM 65 amp automotive alternator (with built in voltage regulator), a used car battery, a pulley and V-belt, a 12 volt cigarette lighter outlet box with fuse, a DC to AC power converter, a low voltage control switch, a scrap of 3/4" plywood, a few scraps of 2 x 4 lumber, 4 wheels, and two battery cables.  We also used a custom designed bracket manufactured for Epicenter to make it all come together in a snap.

In the photo above, we used an 8" pulley on the motor.  Subsequent testing indicates that a 4" or 5" pulley is the correct size to use for this application.

Please note that a safety guard should be installed to cover the belt and pulleys!  This guard is not installed so that the photographs show the most detail!  If you plan to actually use a generator of this type.  Please, Please make sure you install a safety guard!


What can this generator be used for?

The basic generator (gas powered motor, alternator and battery only) can be used as a 12 volt power source.  This is extremely useful for charging battery banks in RVs, campers or in out buildings.  The big advantage to this generator as a charging system is the high current output of the alternator, and thus, the reduced charge time over using solar cells, or AC battery chargers.  The other big advantage to using this unit to charge batteries over merely charging them with a car, is that this generator uses much less gas to do the job (which is critical in an emergency).  Some HAM radio folk use 12 volt equipment that can be powered from the battery until it is low in charge, and then crank up the generator to recharge the battery.  The high output of this unit also makes it useful for car lots or fleets for jump starting cars.

DC to AC power inverterIf a DC to AC power converter is added to the basic system, then a limited amount of 120 Volt AC power would also be available! DC to AC power converters electronically convert the 12 volt DC power to 60 hertz AC power at 120 volts.  These devices just connect to the battery on the generator, and provide AC power outlets for standard household AC power.

These converters are available in sizes from 140 Watts to 2500  watts from our power related pages.  See this page for details.

DC to AC Power Inverters Converters, Universal DC Adapters Click Here to see our DC to AC power inverters

 


What used motor should you use?

As David discussed, his first version of a home built generator used a vertical shaft lawn mower engine (which are very easy to find).  These mowers can be had for a song and can be found just about anywhere. They have several of the key components that will be required in this project.  They have a base that holds the motor, and a cable for adjusting the motor speed.  They also have wheels which are very convenient if you ever plan to move it! The biggest task in making a home built generator is figuring out how to attach the alternator and motor so that power from the motor can be transferred to cause the alternator to spin, thereby producing electricity.

The task is harder if a vertical shaft lawn mower engine is used.

The problem is that there are so many brands on the market, and each one it seams builds there own base.  To make matters worse, there doesn't seem to be a really standard shape to the base. Some models have flat surfaces where items can be bolted to, and some bases don't.

You will notice that David's second generator used a horizontal shaft motor which greatly simplifies the whole project unless you have one of our special vertical shaft brackets for a lawn mower engine. The trick remains, actually mounting the alternator so a belt can be used to link the alternator to the motor. This task is simple when you use one of our brackets. But it IS possible to use a vertical shaft (lawn mower engine) if you use one of our special brackets. Here is what one looks like:

A Briggs and Stratton lawn mower engine+Delco-Remy Alternator+Mounting bracket for home made generator=Build a generator from a Briggs and Stratton Lawn Mower Engine

Be sure to see the Vertical Shaft Project from this page.


In this project, we will concentrate on how to build it using a horizontal shaft motor:

In the simplest form, the motor and alternator can each be bolted to a base.  The exact mounting configuration of the alternator depends on the model of alternator , the motor used, and the belt drive configuration.  The next task is to come up with a way to tension the belt.  What some creative people do, (like David),  is use miscellaneous brackets from cars to mount the alternator to a base.  Then, adjuster brackets found on typical car engines are used to tension the belt on the alternator.

This method requires a high degree of "screwing around" to come up with (or build) the required brackets.  Yes, a few trips to an automotive junk yard will result in finding miscellaneous useful items, but at a cost of several hours of time!

Time is money!

The Epicenter.com crew has designed a simple way to carry out the bulk of this project!

Universal Alternator mounting bracket


Bracket attached to another style of engine

Generator bracket in useWe have designed and manufactured a simple, one piece universal mounting bracket specifically for this task!  This bracket bolts to the motor (using a universal bolt pattern), and allows the alternator to bolt directly to the bracket.  The bracket also has an integral belt adjustment slot which allows the alternator position to be adjusted, which serves to tension the belt.


What will you need to build a home built generator?

3 horse power Briggs and StrattonThe first thing you will need is a used motor.

The key to this design is that it will require a horizontal shaft motor, which can be found on old drum style lawnmowers, roto-tillers, and lawn edgers.  The most common motor size you will find on the used market will be a 3 or 3.5 horse power model.  Larger motors are harder to find because most of them are snapped up for building go-carts or mini bikes.  The most common brand you will find is a Briggs and Stratton.  Newer Briggs and Stratton engines have the gas tank, carburetor and exhaust on the same side of the motor.  If you look at the old style Briggs shown here, you will note that the gas tank is mounted on the opposite side of the motor than the carburetor.  This means that which ever side the alternator is mounted on, the alternator must clear obstructions. Yes, our bracket takes this into account!

When buying a motor, note how the pulley is attached to the shaft. Most motor shafts have a square key way (or grove) cut in the shaft.  This makes it super simple to replace the pulley with the type you will need for this project.  Also note the shaft diameter.  Most motors in the 3 horse power class have a 3/4" diameter shaft.  Avoid purchasing a motor that only has a threaded hole in the end of the shaft!  This configuration will prove to cause hours of wasted time figuring out how to attach the new pulley, as David found out when he built his first version!

You will notice that after looking at several motor models from several manufactures, there are a few features that just about all of them have.  The first is that most have the keyed cut out in the output shaft.  Secondly, they all have four bolt holes at the base for mounting the motor to a flat surface.  Thirdly, they all have four tapped holes on the output shaft cover plate. These output cover plate mounting holes are a key feature of horizontal shaft motors.  Be sure the motor you purchase has them if you plan to use a bracket like the one we designed!

How do you know if your motor has the required holes?

Bolt hole circle.Look at where the output shaft is on the motor.  Then, notice that there are two holes above, and two holes below the shaft.  They will be located on an imaginary circle, 3 and 5/8th" in diameter, and centered at the shaft center.  It sounds more complicated than it really is.  Take a look at the diagram.

We have looked at motors ranging from 3 to 10 horse power, and have discovered that these output cover bolt holes are in one of two patterns.

The following motors use a 3 and 5/8th" bolt hole circle:

There may be other motors that use this bolt pattern.  Larger motors than shown use another bolt pattern which is either 6 1/2" or 7 3/4".

Check the location of the gas tank

Horizantal shaft motor, top view.Photo at right = Top View.

This photo is a top view of a Briggs and Stratton 3 Horse power motor found on lawn edgers.  It shows the location of the gas tank.

Most newer motors have the tank, carburetor and muffler on the same side of the motor.  In the case of the 3 horse power Briggs and Stratton we used, the tank is on the opposite side.  The next thing to determine is if the side of the tank extends beyond the flat surface of the output shaft cover plate.  As seen from this top view, the 3 horse power Briggs does (which adds a bit of complication to mounting the generator).  Our bracket has a cutout which is designed to clear gas tanks of this type.


The next thing you need is an Alternator (with built in voltage regulator).

The Power Source: A GM Alternator(with built in voltage regulator)

Delco-Remy Alternator.We also used a 65 amp GM alternator with a built in voltage regulator.  It is critical that you only use an alternator that has a built in voltage regulator!  If you make a mistake in the selection of the alternator you run a very high risk of damaging the battery, or worse yet, causing personal injury!

One more time. Pay special attention to the selection of the alternator! You must select a GM alternator with a built in voltage regulator. If you are in doubt, consult an expert or parts professional!

To fully understand the reason for the special notice above, lets review a few things about how an alternator works:

We are going to skip significant details relating to magnetics and take a leap of faith; here we describe the effect seen when an alternator is turned--either one that has a built in voltage regulator, or one that does NOT have a built in voltage regulator.  (This discussion assumes that the terminals are connected as they would normally be, and no additional details will be provided for this discussion.)

In the case of an alternator that does NOT have a built in voltage regulator: (very , very bad - don't use!):

And if an alternator with built in voltage regulator is used:

If you select the alternator we used, there are 4 connections that must be made.

The pins an a Delco-Remy 1100934 37A, 3D10 12VNEG alternator with built in voltage regulator.

Pin out for Delco-Remy Alternator.


Consult a parts professional for additional wiring information!

Another note:

When the time comes to crank up your generator, you will need to turn off the switch that goes to the "R" terminal.  If the switch is on, the generator will try to output voltage while you are pulling the starting cord on the motor. You will find that it will be nearly impossible to pull the cord!   If the switch is off, then there is little to no resistance from the alternator.


What else is needed?

The pulley (attach to the motor output shaft):

A pulleyIn our prototype shown above, we used an 8" pulley (with a 3/4" shaft, and key way).  What we found was that the gearing ratio was less than ideal.  We have run additional tests, and determined that a 4" or 5" diameter pulley is correct for this application.  Either a 6" or an 8" will work if you can't find a 4" or 5", but you will notice that the motor speed decreases as a load is applied.  To compensate (if using a 6" or 8" pulley), the motor speed would need to be increased prior to a load being turned on.

With the 8" on the motor, and the motor set to idle, we were able to kill the motor when a 150 Watt load was applied.  If the motor speed was set above idle, there wasn't much of a problem, but the alternator was spinning much faster than is required.  A 6" pulley under the same conditions resulted in a slight motor speed decrease when the load was applied.  The alternator speed was about right.  But when a 4" or 5" pulley was used, there was no motor speed change for the same load.  In fact, it handled the load while running at idle speed, and turned the alternator at a speed more like found in a car.

Pulley and belt data when using the Epicenter alternator bracket.
Pulley Diameter Usability Minimum belt length Maximum belt length
4 " Excellent 35" 37"
5 " Really good  36" 38"
6 " Usable 38" 40"
8 " Undesirable but works 41" 43"

The following E-mail conversation between The Epicenter crew, and David Hooper illustrates the problem:

Epicenter asked David Hooper the following:

"David, I noticed that when I built up a generator using an 8" pulley on the motor, that the motor was not in its normal power range.  The Alternator was also spinning like crazy, and I think it would all work better if the pulley ratio was closer to something you would find in a car, like a 5 or 6" pulley on the motor.  That would spin the alternator more at a speed like found in the car, and would also increase the torque seen at the alternator, so load changes would have less affect on the motor."

David responded:

"I'll go measure, but it seems to me that I tried to use one about an inch or two bigger (diameter) than the size of the alternator pulley so that, with the engine at its 'cruise speed' (about 2500 RPM) the alternator would be at reasonable speed as well - it doesn't put out its max power unless its really humming, but you can't run it 'flat out' forever either, and you've only got about 3 or 3.5 hp to power it!  Everything is a compromise!

I'd try the 5" but it seems to me that mine was more like a 4" - memory fails at this point...Yes the alternator will drag down the engine speed, but if you are over geared, it will REALLY do it!."

In a follow up E-mail from David:

"The 5 inch pulley should do it.  You are absolutely correct in assuming that one of about the same size as is used in the car (about a 6") would be correct to give the right alternator speed.  But remember that most cars spend much of their lives well BELOW 2500 rpm, so the pulley is sized to give a compromise belt speed for water pump, fan, alternator, etc.  In fact many cars have a 'stepped' pulley with a different size for running the Power Steering pump, and yet another for the A/C.

Here we have a dedicated unit, with only a 3 - 3.5 hp engine, so somewhere in the 5 - 6 inch range should be about it.  I never really did any experimenting with different sizes and measuring max output of the alternator.  Does going up from the 5" to the 6" increase output, or drag the motor rpm down for a net loss?  Interesting question!

I just used some 'stuff on hand' and it worked, so I the proceeded to the old maxim 'If it works, don't fix it!'  Perhaps a bit of tinkering might be order after all!."


The Cables

CablesThe small 2 wire plug shown is also available from Epicenter.  This molded connector (with wires) is a replacement part for hooking into the two terminals (R, and F) on the alternator.  It saved a bunch of time making two of the alternator connections and is well worth the cost.

Next, we used standard 6 gauge, 15" battery cables to connect the alternator to the battery.  Yes, they are a bit over-kill, but the amount of time you would spend making your own cables of lesser wire size (crimping the terminals etc.) is more than the cost of just buying a pair!

We had a note from David on the subject, and will share it with you:

"I suspect that the use of 'full on' battery cables is overkill; there are battery terminals that take wing nut & screw (post) connectors available at many auto/RV stores, and you don't need to have all that much thickness of wire here.  Check out the gauge of the wires from the alternator to the battery of a car--about 8 ga should do, 6 ga if you really want a safety factor.  The "2","1","0" or "00" ga. wires in battery cables are just overkill in this application;  they ARE needed in a car to transmit the large current needed by the starter, but at no other time.  Leave 'em in as optional, but costs can be possibly reduced by using cheaper wires (unless the auto parts store has battery cables at really cheap prices!)  My concern is the size of connector needed at the alternator end.  Getting that connector to fit the 'hot' terminal of the alternator without any danger of it touching the case or any other 'ground' is easier with smaller terminals, hence smaller wires!"

The actual length you will require may be longer depending on how you mount everything. 15" is about the minimum length.


OK, so how does all this junk hook together?

A top view of the components(belt guard removed)

Generator top view.The first thing to do is to lay out all the components on your shop floor.  This will give you an idea of how much space you will need to mount all the items on a base.  We found that the smallest size for the platform was the size of some scrap plywood from out back.  The minimum size is 28" long, and 15" wide if the battery is mounted close to the alternator.  This allows the use of less expensive 15" battery cables.  Also note the location of the power converter.  You will need access to the front of the unit to plug in AC devices; this access needs to be away from the belt and pulley.

This configuration also provides easy access to the motor starting cord.

Please note!  Add about 4 inches to the minimum width of the platform so that a guard can be built to cover the pulley and belt!  This prototype was built without a guard so that pictures could be taken, and was not intended to really be used!  This is a very dangerous configuration when a belt cover is not installed!  Please, Please install a belt and pulley guard for the safety of others!  A safety guard can be built using scraps of 2 x 4s, and another scrap of plywood.

The next step is to bolt the alternator adapter bracket to the motor, and bolt the alternator to the bracket.  Then check the placement on your mounting platform. You will also need to verify the mounting hole dimensions for your motor.  The Briggs and Stratton 3 Horse power we used has a bolt pattern as shown below:

The Briggs and Stratton Motor

Motor mounting hole pattern, for a 3 horse power.

Mounting bolt holes for Briggs

Generator front view.Be sure to check your motor for the correct mounting hole locations.  Then drill the holes in the plywood mounting base slightly over-size to aid in positioning the motor.  In the case of the motor we used, the bolt holes are 1/4", so we drilled the holes 3/8" to give a bit of slop so the bolts go into the base a bit easier.

Now position the battery on the base

Provide at least 3" of space between the rear of the alternator and the battery.  This will provide ample space for access to the alternator terminals.  Next, use some scrap chunks of 2 by 4s positioned with the 2" side down, to build a 4" tall box around the battery.  We cut them to length, and then secured them to the base from underneath using 2" wood screws.

It's much easier if the holes are drilled before trying to install the screws.  What we did was to cut the first 2x4, then positioned it on the far side of the battery. We marked the outer location with a pencil. Then we moved the battery, and marked the inside of the 2x4.  We did the same thing for the other 3 scraps.  Once the outlines of the 2x4s were marked, we "pre drilled" the holes in the base.  Next, we positioned the 2x4s (one at a time) back on the base, and drilled into the bottom of the 2x4s from the opposite side of the base, using the holes in the base as a drill guide.  Then we installed the screws through the base and into the 2x4 scraps. Once complete, the battery fits right in the box!

Next, install any type of wheels you might have on hand.  We used a few wheels with casters, but if you have an old lawnmower around, those wheels would work even better!

And finally, bolt the motor to the base, do the required wiring, and install the battery.


How to wire it up

This Tip o'da Week is intended for educational purposes only. 

No guarantees are expressed or implied as to the accuracy of information presented here! Consult with an automotive wiring expert before attempting to carry out any wiring.

The basic wiring

Wiring for Delco-RemyThis is the basic configuration using a Delco-Remy 1100934 37A, 3D10 12VNEG alternator only.  Consult with a parts professional for wiring information.

In this mode, it can only be used for 12 volt DC applications.  A 12 volt cigarette lighter outlet box can be added to provide an easy way to connect 12 volt devices to the unit. I f a cigarette lighter outlet is added, be sure to install a fuse in line with the outlet box.  Most boxes that can be purchased at an auto parts store come with one.  But remember that the amount of power that can be delivered when cigarette lighter sockets are used, can only be as much as follows:

Say the lighter outlet box you select has a 20 amp fuse.  Then the maximum power that can be delivered through the connector is 12 Volts x 20 amps = 240 Watts.  That means that no appliance can draw more than 240 watts or the fuse will blow.  So, if you plan to use a 140 watt, 200 peak DC to AC power converter at full load, it will work fine.  But if you elect to use a larger model at full capacity using the cigarette lighter plug, you will blow the fuse! Larger models than the 140 watt unit will require that you wire it directly to the battery.

Do not attempt to replace the fuse with a higher value!


What does it look like when finished?

Both front and rear views:

Completed generator, rear viewcompleted generator, front view


Another mounting schemebracket mounted on cart

Here is a version we made some time later using a pressure washer cart as the base. In this case, we didn't install a battery in the system as our intended use was to be able to charge batteries that were already installed in cars. This version was more mobile but did not provide self contained battery power nor AC power capability.

The downside of this configuration is that the pressure washer cart does not have holes drilled for mounting the motor with the shaft out the side, just front and back.  Drilling a few holes is a small price to pay for a quick and easy cart though.


Some final cautions!

Our prototypes shown do not have a belt guard installed!  PLEASE, install a belt guard!  These pulleys will take a finger (or worse) unless guarded some how!  The easy way to build a guard is to cut one out of scrap plywood and attach it to the base with wood screws.

If you build something like this generator, you must build it at your own risk!  YOU must determine the merits of this tip for your self, and assume all risks associated with its construction and use.  This Tip o'da Week is intended for educational purposes only.  No guarantees are expressed or implied as to the accuracy of information presented here!  Consult with an automotive wiring expert before attempting to carry out any wiring.

BUY YOUR GENERATOR PARTS HERE!
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Universal Generator Bracket

Two versions of our Horizontal Generator BracketHorizontal Shaft Generator Bracket

Now several versions of our famous Universal Generator Bracket
You can now build your own AC / DC generator!

A unique bracket that mounts a GM 10si alternator to a horizontal shaft gas engine. The simple way to build your own generator!  Add a DC to AC power converter, and you have a super high output DC charging system, as well as an AC generator. Be aware, you must have a battery hooked up to the alternator, or you will damage the internal voltage regulator.

We have designed and manufactured a simple, one piece universal mounting bracket specifically for this task! This bracket bolts to the motor (using a universal bolt pattern), and allows the alternator to bolt directly to the bracket. The bracket also has an integral belt adjustment slot which allows the alternator position to be adjusted, which serves to tension the belt.

We now have 2 versions of our bracket. The long one is the one we have been selling for years. The short version is a new one that is intended for applications when you want a more compact system, and have an engine with no obstructions on one side. These brackets are designed for the small footprint GM 10SI Alternator. Larger alternators will not fit!

Dimensions for Long version:

Dimensions for Short version:

See our "Tip O'da Week" on the subject.

Horizontal Shaft Generator Bracket

Short Version mounted on a Tecumseh OHV Engine

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Long Version mounted on a Tecumseh OHV Engine

Short version mounted at 45 degree angleShort version mounted on OHV engine
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Long version mounted on OHV

Bare Steel Universal Horizontal Shaft Generator Bracket, SHORT Version Price: $24.95

Black Powder Coated Universal Horizontal Shaft Generator Bracket, SHORT VersionPrice: $29.95

28" belt (for the SHORT version of the bracket).  Price: $9.00
(Use with our 4" pulley on motor and standard 2.5" alternator pulley

4" Pulley for 3/4" engine shaft. Price: $14.95

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Bare Steel Universal Horizontal Shaft Generator Bracket, LONG VersionPrice: $24.95

Black Powder Coated Universal Horizontal Shaft Generator Bracket, LONG VersionPrice: $29.95

37" Belt (for the LONG version of the bracket).  Price: $9.00

4" Pulley for 3/4" engine shaft.  Price: $14.95

Alternators Pulleys and Belts

A Note About Alternator Pulleys and Belts

The normal 2.5" pulley (shown here) on a GM 10si alternator is a 3/8" automotive pitch belt. You will not be able to find a 3/8" automotive pitch pulley to go on your engine. The only commonly available pulleys available in standard engine shaft diameters that have key ways are Industrial "A" style models. These require Industrial "A" style belts.

The pulleys and belts we sell to go on the engine are industrial "A" style, 1/2 inch wide. Although the combination of automotive and Industrial "A" style belts is not the ideal solution, it works well for most customers and is the least expensive option. The belt rides a little higher in the alternator pulley, and at the correct depth on the engine pulley. Extreme power users may experience some belt wear, especially if the belt is not tight, or if the pulleys are misaligned even to a slight degree because of the reduced contact area between the alternator pulley and belt side.

There is a better solution! The Special Industrial "A" Belt Pulley for GM 10si Alternator

We are now offering a special 2.5" Industrial "A" style pulley that fits the GM 10si alternator. These will fit any of the alternators we sell, and we will even install it for you at no cost by request. Shown here is the same belt as it would fit our new special alternator pulley. So, for people who plan to run their systems near capacity for extended periods of time, we recommend replacing the standard pulley on the alternator with one of ours.

If you already have your own alternator, or did not buy it from us, we can not guarantee this will fit your alternator. Please look very closly at the diagram for measurements. You may return it if it doesn't work out, but you will be responsable for shipping costs BOTH ways which may be more then the cost of the pulley.

Special Industrial "A" Belt Pulley for the GM 10si Alternator


Special Pulley for Alternator, 2.5 inch,  "A" style industrialPrice: $19.95
Install this pulley to any alternator purchased on this order. (No Installation Charge For This Option)

Alternator Direction and Fans

10si and 12si stock fansStock Fans

Stock Fans for 10si (shown at left in photo above) and 12si alternators (shown on right in photo above). The above photo shows stock fans for the 10SI alternators (like the 63 amp model) and the 12SI alternators.

Most asked questions:

Q:  Doesn't the alternator run backwards?

A:  Yes, in several of these projects the alternator turns in the opposite direction. An alternator will function in either direction.

Q:  Is cooling an issue when the fan runs in the wrong direction?

A:  In most situations, no. The fan still functions but at reduced efficiency. The alternators in our projects are bolted to a metal mounting plate which acts as a large heat sink. We do offer a special bi-directional fan that can be used in place of the stock fan. This fan is as efficient when rotated in either direction.

Q:  Where can I find a reverse fan?

A:  A bi-directional fan is available from us. For a true reverse direction fan you will find them used on '65-'69 Corvairs. But the Corvair fans have an integral pulley which can not be removed and is not the ideal diameter.

Bi-directional fan for 10si and 12si alternatorBi-directional Fans for use with our alternators

Photo above: (back face on left, front face on right)

These fans fit the 10SI and 12SI alternators we sell. If you already have an alternator, we can not guarantee these will fit. They will only fit if the existing fan has a dish in the center, and the dish points toward the alternator. See the above pictures.

Bi-directional Fan for GM 10SI or GM 12SI AlternatorPrice: $24.75
Install this pulley to any alternator purchased on this order. (No Installation Charge For This Option)

Vertical Shaft Generator Bracket

Mounting bracket for home made generatorVertical Shaft Generator Bracket

Now build a generator from a common-style lawn mower engine with our new Vertical Shaft Generator Bracket!

Universal mounting pattern fits all lawn mower engines. Same integral belt adjustment slot and alternator mounting provisions as our horizontal design.

(Bracket allows you to mount alternator as in the photo below):

Build a generator from a lawn mower engine.See our "Tip O'da Week" on the subject.

Dimensions for Vertical Bracket:

Bare Steel Vertical Shaft Mounting BracketPrice $29.95
Black Powder Coated Vertical Shaft Mounting BracketPrice $38.95
2.5" Pulley for engine, 2 1/2" cast iron, 3/16" key way, 7/8" shaft, "A" style industrial.  Price: $19.95
30" Belt for vertical shaft bracket and pulley above, "A" style industrial.  Price $9.00

Alternators - Regulators

Delco-Remy Alternator.Alternators and Regulators

For use with any of our generator projects.

Sold outright! No core charge!
All alternators are remanufactured  with new brushes and bearings, right here in Eugene, Oregon.

If you plan to run your system near capacity for extended periods of time, we recommend replacing the standard pulley on the alternator with one of our special Industrial "A" belt alternator pulleys above.

Be aware, you must have a battery hooked up to an alternator or you will damage the internal voltage regulator if you try to rotate it at normal RPMs.

Model 7122, 63 Amp - External regulator typePrice $49.95
Model 11710, External voltage regulator for 7122 alternatorsPrice $27.50
Wiring Plug for 7122 (you provide switch)Price $5.50

Model 7127, 63 Amp - Internal regulator type, 12 volt. External switch requiredPrice $71.95 (RECOMMENDED MODEL)  (Also see wiring plug below)
Model 7294, 94 Amp - Internal regulator type, 12 volt. External switch requiredPrice $102.95
Wiring plug for 7127, 7294 alternators (you provide switch)Price $5.50

Model 7127X, 63 amp - Single wire, internal regulator type, 12 voltPrice $75.95
Model 7294X, 94 Amp - Single wire, internal regulator type, 12 voltPrice $128.95

DIRECT DRIVE SYSTEMS

Direct Drive Generators

Q:  How do you direct drive a generator head with an engine?

A:  Direct drive shaft coupler assembly.

To connect the output shaft of an engine to a generator head input shaft (or anything else for that matter), a special shaft coupler is required. Basically, three pieces are needed.

Select a coupler half that is the correct size to fit the engine shaft (or driving shaft size), then select a coupler half that is the correct size for the generator head (or driven shaft size). Then the two shaft couplers are joined using what is called a spider. Notice that the shaft couplers each have 3 fingers and the spider has 6 slots. The three fingers from the engine side fit into three of the spider slots, and the three fingers from the generator side coupler fit into the other three slots on the spider. This coupler assembly allows for several degrees of misalignment between the two shafts and protect the bearings from seeing side loads that would result from misalignment.

These couplers are available in several sizes, but we have marked the ones that are needed for our projects:


Special Direct Drive Alternator Coupler

This coupler is custom machined to replace the nut, lock washer and pulley on a standard GM 10si alternator.With this, and our direct drive bracket set you can build an untra compact and reliable charging system with no belts to wear out.

Installing our custom direct drive alternator coupler.

We have had a few customers ask for the easy way is to install our custom direct drive alternator coupler. First you have to remove the nut, lock washer and pulley from the alternator. The only practical way is to block the fan on top of a piece of wood, and use an air impact wrench on the nut. If you don't have one, take your alternator to any shop and pay them a few dollars to do it for you.

Now, to install our alternator coupler you will need an allen wrench to fit the end of your alternator shaft, and a second one goes across 2 of the ears. Hold the shaft in position with the center allen wrench, and turn the coupler with the other wrench as shown. Again we will install this for you on request.

Direct drive alternator mounting assembly.

Direct drive system The next thing need is a way to mount the direct drive system to the engine. Shown here is the complete assembly. Note that we do not sell completed assemblies, just the two plates. The engine plate has mounting slots such that it can fit all engines with bolt circles smaller or equal to 7.5 inches. This covers everything from 3 HP to 20 HP. The plate with the large hole is where the alternator mounts.

Direct drive mounting assemblyNotice from the picture on the right that there are spacers and bolts connecting the two plates. We do not provide the bolts or spacer tubes. The engine plate comes with nuts pre-welded to the side of the plate that faces away from the engine. This is done so that the surface of the plate that touches the motor is free of obstructions.; The spacer tubes need to be large enough in diameter that they can sit over the nuts (the nuts sit inside the tubes). In the example shown, we used square tube for the spacers but we have also used 3/4 electrical conduit for the spacers. The length of the bolts and the length of the spacers must be determined at the time of assembly and are not provided.

Bare Steel Direct Drive Bracket SetPrice: $34.95
Black Powder Coated Direct Drive Bracket SetPrice: $55.95
Stainless Steel Direct Drive Bracket SetPrice: $65.95

1/2" Direct Drive CouplerPrice $18.50
5/8" Direct Drive CouplerPrice $18.50
3/4" Direct Drive Coupler (most 5 HP and smaller horizontal shaft motors).  Price $18.50
7/8" Direct Drive Coupler (use with most vertical shaft motors).  Price $18.50
1" Direct Drive Coupler (use with 8 HP horizontal motors and others).  Price $18.50
Modified Coupler - Special-threaded and Counter Bored for GM Alternators. Custom made to direct drive GM alternators with gas enginePrice $33.50
Spider for all couplersPrice $7.85  ONE SPIDER REQUIRED FOR EACH PAIR OF DRIVE COUPLERS.


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