How to Modify Your Lawn Mower
You're going to have to modify the deck of the lawn mower somewhat, so you might not want to use the family's mower unless you're in a pinch. And don't use the one you borrowed from your neighbor either. You can pick up good used lawn mowers for a song, try garage sales, your local penny saver and newspaper classifieds. We put an ad in the newspaper stating " Wanted good used Lawn Mower" we then pleaded poverty and we got a dozen phone calls with great results spending only $25 dollars for a good mower with all the features we needed. Okay lets get started, but first a word from our friend "Larry the Lawyer". If you build this generator or something similar, you must build it at Your Own Risk, and assume all risks related to it's construction and subsequent use. This tutorial is intended for educational purposes only. No guarantees are expressed or implied as to the accuracy of the information presented here. If you have any doubts consult with the experts you purchase your parts from, before attempting to carry out any of the procedures mentioned here.
Okay, lets get started tearing this baby apart. First remove the handles and cables. The removal is pretty straight forward with just a screwdriver. You can re-attach the throttle cable later or you can control the engine speed at the throttle control near the carburetor. You will most likely have a second cable coming off the handle to the flywheel brake, a safety feature introduced onto walk behind mowers in the early 80's. Remove the cable at the handle and the brake lever next to the flywheel, you can leave the brake lever as is just flopping around ( it may create some drag on your motor ) or you can easily secure it off to the side. If you're not sure which side the lever should be positioned, just pull the starting cord. If it's difficult to pull, the brake is on, if it's easy, the brake is off, now tie the lever off with a twist tie or wire in this position.
Removing the Blade Assembly
Some of these blade hubs can get seized onto the shaft pretty bad after many years and acres of cutting grass. Spray some kind of rust loosening compound onto the area (WD40, RustBuster) if this doesn't work, you will have to use a pulley puller to remove the hub. We schmoozed our local machine shop proprietor into lending out his puller for free, we just left a deposit so he knew it would come back. Now, while your underneath and have the WD40 handy, spray the 3 or 4 mounting bolts you will find holding the motor to the deck. Spin the bolts out and remove your motor for the next couple of steps.
Cutting the Slot
The rear end of the lawn mower deck is a very convenient spot to mount our alternator with a couple of simple metal brackets. But you have to cut a slot in the back of the mower in order for the belt to reach from the motor pulley to the alternator. You need to cut the slot 6" wide by 1" to 1 ½" tall on the rear vertical side of the lawn mower deck. You can cut this slot quite easily by using an Oxy/Acetylene cutting torch or you can use a grinder with a cutting wheel. And if you're in a really energetic mood, you can cut it by using a hacksaw. We need to know exactly where the belt will come through the back off the mower deck, so we know where to cut our slot. So, let's install our motor pulley briefly so we can line up where our belt is going to come out the back. Place the motor pulley as far up the engine shaft as possible and yet still give it enough room to clear all obstacles such as mounting bolts. Now, look through the grass discharge chute. Place a straight edge on the bottom of the motor pulley and determine where the path of the drive belt will end up coming out of the back plate. Mark this spot. Now make this spot the exact center of your 6" by 1 ½" slot. Remember your belt is only ½ " thick so you will have plenty of clearance in case the spot you marked is not exactly centered. Make sure to remove your motor once again before you start your cutting. Now cut your slot using the methods described earlier. If you decide to use a hack saw, you might not be able to cut a "slot." Instead you will have to cut an entire 6" wide piece out from top to bottom. No problem, just bolt a strip of metal or angle iron for a crosspiece along the bottom of the mower deck, to give it some strength again.
Assembling The Project
Mounting the Alternator
In order to mount our alternator we are going to use brackets made from a slotted steel material commonly referred to as angle iron. The dimensions of the angle iron were 1 ½" wide and 1/16" thick. The pre cut slots in this material made it very convenient to make an adjustable bracket for the alternator. The 90 º angling of the metal gives it a lot of added strength, but it was also very easy to cut by hand using a hacksaw. On the left hand side is our pivot bracket which we cut to a 7" length. On the right is the adjustable bracket, cut it to a 9" length. The pre-cut slots on this angle iron will allow you to move the bracket front to back so you can have the belt tension adjustment you need. On both brackets we want about 5" contacting the mower deck. Now drill mounting holes on your mower deck 6 ½ " apart width wise and 2" to 3" inches along the length of the bracket depending on the pattern of the slots on your angled bracket material. Drill your holes 3/8" thick with the first set of holes ½" from the back edge of the mower deck. We extended the slots in the right hand adjustable bracket by cutting the metal with a hacksaw so we could have a wider range of belt adjustment. Use 5/16" bolts with lock washers, now fasten the ends closest to the motor. Even though we selected a relatively flat mower deck, we still have some uneven contouring to deal with. No problem, we just use spacers on the two mounting bolts closest to the edge. Use whatever you have lying around your house, in our case thick washers and a couple of ½ " nuts worked perfectly.
Now take your alternator and mount it with the pulley facing down. One side of your alternator has a longer molded mounting hole in its casing, this side will become our pivot side and is mounted with a 3" bolt. The right side of our alternator now becomes the adjustable side. You will need a shorter 1 ½" bolt to fasten it to the bracket. Use lock washers with your nuts and bolts as well.
Attaching the Pulley and Belt
Position your alternator so that the fan blade clears the mower deck between ¼" to ½". If it's too far away from the deck, you will notice more vibration. Now flip the whole unit over and attach your motor pulley, we used a 5 " diameter pulley (more on this later). Next, we need a drive belt, but what length? Here's a tip for getting the right size belt on your first trip to the store. Measure the distance between the two outer edges of the alternator and motor pulleys in their final position. Mark this measurement down. Decide ahead of time if you want the lighter duty "L" series or the heavy duty "A" series. Now head down to your local building supply or commercial bearing store to buy a belt. When you get there take 2 pulleys off the shelf with the same diameter as your alternator and motor pulleys. Next place a ½" belt around them and stretch the belt out. Do this until you find a length of belt that matches the measurement you marked down from your project at home. Don't do what I did. I drove down to the store with my whole project in the trunk of my car, then ran back and forth into the store exchanging belts until I found one that fit, all the while looking like a complete dork!
Now, place your belt onto the pulleys, grab the right side adjustable
bracket with a pair of Vise-grip pliers, pull toward you until you've
reached a desired belt tension and then tighten the mounting bolts.
Your next step is a simple wiring of the project.
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