Step 5: Replace the Blade With a Fixed String Head

(more photos coming)

Note, with 3 to 5hp, you can run as thick a gauge of line as you care to. The minimum needed is .130! ! ! I recommend .155 or .170, or if you can spend it, that "flexiblade" is unbelievable for cutting power and almost indestructible. I've used the flexiblade string and it's wicked, but it's expensive and only works in quick-change type heads with ratchets. 

There are several ways to do this. You can buy a commercial fixed  "4" string head for brushcutter mowers (about $30), that fits the blade fixing bolt you have. You may have to remove the blade-to-crankshaft adapter and attach it to the bare shaft (not recommended, but it works well, just has less strength than other options). You may need a longer bolt. You may need to find or fit a washer to adapt the string head to mower shaft. Most likely the kits with multiple washers will have yours. 

If your mower has a blade-to-crankshaft adapter with a large flat "washer" on the bottom, this works great to just bolt a commercial fixed-head to it. 

You may also find some quick-detach fixed string heads (2 strings) that bolt up easily to the bare shaft and protect it (they will place the string path higher in the deck, note). These are great, as they allow you to use less string, and make string changes a breeze. 

You can also MAKE a four string head from a worn out blade (labor intensive). 

You will need to remove the blade, clamp it in a vise, and saw off the ends/wings (keeping 5" of the center piece), grind smooth and round the edges, and drill in the pattern shown or similar, to attach the strings. Chamfer the holes to prevent cutting the strings with centrifugal forces. 

You could also MAKE a four or eight string head (leave short strings on and add new ones to opposite sides) for maximum cutting potential.  Draw a 5" circle on a piece of 1/4" plate steel, cut out the circle, drill central hole, check object for balance as a flywheel, and drill pattern for strings. 

Do not make it out of wood. I tried that, and it worked, but the holes wore out and eventually it broke. I made one before with a commercial aluminum fixed-string head and it worked well. 
examples, with many similar products available. 

Oregon brand string head $30 with adapter washers and nuts http://www.amazon.com/Oregon-55-130-Trimmer-Head-Fixed/dp/B0018U2CWU

Echo Rapid Loader head from Home Depot $30  http://www.homedepot.com/p/ECHO-Rapid-Loader-Trimmer-Head-21560059/100056334

Oregon Jet Fit Flexiblade compatible 4 string (the ultimate) $60 http://www.lawnmowerpartsoutlet.com/Oregon-Aluminum-Jet-Fit-Trimmer-Head-4-Line-55-404_p_4677.html

WARNING: Obviously, you will need to kill the mower to change strings. 
Note: You cannot use this modified mower to trim lawns as a trimmer for cutting up to fences and bricks. The wheel gets in the way. You need a conventional string trimmer (portable or wheeled) for that. This is for beating down hiking/biking trails and overgrown lawns. 
<p>This went ok until the engine died. It was a trash find, anyway, and survived hard use, so I do not care. <br>I made a different bush-mower, later, which is still in use, and which has outlasted a couple junkyard engines. It's ugly as heck, and only mows at one (tall) height, but it does the job (knocking down grass on footpaths). The big wheels are in front because it does not need to turn sharply or often, and it rolls over obstacles and tree roots. </p>
I did this before with a heavy 1970s dept. store mower. It worked very well, but the motor was old and died. The walmart Weedeater mower shown is pretty weak. I had to add 2 braces to the top of the deck, by bolting pieces of angle extruded aluminum to it, for strength. The strap at the bottom of the grass chute got knocked out by a chunk of wood, so I have to add a piece there too probably. It's still running like a champ, though. I've mowed miles (literally, the trail is 6mi long, and I've been over it a couple times) with it and it plows down years-old thorn bushes, vines, saplings, deadfall, leaves, thick weeds, and dirt! It's very useful for &quot;shaving&quot; the edges of the foot path where they have grown deeper from high foot traffic and rain. If you make one of these with a 5.25 briggs, it should be unstoppable! That will be heavy, though, so I recommend bolting the wheels straight onto the deck instead of the adjustable casters, (re-use your wheels if you want), and bracing the deck. Old Snapper decks are the boss, and have a 5 speed self-drive with current parts available.
<p>im thinking of making a bush mower but instead of pushing it I will pull it behind my off roading mini bike just have to come up with a hitch please help any tips or ideas</p>
A Trimmer mower is similar to a regular mower but is much better for <a href="http://www.beststringtrimmerpro.com/black-decker-lst136-13-inch-36-volt-lithium-ion-cordless-high-performance-string-trimmer-review/" rel="nofollow">cutting tall weeds</a>. A regular mower just runs over them, pushing them down and out of the way of the blades.
I recommend finding a longer bolt for the air-cleaner, and leaving it threaded in, and use a nut, if you want to remove the filter a lot of times. The plastic in the carb stripped out on this one. I will include an update on how to make a permanent air cleaner stud and mount it to the side of the carb. (bent piece of 1/4&quot; all-thread, with a few nuts). If you want a whole new mower for $80 or less, check on fleabay. Here's a classic briggs pusher for $80 shipped! http://www.ebay.com/itm/Murray-22-Push-Gas-Walk-Behind-Lawn-Mower-Briggs-Stratton-Engine-M22450/360722167148?rt=nc&amp;_trksid=p2047675.m1851&amp;_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D163%26meid%3D832117923481450308%26pid%3D100005%26prg%3D1088%26rk%3D3%26rkt%3D4%26sd%3D130972366616%26
This deck has finally had it after mowing a cow pasture (2.5 acres) with it. hahaha. I'm putting the engine on a converted bicycle trailer lawn mower. (see on youtube bicycle drawn lawn mower, instructables later. Friend is welding the engine mounts, and I've got to get a couple more pieces of tin to finish the &quot;deck&quot;. We're going to use it to mow where a yard tractor can't get in, on a bike trail that is basically a flat road )
The old junker is still running well, but the deck has been beaten mercilessly (rough mtn bike trails, cracked ground, and even dog pens and horse pastures, plus that stump I hit last month, oops), and has cracked again. The Weedeater deck is the flimsiest deck I've ever seen. The points the engine bolts through are reinforced with 1&quot; squares of steel plate. lol. I think I'll bolt another piece of flat stock to it to fix it until I find a high-wheel deck from the 1980s (one of those that is hard to dent with a hammer even). Check your local junkyard or scrap yard. Millions of mower decks in USA will take Briggs 3 bolt motors.
Awesome build Dale! Much safer then mine. I like it!
Also, building your own trimmer head definitely reduces the cost. I had problems with mine backfiring after a lot of usage, I thought it was because dust was by-passing the air filter and had worn out the valves, it seems you're saying that without the weight of the blade it may backfire more often, is that right?
If you mean during starting, yes. The weight of the flywheels on typical mowers is designed to work with lawnmower blades as an additional weight. It's like the crank handle on old timey Ford cars. If you spun it but not hard enough to start the engine correctly, the handle could spring back and turn you! Sometimes those engines could be started backwards, but the mower can not because the pawls on the starter reel and tension of the starter rope prevent it. I had a junkyard find mower that backfired with a standard blade on it (crappy carb and worn valvetrain), and it stung my hand so badly I thought I had a broken knuckle. It went numb and swelled like a tennis ball. Be careful.
Yeah, during starting. Thanks! Again, awesome build!
If you mean backfiring during operation, most likely it's a dirty plug, dirty governor/linkage (don't forget the pivot the carb butterfly sits on) clogged or burnt muffler/screen, or deformed timing key. Check the easy ones first.
Thanks. I like yours better, but I'd make a string head out of a steel disc for it, and use a high-wheel mower for the deck. A removable bar with a swivel caster on it for the front might help when cutting lawn grass with it for the regular haircut. A 2&quot; wide wheel won't block up the grass going into the strings. Might be a PITA on hills though. I have to wrestle my 2 wheel conventional trimmer on hills.
This worked great. I mowed the heck out of miles of grass and thorny stuff. The left wheel pointing in just a bit did what I expected. It helped a lot when mowing on inclines and deflected a lot of vines and roots instead of hooking them behind the wheel.
I drilled two holes in the side of the tube, about 1/2 inch apart, and looped the string through them to tie. I like this better than the ski-rope style tie.
I recommend removing the spring, and using a throttle wire. If you use a non-solid cable, you may have to add a strong spring to pull back the throttle selector when cable is relaxed.

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