I have been a follower of Instructables for about a year, and have learned some interesting and handy things here. This Lawnmower Utility Trailer is my first contribution. This thing measures 3'x6' bed, 8' total length, perfect for hauling leaves and yard trash, but has many other applications. Based on tire rated capacity (and experience), I recommend it for up to 400 pound payloads (each tire is rated at 300 pounds, so 400 pound payload PLUS the trailer weight of 100+ pounds).

This is my second Lawnmower Utility Trailer build, and is a step in the right direction. It all started when my wife was struggling to move chicken manure from the chicken coop to my father-in-law's garden late last summer. He said he really needed to get a trailer, and I volunteered to build one if he would buy the materials. I went to the computer and was surprised at how hard I struggled to find anything like I thought I could use when I looked over the Intructables website, so I set out to design and build my own.

If you are like me, welding is not an option. I wasn't worried about building the deck or the sides, but really had to concentrate on how to come up with some type of axle and some type of tongue-hitch combination.

I spent about a day getting mine built, but think it could be done in about five hours. Total investment for me was about $140, maybe a little less.

Materials needed:

12 ea 2x4x12 Pressure Treated
1 ea 2x10x8 Pressure Treated
2 ea 10" Tire and Rim with 5/8" axle hole (Harbor Freight special, $5 each)
1 ea 48" 5/8" Cold Rolled Steel (came from a local welding shop)
2 ea cotter keys
4 ea 5/8" flat washers
8 ea rafter ties
3 lb 2-1/2" Coarse Thread Deck Screws (at least 150 ea)
1 lb 1-1/2" Coarse Thread Deck Screws
1 ea 10" Gate Hinge Strap(perfect one at Tractor Supply)
3 ea 2-1/2"x3/8" Hex Bolts
3 ea 3/8" Flat Washers
3 ea 3/8" Lock Washers
1 pc Uni-Strut 48" long (available at electrical supply houses)
1 ea 3/8" Hitch Pin

Tools Required:

Circular Saw
Drill-Driver
Deck Screw Bit
Tape Measure
1/16" (small, anyway) Drill Bit
3/8" Drill or Paddle Bit
Square
Wood Chisel
Hammer
9/16" Wrench plus Pliers Socket Wrench
Jig Saw
Pencil
Safety Glasses
Drill Press (recommended, but optional)

Step 1: Build the Frame and Tongue, and Hitch

I found that my 12' 2x4's were actually 12'-1/2" long, so I cut them 6'-1/4" long to get them exactly in half. To make the deck 10 boards wide, I learned that it needed to be 36" wide.

So here I have:
2 ea 2x4x6'-1/4" deck frame sides
4 ea 2x4x33" deck cross joists

I used a "little bit" to pre-drill starter holes for the 2-1/2" deck screws.

Next, I added the tongue-hitch-frame bottom combination board.

Here I have:
1 ea 2x4x8' tongue and center frame
4 ea rafter ties
16 ea (at least) 1-1/2" deck screws to attach the rafter ties.

I suggest you alternate the locations of the rafter ties. I also "toe nailed" a 2-1/2" deck screw at each cross joist as well.

This is the perfect time to go head and add the gate hinge strap to the tongue for your hitch. I used a wood chisel to chip out a little wood to get the thing good and flush with the 2x4. Bolt in with your 3 ea 5/16"x2-1/2" bolt-flatwasher-lockwasher combos, and tighten with 9/16" wrench or socket or pliers. See the pictures.

ONE THING ABOUT THE STRAP HINGE HITCH: I located mine at the bottom of the 2x4, and would recommend that you either move it to the middle, or even add a second one at the top.

Step 2: Finish Frame and Add Running Gear

For the next area of fixing the frame and running gear, I added the two angel braces from the center of the frame to tongue. I measured the total length of my 2x4's here to be 54" from front tip to the back end at where the axle will go to be 54", but the next trailer may be a little different.

The first picture just shows how I laid it out. Cutting that angle at the tongue was hard for me! I measure, marked, remeasured, and remarked, and managed to get it "good enough". I had to cut across, flip the board, then try to match the cut on the bottom again. I secured with rafter ties and toenailed deck screws.

I cut the 5/8" cold rolled tubing for the axle to fit. It has to be the length to fit the axle board + 2 wheel rims + 4 flat washers and still have room for a hole for the cotter keys to hold the tires on.

The axle wheel combo I assemble next. I use a flat washer in front of and inside of each wheel, then put the cotter key on the outside of the outside flat washer. It's ready for mounting.

Uni-Strut is slotted and galvanized, and available at major electrical supply warehouses. It was the easiest way I could come up with to mount the axle. I drilled five holes spaced along its length. I laid the assembled axle + wheels on the axle mount board, then covered it with the uni-strut and used 2-1/2" deck screws to secure.

Step 3: Add Decking and Sides

I needed 10 ea 2x4x6'-1/4" boards to deck mine out. I cut 5 of my 2.x4.x12's in half and they were ready to be deck screwed to the frame.

I used the 2x10 to make a front board for the front side, and will use of the remainder of the 8 foot piece for the tailgate.

2x2's serve well as the vertical supports for the sides and front, with a pair at each.

I recommend that you mount the front, cut the four side rails, then mount the back. I used 2x4's on the outside of the back, and this is a good time to put them, as then that will make it easier to precisely cut and fit the side vertical supports.

Cut the remaining piece of 2x10 for the tailgate to fit. I added a finger hole using drill and jig saw. Cut a pair of 2x2's for inside track plate for removable tailgate.

Step 4: * * UPGRADES April 2013 * * *

Well, I had a bearing go out in the wheels (cheap Chinese stuff from Harbor Freight, no big deal), so I decided to upgrade to a tandem axle.

I've also had a request or two for further details on how I mounted the axles and wheels. I've added more pictures.