So moving around my kayaks, rowboats, with those cheap flimsy wheel things, really doesn't work all that well. I also have a trailer, and recently got the "trailer dolly" from harbor freight to drag it around. I thought well the trailer dolly works so nice, how can I use it to move around my boats?
This was a real easy one, about 2 hours, and goes into the category of "hey why didn't I think of that?" so here it is, and feel free to plagiarize it and claim you thought it up.
Step 1: The BOM.
The big thing on this one is the harbor freight trailer dolly:
Which lists for $60, but with the 25% off coupon (google for it) I got for $40. ( I think is was on sale and then I got 25%off) Its a decent cart with decent wheels and frame. The wood I used was left over pieces from some other projects, the long rails are 2x4x6' the down legs are 1x6, and the 3 cross members. are 1x6's and a 2x4. For hardware I used 5/16" bolt for the legs with nylon nuts. these legs rotate so the whole thing folds flat. to hold the handle down I used 2 U-bolts, and a 5/16x6" bolt, but that's because that is what I had lying around, You can use anything you want to latch the handle to the bottom cross member. I just wanted it to be easily removed so I can take the kayak cart off easily and use the trailer dolly correctly. The Trailer dolly also has a leg to keep it level. this leg is a pain, as it just digs into the ground, so I added some cheap 6" wheels to it as well.
1 harbor freight trailer dolly
2 5/16x 4" bolt
2 5/16x 6" bolt
4 5/16 nylon washer bolt
6+ 5/16 washers
2 6" plastic wheel
1 2x6x1'??? wood
10+ assorted deck screws
Step 2: The Assembly
really a picture is worth 1000 words here. the 1x6 legs are grooved at the bottom so they fit over the dolly axle. the only interesting thing is the notching out of the 2x4's. I did that by setting the blade depth of my circular saw to exactly the depth of the 1x6, and cross cut the 2x4 the exact width of the 1x6. I then turned the 2x4 on its side, drew a line conneting the 2 notches, marked the center of that line, and then lowered my circular saw onto the mark cutting with the grain, not lowering my saw below where the blade hit the notches. I then flipped the 2x4 over, and did the same thing. and this point the whole wood cut out is just held in place with 2 small triangles that I cut out by hand with a hack saw.
I repeated that for the back cross member and then screwed the rectangular frame together. I then turned it on its side, and the dolly cart on it side too, fit a leg into the axle, and roughly guestimated where a flat cart would be and marked how long my legs should be. I also marked where the handle of the cart crossed the long 2x4's so I know where the lower 2x4 cross member should go. I made the lower 2x4 cross member much wider, so that 2 people can push/pull the cart if necessary (uneven road, muddy, etc,)
Step 3: Third Wheel
well it works! quite well in fact. I had to move a bunch of 2x4x12' beams and it was perfect for that too. the only issue was that triangle leg on the dolly cart. Fortunately I had some extra wheels around and a block of 2x6-8" that I could cut to fit inside the triangle. the wood wedge piece was cut and press fit tight into the triangle, and an axle hole was bored out low, and the wheels now replace the leg.