Well, since you mentioned tractors...
I guess I have to post my hillbilly snowplow.
I got this 18HP Craftsman tractor for free and planned on lawnmower racing with it.
Being 18HP it was in the class that costs alot of cash to get into so that plan got scrapped.
Instead I took all the scrap metal and used auto parts I could find and made the hillbilly snowplow.
The plow blade, A-frame, and all the linkage is made entirely from used auto parts heated bent and welded together.
I did the entire thing by eyeballing it. No measurements were taken.
The oxy torch did have to be used a few times to rearrange the design.
But the first test run was a huge success and it plowed the snow all winter despite the leaky tires.
(I reseated the bead on one tire with ether and got a little happy with the explosives.)
Here is the walkthru of what the design looks like.
[youtube]http://www.youtube.com/watch?v=qB43H5x-R4M[/youtube]
The first run, it was working so good I had to grab the cam and refuel.
[youtube]http://www.youtube.com/watch?v=dVPZm5dKfTg[/youtube]