DIY Power Screed

I while ago, I had reason to place about 8 yds of concrete at the same time that I replaced my old lawnmower with a fancy self-propelled one. So of course, I experimented on putting together a power screed. Basically, I chopped about an inch off one side of the blade of the lawnmower (so it would vibrate), and connected some 2x4's. It worked great, right until the engine gave out. Managed to smooth a 10ft x 10ft slab, and about half of the other one before we had to switch to a conventional board screed. FAQS: Q: Why? A: Why not? I like making stuff, this was something to make, so... I made it. Q: Couldn't you have rented or bought a power screed? A: Rented - no. None were available in my area. Bought? Sure. It would've doubled my overall budget, though, and this was "free" in that it was all stuff I was going to throw away in any case. Q: Why aren't you wearing safety boots? A: You need to look closer. I was. No, my pants were not tucked in to them. Q: Did you cut the blade? A: Yes, I cut about an inch off one side so that it became unbalanced. That's the source of vibration.