Lazer,
I don't have one of the edges <B>yet</B>. I can say, it does make sense to me. I know from using a big squeegee (like for a shop floor) to clear walks of slush and light snow, that when I did, I could push it right onto the grass, no harm done. When the snow was packed, from foot traffic, I could pull back on the squeegee, and it would scrape the walks clean. I mean CLEAN. I imaging the urethane edge will "roll" the gravel where it lies, but not move it far, or accumulate it in front of the blade. Gravel is a solid, that can't be compressed like snow. That's a fact. So the edge rides over it, because the edge is flexible, and can compress / flex. Steel is rigid, and doesn't compress, and so it bites in.
The action of the urethane edge flexing, will compress the snow between the edge and the pavement, "squeezing out" the snow, scraping it up. Even hard packed snow can be compressed. A steel edge shaves the snow off. Leaving it in low spots, and riding over it often. This is because the steel can't flex. Ice, is another story, and I will be impressed if the urethane gets that up. This is my opinion of course, but it makes sense to me, at least in theory.
I also think of how I push my green barrels across grass, when overloaded. I never drag a barrel if I can push it with my walk behind. Across pavement, across lawns, it does no damage to grass, no matter how heavy it is. The sides buckle in it's so heavy sometimes, with wet leaves that I jumped on to stuff into it. It still goes right across the grass with no damage at all. Even after years of doing this, the bottoms haven't worn through, and I only can hope the urethane edges are as durable.
I can also say that there is 3 different grades of the urethane edges.
Yellow is for light duty applications, (light duty blade) on pickups, tractors, and small dumps. It is not for high speed plowing. It is for parking lots, driveways, and private roads.
Blue is (special duty blade) for municipal plows, not exceeding 18 - 20 MPH when plowing. It was designed for cobblestone roads, going over manholes, and roads with raised reflectors.
Red is (heavy duty blade) for heavy industrial equipment, that clears at high speed. It's superior in it's resistance to cuts and abrasion, extended wear, and resiliency. Ideal for interstates and highways. It is also obviously the most expensive.
That my take on the edges. I hope to learn more soon.
~Chuck
