How does the blade of a snow plow stay at the perfect level for plowing? They plow right to pavement, yet it seems if they were set too low, they’d plow into the asphalt. Set too high, they’d leave too much snow.
They often ride along on metal skids (or occasionally on small wheels), thus maintaining a more or less constant small distance above the pavement. You can sometimes see sparks from the skids.
That makes sense.
I wonder if they have springs or if it’s flexible so that it can raise or lower with the grade of the road (streets aren’t perfectly level, even in my perfect town). In my 'hood, even the speed humps get plowed.
That last sentence didn’t sound right 
Fisher plow information linky.
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Right up the road from me. Oddly enough, one of my former ship designer collegues no designs plows for these guys.
Most plows (I’m not sure about the giant municipal ones) or pulled up by a chain (hooked on to a hydraulic ram). When the blade is down, it’s riding on the ground and is free to go up and down with the road. Basically, nothing is pushing or holding the blade to the ground except it’s own weight.
Heh - they had to plow the parking lot at my apartment before Christmas, and either the plow driver didn’t know that the building had put in speed bumps or forgot, or whatever, but he managed to tear one speed bump right off the pavement. All that’s left of it is a yellow ragged chunk about 15cm wide. THAT plow, I assume, needed some sort of control for dealing with bumps!
I have a plow and do my own driveway. Plows are also ‘spring loaded’. This allows the plow to fold over if it encounters an immoveable object.
From one of my many jobs in the military as the director of snow removal on an airfield and streets, I know that some larger plows (such as the big rollover rigs) have what is called a “float” positioning lever. This allows the blade to ride over things such as rolled curb edges and small obstacles, rather than standing the plow truck on its nose and catapulting the driver through the windshield.
Plow blades generally don’t clean well below about 2" of accumulation and have skids welded to the bottom edge to prevent gouging of pavement.
Sometimes they work better than other times, too.*
koeeoaddi Street made the evening news last week. 