What stops snow plows from getting caught on bumps, cracks, etc?
If I go shovel a sidewalk, the shovel gets caught on every crack or imperfection, but obviously this doesn’t happen with street plows.
Sure it does if they don’t have enough clearance. Usually the plow just tears up a bit of the street.
There are a few different plow designs. The most common the the bottom edge is hinged. There are big springs holding it in place. It the bottom edge catches on something it bends back until it clears and the springs bounce it back. This style is best for scraping down to pavement.
Other plows, typically the larger ones have feet that set behind the plow blade they keep the bottom of the blade just off the ground so it’s less likely to catch on anything. They don’t do as good a job scraping.
When you watch them plow highways or large parking lots a lot of the time you’ll see a giant plow clear the bulk of the snow, then the full size pickups clean up after them.
As the previous poster mentions, sometimes they just end up taking chucks out of the pavement. While a lip might stop your shovel the plow has enough force to break anything trying to stop it.
Occasionally they hit a curb or something that won’t give. Bent plows and truck frames are a cost of doing business. Being careless can cost some serious money.
I have seen, heard and felt one hit and crack a manhole. That metal ring/tube that the manhole cover fits into.
The snow plows here in St. Paul are dump trucks with three different blades on them: a big, standard type of plow out front that stays an inch or so off the pavement, and a smaller one between the front & rear wheels that’s more spring-loaded. The main one gets the bulk of the snow, then the little one is closer to the ground and takes the last inch or so (if they use it…). There’s also a plow blade on the side so they can clear the emergency lane, or shove the snow the first blade moved even farther off the road.
However, they have to build the roads to be much more even than the sidewalk, and as mentioned above, there’s a reason Minnesota has two seasons: winter and road repair.
Just yesterday I visited Salem, MA, and found that two windows were gone from one store, replaced by plywood. The snowplow had bulldozed the snow through the windows.
What stops the snowplow from getting caught? Nothing, pretty often.
It even took out part of the metal awning overhead.
(There were snow piles 20 feet high in Salem yesterday. The problem is that there’s no place to put it all.)
There are signs all over upstate New York that say “raise plows.” They’re put up in places where the road is permanently uneven - bridges, speed bumps, or temporarily - iron plates in the road from construction.
A manhole cover fits into a manhole frame. Sometimes riser rings are used if the road is overlaid with a layer of asphalt to keep the cover flush with the road.
And yes, plows break manhole frames all too often.
What about a rubber or some such on the bottom edge of the blade?
IIRC, I have seen that on some big piece of equipment. Not necessarily snow plow. Do such things exist or was I hallucinating?
Such things exist. They have a hard life and don’t last long.
Their relative mass. They are much heavier and traveling faster than your shovel.
Pick-up sized plows have the same feature that allows either the ‘bit’, the lower 4" inches of the plow to fold back (I see this on Meyers) Or the entire plow folds over, the way Western plows work (or at least the one on my truck).
Some of the more contractor grade plows also incorporate a shock absorber to slow the return of the plow to it’s normal position. This helps prevent the WANG of the blade as it returns upright.
shunpiker is also correct in that mass and speed come into effect here too. Immoveable object, irresistible force and all that. Something will lose.
Your plow can also fold over at slow speeds if the snow is very heavy/packed or you hit something. I try to back away from that and start again, but sometimes you just have to push through it.
They installed some (very unpopular) speedbumps in a portion of the parking lot at my high school.
These mysteriously disappeared around the first snowfall.
In the spring, they showed up again in a melting snowbank having been plowed right off the pavement.
There are (or were) a series of speed bumps leading up the private road to my place. They get damaged and rebuilt by snowplows every year but this month has been so bad that most of three of them are completely gone. I can just sail right through them now. 10mph speed limit my ass. Snowplows destroy all kinds of things in Massachusetts including roads, curbs, utility covers, cars hidden under mounds of snow, mailboxes and much more. It must be fun to drive one of the really big ones. You can just hit whatever you want and blame it on poor conditions or at least that is what I would try to do if I ever got that job.
Just for some references:
This is a pickup sized plow blade. You can see the plates at the bottom, though many people take them off so they get right down to the asphalt. The plow is mounted with pins at the bottom and held back by the big springs. When you hit something, the whole blade bend forward. Ignore the wheels, they’re just there for moving the blade while it’s not attached to the truck.
Some are also designed so that just the bottom part flips back and it can ride up and over things in the road.
Good pictures/graphics JoeyP. We call those plates feet round here. You can see in your first link that you can add washers to adjust the working height.
Oddly, I don’t have feet on my Western plow. Nor a place to mount them. Working a gravel drive and road, I sometimes wish I did. But I do find that after a few months of snow, it’s get’s so packed that I don’t really need the feet, and would rather cut the packed snow. Considering getting plow feet mounts welded on.
The bottom trip design is far more prevalent in my area.
On both of our last two plows we just took them off and threw them away right away. We really need to get right down to asphalt and we’re not too concerned about the lot. It’s flat and there’s nothing to tear up. It’s more important to get all the snow and ice up than to worry about some scrape marks.
The plow we have at work (just for doing our lot) has the bottom trip. Our last one was the first type. It seems to me, it must take a lot more force to make just that bottom part flip back (leverage and all that) and you’d think it would smash through a lot more stuff, but I would assume they use weaker springs to compensate for it.
And the downside. Every spring we spend an afternoon shoveling and raking all the grass around the parking lot around my shop. The plow makes a mess.
they are useful until the packed snow fills in. keeps you from plowing earth.