Sewer manhole lid worth saving?

[Bill Kahn]

About to throw away am old sewer manhole ring and lid and thought of recycling it. Any value in it being used by one of us here? It is heavy steel, cast I suppose.

If you decide you don't want it, I'll be happy to pick it up. I'll be in Decatur in September if you can wait that long. No, I have nothing to do with it either. While "necessity is the mother of invention," sometimes "availability" can facilitate too.

What diameter? Thickness? Weight?

-Bill (Charlotte, NC environs)

 

[Dhal22]

Maybe, it's still on a jobsite in the mud somewhere, happy to leave it at my shop 25 miles north of Decatur for your convenience.

 

[ebolton]

A few years ago in Boston a truck somehow tossed up a manhole cover in the I-93 tunnel and it landed on the windshield of the car behind, killing the driver of the car. Big legal action resulted. The manhole covers on the entire section of highway ("The Big Dig") were redesigned and replaced as a result. One of several accidents leading to legal problems from that hyperexpensive project. Steel plates falling from the tunnel ceilings (they litterally just glued them up there) and railings that decapitated motorcyclists (including a State Trooper) were other problems.

 

[kb58]

Grinder base?

Or a vice

 

[Bristol-Rivett]

They make great pedestal style welding tables.

 

[Janderso]

Idk on some streets here in Chicago they’re as big and deep enough it would be like hitting a open sewer. And then you see three road repair trucks sitting off in a parking lot with ALL the occupants sleeping.

One day I was driving next to a lady that hit a open sewer cap at 40mph and just kept driving. It had rain hard earlier in the day and pushed the cover off and was in my lane. There was no flooding so when we were going down the road I had seen something in my lane. Coming up to it I had seen the open pipe in her lane and the sewer cover in mine and I moved to avoid the cap and out of the corner of my eye I see this ladies car bounce like in a rodeo and a loud wack. I don’t think she slowed down I was stunned she kept going. I had a good story when I got to work

I think they call that horizontal terminal velocity -Come on, I thought it was funny.
I wonder how fast you have to go so the car tire/wheel will just fly over the hole?
Anyone want to do the math?
The car weighs 2,300lbs.
The hole has a 30" diameter.

 

[Janderso]

I want one! Although I wouldn't know what to do with it. Hopefully you find a new home for it, I'd hate to see it go to the scrap yard.

Well if you can get your hands on 3 more you could do this!

View attachment 312672

These guys do some funny, stupid, & crazy things.

Is that car in Bejing?

 

[Janderso]

 

[RJSakowski]

I think they call that horizontal terminal velocity -Come on, I thought it was funny.
I wonder how fast you have to go so the car tire/wheel will just fly over the hole?
Anyone want to do the math?
The car weighs 2,300lbs.
The hole has a 30" diameter.

In a simple analysis, a free falling object accelerates at 16x t^2 where t is the time in seconds. A vehicle traveling at 30 mph and traversing 24" manhole opening crosses the distance in about .5 seconds, during which time, it would fall about .5 inches.

However, a vehicle has a suspension where the spring is under compression with a force equal to that wheels share of the vehicle weight. To know the vertical displacement, you would have to know what the spring constant was as well as the mass of the wheel and suspension elements. The spring constant could be measured with a load cell. Knowing the amount of compression in normal conditions will give you the compression force and knowing the mass of of the wheel assembly, you could calculate the oscillation frequency. From there, you could determine the vertical displacement in the time it took to cross the opening.

Needless yo say, the shock would occur when the wheel made contact with the far side of the opening, The shock absorber or strut would prevent the spring from rapidly returning to its normal position, creating a very unpleasant jar.

It's best to avoid open manholes altogether.

 

[Winegrower]

RJ, that’s a good analysis, but 30 MPH is 44 ft/sec, so the car takes 2/44 ths of a second, or about 45 milliseconds.
That changes the conclusion quite a bit.

Edit: oh no it doesn’t. See below.