An engineering problem
- Thread starter sbosecker
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rburke65
Well-known member
After reading "best regards, Scott " 27 times I quit reading!
c39er
Well-known member
matt_i
Well-known member
I would opt for an easier solution.
Build a removable support structure of S4 - I-beams underneath it. (S4 if spanning short way, S6 if spanning long way) However on the ends of the I-beam, notch it down to 2" tall rather than the 4" nominal vertical dimension. Weld on a piece of flat bar to make a 2" "mini-I-beam" as viewed from the end.
This requires sort of a "shelf" be set in the upper edge of the concrete, angle iron would be my choice. Set the ends of the beams on that to span the pit. Cross-brace if you feel the need.
When the project is "over" then you can do one of several things. Short pieces of 2" square tubing set as "spacers" but not spanning the opening come to mind as the easiest. It could also be a system of vertical flat bar(s) to provide more support for the grating.
I would not trust the tables, its likely tested with the perimeter of the grating restrained. Rather than free to fold up like a pringle.
Build a removable support structure of S4 - I-beams underneath it. (S4 if spanning short way, S6 if spanning long way) However on the ends of the I-beam, notch it down to 2" tall rather than the 4" nominal vertical dimension. Weld on a piece of flat bar to make a 2" "mini-I-beam" as viewed from the end.
This requires sort of a "shelf" be set in the upper edge of the concrete, angle iron would be my choice. Set the ends of the beams on that to span the pit. Cross-brace if you feel the need.
When the project is "over" then you can do one of several things. Short pieces of 2" square tubing set as "spacers" but not spanning the opening come to mind as the easiest. It could also be a system of vertical flat bar(s) to provide more support for the grating.
I would not trust the tables, its likely tested with the perimeter of the grating restrained. Rather than free to fold up like a pringle.
That pic is almost identical to the pit we put in years ago in my FIL's barn. same size grate (was scrap we had), it is in 6 sections so you only have to remove one or two at at time. in 15 yrs. nobody's ever driven over it, but what I wold do, is just cut some 3/4" plywood to go over the grate for the inspection. should be plenty enough. you could also weld some 2" angle iron underneath vertically to strengthen it. then just cut it off after the inspection.
last cheap idea is to build a temporary bracing setup with some of those red pipe basement lolly columns and 2x10. easy to remove when needed and not too expensive...
last cheap idea is to build a temporary bracing setup with some of those red pipe basement lolly columns and 2x10. easy to remove when needed and not too expensive...
Labels, ?? pits are known to hold fumes.. I don't know what you use your garage for,, but most home insurance companies will drop you if they find out there is a pit in the garage..
but because you are going to do this anyways..
As for something to cover the span.. Think box truck..
The alum ramp that stores under the floor.. is long enough that you could have it cut into 2 and then weld them together length wise.. or bolt them together.. it be light, it have loops at one end to pull the unit out of the pit.. and it hold up a vehicle if one was to end up with a wheel on it..
and it shouldn't be hard to find one in a junkyard..
38Chevy454
Well-known member
I will make assumption the grates you want to use are because you have them already or can get them real cheap?
How about this for an easy solution, just double the grates; i.e. stack them to be double height. You could weld them together, or use some straps to connect them. Yes it takes more grates, but then you exceed the load value to keep the inspector happy. Not as good as the taller height grates, but it seems you have this 1.25 grate set.
How about this for an easy solution, just double the grates; i.e. stack them to be double height. You could weld them together, or use some straps to connect them. Yes it takes more grates, but then you exceed the load value to keep the inspector happy. Not as good as the taller height grates, but it seems you have this 1.25 grate set.
wssix99
Well-known member
Have you thought about putting in removable curbs around the pit? This would give you curbs (like are installed in to the concrete of oil change places) to keep the wheels from going in.
You could have them in place for the inspection, and then unbolt them from the floor when done. Then, when you are using the pit, you could bolt them back in to have the extra bit of safety/assurance when the grate is out.
If you want to keep the grate pristine, you could also weld some additional metal to the grate, extending down in to the pit, between the concrete lips. This should give you additional bending capacity mid-section of the grate. The number of bars, size, etc. would just probably required some paid engineering to spec out.
LS6 Tommy
Well-known member
Not jumping on the "you shouldn't do it" band wagon, but ventilation is a requirement and many towns will deem having a pit in your garage categorize it as commercial use for taxes and other such fun things.
Tommy.
Tommy.
Boobag,
An interesting video. Looks to me like the doofus guiding the driver directed them into the pit but it's tough to say for sure.
Regardless it appears, in this case at least, that the car fell about the radius of the tire and stopped.
Looks like the car & occupant suffered about the same amount of damage as if one misjudged where the garage door jamb was and rubbed against it while entering.
Best regards,
Scott
Keel,
I have discussed ventilation and the inspector's requirements have been met. Rather than trot out all the inspection issues that had been dealt with, I elected to ask for thoughts on the inspection issue that still needed to be resolved. Hence this thread.
I hadn't considered the possibility that an insurance company wouldn't cover a person despite have a certificate of occupancy from the local authorities but I will check into that.
Thanks for the idea regarding the aluminum ramp!
Best regards,
Scott
LS6 Tommy
Well-known member
In the pit? It has to have it's own system. If it was a commercial building, OSHA would classify it as a confined space, too.
Scott, didn't we do the rough math on this whole thing a while back?
Tommy
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I built this pit and drive over the four grates all the time with 4500lb cars.
It's NOT built to code.
I Have used it for 22 years.
Size of 12'X3'.
When I die the next owner can keep it or fill it.
C39er,
May I ask the depth of the grate?
Do you have info on the type of the grate system. Example: Mine is called 11-W-4.
Thanks!
Best regards,
Scott
matt_i
Well-known member
You could also invest in something like a 1/2" steel plate (in sections) with 2" angle iron welded underneath as a stiffener, 12" on center should suffice. Plate will be heavy but I'd expect that to pass. Somewhere like Ryerson-Tull in Atlanta/Norcross should be able to fabricate the plate to your dimensions without a lot of extra cost.
Pits have to be over a certain depth to be a confined space. A big part of it is also fresh-air ventilation. Simple pedestal fans that run 24x7 can supply sufficient ventilation. I am not an expert on the specifics but you can research it like anything else to find out the "letter" of the law.
Pits have to be over a certain depth to be a confined space. A big part of it is also fresh-air ventilation. Simple pedestal fans that run 24x7 can supply sufficient ventilation. I am not an expert on the specifics but you can research it like anything else to find out the "letter" of the law.
HoosierMark
Well-known member
I guess I must be dense. Reread my previous post about the I beam. Your only cost is 1 I beam the length of the pit plus the cost of creating a notch/pocket for it to set in. Now the width of you span is cut in half and your grating should support a car. Isn't this what they do when they put I beams under floor joist? Actually you probably could use 3 or 4 2x8s or 10s for the same amount of support.If the pit is 36 inch wide and the I beam is 4 inches wide you only have a span of 16 inches per side. After the inspection, eliminate the I beam and use the pockets for a light, drink or tool holder. Pretty simple.
hoppsxc140
Active member
Depth is irrelevant when it comes to confined space.
https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=standards&p_id=9797
https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=standards&p_id=9797
c39er
Well-known member
Mine is only 19-W-4! 1" depth.
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bczygan
Well-known member
C39er,
When you write, "grate rectangles", are you measuring from outside to outside of the steel or...?
Thickness of each bar? The "bar" being the 1" tall piece of steel.
Right now, without confirmation of any of your numbers, it seems like your grate is less robust than mine. Yet you say you drive cars over it.
How wide is the "lip" the grate sits on?
I await your answers with great anticipation.
EDIT: I now see you edited your post and you have determined that your grate is 19-W-4.
That grate's bar spacing is considerably wider than mine. I will be very interested in your bar thickness & pit lip width.
Best regards,
Scott
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LS6 Tommy
Well-known member
volleyball
Well-known member
To get to the original problem without adding judgement, it would seem simple enough to modify the grated with rows of angle iron or aluminum to the bottom of the grates. They are beveled at the ends and hang free. They will stiffen the grates to withstand deflection. They also might not add too much weight to leave on permanently. You could weld or simply run bolts through to attach.
You can test the strength with a mock up long before the pit ever got dug.
You can test the strength with a mock up long before the pit ever got dug.
encantofred
Well-known member
I am just finishing my 65x70 detached garage. i really wanted a pit and went down the path of pricing it. if i was you i would make sure with the building permit people and not just the building inspector. they wanted ventalation, drains etc etc. it made it not feasible. and i have a lift as well.
anyway, just be sure it is ok.
i would have loved to have a pit. it would have been for my motorhome.
tom
anyway, just be sure it is ok.
i would have loved to have a pit. it would have been for my motorhome.
tom
c39er
Well-known member
Bar thickness is 3/16". I used 1-1/2" angle fixed to the concrete and set the grates down into the angle.
Just what I did. I make NO warrantees!!!
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Bar thickness is 3/16". I used 1-1/2" angle fixed to the concrete and set the grates down into the angle.
Just what I did. I make NO warrantees!!!
C39er,
So your actual clear span is close to 2' 9". At 2' 11-1/2" mine will be 2-1/2" more than that.
At 3/16" your bar thickness is the same as mine.
Your un-serrated bars are 1-inch deep and my serrated bars are 1-1/4 inch deep.
My bars are spaced 11/16" on center - yours are 1-3/16" on center.
This is very interesting....
Do you mind showing additional pictures?
Pictures with the car tire sitting on your grate; close & from a bit of a distance.
A picture showing the car.
Best regards,
Scott
c39er
Well-known member
My cars are driven straight across the grates when I need to move them from winter storage. I looked through a lot of pics and could not find any with a car tire directly on the grate. I did find only one pic showing a tire on a Go-jak being rolled over the grate...
I know it doesn't help but I tried.. I'll look later tonight.
I know it doesn't help but I tried.. I'll look later tonight.
Attachments
c39er,
Your photograph gave me the confidence to try an experiment today.
I have a 2002 Toyota Corolla that my son uses to get back and forth to college. A Google search yielded a value of around 2400 pounds for this vehicle's curb weight.
I jacked up the front end of the Corolla. Using some concrete solids and one section of my grate, I built a mock-up under the front left tire of this car. I placed one concrete solid under the front right tire and lowered the car onto the grate.
It was a little more involved than that because the floor jack tended to interfere with the mock-up but in the end I was able to make it work.
The mock-up was within a half inch of the grate span of 29-1/2" that I intend to have & the tire was pretty much centered on the span.
For the first test I had a piece of thin plywood on top of the grate. I wanted to spread the load out as much as possible. The plywood/grate held the load fine.
Now I removed the plywood and just had the grate under the tire. Again, the grate held the load of the front left tire.
If this car's curb weight is distributed equally, there should have been a load of 600 pounds distributed over the tire's contact patch. I can't say for sure but I would think the load distribution wouldn't be equally distributed on this fairly light front wheel drive car. I would think the front end would be a carrying a heavier load than the rear.
There was a black mark from the tire on the plywood and measuring the length of it gave a value of between 4 & 5 inches. Let's be generous and call it 6-inches
So that gives us a concentrated load of at least 1200 lbs. per foot on a span just under 3 foot.
I'm trying to figure out what those load tables that I posted at the start of this thread are really trying to tell me.
Best regards,
Scott
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volleyball
Well-known member
With a fulcrum and a bathroom scale, you can get a pretty close appr. of actual weight.
I wonder what the difference it will make when it is a rolling load. Probably less force.
I wonder what the difference it will make when it is a rolling load. Probably less force.