Alexander the grate?

I don’t know about others but here there are Floor Grates made from stamped metal that are painful to step on but not able to hold the weight of a person plus power chair and by brilliant design, they are placed in the natural path where folks have to walk or in my case ride a power chair so if the chair hit one already damaged it would fall into the hole and have a hard time even getting out.

I had built one of these before and it was getting rickety with two layers of 1/4 in plywood, but trying to move a refrigerator over it totally did it in, :anguished:
So now I am building another with 3 layers and hope it holds up.
So I guess it is only the standard size here but in case anyone else has that standard. or if they can rescale it to their needs here is the design.
the small one I made twice this time, but it only sticks up one layer.



What about reinforcing the middle with a slotted box design? The vertical pieces shouldn’t impinge airflow and might give you a lot more strength?


That is why the shape of the holes, it gives it strength in both “X” and “Y” direction and if a wheel (or refrigerator) is turned it puts a very strong twist. I made this ne 3/4 in but might add another layer if this one also shows a problem.

“by brilliant design, they are placed in the natural path where folks have to walk…”
Oh yeah.
What kind of plywood and what kind of glue?

It is Revolution Plywood. Not the strongest but I am out of oak. I am using the Gorilla Wood Glue

Do you have access to Baltic Birch plywood? Much stiffer per thickness than almost any other plywood. Definitely use it if you can.
The Gorilla wood glue should be sufficient, as the grate only gets loaded intermittently. A more rigid glue than PVA would provide greater stiffness under constant load.
Discussion here if anyone cares to dive in to “glue creep”:

Does it seem to be flexing more across the width or the length, when installed in the floor?


I think the twisting weakened the thinnest areas that then gave way to heavy weight, with the added thickness, hopefully it will last longer than my last refrigerator.

The glue is stronger than the wood.


Not something I have heard of though I may have seen it.
There are two comments that come to mind. In one case there is the issue of square cube law (another rabbit hole) but basically why an ant can lift many times their weight, and a human can lift more than an elephant in percentage of body mass. In the case of 3-inch thick wood vs a quarter inch the forces are over 150 times greater in the movement of the thicker wood. Then there is the issue of horizontal vs vertical forces and add in lots of crossed fingers for extra credit, and the issue they are speaking of is very different.

Yup. I figured you were savvy enough to use proper glue but if one were to use rubber cement, for example, 2x1/4" pieces would be more flexible than 1x1/2" piece, for otherwise identical material.
Hope the new version works for you!

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Hope it holds up for you! Nice that you can recreate as necessary.

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