I am building a rather large cart for use in my kitchen. Due to the dimensions of the room the top (marble) is about 5' 7" long, 14" wide and is quite heavy (estimated 150 pounds).
My largest concern is how narrow this top is making the center of gravity close enough to the edge that this could be toppled sideways by my three year old. My thinking is that if I place the wheels offset a bit – say 18 to 24 inches wide – this should counteract this risk. Anyone have a chart, etc to describe how wide I need to make this to be safe?
EDIT – I'm thinking that the top for this cart would be 36 inches tall.
EDIT – Based on the discussion here I went with locking casters on one end and fixed casters on the other along with a 24 inch wide base. We also tried pulling the completed unit over. It felt like it took about 100-120 pounds to get any motion on the lateral face. If necessary I also left space on the bottom for a counterweight.
Best Answer
Even without knowing how thick it is or how heavy, that's a lot of marble. You really need to attach this to something, somewhere. The wall, the floor... Without that, you would have to have a serious counterweight at the bottom, at least as heavy or heavier than the marble.
Why not just attach it to the wall or the floor?
When your child's health is at risk, I would double-up on precautions rather than find the bare minimum level of acceptable safety.
Your three-year-old will be stronger than you expect, and even if not actively pushing against it, could fall against it, setting off a chain reaction.
Think for example, if you have something on top of the island, like a vase. Even if you manage to keep it from tipping while on wheels, it can still move. If your child pushes or falls against the island, the island can move in one direction, the objects on top will move in the opposite direction and tend to fall on the side that your child is on.
I would not risk this situation with my child or anyone else's child, even if the top of the island was made of wood. Whenever it falls over, it will hit whatever is on the otherside like a sledgehammer.