Here is something I finished today. Well, almost. I need two screws to attach the handle. It's my second Harbor Freight welding cart.
I highly recommend this kind of cart. I have had other carts that were sturdy, but they put my machines way down low where they were hard to use, and they had nearly no storage. This one puts everything up around eye level. If you have OSHA-type concerns about machines falling over, which is nearly impossible, you can always run screws through the top of the cart.
It will hold 120-cubic-foot tanks, but I want to put smaller ones on it because I already have big tanks on my other cart. This second cart will assure that I always have gas when the big tanks run out.
My first cart had both pairs of wheels the same distance apart. That was a mistake. A trapezoidal setup makes a cart just about impossible to rock, and rocking leads to tipping. I'm going to cut the first cart up and redo it like this one. Making the crossmember under the platform is kind of a pain, but it worked out well. I used rectangles of 1/4" plate and set them into the 1" tubing so it's 1" thick even with the plates attached. This keeps the cart height constant from one end to the other.
I also made the wheelbase shorter on this cart so it will turn in a smaller area. The other one has the wheels out on the ends. That isn't necessary. The platform is 11 gauge, and only 4" extends past the casters, so it doesn't need to have tubes or wheels under it the whole way out.
I used epoxy putty to cover some of the welds. I like it because using too much weld is really stupid. It creates distortion and wastes time. Epoxy makes seams look nice and closes them up without distortion.
The height of the tank restraint is 20". If you build a cart, you need to look at tank sizes before you add your upper restraint.
The paint is Herculiner from spray cans. Seems very nice. Truck bed coating is a lot better than paint.