the name for that is an overhead single beam bridge crane this means that neither end of the beam will be fixed.
I have designed, built and had bridge crane,both anchored and free standing Jib cranes and gantry cranes to Mill specs. One of my free standing Jib cranes had a 28 ft total swing diameter with a cap of 8 tons at the full radius limit de-rated to 3 tons to meet the stringent Mill Spec. A 12 ton portable gantry crane and a 60 ft span single beam 10 ton bridge crane that when it was tested for certification only had 10 mm of deflection hoisting a 15 ton load and 15 mm deflection @ 20 tons while jogging the loads I even made a 600 ft monorail system for a camel hospital to transport injured racing camels
So since you are planning on a small bridge crane we need to discuss what you plan for the rails, what sort of structure you are going to install this in Just about anything is doable and can be made safe as long as all information if forthcoming.
For instance for the rails 3" track used in suspending commercial sliding doors with 2 sets of truck rollers mounted to a 2 ft long carriage bolted to each end of the bridge beam would work much better than trying to use tubing for the rails this way you could take advantage of attaching the rails to every ceiling truss if this were to be used in a home garage. But if this is to be in a steel structure with the trusses at 10 ft apart then it would be better to use at least 4" I beam 6 inch if the trusses are 20 ft