Here is MY result of a few afternoons last week of building a second trolley!

I found the trolley jack under the house that my housemate left there when she moved out so i put it to use (hence its ratty appearance compared to the silver painted metal of the trolley)
I had initially built it with using a scissor jack in mind but changed to the hydraulic jack at the last minute when i wasn't happy with how it worked.

Most of the metal used was either given to me or i already had it laying around, the only things i had to buy were the castors, a few bolts and a can of hammered metal spray paint!