Tom H -- very creative dollies. I especially like the idea of going vertical. I took a little different route to going vertical. In addition to needing a more efficient way to store my various tractor implements, and other large items (such as the several military generators that have followed me home), I wanted a way to be able to unload wood-pellet pallets from my truck w/o having to do it bag-by-bag.
My solution was a walk-behind forklift. I watched craigslist and ebay for months until I found one that fit my needs for a low enough price. It is a crown 20MT:
This one is available with three different height specs, mine being the middle one of about 9 1/2 feet. The lowest lift one has a single stage mast, and this one one, and the higher one, a two-stage mast. This middle one has the lowest down height of the three, and can fit through a 7-foot high garage door (might be handy to get my pellets into the house-attached garage). It has a 2000lb lift capacity -- just enough for my wood pellets. This unit also takes up a lot less floor space than a regular forklift, and is light enough to haul on a small utility trailer. If I park it with the forks under a pallet, it only takes a few square feet of additional space beyond
So, since I got this, I purchased some used pallet racking for a few hundred, and got all my "stuff" off the floor. This freed up enough floor space to now be able to park my truck (crew-cab F-350) and utility trailer inside. I kept the lowest shelf high enough park the front of my one car under one, and other items such as walk behind snow blower, push mower, etc under others. Off season implements (such as the snow blower right now), and infrequently used implements get put up on the higher shelves, and items I'm currently using, or use frequently are on the floor under the shelves where they can't be quickly dragged out to use. My shop is a pole barn that has 10 1/2' high side walls, and trusses on 8-foot centers, so I'm able to store things on a top shelf at a height of 9 feet, with the item fitting up between the trusses.
I also plan on putting storage racks higher on the side walls of my garage (which has 10 1/2' high walls) for extra lumber and other bulky items to get them up and out of the way -- the fork lift makes it easy to get these items up.
At a total investment of about $1200 for the forklift and pallet racks, I was able to free up about 400 square feet of floor space. This is a LOT less money than it would have cost to build another building to store this stuff in. It is also a lot easier to get at things too, as I don't have to move a lot of stuff out of the way to get at what is in back (which is always where what I need ends up being). Since I now have all my implements on pallets, I also picked up a "manual" pallet jack for about $100 (again off of craigslist) which makes it real easy to position them to mount/unmount on/off the tractor.
Click on these pictures to see larger ons:


