The Hoist Cart Project, part 1: The Cart

I already made a few posts here about the hoisting cart, but they were rather sparse and incoherent.  The next few posts are intended to describe each of the major parts of the project.

 The basic cart came to me as an alley gift, found with a bunch of other trash for the Large Item Pickup Day, one block from my shop, and less than a month after I realized I needed to make the hoist mobile.

(rather than fastened to the rafters over one end of the mill table, where it could only be used on one machine)

The cart turned out to be the bottom of a hotel bell-cart with a rated capacity of over 1,000lbs.
The deck is made of 3/4in hardwood ply, there are two steel hat sections running the length of the underside which create tremendous strength, and four casters are mounted to the hat sections. 
The casters are rated for 800 lbs each.

Finishing the cart proper involved adding an upper deck of 3/4 ply, both to give the thing a reasonable work surface and more importantly, something to hold the mast upright.

Uprights between the two were fabricated from black pipe and flanges.  Diagonal bracing made of 0.75in strap and welded to the tops and bottoms of the uprights transfer forces acting on the mast back down to the bottom deck.  Counterweights are mounted beneath the decks at the end opposite the mast to keep it from tipping the cart when a load is on the boom.  Outriggers at the mast end, prevent it from tipping the cart when a load on the boom is swung around.

Seen in the photo is a 7gal water jug acting as a small counterweight for basic mechanical testing.

 The cart is mostly completely now, save for filling the lower counterweight with lead shot, and fabricating and installing the outriggers.  That will happen when finances permit, but that could be a while because someone in Washington nuked the low-income insurance program I was dependent on, so I am more broke than ever before.



The rest of this post contains details about the custom hardware which was fabricated to hold the mast to the two decks.

Because the mast needed to be as tall as possible to be useful in my shop, and because the door opening is much shorter, the mast needed to fold down, complicating the mounting of it.

For the top deck a hinged mount was created and welded to the mast.  The hinges are two large bare-steel "weldable" (no holes) hinges from the hardware store.  To disassemble the mast from the cart, the hinged bracket can be unbolted from the deck surface.

Because all of the weight and bending moment on the mast is concentrated where the mast connects (at right angles, even!) to the two decks, the brackets were made very wide and deep, in order to engage a large area of the plywood.  Both brackets fit tightly on the plywood, and are clamped tightly in place with many bolts once installed.  This ensures the plywood does not see concentrated forces which could bend or break the wood fibers, leading to eventual failure.

Since I wanted a very close fit of the mast to the bracket, a hole saw cutting out the notch would not do.  I set up a fly cutter for that diameter, and used the mill to make the notch, ala the short video...

The lower bracket is designed to guide the bottom of the mast into place when it's being erected.  It has some holes and a bolt to make sure it stays put, and because the bracket creates a lever which tries to break off the edge of the deck, I added a brace under the deck to transfer the downward weight of the load to a wider area of plywood.

That's really about it.  Once fit and function were verified, the parts were degreased, abrasive blasted, primered, and painted safety yellow in a vain attempt to shave my shins in the future.

The outriggers are not installed yet, but when they are installed, they will look something like this...

I really wanted them to swing out or slide out, but I couldn't make it work in the space available.  So there will be a pair of sockets mounted to the bottom deck, into which the outriggers will slide and be retained with a pin.