Unnecessarily Complicated Hay Feeder for Rabbits

I like building things. This is what happens when someone who likes building things makes a hay feeder for his pet rabbits. It's not the easiest option, or the cheapest, but it works great and has lasted for years. And, most importantly, it was fun to build. 

Materials: 

• cinder block
• self-adhesive felt pads
• 29 quart clear plastic bin, with latching lid (16.7 in wide, 12 in deep, 13 in high) (or similar)
• lumber scraps, big enough to fill the holes in the cinder blocks
• wood screws, shorter than the thickness of your lumber scraps
• 2-part expanding foam
• 1/8" thick hardboard sheet
• cardboard may be a good substitute
• filler material of some sort 
• expanding foam
• cardboard
• wood
• something else? 
• zip ties
• panel from snap-together wire shelving, commonly used for making rabbit enclosures
• Example: https://www.bedbathandbeyond.com/store/product/relaxed-living-12-inch-wire-cube-grid-in-grey/5313247?skuId=67335244&poc=821077
• Rubbermaid Commercial  7-1/8 gallon gray undivided bus/utility box (FG335100GRAY)

Tools: 

• saw for cutting wood - just about anything would work in a pinch, I used a table saw. 
• hot knife / soldering iron for cutting plastic
• drill/driver for drilling holes and driving screws

Here is the finished example. 

Start with a cinder block. Put self-adhesive felt pads on the bottom to prevent damage to your floor. The felt wouldn't be necessary if your floors are carpet. 

Cut a hole in the front of the bin. The plastic can be brittle. The best way I found (after destroying my first attempt) was to use an old soldering iron as a hot knife to melt/cut through the plastic. Do this somewhere well ventilated, it doesn't smell great. Also, be warned - hot things are hot and can burn you. 

Leave enough area around the opening to fasten the wire panel using zip ties. I left it so there was about 1 full square of material left on each side and on the top. The bottom was cut much closer to keep from blocking access to the hay. The soldering iron worked well for poking holes through the plastic for the zip ties. Trying to use a drill near the edge caused the plastic to crack; I don't recommend it. 

With the opening in place, attach the wire panel using zip ties. Below you can see how much plastic I left on the top, bottom, and sides. It also shows where I used the zip ties. 

Cut the wood scraps so that they fit well into the holes of the cinder block. They don't have to complete fill the holes, but they have to be in contact with each side of the holes. My scraps were oddly shaped off-cuts from a 2" x 6" pine board. They look odd, but they work just fine. 

Once you get them fitting well, the next step is to figure out where they need to be attached to the bottom of the plastic bin. The easiest way is to set the bin on top of the cinder block with the bus tub in place. The bottom edge of the wire panel overlaps inside of the litter box; this sets the position front-to back. Center it side-to-side, and then mark where the edges of the cinder block holes are. Drill holes and use wood screws to attach the wood so it sits within the marks you made. The screws are installed from inside the bin. They screw down into the wood, holding it in place. I think I used three or four screws on each one to hold it securely. 

Here you can see the way the wire overlaps the litter box. This hold the litter box in place, and it ensures that any hay that is dropped falls into the litter box. 

Fill the back 2/3 of the bin, to force hay toward the front of the feeder. The next step is probably the most difficult, because of the materials used. I had some leftover 2-part expanding foam. The downside to what I used is that the foam is expensive, difficult to find locally, and the uncured components aren't the most friendly of chemicals. I put in a divider to contain the foam. The foam exerts a surprising amount of force, so I used 1/8" thick hardboard or Masonite that I had scraps of as a divider. I packed the other side with layers of cardboard and wood scraps to keep the hardboard from bowing out too badly. I drove a few screws through the sides and bottom that extended into the area the foam would be poured. This was done to anchor the foam in place once it cured. Then I poured the foam and let it expand to fill the space.

The easiest alternative I can think of would be to cut layers of cardboard and stack them vertically against the back wall until it is 2/3 full. Then a couple holes could be drilled through the stack and bolted against the back side of the bin.

  

Here is one optional improvement. I had some leftover casting resin, which was expired and had started turning yellow, making it useless for its original purpose. I used the resin (and some gravel as a filler) to create a steep angled bottom on of one of the feeders. This pushes the hay toward the outside edge, and works very well. (In the picture below, disregard the larger holes I opened up in the wire panel. This was my first attempt, and I was thinking the holes were too small. They are not; there is no need to make them larger. This just ends up with more hay in the bottom of the litter box.)

If you have questions or comments, post them below. As a reminder, comments are moderated to eliminate spammers. Your comment won't show up immediately, but I will review/approve them and respond.