Wednesday, July 9, 2014

Cat Shelves I

There is one single project that just about taught me everything I know to date about being a decent CNC machinist. The process is still being optimized, because we plan to make these in larger numbers - but it's still a little complicated to make...

This all started last Christmas, when my girlfriend saw a show called "Cat from Hell", where Jackson Galaxy explained that a cat is usually most happy when it's sitting on something high up in a room. We have 3 cats by the way and they are sometimes not so happy, ouch. Typically, you would want to have something like a climbing post or something more fancy, such as a jungle gym going from the floor all the way to the ceiling. On that show, they showed an arrangement of dedicated bookshelf type platforms that would mount on the wall, for the cats to sit, sleep and climb around on.

Turned out, that there are plenty of these already available on Etsy, some quite nifty and some not so, most of them are flat bookshelves basically, some even with ugly metal mounting brackets. I looked at that for a while and coming from a furniture design and esthetic world, I thought that there had to be a better way to blend these nicely into someone's living room.

This project's goals were:
- Have some kind of carpet padding on the top for the cats to rest on.
- Make it structurally sound and fit for anything a customer could throw at it (as in weight).
- Allow for funky shapes, such as waves or cradles - not just a boring flat shelf.
- Make these shelves' "float" on the customer's wall. No visible brackets, no visible mounting aids such as screw heads or supporting backers or brackets.
- Make a conversation piece.
- Make it so the cats love it and use them a lot (luckily we have a focus group of 3 around already, lol)

Statics / mounting method:
So how much weight is this arrangement going to have to hold??
I did some research and found the worst possible case:
There was once a cat called Himmy who lived in Cairns, Queensland.
Himmy is the heaviest recorded cat to date, weighing in at a staggering 21.3kg (46.8lbs).
(Sorry, I don't have a picture - but that might be a good thing, lol)
That should give us an idea on what that shelf needs to hold in terms of weight.
I went a little further though, this should not break or rip out of the users wall at exactly 46.81lbs pounds of cat jumping around on it (what about two cats on it)?? Let's just say, we design this to withstand a hefty 80lbs of weight anywhere on the shelf?

The solution I came up with are RSS structural screws, 5/16th by 6", but how do you hide these in a floating shelf? The other problem was to make them wavy and get away with it??
I thought about laminating plywood in forms first, but that would have caused it to become a non-product, because it takes too long.

In the end, I came up with a system that would work on a CNC. This product takes a lot of tool changes and quite some manual work on the assembly and finishing side, but does have all the attributes I mentioned above. I've already been told on several occasions that we should get this system patented, but decided in the end that it's too expensive to go through with it. Make your own if you feel like it, if you can get the process down and compete ;-)

So here is how we make them: Instead of cutting flat shelf pieces per say, we turn the whole thing by 90deg on its side and machine the slices instead. Each slice has index holes for a 1/4 dowel rod to go through to aid in the assembly process. The dowels also make up the pins for the cap to index on (more on that later).

Another thing to notice is that we're using the holes for the structural bolts that go in later as hold down opportunities. This allows for cuts that don't need tabs and also to minimize the waste on the wood (this is poplar).

The assembly and glue-up of these slices (there are 10 in total for each shelf) is a bit tricky. I had to make some custom cauls (much like these:, it takes a total of six caul sets for gluing up one shelf.
Without the cauls, it would still go together ok and align on the dowel rods, but just not close enough to avoid a lot of sanding to get a nice surface.

The structural screws are inserted into the assembly during the glue-up process and are completely hidden/embedded inside in the shelf assembly.

The screws need to hit a stud in the wall, when I made the first shelf I hit one stud, but the corresponding screw that was 16 inches over, just hit the drywall with nothing behind it. So, what happened??

Turns out that older houses typically have 24" stud spacing in the walls - instead of 16", as that was ok back then. Our house is one of these older ones (built in the 50's). Today, the stud spacing would be 16 inches on center as required by code.

Once I became aware of that difference in stud spacing, I changed the design of the longer shelves to include two more structural screws that can now be used optionally, to accomodate both situations. There's a total of 5 big bolts embedded inside each shelf now, I came to call this final design V2.0 ;-)

I guess if you can't find any studs or wanted to mount this on a stone wall, you could use all five bolts with plastic anchors to mount this to a wall safely (depending on the weight of your cat, or how many cats you have in total, should they all decide to mingle on one shelf). Perhaps we should just include 5 plastic anchors in each shipment anyways, just in case anybody ends up in that situation. The other problem is that the structural bolts I selected need a T30 screwdriver to work them into your wall, so I'm planning to ship one screwdriver with each shelf once we get there (I found some at about $5 each, so that won't be a big problem).

To conceal the access holes for the mounting bolts and to make the shelf look classy, each shelf comes with a cap that snaps onto the front of the shelf once it is mounted on the wall. The cap is held in place by several embedded rare earth magnets and indexed by the slightly tapered ends of the 1/4 dowels that go through the shelf. It really "clicks" in place when you put it on.

Turns out you have to pull pretty hard to get the cap back off, to overcome the holding power of the magnets, so we think that there is no way a cat could do that by accident or by trying to hang off it with its claws.

So far we've been testing with different finishes and optimizing the process of actually making them, but the cats already love them. This could be doing really good on Etsy (I really hope).

We are also experimenting with very intricate mother of pearl inlays for the caps, depicting little jumping cat silhouettes or lettering, perhaps the name(s) of your cat(s). These will be available soon as optional upgrades to the product itself, once we figure out the process of actually making those (getting really close now :-).
The first tests were done by trying to cut the inlays out of old CD's and DVD disks, but that didn't work out so well, so we decided to go all the way and use real mother of pearl now (that's expensive stuff).

There are a few different carpet choices so far, we have some scraps and mats piled up already for you to choose from. Another point of selection is the finish of the underside of the shelf and the cap piece that hides the holes for the structural bolts, which can be a different color from the shelf itself. So far we can stain both pieces to make them look like Antique Oak, or Walnut. Dark Cherry, Maple, Mahogany, Pine, Clear Coat (Poplar), a combination of both or whatever else you want it to look like, we'll experiment - just let us know.

Target pricing is about $95 for the big ones ("wavy" and "cradle") and perhaps $65 for the small ones (each). Do you think that's asking too much?

By the way, these are now available at our new Etsy store, check it out:


  1. can the carpet be replaced?

    1. Absolutely. The ends of carpet tucks into slots under the shelf. I purposely did not glue it into these slots and used only a couple of staples at each end. On the top face it is held down with carpet tape.
      To replace it, I recommend lifting it up in the middle of the shelf a little bit and cut it half. Then pull the two halfs off the carpet tape until the staples are reached, which should now be visible from under the carpet. Using a screwdriver, lift the staples out and it will slide right out of the slots.
      Put fresh carpet tape on the shelf, slide one end of the carpet into a slot and wrap it around the shelf. Tuck the other end into the other slot and affix with staples. If you don't have a staple gun, small tack nails can also be used.
      We provide cheap carpet replacements or can optionally send you the measurements for free, so you can cut your own.
      Thanks for your inquiry and please let us know if you have any other questions.

  2. Eddybare and Prudence: Thank you for your kind words :-)

  3. I would like to make two of these for myself only. Have cats. If I get stuck can I ask for help?
    Great project you should sell many.

  4. That's an interesting twist on shelving. It's a good niche market for you that's for sure.

  5. Very efficiently written information. It will be beneficial to anybody who utilizes it, including me. Keep up the good work. For sure i will check out more posts. This site seems to get a good amount of visitors. cat wall shelves

  6. Very efficiently written information. It will be beneficial to anybody who utilizes it, including me. Keep up the good work. For sure i will check out more posts. This site seems to get a good amount of visitors. whatsupp