StumpChair (facebook.com/StumpChair) was met with quite a bit of success in the past few years and it got me thinking about what else I could make into a chair. Rocks seemed liked like the next logical place to go. Drilling holes in rocks is much more permanent and damaging than in stumps so public installation didn't seem appropriate without permission. For this first version of the RockChair I decided to bring a rock into the shop. This rock was purchased from a landscape supply company and the chair was assembled entirely legally at the Pier 9 in San Francisco. Aside from that, the process is almost identical to StumpChair. (http://www.instructables.com/id/StumpChair/)
Step 1: What You'll Need
A Big Rock - Boulders can be purchased from landscape supply yards as mine was, or you can probably find one lying around if you don't live in a city.
A Chair Back - I always have an eye out for broken chairs that people are discarding. Discarded chairs are surprisingly common.
Epoxy - You will probably need more than you anticipate.
Spray Paint (or brush on paint if you want to get fancy) - Only if you want it.
Hammer Drill - A regular corded drill will probably work but hammer drills really are amazing tools for drilling in stone and concrete.
Masonry Drill Bits - WARNING regular drill bits for wood or metal will NOT work.
A Cart - This is optional(ish). If you have two strong friends who are willing to help you out you probably don't need a cart but it really will make the whole thing easier. Instructions on making a simple cart are in the next two steps.
Safety Glasses - I forgot to put them in the photo because they were on my face already. Oops.
Step 2: The Cart Part 1
My cart is square because it was easy to build and because I do not intend on keeping the chair on it for long but, if you want this to be a Rolling Stone Chair (yes, just like the band) you might want to consider making a cart that fits with the shape of the rock. It was suggested to me that attaching the wheels directly to the rock could be cool, and I agree.
You will need:
4 Caster Wheels
1 Piece of Plywood (about 2 by 2 feet)
Some Lumber (about 4 feet)
16 Round Head Screws
16 (or more) Wood Screws
A Drill (with drill bit and driver bit)
Safety Glasses (for an Instructable about how to make your safety glasses hold a pencil click here http://www.instructables.com/id/Safety-Glasses-Pe...)
Step 3: The Cart Part 2
1- Measure your plywood.
2 - Cut your lumber to the width of the board in the long dimension.
3 - Cut the other two pieces of lumber to fit between the first two on the short sides.
4 - Screw all the pieces down.
5 - Place the casters in their appropriate locations and mark off the holes with a pencil.
6 - Pre-drill holes for caster screws.
7 - Screw on casters.
8 - Screw on a stabilizing rail. The rock I chose was not flat on the bottom and needed some help sitting still. Adding a pice of 2X4 on the top of the cart kept it from rocking too much (yeah I know it would have been a better pun if I let the chair rock).
Step 4: Get the Rock
Like they say on all of those ads for jewelry stores, finding the perfect rock isn't easy. In this case landscapes supply stores may be your best bet. Of corse, it is possible to pick up your own rock from a field, forest, desert, or abandoned quarry, or from the moon, but it is way easier to get it from somewhere with a forklift.
The perfect rock means something different for everyone, but I do have a bit of advice. Fist, it should be flat or consistently curved on the bottom if possible. Second, It should be relatively comfortable to sit on. Third, It is nice if you can pick it up with two or three people (but I would love to see a RockChair on a really giant boulder so don't let this be a limiting factor for you).
If you are transporting it with your own truck I suggest placing it on a pallet and using ratchet straps to keep it in place. It will way less likely to roll around and cause you extra damage this way.
Once you get the rock to it's final (or temporary) resting place, use a forklift if you can to take it out of the truck and put it directly onto something that rolls. You will probably want to be able to move it around.
In my case I had to employ the help of a friend to move it from the cart we originally put it on to the one I built. I did smash a finger slightly in the process so be real careful if you end up moving the boulder by hand.
Step 5: Chair Preparations
I can't say it enough, if you keep your eyes pealed while traveling in the city you will probably find a broken chair pretty soon. Right before trash pickup is usually a great time to collect broken treasures of all sorts.
Sometimes it is really easy to remove the legs and seat from a chair but I suggest using a chisel and hammer to get the seat off without breaking any of the spindles. (If you recognize the photos of dismantling the chair it is because they are from the StumpChair Instructable).
It is not necessary, but I like to paint the chair backs bright colors before installing them. Spray paint is the easiest for this step. For easy hanging of the chair back threaded a small wood screw into the bottom and tied it up with some string.
Spray quickly and evenly to get a consistent coat and wait until it is completely dry before touching it.
Step 6: Drill Drill Drill
Before you start drilling it is a good idea to mark out your hole locations. The easiest way to do this is by simply placing the chair back on the rock in the desired location and drawing dots, circles, or smiley faces where the holes should go. It is not the most accurate method, but you are just making a rock into a chair, it'll be close enough.
WEAR YOUR SAFETY GLASSES PLEASE!!!
Now for the real fun part. Chuck up the appropriate size drill bit in your hammer drill and start drilling. Make sure you are drilling at a slightly leaned back angle to match the angle of your spindles. If your spindles taper, start with a bit that matches the smallest diameter and work up slowly if you need to. It is nice when you can get the spindles to fit in as snugly as possible.
Hammer drills are a ton of fun but don't get carried away. These holes don't need to go super deep. I made mine too deep and needed to use way more epoxy than otherwise necessary.
Fine adjustments are tricky with a hammer drill but if you need to adjust a hole brute force will probably work out better than in most other cases.
Step 7: Test-fit and Glue
You are almost finished now. It is time to glue in the chair back. I recommend using epoxy because it sticks to stone, wood, and most other materials pretty darn well. Like I have said before, you will probably need more glue than expected, so don't be shy. Squirt out a bunch on some scrap paper and mix it all up. Most epoxies require equal parts hardener and resin but you should read the bottle first before mixing. You don't want your epoxy drying before you are ready, so mix it quickly.
Use a stick or some other sort of disposable tool to apply the epoxy to the inside of the holes. Be careful to not get too much on the stone outside the holes because it will probably stand out quite a bit when it dries.
Once you have applied sufficient glue to all of your holes line up the spindles again and hammer it in there. Don't be shy here either. Having a really tight fit now will pay off in the long run. Oh, I think I forgot to mention the rubber mallet in the list of tools required, sorry everybody.