My drawings and measurements are metric, so if you use imperial measurements (and correspondingly buy materials in imperial) you'll have to tweak and possibly redo the drawing/measurements to suit your needs. Also, my numbers are a bit wacky (for example, the drum is 1152mm in diameter rather than my intended 1.2m). Many of these odd numbers are a result of mistakes I made during my process. I wanted to learn, and so I didmaking many mistakes along the way. As wacky as some numbers are here, I have used them in this instructable because I know for a physically-constructed fact that they work. And as to the pictures, I did the project nearly two years ago now; I took pictures for what I could--planning for an instructable eventually--but was sometimes too caught up in building and learning for pictures. But that's the point, right?
A final warning: this project isn't super low-waste (mostly for plywood), nor is it super low cost (assuming you have access to all the tools, it's about $300 to buy all the materials/fastners/paints). You will, however, end up with a bizarre and unique piece of furniture that tells well your skills and obsessions.
Skills/tools: In this project, you will [learn to] weld steel, plane wood, staple-gun fabric, paint with a very viscous paint, cut fabric, cut wood, cut and de-burr metal, sew stretchy and non-stretchy fabrics, drill metal and wood, use a router to plunge-cut and to edge, sand, and glue. Though not in that order. It's a lot of skills (and access to a lot of tools), and definitely a good project to learn a wide range. That said: IF YOU HAVE NOT BEEN PROPERLY TRAINED IN ANYTHING EVEN REMOTELY DANGEROUS IN THIS PROJECT, PLEASE ONLY DO SO WITH SOMEONE EXPERIENCED WHO CAN TEACH YOU PROPERLY. Wear safety glasses when appropriate (i.e. all the time) and hearing protection when using loud cutting tools, fume protection while painting, and all kinds of protection while welding. Be safe, build well, learn much, and have fun!
7.7m length 3mm thick MDF, 700mm wide
2 sheets of 1200mm square, 19mm thick plywood (or one sheet 2440 x 1220)
8.6 m of 25mm square steel tubing
1.8 m of 50mm square steel tubing
4 steel plates - approx 100mm x 25mm x 3mm, exact size not crucial
2 steel plates - 50mm x 50mm x 3mm
2 x 150 mm long M16 hex-head bolts
8 x M16 nuts
8 x M16 washers
8 x 30 mm long M12 Coach Bolts
32 x M12 washers
8 x M12 locking nuts (or use 16 normal nuts, 2 for each bolt)
heaps of staples
32 x 25mm long wood screws
24 x 40mm long wood screws
a medium-small bottle of wood glue
a medium-small tub of wood-filler
1L paint primer (preferably white)
1L hammer tone/hammered finish paint
1 can spray-on (or small can of brush on) clear coat lacquer
1.5m stretchy white fabric (the stretchier the better - optimally lycra/spandex)
1.5m stretchy black fabric (the stretchier the better - optimally lycra/spandex)
1.5m strong, static (not stretchy) white fabric
4m length of rounded black/grey foam padding (like water pipe insulation)
Make sure to download the PDF attached to this intro; it contains the drawings for this whole project. Useful stuff.
Step 1: Research and Design
In addition, I looked for some pictures of papasan chairs so I could get an reference for the amount of dip I would need to be comfortable. In addition, a friend measured their papasan to have a diameter of 1170mm, so I used that as a beginning point in my design.
To figure out the dimensions of things, I sketched what I wanted in 3D in Vectorworks (starting in Google SketchUp for rough ideas), working through a number of revisions until I ended up with the PDF attached here. Each revision either brought me closer to what I wanted, or else compensated for my mistakes while building.
Step 2: Cut and drill metal
My drawings were pretty precise, so I worked slowly through, measuring angles and lengths twice before each cut. To cut, I used a stationary cold-cut saw, a circular-saw that cuts slowly through metal while bathing the blade and material in a lubricating fluid that keeps the material and blade slick and cool. It's essentially a metal chop saw, good with straight, level, repeatable cuts through steel and other metals. Since all my pieces are duplicates of others, I set up jigs for each length. To do so, I clamped scrap steel to the saw's track to stop the steel tubing at a specific distance from the blade (see picture for an example). You can figure out what is needed from the drawings attached to this instructable, but for simplicity, the cut list is as follows:
25mm square tubing:
A: 8 base exteriors @ 497mm along longest edge, cuts leaning in at 22.5 deg each
B: 2 base interiors @ 675mm along longest edge, cuts leaning in at 45 deg each
C: 2 base interiors @ 766mm along longest edge, cuts leaning in at 45 deg each
D: 2 drum struts @ 562mm minus the thickness of the small metal plates listed in materials (mine were 3mm thick), cuts square at 90 deg
50mm square tubing:
E: 2 @ 401mm along longest edge, one cut square at 90 deg, one cut leaning in at 72.8 deg
F: 2 @ 260mm along longest edge, one leaning out at 55.7 deg, one leaning in at 72.8 deg (see drawing for clarification)
When cutting, make sure to clamp the piece you're cutting super-super tight, and wait to cut until the cutting fluid flows over your piece.
After cutting everything, de-burr your cut edges by running the sharp, newly cut edges over a sander for just a second each, or until they aren't sharp any more. This is to save your hands (and the floor that the bat signal will sit on) some painful cuts later.
Finally, drill the holes you will use to mount the frame to the drum. Do so with a drill press if you have one available, but a hand-held drill is ok too if you're very careful to drill very straight/vertically through both sides of the pipe. Take your time and use cutting fluid to cut straight and clean. Drill 25mm from the top (square cut end) of the longer 50mm square tubes, and in the center of the shortest, square-ended 25mm square tubing, using a bit just wide enough to accommodate your m16 bolts. Also drill holes near the ends of the four smaller metal plates you have, leaving at least 30mm of space between the holes to later attach to either end of the short metal drum struts. Use a bit just big enough to accommodate your M12 bolts for these.
Test the fit of everything by laying it out how it will go together. If satisfied, wipe off all your cutting fluid (with cleaner if need be) and if you need to de-burr your drilled holes. You're done with metal cutting!
Step 3: Create a welding jig
Why is this necessary? When you weld pieces of metal together, they heat up and cool, shrinking in the process. This leads to some deformation in pieces with either many pieces or many welds. A jig seeks to prevent this by holding the pieces in place while welding, thus reducing deformation. Since this whole thing is supposed to be symmetrical and rest flat on the floor, a wobbly, deformed octagon would just be sad. Thus, use a jig.
Thankfully the base is a regular shape, so you can just make a jig for two joints and rotate the base around between welds. So to make this, draw out how three pieces of the octagon should theoretically join up onto your worktable (or, ideally, on a scrap piece of plywood so you don't later char your worktable while welding) (also, use a ruler/protractor rather than freehand), then lay three pieces on your drawing, fitting them together tightly to test your theoretical drawing. Then screw small wooden blocks around your pieces so that the blocks tightly hold your pieces all together. Make sure to leave room around the joints between pieces so that you can have access to weld. With the blocks securely in place, add two of the struts that fit inside the hexagon and add securing blocks for them. You're done!
Step 4: Weld the base and metal drum supports
I will, however, say some things applicable to this project that I learned that worked well for me. First, know that deformation by heat is your absolute enemy, especially since we want the octagon to sit flat on the floor. So instead of welding one joint fully, then the next, then the next all the way around, tack-weld the octagon together, just two or three tacks per joint, working to create a few multi-side pieces, which you then join together at the end. By tack weld, I mean weld a single point of an edge between pieces. This will help by forming your shape and solidly connecting the pieces before building up so much heat that it warps the piece. Then, with the entire flat base together (all 8 sides and the four interior pieces), check that it's flat. Most likely it won't be, so adjust the joints by hitting them with a mallet or else picking the frame up then flopping the wonky joints back down onto the table.
Once everything is flat, then you can fully weld the joints. Don't work straight around in a circle, instead alternate inside, outside, and top, skipping a few joints each time. Again, the idea is so that you spread out any deformation so that you don't bow the whole thing with too much heat concentrated on any one side. Once you're satisfied with a fully completed octagon and interior supports, grind down the welds on the bottom so that it will lay flat on a hard surface without rocking.
Next is welding the 50mm square tubing to make the side arms of the base. It's pretty straightforward. A jig shouldn't be too necessary for the single joint, instead clamp each piece to the table, tack some points on the joint, and weld it solid. Finish it up by tacking and welding the arms to the center of the interior supports of the octagon (as seen in the drawing), and welding a 50mm x 50mm metal plate cap on the top of each arm (or just use plastic caps that fit in the ends).
Finally, weld the ends of the short 25mm square tubes to the center of the small metal plates you prepared earlier by drilling holes in the ends. This should give you a pair of pieces that look like the end of an I beam, 562mm long, with a hole drilled perpendicular to the direction of the top and bottom plates.
And with that, you are done welding and all metalwork! Take off your mask and see the world again.
Step 5: Cut wooden rings
I used a router with a plunging bit and a circle guide (if you don't have a circle guide for your router, instructions on one way to make one is here: http://www.diynetwork.com/how-to/how-to-cut-circles-and-curves-with-a-router/index.html) An alternative to this is to carefully freehand a jigsaw, but I don't think that either of these would be quite as clean or precise. The router worked wonderfully well for me, though a big circle-jig for a band saw could also work (but be really unwieldy). Choose according to your availability.
Assuming you use a router, set the bit to be just outside the outer circle using your circle guide, plunge a few mm, and start cutting, slowly working around the circle. Cut in shallow layers, only 4-5 mm deep each time (maybe less for less powerful routers) - deeper will increase your chances of catching on a bad bit in the ply and either ripping the wood or forcing your router off its path. Also, make sure (especially during the first revolution) that your circle guide isn't slipping, letting you wander off your circle. Stop when you're through both pieces of ply.
After cutting through, un-plunge your router and reset your circle guide so the bit is just inside the inner circle. Repeat the cutting procedure. Once fully cut through, unscrew it from the table top. Copy the 1/8th (i.e. 45 degree) marks onto the second ring (the one that was below). Finish up by lightly sanding the edges with 80-grit paper or so to make sure they aren't sharp and splintery.
Step 6: Cut wooden supports for drum frame
Also, it would be really handy to have at least one scrap piece of timber (any thickness) around 1350 long to use as a temporary cross-brace later. Make one out of a couple overlapping shorter pieces, also from the same scrap wooden circle.
Step 7: Construct wooden drum
On the empty marks, you will attach the two metal struts. Position them so the mark is in the center and the hole drilled in the strut points in/out of the circle. Drill holes through the wooden rings as to line up with holes through the metal plates. Insert your coach bolts from the wooden side to secure the struts firmly into position, using a washer and a locknut for each bolt (locknut because we won't have access to here ever again after skinning the drum, and it would suck to have a nut jog off and rattle inside forever after).
Now put the drum so far on the ground, struts pointing up. Put the other wooden ring on top of the struts so that its 1/8 marks line up with the struts. Now attach the struts to the top ring, being very, very vigilant to keep all the struts square to both rings. To this end, I suggest starting with the metal struts, using their strength and rigidity to help straighten the other pieces. Skinning the drum later is much easier if everything is square, so take your time.
When you are done, add the piece of cross-bracing you prepared in step 6 between two opposite wooden struts. This will help keep things square for skinning. Now roll the thing around your space, and marvel at how nicely it rolls! You've painstakingly invented a wooden wheel!
Step 8: Plane Drum
Adjust the plane to cut relatively shallow and take long strokes, aiming to take off long curly shavings rather than short, chattering ones. Your end goal is to make both the inside and outside of the struts flush with the rings. If the struts is slightly within the rings, that's ok.
Step 9: Skin drum with MDF (and drill holes)
The general process is: skin the outside of the drum with 3mm MDF, the take out the cross-brace and drill through the outside skin where it lines up with hole in the metal struts. Then skin the inside with the same MDF, and drill through it too at the same place. Before securing anything, test-fit the length of the MDF and leave it wide to overhang on either side. Finally, use a router to trim the overhang, rounding the edge a bit to keep it from feeling sharp.
The MDF I got wasn't long enough to wrap all the way around (I'm not even sure you can get MDF that's 3.8m long), so I had to use two sheets each to skin the inside and out. In doing so, make sure all the joints split a strut so that both sides can be secured.
To test fit a piece, first clamp one end square on a strut with a bit of overhang on both sides of the drum. On the outside of the drum, you can then roll the drum over the MDF until you get halfway around. At this point, mark how you need to cut the MDF such that it ends in the center of a strut. Remove it and cut where you marked, then test again. Repeat as necessary. When you're satisfied with the fit of a piece, spread glue along one end of the MDF, clamp the edges in place when it's exactly where you want it, and secure it into place with staples (brads will likely rip out/through something as thin as 3mm MDF). Work your way along the length of the MDF, spreading glue on the drum before rolling the skin on and securing it. Make sure to staple along the length of the struts and not just around the rings.
Once you're done with the outside, drill through the outer skin to match the holes in the metal struts. Remove the cross-brace and use the same process on the inside. Just know that the inside is more difficult than the outside and that you will need significantly more clamps.
Finish up by drilling the metal strut holes through the inner skin and routing the excess MDF off the top and bottom of the drum with an edging bit (one with a rolling guide to cut flush with the top/bottom), then with a shallow rounding bit to dull the edges.
Congratulations! You're done with wood construction! Woo!
Step 10: Fill holes and sand
Use wood filler or putty to fill in the divits made by staples in the MDF, the joints between MDF sheets, and small spaces between the MDF skin and the rings. Fill up those bits with putty, let it dry, and sand it smooth. Just a single sanding should be fine; you'll cover it with a very thick paint later.
Step 11: Paint Drum
After opening a hammered-finish paint, make sure to stir it very well. It contains two different solvents that separate out at different rates, which is what gives the pigment the hammered look. Once you start actually painting (use a wide brush), it's like painting with honey. Hammer tone paint is extremely thick, sticky, and viscous. You need to glop a bit on and spread it around because it's so thick, but try to spread it as evenly as you can. A 1L can is enough to paint the outsides, top, and bottom of the drum. If you want to paint the inside (I skipped this - nobody was going to see the inside of mine where it was going to be sitting), you'll likely need more.
The paint I used took 24 hours to dry fully. Once it's done, remove the base's covering. Spray down everything you've built (base and drum) with a clear coat lacquer to protect your steel from rust and your paint from chipping. Hammer tone is difficult to repair with a good effect and rust is dirty and just not good.
Step 12: Cut and Sew lower fabric
To prepare the static cloth, you're essentially going to make a large circle of cloth, fold the outer cm in twice, then pin and sew the fold-over in place. The fold-over will keep it from fraying and make the edges a bit stronger. I first did this with a circle 1.5m in diameter, but after holding it on the bat signal with a friend's help, decided to make it a bit smaller. I'm not sure the exact diameter I ended up with, so adjust to fit (preferably before sewing so as to not have to sew twice). As an alternative to the folding/sewing, you can use an overlocker to cut and finish the edge of the fabric in one go.
Step 13: Staple lower support fabric onto bat chair
Step 14: Draw symbol, cut, edge, and iron fabric
The interior of the drum has a diameter of 1068mm, so cut a circle from your stretchy fabric with a diameter of 1108mm (Important: mark/cut the circle out while the fabric is under absolutely no stretch-strain). Just like with the static fabric, fold back the edge twice (1cm each time) and sew around the edge. You should end up with a circle with the same diameter of the interior of the drum. When attaching it, you'll need to stretch it just a little (seriously not much) to attach it. This will pull it taut enough to generally stay flat (as should happen on the front of a search-light) while having enough stretch left to sit back into.
Finally, iron both stretchy pieces to get out all the wrinkles and creases so they'll lay flat on one another when sewing them together.
Step 15: Sew decorative fabric together
Step 16: Staple upper design fabric onto bat chair
Don't do what is shown in the picture.
Step 17: Foam front edges
I suggest using slit water pipe insulation (like that seen here: http://goo.gl/qgLLN), cut in half with a hot wire cutter or wet Stanley knife blade. It's fairly cushy, would look fairly nice, and each half would already have an adhesive edge to stick to the front face of the drum.
Please let me know any questions/suggestions/corrections you have!
And, for real, let me know if you make this (or a project inspired from this). I'd love to see your creation!