By David Kuijt
In 1999 I made an Aztec Pyramid out of foamcore for a game I play (De Bellis Antiquitatis, or DBA). I put the description of how I made it, with lots of pictures, online at an Aztec Step Pyramid Page
So in May 2005 I received a surprise email from marketing people in a company (Alcan Composites) that makes foamcore (and other products, including Sintra). They had found my Aztec Pyramid page on the web, and wanted to see if I was interested in building something similar out of Sintra for their company to use as a focal point in trade shows; they were expanding their market into Mexico and Central America.
Sintra is expanded PVC. It weighs about the same as wood, and works with woodworking tools although you need a special no-melt non-chipping sawblade to work it with a tablesaw. You can glue it up with PVC cement to get a very powerful bond that sets within about five seconds -- an excellent working period for small pieces, but difficult when you have to glue large areas as the glue may set before you get the parts together.
By early July we had agreed upon a contract and they had shipped me the materials, and I started working. So here is the result.
The first step (after the design phase) was to make the nine levels of the pyramid at the right height. Cutting Sintra on the tablesaw (with my brand-new plastic-cutting tablesaw blade) was a breeze, so I whacked out mass quantities of vertical walls. Each level was constructed separately by cutting a square of 10mm Sintra and then gluing four walls onto it.
The walls were inset 1/2" so as to be hidden -- they are structural, but invisible in the final model. The image above shows four levels with their walls ready for final cutting to length and then gluing; the first (lowest) level is partially visible, upside down, on the left. Also visible is the 1/2" measuring tool that I created to mark the inset for the walls.
Here is another view of the construction of the different levels. In retrospect I could have cut out the centers of almost all the levels to make the pyramid lighter -- it might have cut ten pounds or so off the weight of 80 pounds or more for the finished pyramid. On the left of this image you see a small stack of levels finished.
First view of the layer cake. The finished levels are all stacked up to ensure that the proportions are OK and that I hadn't made some egregious error yet. None of the levels are glued together yet -- just stacked together.
Second view of the same stage, looking down upon the pyramid. The crude table it is sitting on is a 4x8 sheet of plywood, which gives you some idea of the scale of the finished pyramid.
Angled (sloped) walls suddenly appear. The sloped walls are a fundamental part of the design, and caused the first major delay. I spent six hours trying to figure out how to cut out pieces on the tablesaw such that they could be bent using the heat-gun and back-bevel technique and the result would be an angled wall corner such as you see in the image above. After six hours and much experimentation it was clear that there was no way to make those cuts on the tablesaw in a mass-producable and precise form. A single angled wall section is easy; making one that can be bent to go around a corner would be easy if the wall were vertical, but becomes difficult for a wall sloped at 75 degrees or whatever the angle is. So eventually I gave up and built a jig to hand-cut the corner angle -- the corners would be two pieces glued together, not one piece bent.
The finished sloped walls in the image above are simply cut out on the table saw with the blade set at an angle, then cut at 45 degrees for the corners by hand in a jig. I made them all a bit overlength -- no need to waste time in precision cutting their length, as I had already decided to cut the slots for the stairways after the whole thing was put together.
The top four levels are glued together at this point; the three middle levels are also glued together, and the bottom two as well. This image shows the top four levels stacked (but not glued) on the middle three. Notice how the gap for the stairway is not precise from level to level at this point.
Here you see a closeup of the angled walls, and how they interact with the structural vertical walls behind them. Note the parallelogram cross-section of the sloped walls to give them a flush gluing surface to the bottom of the upper level and the top of the level below.
Almost all the sloped walls are now glued on, and all the levels are now glued together. At this point I realized I had made a minor error -- I needed to have a bottom surface to the pyramid to attach the bottom of the sloped walls on the lowest level. Without a bottom surface the sloped walls would become damaged when the pyramid was picked up or moved -- I already had a good impression that it would take two people to move this thing most of the time, given its size and weight.
Once again, note the different widths of gap where the stairways will eventually be installed.
Speak of the devil (stairways) and they shall appear. This image shows the slats that will make up the stairways. There are four stairways on the original temple in Chichen Itza, each with 91 steps. One step on the top gives 365 steps total. To make a 91-step stairway I cut 91 slats of 4mm Sintra to length. Gluing each stair, one at a time, would be a terribly finicky process, rife with potential for error, glue in the wrong place, and permanent brain damage (PVC cement is noxious, noxious stuff).
So what I did instead is much simpler. I measured how long the stairway needed to be (see the slat of Sintra placed at an angle on the pyramid in this image, giving me the measurement of the hypotenuse of the stairway triangle). Then I took two braces with a 45 degree angle (pieces of wood molding, as it turned out) and attached them to a sheet of hardboard at the appropriate distance from each other. Then I simply laid the stairway slats on the sheet of hardboard so they were all equally spaced and at the right angle. Finally I slopped mass quantities of noxious PVC cement on the back of this arrangement so it would glue the back of the stairway firmly together. (I had previously tested this idea on some cutoff pieces of Sintra to be sure it would actually work)
On the far right of the image above you see the slats laid out on the hardboard sheet. Note also that the final angled walls have been applied to the pyramid here.
Second major delay. I had planned to cut the slots for the stairways by hand. Handsaws are quite precise, and power tools are a great way to make mistakes much much faster than by hand. Didn't work out -- I would have needed a handsaw with a 36" blade to do these cuts by hand. Go to plan B -- cut the slots on the tablesaw.
This idea was a bit scary. First, I'm working alone in the shop. Manipulating a large heavy pyramid on a tablesaw by yourself is not all that safe. Second, one error and the whole pyramid could be ruined. I was making this pyramid on a rigid timetable -- Alcan needed it for a trade show on in Mexico on August 1st, and I had to deliver it on time. Ruining the pyramid on the tablesaw would have meant asking them to ship me more materials and missing the deadline.
To increase the safety factor and reduce the chance of ruining the pyramid, I built a jig for the tablesaw. This jig was a piece of plywood with two runners to fit into the tablesaw grooves. The pyramid could be placed upon the jig and the whole jig slides on the tablesaw bed. This makes the whole process much more controlled. It also allowed me to make angled cuts where the top of the stairway is more shallow than the bottom of the stairway -- a virtual necessity, since the stair starts right at the top of the pyramid and then angles out, so in final position it is more than 5" away from the base of the pyramid.
Above is another view of the pyramid on the jig in my basement shop. I really need to finish constructing my shop, also -- I only barely got the basement lights and electrical set up in time for the pyramid project.
This view shows how the slots for the stairway will cut through the angled walls of the pyramid. It also shows how large and awkward this thing is, sliding on the tablesaw. To give you an idea of size and weight, it is pretty much comparable to a credenza or an empty desk with drawers.
A miracle occurs -- I cut all 16 cuts without miscutting the pyramid or losing any fingers. After 15 minutes shouting "Eureka" (I didn't know any ancient Mayan victory words) and doing the Church Lady Power Dance in my basement, I took this picture. The stairway slots are clearly visible, and I have mostly finished chopping out excess pieces of angled wall with the wood chisel and carving mallet visible. More chopping will still be necessary on the top two levels right where the mallet sits, because the path of the stairway will need some more depth there where the stairs would otherwise bump the floor of the level.
Now the fun stuff. The original pyramid has a bunch of astronomically significant masonry details that I wanted to replicate in the finished pyramid. Alcan did not want any painting on the pyramid -- it would obscure the fact that the pyramid was made of Sintra, for one thing -- but I wanted to replicate the fine architectural and masonry details such as I could. In this case, it wasn't difficult. I took a couple of pieces of cardboard, cut them to size and laid them on the sloped pyramid walls at one of the corners, then taped them together across the corner. This gave me a template for an overlay piece. Marking a sheet of 1mm Sintra with this overlay, I cut 36 angled pieces of various lengths out of the sheet with an exacto knife. Then I cut out slots of appropriate sizes using an exacto knife and wood chisels as shown in the image above.
The four pieces shown are the architectural details for the second level from the top, I believe. After cutting them I carefully scored the underside of the angle and then bent them so they would wrap around the corner without needing further adjustment. With thicker pieces of Sintra I would have needed to work with a heatgun to get the bend right, but with 1mm pieces I could just score and bend it.
Here we go -- the pyramid is starting to take its final appearance. After all the details were glued down I could trim the pieces flush with the slots for the stairways. I needed to cut the stairway slots on the tablesaw before gluing down the masonry details because sliding the pyramid around on the tablesaw left scrapes and marks that were hidden by the details; if I had cut the tablesaw slots afterwards the masonry details would have been marred.
Stairways in process. I cut the large sheet of 91 slats into four stairways, then cut stair rails out of 13mm Sintra to glue onto either side and form the stairways. This image shows one stairway being glued up, and another pair at the top of the screen waiting for clamps and glue. At the top right you see a small stack of the stair rails, showing their triangular shape.
Stairway glued into place on an upside-down pyramid. Why is the pyramid upside down? I don't remember. I could make up an answer, but why bother...
Another view of the bottom of the pyramid, clearly showing the way the stairways fit into the slots previously cut on the tablesaw.
Home stretch. Last major architectural detail is the top of the pyramid -- El Castillo, like all Mayan pyramids, has a ritual building on top. The ritual building has three rooms, lots of doorways, etc.. One of the books I had purchased while researching this project had a very good plan of the ritual building, so I could construct the interior rooms with confidence. The image above shows the upside-down ritual building, mostly finished. The picture in the left side of the image is El Castillo itself, showing the ritual building with the three doors on the front.
Almost done. This image is clickable to get a much larger detailed image of the almost-finished pyramid. You can now see what the whole thing looks like, right-side-up, with the ritual building on the top.
Notice the small doorway cut into the side of the north stairway -- in the real El Castillo, that doorway leads to a stair that mirrors the North stair, climbing up into temple to a small ritual room underneath the main temple. I had long ago decided NOT to replicate that invisible bit of detail on this pyramid, but I did cut the doorway for that stair, so I could pretend that inside there was the stair and so on.
Minor architectural details -- a view into the ritual building from the front doors. I attached simple lintels of 1mm Sintra, but didn't have good enough photographs of the front of the building to add any more details.
Final detail. The North stair of El Castillo has two huge decorative carved Kukulkan (feathered serpent) heads at the bottom. I carved these out of 10mm Sintra with an exacto knife and glued them into place.
Another view of the North stair, showing the Kukulkan heads and the doorway to the interior stair.
The saddest part of this whole project. Within hours of having finished it (on time!) I had to build a crate for it and ship it off to Alcan, so they could ship it off to Mexico for their trade show. Here the pyramid is ensconced in its partially-complete crate. The four sides are hinged to fold down for unpacking; that way the crate can be reused. A fitted and padded lid (not shown) is attached and screwed down into the side braces. Simple thin plywood sheeting will be screwed down to each side to give it more dimensional stability and resistance to shipping damage and abrasion.
There was a slight adventure with the shipping -- for one thing, two strong men could only barely get it out of my basement, and the first shipping company took the crate, then sent it back 24 hours later because it was too big (which led me to wonder whether it had expanded while under their care, since the shipping dude had measured it twice while he was picking it up in the first place, so the size (48"x48"x25" crate) and weight (108 lbs) should not have been a surprise). But a second shipping company took it happily enough, and away it went to St. Louis, and afterwards I'm sure to Mexico.
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