Step 2: Create end caps for PVC pipe
This next step is the most tricky and involves the most work pretty much of any of the steps. This step seems so small in terms of the whole project but it will take a significant amount of time. Set aside a whole weekend for this one. It might only take you 1 of the two days, but it will probably take more time than you think.
In order to have the design work, the PVC Pipe used as a space filler at the apex of the wall has to “float” in place with the main threaded rod (which runs through and connects the rounded ends of the 2×4 main support beams) running through its center. To make that happen, the PVC needs something stuffed in its ends through which the threaded rod can pass and which will hold that rod in the center of the PVC pipe. I searched high and low for some sort of standard fitting which would serve this purpose. No single fitting nor combination of standard fittings that I could assemble would do the job so I had to create these “End caps” myself. If I had a lathe that could turn a big block of aluminium, oh yeah … and the skill to operate it, I might have made this ditty out of aluminium … but having neither, I decided to use a chunk of wood. My plan was to fabricate a disk of wood, about 2-3″ thick and of a diameter which would snugly fit inside the end of the PVC pipe (inside diameter of exactly 4″). Furthermore, I planned to drill a hole in the center of this disk and line that hole with copper tubing as was done in the main support beams.
To cut the disks, I first thought of drawing the 4″ circle centered on the face of a nicer quality (non-pressure treated) 2×6 (the actual dimensions of which would be 1.5″ x 5.5″) and then using a scroll or jig saw to cut out the circle. I thought about how tight the tollerances for this to simply “friction fit” inside of the PVC pipe end openings and figured my scroll saw would not be accurate enough (yeah … I blamed the tool rather than the operator … go figure ). So, how then to cut a perfect circle in a 1.5″ piece of lumber exactly 4″ in diameter. Another challenge I was worried about was how to exactly center the 7/8″ hole in the exact center of the disk once it was cut out. Hmmm ….
Hole saw. That was the solution that popped into my head. If you have not seen one before, here is a pic of one.
A special drill bit is inserted into this “cup” shaped saw through the hole in its center (the hole is threaded to match a threaded collar on the drill bit). This drill bit acts as a guide when aligning the hole saw (since it is perfectly centered in the middle of the hole that this saw will cut). This saw will cut a circular hole in a piece of wood. We don’t really care about that … what we want is the piece of wood that the hole saw cuts OUT of the bigger plank. Note that once you pull the piece of wood from inside of the hole saw after cutting the hole in the larger plank, that disk will have a small hole drilled through its center as a result of the pilot drill part of the hole saw mentioned above. This small pilot hole will serve as the first hole in the series of increasing diameter holes which we will drill through the center of this disk until we finish that hole off to a diameter of 7/8″ with the auger bit as we did in the main support beams in step 1 of the project.
As for size of hole saw, I experimented and looked around the tool section of Home Depot and found that a hole saw advertised as a 4 1/4″ (4.25″) hole saw had a diameter between the INSIDE of its teeth (which would be the size of the disk of wood created when you drilled the hole through a larger piece of wood) of almost exactly 4.00″. Actually it was an extremely small amount bigger than that measurement which was great since I intended to sand the edge of the disk slightly after cutting it out so I figured that the finished, sanded disk would be pretty darned close to having a 4.00″ diameter which should exactly match the inside diameter of the PVC pipe.
Again, this work must be done on a drill press with the work surface supports and bar clamps holding your wood since this size of a hole saw tends to try to grab the wood and spin it out from under your hands. You also want to ensure that everything is level and square so that the disks are nicely shaped and the edges are square to the flat surfaces of the resulting disk. Here is the drill press I use … a rather inexpensive Craftsman from Sears … but it works well enough for my purposes.
Ok. So I proceeded to cut out such a circular piece from a 2×6. I then used the disk sander part of my “bench style” belt sander (I should insert a pic of this handly little beastie here) to smooth the edges of this disk of wood. This particular unit has a small support platform that you can mount right in front of the disc sander surface. This provides you with a flat surface on which to rest your work while you push it up against the vertical surface of the spinning disc of sandpaper. This platform is not fixed at 90 degrees to that spinning disk but, rather, is adjustable from a 90 degree angle to a 45 degree angle. Thinking that I wanted this disc to fit snugly inside of the pipe opening, I decided to put the angle at about 88 or 89 degrees giving the sides of the finished disk a wee bit of a bevel/wedge appearance relative to the flat surfaces of the disk.
So, I took my cut out disk, and tested it against the PVC pipe end. Slightly bigger than the pipe opening. Good. Sanding phase begin. Glove up and take the disk once around against the sanding disk. Try again. The tapering seems to be a good idea. Not enough sanded off yet though. Back and forth I went. Sand around the edge, then test, then sand, then test …. eventually I got the piece to fit fairly securely in the end of the PVC pipe. But it was ever so wobbly (as would be expected from the hand sanded and thus slightly imperfect wedge shape (even if it was only a degree or two off from 90 degrees). Also, over time, I suspect that either the PVC pipe might crack from the pressure of the wedge shape or the wedge shape might just stretch the pvc pipe enough to slip inside (very little preventing this actually since I didn’t make the wedge angle very steep at all) and that would blow the whole thing as the PVC pipe might then become very unstable.
Sigh … thank God I only made one as a prototype. Grrr. Now what?
Ok, if the disk idea was good … which I thought it was, then let’s do it again. I decided to make a 2 piece disk – one piece would be as I just had made but with the angle of the edges changed back to 90 degrees relative to the faces — so it would slip inside the PVC snugly, but not as a wedge. The other piece I would make using a different hole saw … one which would produce a cutout circular plug with the exact diameter of the OUTSIDE of the PVC pipe which was actually 4.5″ across. That bill was filled by a hole saw of an advertised diameter of 4 3/4″ (4.75″). Now I would have two disks of wood, each with a centering pilot hole in their middle. One of these disks would be about 4″ in diameter and would be 1.5″ thick (cut from a 2×6) and the other would have a diameter of 4.5″ and would be about 3/4″ thick. I decided to cut that one out of a piece of 1×6.
Here are the remains of my (multiple) attempts at these initial cuttings. I suggest that you cut a bunch of these out even though you only need 2 for this project. I actually made 4 because an earlier iteration of my design called for an extra pair of support beams in the middle of the structure which would have required two pieces of PVC pipe and thus 4 end caps. In any case, here are the carcases of the 1×6 and 2×6.
Once the disks were cut out, I sanded the edges of the 4″ diameter one until it fit snugly (very) inside of the PVC pipe end. I sanded the edges of the 4.5″ diameter one until it very closely matched the outside diameter of the PVC pipe (very little effort needed here — it was darned near exact right out of the hole saw). When sanding the edges, make sure you keep turning the disk and sanding the circumference evenly so you don’t throw off the roundness of your circle. I didn’t find a great way of doing this exactly and a few of my end caps had one or more slightly “flat” spots … but not enough to really be noticable by anyone not as anal as myself
As the finishing touch, for each disk I sanded a sligh bevel on one of the “sharp” edges between one of the flat faces and the side wall all the way around. Don’t do this to both of these “edges”, just one on each of the two disks per end cap. The “sharp” edges will face each other and be joined together in the next step. The “rounded” edges will face out. One will go into the pipe the other will become the extended edge/end of the PVC pipe. Rounding the one that goes in the pipe makes it easier to insert the finished end cap into the pipe end. Rounding the one that is on the outside makes for a nice finish to the whole assembly. By not rounding the “inner” edge of the larger disk, this allows it to “extend” the PVC pipe’s outer diameter without a visible break or seam … well at least it allows for a smooth interface between the pipe end and the wood end cap … no “dip” or ridge.
Ok, now to assemble the sanded and fitted disks into a finished end cap. Since each of the two disks had a centering hole in the middle, I used a drill bit of the same size as the one that the hole saw used as a pilot drill to insert through both center pilot holes to line them up perfectly. I then clamped on two sides using small “quick clamps”. With this done I drilled two small holes through the outside (larger) and part way into the thicker, inner disk. I believe I used 1.5″ long stainless steel wood screws to screw these two pieces together. Note you want to position these screws as in the picture shown below because you don’t want them to be too close to the actual center hole. You will be drilling that hole out to be a finished size of 7/8″ in diameter remember … and then gluing in a copper tubing insert inside of that hole as we did in the main support beams to act as a race or guide for the threaded (or smooth) rod that will be running through the center hole. You must counter sink the screws slightly so they don’t stick out at all … their heads must actually be a little below the surface so they don’t interfere in the capped PVC pipe being able to rotate freely. Once you have secured the two pieces together with the two screws in this fashion, you can then go through the same drilling process as you did with the main support beams when drilling the 7/8″ holes in those members. Note that you will probably have to auger from both sides of this assembly unless your drill press has a travel range capacity of more than 2″. Mine did not. Also, remember to have some sort of a thin piece of wood between the underside of your end cap and the steel platform of the drill press to protect the outer cutters of the auger bit from hitting the steel of the support platform and ruining them.
Once the hole is drilled and finished, clean it out with the wire brush, and, as before in the main support beams, mark, cut and clean a piece of copper tubing for this combined end cap and then glue it in place as you did for the main support beams. I found that getting both end caps done and the tubing cut for both and then gluing both at the same time was more efficient. Just make sure you keep the right pipe piece with the right end cap to ensure the right sized pipe for each cap. I found that using the dremel tool as before to bevel the outter edges of the pipe ends after the glue dried as before in the main support beams really made it easier down the road when trying to insert the rod through these tight-fitting holes really helped.
Below are pictures of the finished end caps as well as pics showing them being inserted into the PVC pipe as well as after they have been fully inserted.
Believe it or not, the trickey parts are now basically done. All of the pieces are pretty much in place and ready to be assembled. So, the next step is constructing one of the panels.