Making Wooden Hypercubes

the_smallest_one.jpg

Accuracy is everything when you are trying to make this shape, or you get ugly corners.

Or worse.

This is the smallest inside-out projected tesseract model I ever made out of 1/4 inch thick wood using the CNC overhead CAD/CAM router.

It’s small enough to hold in my hand, and you may already have seen the picture of me doing exactly that on my blog and on Facebook.

The router eventually broke down and we had no funds to repair it. But while it lasted it was a glorious thing. The vacuum table held the wood flat and motionless, and the the computer numerically-controlled 3-axis overhead router would glide through the wood, cutting the edge bevels for two rhombi at the same time as it grooved through the thin birch maple and oak panelling while the attatched shop vac sucked up all the sawdust. Then we would shut it off and collect the rhombi.  The required tolerance demanded such accuracy.

The rhombi were glued together with Elmer’s carpenter wood glue; the seams were kept pressed together for the time needed for the glue to dry by using stretched duct tape to exert continuous tension. Of course, duct tape leaves its own glue residue on the wood, which had to be thoroughly cleaned and sanded off before we could apply the stain or in some cases clear polyurethane sealant. This one I made for myself, too small to be a loudspeaker, so I did not bother to stain it. I like the look of natural wood grain just as much as stained wood.

hypercubesOrdinarily, the design would have included four half-rhombi and a square to mount the woofer on. But I liked making this one a complete rhombic dodecahedron since it would never hold a woofer. I have kept it with me over the years, as I was forced to turn from hypercube speaker builder to career programmer. A memento, if you will, of my life that could have been, that must have been…on another timeline.

The rhombic dodecahedron can be thought of as the boundary of a inside-out projected tesseract. It is also identical to the boundary of the parallel projection of the hypercube onto 3-space.


tripanelsWe worked out assembly-line methods for the building; after spending a day cutting rhombi, half-rhombi and squares we would spread out some newspaper on the warehouse floor. First we would glue three rhombi at a time together and then set the 3-panel subassemblies to dry. By the time we had finished glueing all of the 3-panels we needed together, the first ones were dry enough to proceed. Then we would take two 3-panels and glue them together to form a 4-edge corner subassembly, a hex-panel.

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hexpanelBy the time we finished the hex-panels, the first ones were dry. Then we would take a hex-panel, glue in two more rhombi, and it would be ready for the four triangles (half-rhombi) and the square baffle plate.

After the glue dried, the duct tape was stripped off and the cabinets were sanded, stained, and sealed. Then we were ready to install the backplate in the rear rhombus where the input terminals go, the frequency-dividing crossover network that sent the highs to the tweeter and the bass to the woofer. And then finally the woofer would be front-mounted onto the baffle plate and sealed to it with a bead of silicone rubber.  No one taught us; we had to work it all out for ourselves.

hypercube-loudspeakerBut the end result was always worth the trouble of learning how to make it. We thought they were beautiful.

Not everyone agreed, obviously.

Their loss.  Next post, I’ll cover more details about how they were tested.

Must sleep. –MRK

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13 Responses to “Making Wooden Hypercubes”

  1. Thanks for reading, Natasha. I like your design at http://goodasgoldtraining.com
    –MRK

  2. “do you have facebook or myspace?”

    I am on Twitter as gamesavant.
    I am on facebook as matthew Kennedy.
    –MRK

  3. so bored says:

    do you have facebook or myspace?

  4. Natasha says:

    thanks for interesting info! hi from DC :)

  5. Hello there! I know this is kinda off topic however , I’d figured I’d ask. Would you be interested in trading links or maybe guest authoring a blog post or vice-versa? My blog addresses a lot of the same subjects as yours and I believe we could greatly benefit from each other. If you’re interested feel free to shoot me an e-mail. I look forward to hearing from you! Excellent blog by the way!

  6. “Hello there! Do you use Twitter? I’d like to follow you if that would be okay. I’m undoubtedly enjoying your blog and look forward to new updates.”

    Sigh. Yes. I am gamesavant on twitter. I have mentioned it before. I have even made some of the pictures links back to my main website at http://www.matthewrkennedy.com where you WILL see a Tweet button and a Follow me button. if you are on twitter, use them! If you are not, join twitter for free and then use them.I have few followers, still! people out there are asleep, maybe. I am trying to wake them up! Add your voice to mine! Join me in this great adventure, the adventure of my life. Please help! GIVE. And on the other website you might learn something.
    –MRK

  7. Hello there! Do you use Twitter? I’d like to follow you if that would be okay. I’m undoubtedly enjoying your blog and look forward to new updates.

  8. Hi Doug! interesting. I have used clear packing tape for mailings, of course. There is something about duct tape that appeals to my engineer genes, i guess. You know, that old joke that you can fix anything with duct tape and super glue or whatever. Interesting suggestion, however. I know that there is a lot I don’t know about tape. –MRK

  9. Doug S says:

    Random thought to those dear readers..

    I found w/ kayak building stuff… Better than duct tape and painters tape is clear packing tape - it holds well (better than painter’s tape), stretches but does not leave a reside like duct tape.

  10. Yes, it was Tom. Functional beauty. Shirly got us appointsments and we made several sets to take to an AES convention. I dined with Dr. Kontrimas founder of RADIAN and told him how much I appreciated his drivers. They are like Tannoys but easier to obtain. As usual my timing were a little off. I took a walk in Central Park, and while I was gone someone came up to the hotel suite and fell in love with the range of speakers we had from small to large with a wide assortment of expensive and less expensive drivers. This encouraged Shirley. Then she went out and I manned the suite. And of course someone else came to see and hear them (we had a switchbox to flip sound from one pair to another for comnparisons with std tech. Unfortunately for me, the someone who showed up while I was manning the post….was an engineer from JBL. Oh, he listened, looking angrier all the time. Heh. OOp Thunder have to log. Yes go ahead. I will look into adding other things. –MRK

  11. Tom Weiss says:

    I don’t think there is a problem with linking to the Wolfram Demonstration project site, as long as we are not doing so for commercial purposes. It is mostly under the Creative Commons & MIT Open Source Initiative licenses.

    Here are their terms of use: - http://goo.gl/69HVG

    Creative Commons License: - http://goo.gl/D3J3a

    MIT License: - http://goo.gl/lgrzV

    This one here is one of my favorites: http://goo.gl/zlYmU

    Here is info about the Computable Document Format (CDF): - http://goo.gl/lnBCN

    Here is the Wolfram CDF Player download page: http://goo.gl/nsCCW

    I’ll see what I can do about putting together the initial text for a construction guide - you have a digital camera, right? I have a camera in my cell phone, but the rez is pretty low and I have no rhombi - Hopefully, you still have some rhombi left over from your CNC runs (God, that machine sounds like it was a thing of beauty!).

  12. Holy COW Tom! I was giving it away but was going to let them think about the angles and ask before being so generous! As usual, you anticipate with precision and alacrity. That Wolfram page is just beautiful; their rotatable RD graphic makes my poor java applet look like trash. I wonder if there is any hope of getting permission to link to it? I’d love to have such beauty if we can avoid litigation.

    Yes, of course, you are right. I was planning eventually to include a step by step sequence of photos and text to show the complete building process, but I just havent had the time to make much of a start on it. The idea is to put in the bare bones first, then flesh them out with more pictures and text, improving them as we go just as I keep improving other articles. Building up credibility with this blog has begun to weary me into zombi-mind, barely conscious compared to how I usually think. I am so glad that you are here now to shake me out of my complacency, old friend. You are like a jogging partner who helps me pick up and keep the pace by challenging me to stretch myself to keep up. Why don’t you take a crack at starting on the construction text…then I can put in my 2 cents and offer suggestions on how to phrase the text so that you will not exhaust our readers into comas trying to keep up! Folks, in case you havent guessed, the reason Tom and I became close friends in high school was that he confused the same people who bored me. Believe me, listening to Tom talk is never boring! For those of you who have never had the opportunity, if you do not prepare yourself with choline bitartrate and B vitamins to boost your brain activity by supplying neurotransmitter precursors, Tom will soon have you holding your head and trying not to pass out. The man makes Superman’s old foe Brainiac look retarded! So glad you are in touch Tom. The universe is such a less-boring place with you in it. –MRK

  13. Tom Weiss says:

    I’m thinking we need to put together a detailed step-by-step guide to making Hypercube Speakers, complete with photographs.

    We need to specify the exact angles of the rhombi - 70 & 110 degrees is close, but we need to specify it down to the minutes & seconds - 70.53 & 109.47 degrees. (Am I the only one who is bugged by the fact that this is mighty eighty close to the hydrogen bonding angles in a water molecule? - But I digress…)

    We also need to mention that the bevel is 30 degrees for the rhombic edges (and the cutting tool needs to be set for 60 degrees to get that 30 degree bevel, a situation that does not arise with the usual square box bevel angle of 45 degrees) - and speaking of 45 degrees, that’s the bevel angle for the minor-axis edge of the half rhombi and of the square baffel plate, assuming the use of the square truncation.

    I forget what the bevel angle is for the major-axis half-rhombic edges and the triangular baffle plate edges when the triangular truncation is used,, but I could probably recalculate it with a little effort.

    http://goo.gl/99qQ5

    I’m also wondering if the use of painter’s tape instead of duct tape would minimize the glue residue problem that is such a pain in the butt during the finishing stage - assuming painter’s tape will serve to hold it together while the glue dries.

    I’m also thinking that a polyurethane glue like Gorilla Glue might work better - you use a spray-bottle of water, and mist the edges just before applying the glue - water activates it and it dries quicker. Very high bond strength.

    What do you think? More people may build them if they had such a guide.

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