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Nickname:?Clive Maxfield???? Articles(444)???? Visits(533057)???? Comments(79)???? Votes(236)???? RSS
There is so much amazingly cool "stuff" to see and do that I'm amazed I find the time to get any real work done. In my blog I will waffle on about the books I'm reading, the projects I'm building, and the weird and wonderful websites I blunder across. Please Email Me if you see anything you think will "tickle my fancy."
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Posted: 09:57:25 PM, 30/12/2014

BADASS Display: Recovering from mistakes

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Good grief--how time flies! I first determined to build my Bodacious Acoustic Diagnostic Astoundingly Superior Spectromatic (BADASS) display way back in the mists of time we used to call April 2014, so this project has already been running for around two thirds of a year.

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On the one hand, this does seem like a rather long time. On the other hand, when I think of how much is involved, and also how I'm interleaving this with a bunch of other projects, it really doesnt seem all that bad.

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In this column I thought I'd bring you up to date with the current state-of-play, and also explain the comedy of errors I've been making recently. But before we plunge into the fray with gusto and abandon, on the off-chance you arent overly familiar with this project, the following table of article links will describe how we've gone from an initial concept like this...

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...to the present incarnation of my little beauty, which looks like the following (note that this image was taken in my driveway after I'd finished working on it this past weekend, which explains the houses in the background):

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Phew! When I come to look back on all of these articles, I think it's amazing I've come as far as I have in only eight months (LOL). And so we come to the recent series of mishaps that I've been fighting my way through.

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Here's the main cabinet sitting on our back porch. I brought it outside because -- for some reason -- I couldnt manage to take a decent picture inside. I routed out the main panel in the middle, while my master-carpenter chum, Bob, made the surrounding cabinet.


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I must admit that I was quite proud of this because it was the first time I'd ever routed anything. The only slight slip-up was the left-most vertical channel in which I set the jig up the wrong way, but since this wont be seen by the user, I'm not losing any sleep over it.

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In the image below we see the large display panel and the smaller control panel -- both made out of hardboard (pressed-board) painted to look like brass -- attached to the main front panel. This scene all looks so innocent, doesnt it? In reality, however, there were numerous "gotcha's" that reared up to bite me.


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Let's start with the display and control panels. Initially, I created these out of 1/8" hardboard, which I lovingly crafted to fit into my routed front panel. I'm not a woodworking expert, so this took me quite a lot of time. When it came to drilling the holes for the acorn nuts around the edges and the array of lenses in the middle, I worried that there would be small but annoying errors if I did this by hand. Thus, my chum Willie whipped up an engineering drawing to drive a CNC machine, and my friend David at a fabrication facility just down the road ran the panels through his machines.

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Unfortunately... David made a similar mistake to mine -- he subtracted 7/32" instead of adding it to the 0,0 point, with the result that all of the holes ended up 7/16" out of whack.

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"Oh dear," we both said (or words to that effect). This was a bit of a blow, and no mistake, but these things are sent to try us, so I got another piece of pressed board and we tried again. This time David drilled the holes first, and then carpenter Bob shaped the panels to match the routed areas.

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Now I ran into a new problem, which was that the original hardboard was 1/8" thick, while the new sheet was 3/16" thick, which meant it protruded in front of the main front panel by 1/16" instead of being flush. "Oh, well," I thought, that doesnt really matter. Actually, if the truth be told, having the display and control panels protrude by 1/16" actually looks rather good. "Things all work out well in the end," I said to myself, cheerfully, little realizing the horrors that were to come...


Just to remind ourselves, we left the cabinet in the state shown below, with the display and control panels attached to the main front panel using brass acorn nuts.


Ah, if only that were all that was holding things together. As fate would have it, however, before I attached the acorn nuts, I realized that the hardboard was bowing out a little in the middle. "I'll never need to take these panels off again," I thought, "so there won't be any problem if I glue them to the main front panel."

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So that's that I did. I lay the whole cabinet on its back, glued the display and control panels in place (using the four corner bolts to lock in the alignment), and weighted everything down with books until the glue had set. Then I removed the books, stood the cabinet up, and attached the remaining acorn nuts and bolts, leaving things as shown above.

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It was only then that I turned the cabinet around to look at things from a rear perspective. You can only imagine my disbelieving horror when I observed that the vertical channels I'd routed were obscuring the edges of the holes for the Fresnel lens/LED assemblies as shown below.


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"Well, that's a tad unfortunate," I said to myself (or -- you guessed it -- words to that effect). Now, it wouldn't have been a major effort to widen these channels in the main panel using my router, if only some plonker hadn't gone and glued the display panel onto the main panel (sob sob).

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This is where another Bob comes into the picture. (I'm like the little boy in The Sixth Sense movie -- "I see Bobs everywhere"). This Bob is ensconced in the office next to me. While I was bemoaning my fate to Bob, he explained that he is a master at making mistakes, which has helped hone his skills for rectifying them again. After I'd explained the problem, Bob helped me to devise a solution.

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In the image below we see the simple jig Bob and I concocted to allow me to widen the channels without having to remove all of the acorn nuts and bolts. The router bit is set to such a precise depth that it completely removes the main panel material whilst leaving the rough backside of the hardboard totally unscathed.


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Now we were really cooking on a hot stove, as it were. The following two images show the cabinet with its 16 x 16 = 256 array of Fresnel lens/brass washer assemblies attached (once again, both of these images were taken in my driveway after I'd finished working on my little beauty this past weekend, which explains the houses in the background).

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Well, when I say "attached"... as fate would have it, there's a teeny-weeny problem. The body of each plastic Fresnel lens is threaded, and each lens comes with an associated plastic threaded ferrule-type thingamabob that screws on behind the panel to hold its lens in place.

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Initially, I was thinking that these ferrules would be all I would need to attach the lens-washer assemblies to the display panel. The thing is that the brass washers hold the lenses a little way in front of the panel, so only a small portion of the threaded backside of the lens protrudes through the back of the panel. If only the panel were 1/16" inch thinner -- but no, some drongo had to go and replace the original 1/8" thick panel with a 3/16" version.

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Isn't it amazing how little decisions can come back to bite one downstream in the development process? The end result is that I now need to glue the ferrules onto the backside of the lenses. The ideal adhesive should be something that works with hardboard and with different types of plastics (including PVC derivatives, which is what the ferrules appear to be made out of). This adhesive should be thin enough to be applied with a paintbrush or by dipping the end of the ferrule into it. It should give me a "work" time of say 20 to 30 minutes so I can pour some into a small bowl and work with it without it drying out too quickly. It should dry white or transparent so as to not absorb any of the light from the LEDs, and it should not dry brittle because I don't want it to crack if I move the cabinet around. Do you have any suggestions?

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I don't know about you, but even with these little "gotchas," I think this BADASS Display starting to look very, very cool. The next step -- after I've finally fixed the lens-washer assemblies in place -- is to add the LEDs and the control electronics. I have all of this standing by. I really think there is a good chance I will have everything completed by the end of the Christmas holidays (apart from the final programming, of course). Watch this space for ongoing developments...

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