Teddy Top – First Pass

Posted: 22nd February 2015 by Quinn Dunki in Hacks

This idea may yet see the light of day.

 

A while back, I had this idea to create a thing that would turn an Apple IIc into a laptop. Unfortunately, this project has pretty much been one set back after another ever since. Most recently, I decided maybe I didn’t want to fill my oven with toxic fumes after all, and abandoned my plan to vacuum form the shell. Building a vacuum former was fun, but after talking to a friend with a lot more 3D printing experience than me, I decided to give that another whirl.

I made some changes to my design, most notably adding more structural ribbing on the underside. This was pretty easy to do. I already had tabs in the model for holding the LCD panel and control board, so I simply extended those to the edges to form stiffeners. If it was still warped, my friend and I had some ideas for how to straighten it.

The 3D print came in, and it was warped a little bit once again, but much less than before. It’s definitely usable this time around. The warping basically sorted itself out as things were mounted to the shell, as we’ll see.

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My first ever 3D print!

 

Some things to note about a Shapeways print if, like me, you have never done this before. This is their basic “flexible and strong” plastic. It’s the cheapest material they offer, though it still isn’t cheap. They are Selective Laser Sintering prints, and they feel like what they are- nylon dust glued together really elaborately. The surface feels like fine-grain sandpaper, and it has a kind of “grit” on the surface that never seems to come off. It feels like it needs vacuuming, but vacuuming doesn’t help. This material is pretty strong, but my model was a little too thin in places. I would not go less than 4mm for anything structural. The sidewalls that you see above are 2mm, and the top edge split a bit at the seam. The precision of the process is impressive. You can actually see little sub-millimeter errors that I made in my 3D model. If anything, I was more limited by the precision of the modeling software (the free version of AutoCAD’s 123D Design) than I was by the SLS process. Most of the issues are not printing problems, but rather, small errors in the 3D model that I couldn’t see in the software. For example, my split seam is likely because the polygon edges are closer together in that area than it appeared, or there’s some other oddity in the geometry that I couldn’t see in 123D. I don’t blame Shapeways’ process for this. Giving yourself some margin of error in the geometry is a good idea for structural areas or weird angles.

 

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Here you can see the new structural elements. I also took this opportunity to chamfer the edges/corners, and improve the fit in a couple of areas. AutoCad 123D Design has some issues (notably in the inability to position things in absolute space), but it has some great tools for rounding corners and such. It’s hard to complain too much about a free tool, though. It’s pretty great for what it is. I certainly recommend it as a tool for modeling 3D prints.

 

Here’s the 123D model for this. I went back and forth on whether to offer this up for sale on Shapeways or give it away here. I’m opting for the latter. If you want to support Blondihacks in such endeavors, become a Patreon patron of Blondihacks. That’s how you can acknowledge my efforts. If you improve on this design, or try it out yourself, let me know!

One of the gotchas with 3D printing is that you have to anticipate every contingency ahead of time. If you make any small errors in your design, you may end up reprinting it, which is very expensive. If, like me, you need to make some small alterations after the fact, there are options. It drills nicely, and takes wood screws quite well with a pilot hole. Cyanoacrylate glues work very well, as does the water-cured Gorilla Glue brand adhesive. The latter is especially nice if you need to glue it to a dissimilar material such as wood. For making large scale cuts, I found tin snips work really well. For more delicate cuts, I found the metal cutting wheel on the Dremel worked the best. It actually just melts the stuff, but this seems to work better than any other method. The melted blobs around the “cut” are easily removed with a knife, leaving a clean, sharp edge. This works for notching and beveling as well. I wore a respirator while doing a lot of cutting, because it smells really bad when it melts, which probably means it isn’t good for you. Also eye protection of course, but I assume that goes without saying.

I can’t proceed without a word on price, however. This shell was close to $250US. I know, I know. That’s vastly more than I would usually ever spend on a project like this, but it was an interesting learning experience, and the end result is pretty cool. Call it tuition to 3D printing school. I’m now seriously considering buying a 3D printer of my own, because it would pay for itself after a few more projects like this. If you’ve ever wondered why 3D printed things you buy on Etsy or Tindie seem so “overpriced”, this is why. 3D printing is damned expensive right now. I imagine the price will come down in the coming years, but right now it is a luxury process. The end result is undeniably attractive, though. With very little effort, you can chamfer edges and corners, for example, and make all kinds of complex shapes that would be very difficult any other way. For certain kinds of jobs, this process is definitely worth the price.

 

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Luckily I seem to have measured correctly! My display and driver board fit very nicely.

 

With the shell looking good, it was time to move on to the mounting system. It’s important to me that the Teddy Top mount non-destructively to the computer, because this IIc Plus is pretty special to me. Since there are no handy mounting points we can use, that really only leaves one option- some sort of clamping system. The clamps have to be very odd and complex shapes, however, so I knew this was going to be a fabrication challenge. I started with aluminum angle stock, and with a couple of strategic bends and cuts, I was able to form almost the entire shape from a single piece. I needed a thicker piece on the bottom to take a threaded fastener (as will become clear in a minute). Joining thin, small aluminum pieces like this would be best done with a TIG welder, but that’s beyond the capabilities of my home shop (and its owner). Instead, I used the hacker’s TIG- JB Weld. This stuff is a flavor of epoxy tailored for metals, and if you prepare the surfaces carefully it actually works pretty damned well. It’s impressive stuff, to a point. It’s no replacement for actual welding, but as glues go, it works better than you might expect. In the automotive world, just about every racing team has a story about JB Weld repairing something during a race that should have put them on the trailer.

 

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Real fabricators weld. The rest of us JB Weld.

 

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Here’s a test fit of the corner clamps. You can see how I planned for this with cut-outs in the top shell.

 

In that photo, you may also notice there’s plastic under the top of the clamp as well. This is a separate piece that I 3D printed along with the shell to hold the hinges along the bottom. It’s a special shape, because it needs to jog around a cut out in the top of the case where the handle folds up.

 

With the basic clamps done, the next challenge was hinges. Modern laptop hinges are an unsung triumph of engineering. They hold up something fairly heavy, yet allow you to effortlessly and smoothly open them to any angle, where they will stay until the heat death of the universe, or you decide to adjust it (whichever comes first). They also take up almost no space, and limit range of motion as needed by the electronics. All of this is not easy to achieve. The common term for this construct is “friction hinges”, and I made two attempts to buy them. The problem is that the ones you can buy are intended for things like cabinet doors, which have a lot of weight on them, and a lot of leverage as well. They are much too stiff for this application. You can also buy adjustable friction hinges, which allow you to tune the stiffness. This is quite a neat idea, but these turn out to be very bulky. A couple of expensive experiments later, and the junk pile has some fancy hinges sitting on top of it now.

 

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The left hinge is torque-adjustable (very cool), but huge. There was no way to fit it into the design, though I did try. The right hinge is the weakest non-adjustable friction hinge I could find, and you can barely even move it with your fingers.

 

Then, inspiration hit. I didn’t necessarily need a smooth, precisely torque-rated friction hinge. I just needed a hinge that’s a bit hard to move. In other words, a poorly functioning hinge. I can make that! I bought some regular brass hinges from the hardware store, and proceeded to jack them up real good with a 3lb sledge.

 

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Sometimes the answer really is, “bigger hammer”. A few whacks on the pin messed up the hinge enough that it was now dragging through its range of motion. Presto, friction hinges.

 

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Here’s a quick test fit with the brackets, hinges, and mounting plate. Looks like it’s actually gonna work!

 

Next I needed to mount the hinges on the hinge plate. For this, I used some wood screws, and cut them flush on the bottom. The SLS material seems to take wood screws quite well (with a pilot hole, of course).

 

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The latest verse in my ongoing love-letter to the Dremel diamond wheel. I don’t know how civilization functioned before that was invented.

 

Then, naturally, the hinges need to be mounted to the lid. This was an area that I didn’t spend enough time thinking about when building the model. Some part of my brain said, “Oh, I’m sure I’ll figure something out for that”. Well January Quinn, now February Quinn has to make good on that. Thanks a lot. I decided the plastic needed to be thicker where the hinges mount, both for support, fastener holding depth, and alignment. Rather than go back and reprint the whole thing, I added some pieces of wood. They’re attached with Gorilla Glue, which is a unique water-cured adhesive that works well on a wide range of materials. It’s my go-to when gluing dissimilar things like wood and plastic. This stuff takes some practice to use. The water is critical, clamping is very helpful, and be aware it expands a lot while curing. Once you get used to its peculiarities, it’s good stuff.

 

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A couple of little filler plates from some scrap wood, and we’re ready for hinges.

 

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The hinges went on easy-peasy, thanks to all this prep work! Here’s a good look at the Tetris-shaped hinge mounting plate. I 3D printed that as well, since the shape needs to be precise and weird.

 

Now we need to finish the clamping system. My original plan was to use thicker material on the bottom of the clamps, so that I could drill and tap for screws. These screws would then press against another plate that rests against the computer, applying pressure to hold everything, without marring the plastic in any way.

 

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This seemed like a good idea on paper, but in reality it didn’t work out. The side of the machine isn’t perfectly square, my clamps aren’t exactly straight, and the underside of the machine has a chamfer in just the wrong spot. Sometimes the real world spits all over your CAD drawings.

 

While fiddling with that, trying to get it to work, I noticed the rubber foot next to my clamp. It has a plastic ridge next to it. This could be perfect! I could make a little piece that would anchor against that, and make it thread into the same holes as my original clamping plate, for tightness adjustment.

 

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This actually seems crazy enough to work! I just need to shorten those bolts.

 

A quick protip on shortening bolts- thread a nut all the way on to the bolt before cutting it (with the Dremel diamond wheel, naturally). That way, if the threads get a bit messed up by the cutting and filing, they’ll get cleaned up when you remove the nut. Also, when cutting a bolt, you’re losing the starter thread. This will make the bolt trickier to get started in a threaded hole. Another tip is to turn the bolt to the left with gentle pressure against the hole. You’ll feel it “click” when the threads are lined up and you can then start turning to the right to thread it in. This is a common mechanic’s trick, since you’re often threading fasteners blind on a car, but it also works great on cut bolts with no starter thread.

 

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One final test fit before finishing work begins. Looking good, and my sledgehammered “friction hinges” are doing their job!

 

In order to unify the wood pieces with the design, and also give a nicer finish to the SLS plastic, I opted to spray-paint the whole thing. Any project worth doing is worth a little rattle-can love.

 

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Don’t have string handy? Try dental floss. Pound-for-pound, it’s the highest tensile strength material in your house, not counting the spider webs in the attic. Amazing stuff.

 

Painting also seals the surface of the SLS print, which makes it much nicer to the touch. I’d recommend some kind of spray coat for any SLS 3D print, if this is how they usually are.

 

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With a nice coat of paint, I then lined the clamping area with felt to keep from scratching my lovely Apple IIc Plus.

 

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Here it is, all mounted up. Looking good!

 

The next step was to get the electronics installed. I needed to clearance a few things, and add a couple of mounting screws, but for the most part, my planning in CAD paid off here. Everything fit together just like I had hoped way back when I did the foam core mockup.

I was hoping the LCD and driver board would simply be a friction-fit, but that wasn’t quite enough to hold them securely. Instead, the junk pile coughed up some tiny little self-tapping screws, pilfered from who knows where. Haveth ye faith in the junk pile, and the junk pile will provideth for thee.

There was one small clearance issue with the driver board. The power connector for the backlight needs to exit stage left, but my plan was to desolder it and reorient it. The connector proved resistant to all forms of desoldering without destroying it in the process, so instead I cut a hole in the rib for the plug to pass through. This had the added benefit of helping to secure the PCB.

 

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The wiring is secured with a scrap piece of plastic from one of my test prints. It’s friction-fitted for now, but I’ll screw it in place later.

 

This is still a rough prototype of what Teddy Top could be, but so far it is achieving all my goals:

  1. Flip-up LCD display with no external power source.
  2. No interference with the Apple IIc’s carry handle.
  3. Non-destructive mounting system.
  4. Still fits in the original Apple IIc carrying bag.
  5. No interference with any ports or features on the back or sides.
  6. Compatibility with the IIc and IIc Plus

 

To demonstrate success on all these points, here’s a demo video.


Download Video from YouTube | YouTube to MP3 | Replay Media Catcher
 

I’m pretty pleased with how this turned out. There’s a few things I would change in the 3D print, such as support for mounting hinges, and retainers for the wiring and LCD. I think I would also try designing the hinges right into the 3D models. I think each hinge half could be modeled in to the shell and bottom plate, respectively. Then a long thin bolt with a nylock nut could be put through, thus giving you a tension adjustment. I’m not certain it would work, but if I print this again for any reason, I’ll try it. Overall though, I think Teddy Top is coming along nicely. I have a few more ideas for things I want to add, so stay tuned!