by Eliot R. Brown

I had just taken my son to see the third Harry Potter movie—“Harry Potter and the Prisoner of Azkeban.” I had fallen in love with the whole Harry Potter series on the strength of seeing the Knight Bus for the first time. I have had a love affair with double-decker buses since I was a kid. I had seen this crazy British Rocker movie that featured a bunch of “kids” who seemed to live and travel around in a double-decker bus! Seemed like a cool lifestyle to me. Of course, double-deckers had been used in Manhattan a long time ago, but had been phased out after World War II. Then, in the mid-1970s when the Borough of Manhattan attempted to make use of British Leyland double-deckers—and for the same route in Manhattan they were famous for in the 1930s—I discovered that at 6’-3” I had out-grown my dreams...

Along comes Harry Potter and poof! there was the Knight Bus in all its electric purple glory—and not a ‘double’ but a triple-decker! Well if double-deckers barely fit in urban settings—triples surely did not. I learned that the filmmakers had to unbolt and bolt back the top sections of the pair of buses fabricated to even get them into the smaller center of London where various scenes were filmed.

But no matter! Off to the various kid shops to find what surely must be a wonderland of Harry Potter Knight Bus replicas... big, small, cheap and solid brass! Why the redoubtable Corgi toys—an English mainstay—must have a dozen versions alone!

After a painful scouring of the local shops and then a long internet search, I realized there was no Knight Bus toy. There was a horrid clunky and overwrought Bus that was a figurine carrying case. That was IT!?

How could the toy franchises that had flooded the market with enough Star Wars toys to cross a nerd-geek’s eyes, grind out a dozen Marvel Comic’s Classic Covers recreations and endless editions of Spider-Man and Hulk figurines doing pointless things have failed me?

But fail they did. So badly that Warner Brothers—the owners of the Harry Potter movie world—have changed their "amster" licensors. Harry Potter's Knight Bus is a slam-dunk idea that should have been high up on the list and may yet be. [Ed. Note: In late 2007, Cards, Inc. a division of Corgi International Ltd., did indeed start making “die cast metal collectable” Knight Buses. But I was first!]

While staring at the psychedelic colors of shelf upon shelf of crazy toys, I did note there were one heckuva lot of radio-controlled vehicles. Cheap too. I thought, that too, was an “obvious” KB toy idea—an r/c version that would scoot around just like the real thing. Resentment foamed up within me—I wanted this badly. I was muttering to myself by this point—at an altar of awful X-Men movie toys. How badly? I asked. Badly enough to make one yourself... ? Hmmm—the cheap r/c car body just popped right off the little r/c car. I did run a vacuum forming company after all... I was looking for interesting subjects...

I bought one of the r/c cars for study. Sketch time. After collecting every image of the Knight Bus off of the internet—which wasn’t much at the time, about 2004-- I figured out it would work. With a little fudging here and there—no interiors or solid window detail; painted windows using florescent paint; few surface details—yes, I could live with all of these.

The starting point was the unchangeable wheel base. Using that dimension to line up the wheels of the KB photos—I used Photoshop to stretch an oblique side-shot of the bus and the distinctive window pattern was snugged to fit. The few Photoshop tricks I knew served me well—who knows what I could do if I really knew that program!

Before… (this image grabbed from a Harry Potter fan site)

After… some Photoshop stretching.

These two shots show the “before” shot that was clear enough of the side to stretch into the “after” side shot. From this picture, I pulled enough proportions to get the distinctive window pattern onto the bus profile. You can see below, the much larger wheel wells and openings.

Using standard blocks of basswood from Micro-Mark, I spent a little time fitting the wood to the 1:1 drawings on my table-saw.

The three-view drawing along with solid basswood pieces laid out to the right sizes.

I then spent some time figuring out the one aspect that worried me about vacuum forming this shape. I really wanted the driver’s indentation in the shape. But that meant a severe undercut—the bane of vac-formers everywhere. The first thing that hit me was that the pattern needed to be made in two parts. While the giant indentation locked the front end of the bus into the plastic form, I could slip out the rear...

Here’s the indentation:

It’s been touched up with a little quick-setting plumber’s epoxy putty. You can just see the start of the vent holes drilled so that the vacuum can reach into this area. Will there be enough “suckage?” I did not know at that point.

Here are the two halves.

You can see an angled hole – I used a countersink bit for that -- to accept the longish sheet-rock screw so that the head sits flush to the bottom of the pattern.

Above: Here are the two pieces assembled—with the screw in place. The larger hole is the one that connects to the vent hole in the driver’s indentation area. Will it work!? I knew I would need a clean lower edge, so—below-- I built an additional riser of plywood to fit the base and also a beveled edge riser also made of ply. I traced the bottom of that intermediate riser for a line to follow. I tilted the blade of a very noisy jig-saw to 45° and made the cut free-hand. There was a lot of nerve-wracking vibration as the piece dropped out of its hole... I recommend ear protection as well as eye!

Here you can see the patterns with their risers. The bigger holes on the risers are for the vent connections to the vacuum table surface. There is quite a lot of screwing and un-screwing “procedure” for each “shot” or plastic forming session. So I made use of a small battery powered screwdriver. That also prevented over-tightening the screw into the wood each time.

It was time for a vac-former session. I selected some .030” styrene. I had used the risers to elevate the pattern because I knew there would be some webbing...

‘Webbing’ is when the plastic is asked to stretch or wrap itself too far. You can see a fine example of webbing in the pic below. The heated plastic-- which acts like limp balloon rubber—will at first stretch nicely between the pattern’s top and the frame. Then it is pulled down by the vacuum so that it “travels” all the way down the side of the pattern and then along the table top. This, together, adds up to a greater distance than that first, straight stretch. At this point, any of you mathematically-inclined might see an ordinary right triangle. The length of the two sides of the triangle are greater than the length of the hypotenuse.

The webbing shows up where it does, at the corners, because the distance from the corner of the pattern to the corner of the vac-forming table is greater than the distance from the middle of the pattern to the middle of the table. In other words, the corners are where the greatest demands are made on the plastic to stretch the furthest. Often, it just won’t do it!

The bevel or 45° angle is there to give the plastic an easier transition from that diagonal dimension to the table top. For small objects it works well. For something like the KB, which is very tall and thin, not so well.

Look at that useless mess! Yeeeoww-eewww...

There was not enough suckage to get the driver’s indentation either. Oh well, one problem at a time.

So, if one beveled riser is not enough, then how about two?

In this pic you can see the risers—no need to finish them—and the table top. I use masking tape to close off unnecessary vacuum holes. Not only to increase the power of the vacuum to the “area of influence” but also to leave a little suckage for the driver’s indentation.

Now will two risers work...

Hmmm. Better, but not good enough. A third beveled riser... No; I needed a better way—ah! Eliminate the risers altogether.

This time I believe that I solved the indentation suckage problem by directly hooking up the vacuum to the hole! Clever, huh?

Well... no indentation worth mentioning, but the body shape is formed! I did need to stabilize the two pattern parts. I built in another brass support.

You may note a little higher elevation of the pattern. This is one of big questions I get a lot, what height can you form to? The answer really involves the overall shape—but you can see that 7”+ can be easily dealt with.

This picture shows that I am using a very manual, old-fashioned film camera. I ripped the sprocket holes on this last film advance...

...making a nice double exposure! But you can see the successful form.

Since I was feeling listless, I felt I needed some quick satisfaction. So I cut out the body shape and planned to make the window pattern in it. I built a little work prop that would hold up the pattern so that I could work on the plastic – well, almost comfortably.

Here you can see the first transfer of the pattern. Yes—the art is flipped end-for-end to line up the construction lines. So that is the driver’s side window pattern where it doesn’t belong (As it turns out, that is a little door for the driver’s compartment. That driver is completely isolated from the passenger portion of the bus! New York City bus drivers have been cheek-by-jowl to their passengers for ever! But imagine what us New Yorkers would’ve done to that piece of glass that separates them from us over time... drawings, words, cut out pictures!)

I built a small angled jig to hold the pattern at a convenient angle to work on.

I found an architectural template that had the correct shape for the window—much easier! I ran a dissection needle (discarded from a kid’s microscope set) around the inside of the template to score a line. It was then easy to pick out the window. I was hoping to form again over this window pattern and give me a nice line to paint up to.

Here’s a little further on:

Above: This shows the wheel well shapes. When formed over again, I would use these as a guide for cutting out the openings. It was at this point that I cut out and shaped the front grill—you can just see the reference pic above the bus. I used a piece of .040” styrene cut and sanded to shape. (You can just see it in the picture below, peeking out around the oven mitt and plug shape.)

Now, the problem of the driver’s indentation. I took some of that epoxy putty (very useful stuff! Made by Oatey and available at Lowe’s and Home Depot in the plumbing section. At 4 ounces for about $5 it is relatively cheap. Do not be mislead by the “15 minute” working time claim—it is more like 5! But within that time you can get a lot of quickee shapes done and water-smooth them too. Immediate wash-up is a must!) and poked it into that indentation—I had a short piece of brass handy to use as a handle. As sticky as that stuff can be—I used a small piece of “Saran Wrap”—like material to act as a barrier between it and the pattern. When the epoxy had hardened, the Saran Wrap just peeled right off.

Here’s a test shot to see if my “window” concept worked. I planned on simply dumping some paint, letting the slight raised pattern guide the paint... well, this part of it worked! It looked good.

Now that darned driver’s indentation problem. It soon occurred to me that I would need to work a lot quicker than leaving the forming tool to one side. I would need to hold the tool in my mitted hand while I was forming... took a bit of thinking to get it, but:

Yes, that pizza-colored ratty shape to the left is The Kingston Vacuum Works oven mitt. The “UP” is placed there, because you do not want to waste even a second stuffing that forming tool in. As you can see, it worked. Below, you can see the pieces all taken apart. This is the first test shot to make sure things look good before I go on and make the rest. You can spot the front grille work—simply applied to the “outline” form. That shape should easily receive some black paint. I was looking for “easy” in most of this project!

Here’s what taking apart the two-part pattern looks like:

One side of the pattern is half-pulled out by the screw—it was a tough pull.

Each forming shot was fairly tedious, requiring that the pattern be assembled, formed over, “indented” and taken apart each time. It added quite a lot of time to what is normally a very quick process. I must admit this is a bit further than I get with most of my kooky projects, so here is the fleet!

Here is a wider shot, showing all the pieces and parts up to this point:

I then decided to prepare all the bodies so they would fit the r/c chassis.

Here is a close-up, below, of the interior bracing that also provided a way to hold up the body for priming and doing the body color. By cutting a slot into the long piece of plastic, I could manipulate the body without touching it.

It is a shot like this one below, that reminds me that I really did finish something. This was great progress. The car body that came with the r/c “guts” popped right off and my little effort…

…popped right on! Very exciting at this point.

These are quite excellent little devices—they do it all! Steer, go backwards—their only slight drawback is that they only have one speed. Crazy fast! However, perfect for Harry Potter's Knight Bus! You can see below that there a small blocks added to attach the body to the car chassis.

I made a jig out of some scrap plywood to hold up the whole fleet for painting. To prevent them from falling over or sliding, the jig had to be fairly tight. I would also be moving this thing around. Below, is the interior of my inadequate, underpowered spray booth. For future reference—if you’re making your own, it is considered a minimum requirement to have 100 cubic feet per minute of fan/blower for every square foot of booth opening. The fan should also be a “squirrel cage” type or some other type with the motor enclosed to prevent explosive gasses from possibly being exposed to a spark! Now my booth opening is 2 feet by 4—pretty big. I should have an 800 cubic foot per minute fan! For the most part, the paint stuff goes up and out. I used a conventional “box fan” before I learned of the proper ratio of fan to area… So, some of it backs up into the house—ticking off the normally patient wife. In the summer time, I can “over-pressure” the whole house with window fans and that helps a lot. In the winter, I wait till no one’s home…

Here is a line up of primered bodies. I use Krylon brand auto-body spray paints. They’re mostly formulated for fiberglass body parts and so “give” a little. I was not planning to sand this project (a plus!), but when needed, this paint can be sanded to a glass finish. It also fills in light scratches, comes in black and white as well as this useful shade of gray.

Here’s my beauties! I used the color “Grape Pearl” from the line of “Colors by Boyd” specialty auto body paints (manufactured by Testors for automobile modelers—and us!). These paints are a “kooky” range of extra-spectrum pigments that seem to have some fluorescent qualities mixed in. These paints answer the need to replicate the wild colors applied to cars in the 50s and 60s. But Grape Pearl seemed to match Harry Potter's Knight Bus as closely as the description, “violently purple” by the good Ms. Rowling could, in real life.

After briefly considering making the body in clear and installing yellow LEDs, I decided I wanted to finish this project within my lifetime. I also considered making a paint mask—but I could not see how to peel it up so it could be used on all the buses—nor what to make it out of. Nope, I painted all the windows by hand. But that neat, inner glow; what to do? I looked around and finally bought some Testors flourescent yellow.

I then made this little brace (table-like thing shown below) with which to hold the bus still while I moved all around it. The human hand has preferential arcs that it easily moves in. The smoothest motions of a brush are along those natural arcs. So by making this thing, I could move the bus all around and paint where the window fell under my brush. This simple jig just held the bus in a little opening so that I could work on all the windows while some were drying.

You can see a small piece of Masonite board, which is supported above the window. I would rest my hand on that Masonite.

Below, you can see the working surface, looking “up” into the bus. This level was adjusted and held in place with a wide-jawed Vice-Grip. The low-tack tape holds everything firmly, but not permanently.

The part of the process that I did not photograph was the making of the signage. I used Illustrator to accurately place the type for the small signs on the bus. Using an art program allowed me to measure the height and width of the areas needed. I probably could have used MS Word or any other word processing program to do the same thing.

I simply printed the signs out on clear sticky label material. By using clear, I could put a layer of flourescent yellow where the signs where and thus imitate their being lit up from within, just as the bus is. The type was whatever was not too jarring at that size. It was not really related to what was used on the real bus.

Here is a blow up of the three bits of signs that are in several places on Harry Potter's Knight Bus. They are legible on the bus—which is a tribute to Adobe Illustrator driving a Hewlet-Packard inkjet printer! Of course, I stacked up many of these on the original and ran out a few copies.

The final painting step for the body was to seal it all with a clear satin finish from Testors.

The last body detail was to use a blindingly purple Sharpie marker to go over the wheel rims. This was very satisfying as it was the end!

This is what the “Micro Blast” toy looked like: it came with a nice controller and a recharging platform. You get about 30-40 seconds of hard-driving around and then park it on the charger for a very quick charge and you’re ready to go again. Neat. Also in this shot, is The Knight Bus body.

It was a little time-consuming to cut out and apply all the signage. But the results were very much worth it. I used a master template to make sure that all the cut outs were as uniform as I could make them. I used a fresh #11 X-Acto blade so as to only cut once!

There you have my trip into toy land. I boxed up the best-looking one and its controller with some simple instructions on how to pull things apart or put them back together—and sent it off to J. K. Rowling’s publishers. I would let them decide if they could send it on to her. Not too long after I got a very nice note from one of Jo’s assistants, who thanked me.

I also sent one to a dear friend who is a thorough-going Potter fanatic and who brought her Knight Bus out to each subsequent Potter book’s midnight release. She lets everybody have a spin around the floor. Now that’s a magical toy!

Final Note:

Just so you know—The Knight Bus and Harry Potter publishing rights are © J. K. Rowling and that and everything else Potter is TM and © Warner Bros. Entertainment Inc.

This article and its photographs unless otherwise noted, are © Eliot R. Brown and The Kingston Vacuum Works.