Introduction: MoonPi, the Rain Barrel Kids Play Rocket
Just after Halloween, my 3 year old daughter came to me and announced she wanted to be an astronaut and fly to the moon! She kept talking about flying a rocket to the moon for days on end, so naturally, I started thinking of ways to make her dream come true.
Her rocket is a former rain barrel (former food container technically), with flight controls and a Raspberry Pi2 model B combined with an Adafruit 2.8" touch screen hooked up to push buttons that select different space related video files to play.
I give you, MoonPi, the rain barrel kids play rocket!
List of materials
- Rain barrel (large enough in size for kids to get inside)
- Raspberry Pi (for the flight computer)
- Adafruit PiTFT 2.8" (320x240) touchscreen
- 4 momentary, normally open, LED illuminated push buttons (selecting the video file to play)
- 1 LED illuminated switch (power on/off for the Pi)
- Selection of jumper wires (to connect the switches to the GPIO Pi pins)
- Truck/boat trim (approx. 13' in length)
- Fishing boat seat
- 2' square plywood sheets 1/2" thick x2 (front and rear bulkheads)
- 4 pine boards, approx. 22" x 10" x 3/4" (tail stabilizer fins)
- 4 pine boards, approx. 14" x 8" x 1.5" (barrel anti-roll launch pad feet)
- assorted lengths of 2" x 4" to act as seat rails, and the steering wheel
- Liquid tight electrical conduit
- Small speaker w/built in amp. USB powered
- Avionics themed coasters
- Play steering wheel
- Assortment of screws and washers (lots)
- Black spray paint
- Grey spray paint
- Yellow spray paint
- Electrical box (plastic)
- Keystone RJ45 jack and matching single port face plate
- USB cable, long enough to reach from the engine end of the barrel to the PI in the front
- Cat5e network cable, long enough to reach from the engine end of the barrel to the Pi in the front
- Battery supplying 5vDC up to 2A
Step 1: Acquiring Donkey Kong's Barrel
Grab your hammer Mario! Forget the princess (she's in another castle anyways), we're off to get a rain barrel!
Finding an appropriately sized rain barrel was fairly easy.
There are many farm and garden supply stores in the area and they carry barrels of all different sizes.
One thing that may save you money (thanks to the sales woman at the store I went to), I had no use for the debris screen and spigot since I was going to be cutting a large hole in my barrel and it will never hold any water. She sold me a barrel that had not had these parts installed yet for a fraction of the price of a fully armed and operational rain barrel.
Cost was about $20 Canadian.
Be sure it includes the solid top cap, we need to mount the rocket engine to it as well make a space to hide the power pack and network connection.
I learned that barrels of this nature are usually former food stuffs shipping containers. This fact became obvious when I opened mine up and got a whiff of pickles. Nice to know they weren't used to store PCB's or worse yet... broccoli! Oh wait...
I used a lot of dish soap and stiff bristle brush to scrub inside and out, then hit it with a commercial steamer, then more soap and brushing to be sure the smell was gone and it was in fact clean since it was going to be inside and played with by kids.
It took an entire day of washing, scrubbing, letting it sit with soap in it, steam, rinse, repeat. But in the end, it was good as new.
Step 2: It Slices, It Dices! It Makes Cockpits in Rainbarrels!
With my squeaky clean rain barrel home, the next step was to sketch and cut the opening.
I wanted to make it large enough for a 3 year old to get inside with room to spare, but also retain the rigidity of the plastic barrel so it didn't fold in on itself under a child's weight.
The barrel I picked up had two 'ribs' molded into the plastic (seen in the photo) that add to the structural integrity. On the outside edge of each rib the barrel flares out before continuing to the rounded top and bottom providing even more rigidity.
I used a large rectangular piece of drawing paper that was about the size of the opening I wanted to make, folded it on itself twice (once horizontally, once vertically), then cut the 4 paper together corner to be have a rounded edge. Unfold the paper and all four corners are now rounded (who remembers cutting out snowflakes in elementary school art class using this technique). :)
I taped the paper to the barrel where I wanted the hole and traced the paper's edge with a wide tip marker, getting part of the mark on the paper and part on the barrel's plastic.
Now that I have a cut line, it was a simple matter of drilling a few pilot holes and then cutting along the lines with a jigsaw.
The plastic cut very well, but the plastic "sawdust" makes one heck of a mess. I recommend cutting outdoors.
Step 3: Building Spaceworthy Bulkheads
With the cockpit hole cut, the next step was to cut and place two bulkheads into the ends of the barrel.
The front (originally top) of the barrel's bulkhead would become the control panel and the back (originally bottom) bulkhead would provide a back stop as well as keep hands off the power supply and network jack that will be located on the other side.
I love Pie, but Pi works better to figure this out...
The barrel's circumference is approx. 69.15"
So, 69.15" ÷ 3.141 = 22"
Now we know the diameter of the two circular bulkheads. Next we need to mark out the cut line on each piece of 2' square plywood.
A neat trick for making a perfect circle on a piece of wood:
- Find the center of the SQUARE piece of wood by using a straightedge and drawing a line from opposite corner to corner.
- Where the lines intersect is the center.
- Since we know the diameter of the circle is 22" we can divide that in half and get the radius of 11".
- Find a scrap piece of thin wood, or stiff cardboard.
- Cut it to 13" or 14" long.
- Drill a pencil sized hole close to one end of this scrap (card)board, in the middle.
- Measure from that hole, in 11" and make another mark in the middle.
- Drill a hole here, sized for a small nail.
- Place a nail through this hole and hammer it slightly (not all the way through) into the exact center of the 2' wood we need to make our circle on.
- You now have a rotary arm that, if a pencil is placed at the outer hole and the arm is rotated around, will etch a perfect 22" circle on your wood.
- This will become the unseen backside of the piece, since it will have a small nail hold in the center (if that matters).
Once the cut line is drawn, use a jigsaw to cut out your front and back bulkheads.
A quick sanding of the edge to remove any roughness and we're onto the next step!
You can see in the photo that the circle fits perfectly inside the barrel and as a nice bonus, if you stand the barrel up the bulkhead will lay flat and rest on the barrel's sides where they round inwards. Remember this when it comes time to secure the bulkheads to the barrel. :)
As Al Bundy once said, "There ain't no mix up a sander can't fix up".
Step 4: Adding a Window to the Interwebs and Beyond!
With the scent of freshly cut pine still lingering in the garage air, it's time to create the screen opening for our Raspberry Pi with the attached Adafruit 2.8" touchscreen and 5 circular push button controls.
The Pi itself will attach to the backside of the wood, while the touchscreen will extend about halfway through the opening.
The buttons will sit tight in holes drilled around the Pi display and be secured to the wood using their included nut from the backside.
The screen is protected by a piece of custom cut clear acrylic inset to be flush with the surface of the wood using a rabbet bit in a plunge router.
Measure out the screen itself (not he attached circuit board underneath it) and mark the dimensions on the wood wherever you want it to be. Mine is in the upper center of the "console" bulkhead.
Drill some pilot holes and cut out the inside of the screen marks.
I got to purchase a shiny new Freud rabbeting bit with several interchangeable bearing sizes for this project (that's my excuse anyways).
Select the bearing to use depending on the amount of rabbeting you want. I didn't need much since it was just to have somewhere for the acrylic to attach to.
Set the depth of the plunge router to the width of the acrylic sheet you have. That way it will lay flush with the wood once in place.
Remember, the corners of your route will be round, as is the nature of the spinning bit, so you will need to cut and file your acrylic to match.
For the buttons, I opted to space them evenly with two on each side of the screen. The power on/off switch is located at the top center.
All the buttons I purchased were the same diameter, so I was able to measure and mark out the spacing fairly quickly and then zip the holes into the wood with my drill press.
I powered the Pi with a USB equipped cellphone charger battery pack located in the rear of the rocket. Left playing videos on a full charge it ran for over 9 hours straight. There is also an Ethernet jack that runs from the rear up to the network port on the Pi to make it easy to SSH in and change the video files up.
I used a length of 1" diameter liquid tight electrical conduit to run both the USB power cable and the Cat5e network cable from the back to the Pi in the front. The conduit runs out the rear bulkhead, down the right hand side of the rocket, then into the front control bulkhead through 1" holes in the wood. Be sure to save yourself some headache and drill those two conduit holes before painting and mounting the electronics... unlike I did. lol
Remember to check and make sure that where you are mounting buttons won't be in the way of the Pi or it's connection ports once everything is attached to the backside of the board!
Now that all the cuts and made and holes have been drilled, it's time to give it a sanding to remove the rough edges and then paint the wood before attaching any of the electronic components.
Give the paint ample time to dry before handling. Nothing worse having fingerprints in nearly dry paint (trust me)!
Step 5: Avionics on the Rocks
With the cockpit control bulkhead all cut and painted (and dry), we can start mounting the electronics and other components that will provide flight data to our astronaut hero!
I mounted the Pi in a layered plastic case, partially to protect it but also to give me something to secure the Pi to the wood with other then the bare circuit board, but mostly because this case was the cheapest at the time to allowed space for the Adafruit screen.
The Adafruit 2.8" screen sits on top of the pi, directly connected to the GPIO header. The screen itself fits into the display hole you cut in the previous step.
I used a marker and wrote on the surrounding wood where they go & what they do for all the wires, since I won't remember down the road when I might have to fix something. I'm sure NASA does the same thing...
Be sure to write down the GPIO pins you are using for the trigger buttons so you can write your Python code to reflect this later, else you have to take the front bulkhead apart again to see (or a lot of trial and error polling GPIO's)!
The Pi is powered by a USB cable coming from the other end of the rocket, through a liquid tight conduit, along with the network cable.
Be sure to put a little dab of PL on the connections to ensure it can't come loose after the fact!
The avionics are actually specialty drink coasters meant for pilots and aircraft enthusiasts.
The displays in them are actually a good quality plastic, not paper stickers. I went with the vintage set of 6, but the company makes many different designs and even some replicas of specific real world aircraft.
Plus, they were made in Canada. :)
I removed the soft foam backing from each of the coasters (so they can't be torn off by little hands) and measured out for even/level mounting. I used PL adhesive and a lot of clamps to secure the coasters a few at a time to the bulkhead.
It only takes a few hours of curing time to get a good strong PL joint with something this lightweight.
The steering wheel is actually from an outdoor playground set. It was about $11 at a hardware store.
You could recycle an old GT toboggan wheel or video game flight simulator yolk too.
The steering wheel was easy to install, I just attached a scrap block of 2"x4" to the backside of the bulkhead, drilled through the bulkhead and into the block with a bit of slightly less diameter then the center mounting screw included with the steering wheel, threaded it in and tested it by spinning the wheel and making rocket engine blastoff noises.
Again, straight out of the Saturn V engineer's handbook... BRRRRRRWWWWWWOSH!
The final part of this step was to fill in the seam around the screen and wood for the display screen.
I used painters tape to create an even space around the screen edge and the rabbeted ledge. I used a tube of black caulking and smoothed it with my finger. Once done, I removed the painters tape, taking all the over spread caulk with it.
Nice clean lines, and no unsightly seam between the screen edge and the wood.
Wait for the caulk to cure before securing your cut acrylic to the rabbet.
You can see an orange amplified speaker in the photo of the backside of the bulkhead. This is powered via the USB port on the Pi and gets it's audio directly from the Pi's 3.5mm audio jack.
I wanted a tiny speaker grill to put over top of it on the good display side of the bulkhead, but I couldn't find one small enough, so I just re purposed a small floor drain cover.
Step 6: Houston, We Have No Problem With Our Wooden Stabilizer Fins...
To give the rocket some speed and stability (and keep it from rolling over on it's side) I built 4 stabilizer feet to keep it from rolling, and 4 tail fins, because they look cool. :)
For the tail fins...
I matched the curvature of the attachment edge with the barrel, then drew out a purely aesthetic shape for them.
I used my trusty rabbet router bit to put a nice edge on both sides of the board, then used the first finished tail fin as a traceable template for the other 3.
The tail fins were attached inside the (originally top) rear of the barrel using a line of PL and multiple wood screws with washers to spread the pressure of their heads out over the surrounding barrel plastic.
Getting into this space was a trick if you have bigger hands. A stubby Robertson screwdriver is a must.
The stabilizer feet...
The feet were made in a similar manner.
One side of the wood block cut to match the curvature of the barrel and then the other three sides styled to try and appear 'spacey' and launchpad-ish. They act like permanent wheel chocks.
The holes drilled in them are purely for aesthetics. I figured more holes = more speed... These are speed holes...
I was on a roll with the rabbet bit, so they received the edging treatment too.
The feet were attached from the inside with long wood screws and washers.
Because they don't extend far from barrel's body and there is no forward / reverse movement, I didn't connect each side together to stop twisting. So far so good.
The stabilizer feet were painted a grey colour, and the tail fins sunshine yellow.
The best way I've found to spray paint something that requires coverage on all sides is to screw a small eyelet into an edge that will be hidden, then hand the piece from the eyelet so you can get to all sides.
Spray the piece over time with multiple thin coats instead of thick drippy coats and leave it hanging to dry.
Step 7: I'm Stuck on You... Customizing Your Custom Rocket
I wanted to decorate the rocket's body and tail fins with various space related imagery.
I thought about buying some printer labels and making my own stickers, but they probably wouldn't stick well to the rain barrel plastic.
I remember from the 1980's the craze of decoupage (especially of notebooks) using a product called Mod Podge.
Basically, it's an adhesive and sealer for paper or fabric and it's non-toxic. Perfect! The 80's shows us the way once again! Go Cyndi Lauper!
I found a wide selection of space related images and printed them off on a colour laser. I spent countless hours cutting out all the intricate little nooks and crannies of each paper print.
I purchased a bottle of the heavy duty hardening version of the Mod Podge product and a cheap foam applicator brush. Any craft store will carry this stuff.
Basically, you just use it like glue, so coat the backside of one of the prints, place it on the rocket body or painted wood somewhere, then apply coat after coat after coat onto the image itself to build up a protective layer giving about 10 to 15 minutes to dry between coats.
I was surprised how well this worked. Especially on the rocket's body, where I didn't think anything would stick for long.
I will be using this in the future for other projects requiring custom decals on non-sticky-cooperative surfaces.
Or maybe my wife's car... I'm sure she would love a big Planet Express logo on her hood!
Booya, she is going to be sooo surprised on her next birthday...
Step 8: Trim Out Your Ride and Impress the Moon Maidens
The cut edge of the rain barrel, once filed down, isn't sharp, but it is unsightly.
I found a source for 14' of hard rubber truck/boat edge trim with metal molding stiffeners built in.
It worked perfectly on the edge, bending and forming to the curves of the rain barrel cuts. Some of the curves were at a fairly sharp angle too, but no issues.
I wondered about using a little PL to secure the trim to the edge, but so far the kids haven't pulled it off or had it fall off by accident. It's still an option if it becomes an issue, but so far so good.
I used side cutters to snip off the remaining tail with no issue.
Installing the front and back bulkheads
I should also mention that at this point I installed the front control bulkhead and the rear.
I stood the barrel on it's (original) end and let the back painted bulkhead fall into place. Some gentle pushing to seat it down as far as the barrel's curvature will allow making sure it's level, then a whole slew of 1" wood screws running all the way around (you can see some in the photos).
If you wanted to get fancy, you could make them look like rivets.
I flipped the barrel and repeated the process for the front bulkhead. This one was a little trickier, since the liquid tight conduit was dangling out the front of it.
Be sure to connect the USB power tot he Pi and the network cable to the network port before closing up!
Once in place, a ring of wood screws held it in place, and the conduit can be feed into the back bulkhead's 1" hole to complete the power and network cable path.
A few GNDN identification decals never hurt either...
Step 9: Sure It Seats 1 and Travels at 11.2KM/second, But Does It Have Airbags?
I played with ideas for the actual seat but the best I could come up with was using a fishing boat seat.
I kindly had offers from a few friends who had old ones from boats long scuttled, but the problem was... they were boat seats.
They had ripped fabric, water logged foam and smelt like boat gas.
Very kind offers, but not something I wanted in a kids plaything.
You can pick up a new basic boat seat for about $30 to $100 Canadian depending on the quality, material, size and features.
This one was on sale for around $60 if I remember correctly (or my wife asks). :)
The width of the seat vs the curvature of the barrel sides made it sit elevated by a few inches above the lowest point of the barrel "floor".
I used a 2" x 4" on it's edge as the main attachment point and a square piece of scrap plywood for the attachment on the seat itself.
The plywood is attached to the seat using the manufactures supplied bolts and existing builtin points.
I just had to measure the attachment points and transfer the pattern to the plywood.
This worked well for attaching the seat so it couldn't pull out, but each side needed support as well so if a child stood on one side, it didn't twist the seat and snap it off the 2" x 4".
I ran a piece of strapping down each of the sides, at the height where it will support the seat edges and keep it from tilting.
Each of the pieces of strapping and the 2" x 4" are attached to the barrel using wood screws and washers. The wood screws attaching the 2" x 4" are quite long, and actually extend all the way through the 2" x 4" and into the seat attachment plywood.
You can see the bolt pattern for the seat supports in the photo of the underside of the barrel.
Step 10: Fine Tuning the Precision Engine
The engine nozzle itself is made from a piece of HVAC pipe.
I removed the sharp edge of the seem using a file, screwed a circular piece of wood into the center at the tip, then spray painted the whole thing black using the rubber spray paint left over from my ApplePi vintage Macintosh instructable.
The circular piece of wood inside is to keep it from crushing under the exploratory weight of a kid and it also gave me a place to Mod Podge my super amazing engine flame sticker. BRRRRRRWWWWWWOSH!
The engine is attached to the barrel lid using PL.
Once the PL had cured, I masked off the lid plastic (see photo) and then painted the PL black to help disguise it.
Behind the rocket engine you can find the battery power source and the network port for the Raspberry Pi.
SSH is enabled on the Pi, so anytime I want to change the videos that play with the 4 buttons, it's a simple matter of plugging the Pi into the home network and loading on new video files.
Step 11: Blast Off!
The big reveal was Christmas morning, 2015...
This is what building your own toy projects is all about!
The huge smiles and hours of adventure play the MoonPi Rocket has received can't be beat.
Just so long as daddy doesn't have to wear a red shirt and go on a landing party mission...
Thanks for reading!
Please feel free to contact me with any questions or suggestions on any aspect of this project!