How to Make a Quick-and-Easy Water Rocket (Science Project)

How to Make a Quick-and-Easy Water Rocket (Science Project)

Although store-bought water rockets were once an almost universal part of childhood (at least in suburban middle America, where I grew up), DIY water rockets are almost unheard of in the United States, despite being common in the United Kingdom. The key to the DIY water rocket is the ubiquitous plastic soda bottle. (Often called PET bottles in the UK, these are basically made of polyester, just like your favorite pantsuit.) A soda bottle can easily withstand 150 pounds of pressure per square inch—significantly more than a car or bike tire, and more than enough to launch it into flight.

The following design dispenses with many of the concerns regarding valves, firing mechanisms, pressurization, and so on, because the unit is impossible to over-pressurize, thus eliminating the risk of a rocket explosion. It’s quick and easy (no more than 5 minutes to construct), practically free, fun to make and launch with your kids (while teaching them some basic principles of physics), and, depending on the quality of your bike pump, can arc a bottle 30 feet at speeds safe enough to shoot at your pals, or send a rocket soaring a hundred feet skyward.

What You’ll Need

Figure 1: A finished quick-n-easy water rocket and launch tube

Tools

• an electric drill with 1/4″ and 3/8″ bits
• a utility knife
• a ruler
• a pen
• a bike pump

Supplies

• a wine cork (A used cork is fine; if you’re buying new, a #9 straight wine cork provides a tight fit.)
• an old tire stem from a bike or car tire
• one or more 20 oz water or soda bottles
• a section of tube wide enough to accommodate your bottles (such as a 3″ cardboard mailing tube, or an oatmeal, potato chip, or snack can)
• a thin dowel or garden stake
• duct tape

Figure 2: Tools and supplies

How to Build and Launch Your Water Rocket

Step 1: Start by acquiring a tire stem. Tire stores usually have lots of used stems lying around, since the old stems are discarded when new tires are installed. These shops are very frequently staffed by young fathers who will think building a water rocket sounds awesome, and will be eager to give you as many stems as you need. Make sure to tell them that “broken stems are OK”—a broken stem is one that’s had its bulbous end snapped off (you can see this round end on the top of the stem on the left of Figure 3); broken stems work just fine. Alternately, head to a bike shop, where lots of leaky bike tire inner tubes are probably on hand. A car tire stem is a separate unit from the tire and the perfect dimensions for a soda bottle water rocket, while bike tire stems are integrated with the tube and will need to be cut loose. If you’re using a bike tire stem (shown at the right in Figure 3), cut away all of the surrounding rubber.

Figure 3: A car tire stem (left) and bike tire stem (right); most of the inner tube has been cut away from the bike stem.

Step 2: To build your launch plug, cut the cork in half, and then drill a hole through the middle to accommodate the tire stem. Cork is a little trickier to work than other woods, since it tends to tear apart. Running the drill fast, start by drilling a 1/4″ hole. If you’re using a bike tire stem (which is a bit narrow), this should be fine (although you’ll likely need to generously ream the hole, or even bump up to the 19/64 bit. For a car tire stem, switch to the 3/8″ bit to expand the hole. In either case, the cork will offer a very snug fit (important for pressurizing the bottle). Test to see which end of your cork fits best into the bottle you have, and measure 1/8″ from that end of the cork. Mark this “safe point” (which I’ll explain later).

Step 3: Insert the threaded end of the tire stem into the “safe point” end of the cork, and push it through. Twisting as you go will help you work it into the cork. All of the brass threads should be pushed entirely through the cork, as shown in Figure 4. (You can use a utility knife to trim down the cork if it ends up being a little too long.)

Figure 4: The completed launch plug (note the line marking the “safe point”)

Step 4: Set your launch plug aside and build the launch tube. Cut a 7″ length from the mailing tube, and duct tape the garden stake to its side. (For a more permanent launch tube, consider using a piece of 3″ diameter PVC, and securing the stake with a pair of #44 hose clamps.)

Step 5: You’re ready to launch! Head outside with your bottles, launch tube, launch plug, bike pump, and a jug of water. Stick the launch tube stake in the ground so that the tube is at a roughly 45-degree angle, with enough open room at the bottom for you to attach the bike pump.

Step 6: Fill the bottle 1/3 full with water, and then stick the launch plug in the mouth of the bottle, so that the threaded end of the valve stem sticks out. Insert the plug only as far as the “safe point” you marked in step 2.

Step 7: Slide the rocket into the launch tube, connect the pump to the valve stem (Figure 5), and start pumping vigorously. After a dozen or so pumps (depending on the quality of your pump) the cork will pop and the rocket will go spraying across the yard, clearing at least 20′.

Figure 5: Ready to launch!

Water rockets launched with the plug inserted to the “safe point” and powered by normal hand-pumped bike pumps are pretty safe and suitable for a mortar-style water rocket duel: combatants work in teams—a gunner and a loader—situated at least 15′ to 20′ apart. Armed with a stockpile of empty bottles and water, the two teams blast away at each other until they grow bored or hungry. It’s more fun than a squirt gun fight, and less dangerous than a bottle rocket fight.

Building a Better Rocket

Because the force driving the rocket depends on the pressure of the water spewing out the back, you can improve flight time and distance in two ways: increase the pressure in the bottle or make the water transfer momentum more efficiently.

Start by experimenting with driving the cork farther into the bottle and using different launch angles. A deeper cork requires more pressure to pop, so you can expect longer flights. The limiting factor here is your pump; any old pump will be able to launch a rocket whose plug is inserted only to the “safe point,” but as you drive the cork deeper, you’ll need more pressure.

If you’re using a very cheap bike pump, the back pressure can overwhelm the seals on the pump before the rocket launches. If the water is spraying out of the pump and onto your cuffs, it’s safe to assume you won’t see a lift-off with that setup. If you experience such a launch failure, grab hold of the pump’s valve and the launch plug. Then, without leaning over the launch tube (you don’t want to catch even a low-power water rocket in the face), reach down and grab the end of the bottle, jerking it off the cork. Water will spray everywhere.

Predictably, if a better hand pump gives better launches, then an electric compressor (shown in Figure 6) will be pretty awesome—higher, longer flights; shorter pressurization times; less effort; and more noise. That said, Do not shoot a rocket at your pal if you’re using an air compressor!Someone could lose an eye or a tooth.

Figure 6: An electric air compressor

You can also experiment with making the water a more efficient working mass for accelerating your rocket. In terms of volume, this is a case of “less is more;” although having too little water means a disappointing thrust, too much water makes the rocket too heavy to overcome the weight of its own fuel. Denser propellant, on the other hand, will give you greater thrust (because it will transfer more momentum) without increasing the “burn time” (the amount of time it takes to vacate the heavy fuel, which is weighing down your rocket). You can make the water denser by adding dish soap or salt.

Of course, you can also improve the rockets themselves, as shown in Figure 7. The most obvious way is to move up to a larger size soda bottle. Regardless of bottle size, though, if you’re interested in maximizing height, you can add a simple nose cone and stabilizing tail (the nose cone is cut from the top of an identical bottle and glued in place). Keep in mind that adding a tail may necessitate using a screw-on valve stem extension to connect the launch plug to the pump. Auto supply stores sell these extensions for less than $10; they can be handy if you need to check the pressure on a wheel with a fancy rim, or if you want to top off your spare without unbolting it from its storage cubby.

 

Figure 7: A pair of improved rockets with nose cones and tails (left), and a detail shot showing the cut-aways on the tail of the smaller rocket (right).

Editor’s note: This is a guest post from David Erik Nelson, author of Snip, Burn, Solder, Shred: Seriously Geeky Stuff to Make with Your Kids.

How to Make an Olive Oil Lamp

How to Make an Olive Oil Lamp

Olive oil is a very useful product in the kitchen, but you can also use it as a fuel source. In ancient times, certain grades and varieties of olive oil were used to light up rooms and houses. If you want to go green and use an alternative fuel as a light source, here’s how you can make an olive oil lamp. (Want to know other uses for olive oil, read 13 practical uses for olive oil)

Why Use Olive Oil?

For thousands of years, people have used olive oil as a way to flavor food, but also as a source of light and heat. Among Jews, Eastern Orthodox Christians, and Muslims, olive oil is considered sacred. It is used in many religious rituals and ceremonies as a fuel for lights, lamps, and lanterns. Olive oil has a very high flash point (190 degrees Celsius for virgin oil, and 210 degrees Celsius for refined oil), which means it does not burn as easily as other vegetable-based oils. Olive oil is also odorless when burned, although you can add other aromatics like herbs to give the burning oil a pleasant scent.

While olive oil used for cooking may be used for lamps, certain grades of oil may be used for lighting purposes:
Lampanate oils are a grade of olive oil used exclusively for burning. Lampanate oils are not fit for cooking or human consumption.
Aged oils. Old batches of olive oil can be used for some recipes in the kitchen, but they’re a cheaper source of fuel for oil lamps than extra virgin olive oil. Aged oils also have a higher smoke point.
Rancid oils. Instead of throwing away rancid batches of olive oil, you can still use it as a fuel for olive oil lamps. The fuel itself may smell bad, but the burning oil will not release any unpleasant smell.
Things You’ll Need

To make an olive oil lamp, you need the following tools and materials:
Glass jar
Craft wire (the length must be at least twice the height of the jar)
Wick (you can buy wicks from an arts-and-crafts supply store, or you can make an improvised wick from scraps and strips of long-weave cotton cloth)
Long-nosed pliers
Olive oil
Steps

To make an olive oil lamp, follow these steps:
To make the wick holder, make a J-shape from the craft wire. Shape the wire so that you have a flat base for the wire to rest, a small hook at the end to hold the wick, and a larger hook at the other end to prop and secure it to the rim of the jar. The hook for the wick should be at least an inch high from the bottom of the jar.
Thread one end of a wick or other wicking material into the coil. At least a quarter inch of the wick must be above the surface of the oil when you fill the jar. That way, you don’t risk burning the oil or smothering the flame.
Fill the jar with olive oil, making sure that you leave enough room for the exposed quarter inch of the wick.
Allow the wick to absorb as much of the oil as it can before lighting it.

If you want a scented olive oil lamp, try adding some aromatic flowers and herbs to the oil. Remember that once you have used a batch of olive oil for lighting or fuel, you shouldn’t use the same batch for cooking or flavoring your food.

Watch The Video

Bushcraft Oil Lamp

Go Green and Burn Olive Oil in Oil Lamps

How to Build a Mouse Trap Car

How to Build a Mouse Trap Car

Introduction

Toy cars can be a lot of fun to build, but most of them involve the use of some hard-to-come-by materials and tools that can be difficult to use. Not so for a mouse trap car though, as you can make one in as little time as a couple of hours. They are perfect for racers, as they are self-powered. Moreover, most mouse trap cars only cost a few dollars to build (as long as you have the necessary tools around your garage). So, if you want to build your own toy car, but have no idea where to begin, the mouse trap car may be perfect for you.

The Power behind the Design

Mouse trap cars are so much fun because they come with their own power supply built right in – the mouse trap itself. Specifically the spring on the trap. By using a string to harness the power of the spring, you can easily drive the wheels of your mouse trap car. Almost all mouse trap cars use the same principal to operate, but the car described below was chosen for this guide because it is very easy to build. After making this car, you can try out your own designs using the same propulsion mechanisms outlined here. You can create almost any design you can imagine with a simple mouse trap and a few wheels.

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Materials

You need the following materials to build your mouse trap car:

• A mouse trap (of course).
• Two metal rods that are each 4 mm in diameter and 15 mm longer in length than the width of the mouse trap you are using for the car. These rods will act as the axles for the car.
• Four eyehole screws that are barely large enough to put the metal rods through.
• Plywood or any other type of thinly cut wood for the wheels.
• Two rubber bands.
• String.
• Washers with an inner diameter of 4 mm.

Tools

While the materials for a mouse trap car are easy to come by, you may not have all of the a tools necessary. To build the car, you will need the following tools:

• Drill with a 3.7 mm drill bit.
• Jigsaw (a coping saw will also work).
• Compass to make a template for the wheels.
• Hammer.
• Vice.
• Hacksaw.
• Wood file.
• Wood glue or super glue.
• Epoxy (the type of glue that comes in two parts which you mix together).
• Plies.
• A small Jeweler’s File.

Building The Body

To begin construction, you need to use your pliers to pull the wire that holds the mouse trap open out of the trap. Also remove the bait holder, as this part is not necessary. Keep the wire catch to the side though, you will use it later. Also pull out any staples that may have held the previously removed parts in place. When everything is removed, take the eye hooks and screw them into one end of the mouse trap approximately 8 mm from each edge. If the wood begins to split as you screw the eye screw in, simply drill a small hole first.

Wheel and Axle Assembly

You can make the wheels by using the compass to create four 75 mm circles on the plywood. The wheels can be larger or smaller if you choose, but 75 mm is a good size for relatively long distance runs. When the wheels have been sketched, cut along your freshly drawn line with a jigsaw and file them down along the edges so that they are nice and smooth. Then take the rods and place them in a vice. Cut them to exactly equal length and file the ends so that they are nice and smooth as well. Cut about half way through one of the rods with the hacksaw and use the jeweler’s file to widen the slot enough to allow the wire catch that was removed from the trap in an earlier step to fit into the groove snugly. Cut a 7 mm piece of the wire catch and file down the ends. Using the epoxy, glue the piece of wire into the slot on the axle so that the wire overhangs only on one side. Let the epoxy dry overnight.

Mounting the Wheels

When the glue is dry, place the axle with the wire at the rear of the mouse trap (where the jaws of the trap rest when the trap is set). Place the other axle through its respective eye holes screws. Add washers to the end of the axles so that the axles will not slide out. Drill a hole into the center of each of the wheels with your 3.7 mm drill bit and then slide the wheels onto each of the rods.

Mounting the Engine

Now for the actual power behind the mouse trap car. Take your string and tie it to the middle of the jaws of the mouse trap (the part which snaps down on the mouse). Tie a loop in the other end so that the loop is located exactly at the rear axle. Cut off any loose ends. Take the two rubber bands and place one around each of the rear wheels for extra traction. You can glue the rubber bands into place so they will not slide off.

Powering up the Car

To use the mouse trap car, simply raise the jaws of the trap slightly and take the looped end of the string and place in over the wire that was attached to the rear axle. Reverse the car to allow the string to wind around the axle and pull open the jaws of the trap. Release the car on the ground and it will speed away.

A mouse or two at home can be easily caught with a well-crafted mouse trap, but if you’ve swarms of them running around your feet, maybe you should try these techniques how to get rid of mice. Of course, you also want to get rid of those nasty gnats buzzing around your face, so check out these tricks on getting rid of gnats, to drive them away from your home as well.