Penyambungan 2 botol untuk dijadikan badan roket air

Salam 1 malaysia,

Selamat menunaikan ibadat puasa bagi peminat2 roket air yang beragama islam.

Kali ini saya akan memperkenalkan satu kaedah untuk menyambungkan 2 botol minuman untuk dijadikan badan roket air. Kaedah ini dinamakan teknik peyambungan injap. Peralatan yang diperlukan adalah: 'valve' tayar motorsikal/basikal, paku lebih kecil sedikit drpd 'valve' tayar, pisau.

Langkah 1
Panaskan paku dan tebuk satu lubang pada bhg bawah botol dengan menggunakan paku panas tersebut. Tebukkan satu lagi lubang pada penutup botol minuman tersebut menggunakan kaedah yang sama seperti di atas.

Langkah 2
Kemaskan lubang yang di tebuk dengan menggunakan pisau supaya 'valve' tayar dapat masuk melaluinya. Pastikan lubang tersebut sama saiz dengan 'valve' supaya angin tidak dapat keluar melaluinya semasa angin dimasukkan ke dalam botol.

Langkah 3
Bagi mengelakkan
Masukkan 'valve' dari bahagian dalam botol(peringkat ini memerlukan kesabaran kerana agak sukar memasukkan valve dari bhg dalam botol, saya masih lg sedang memikirkan apakah alat yg sesuai digunakan utk memasukkan 'valve' dari bhg dalam botol  sehingga keluar). Bagi mengelakkan sambungan yang dibuat daripada angin terkeluar semasa pelancaran, ambil tiub basikal dan letakkan pada bahagian atas sambungan dan bawah sambungan.

Selamat mencuba.......semoga berjaya.

'Slide shows' gambar pertandingan teknologi pelancaran roket sempena FST negeri Johor 2010

Tempahan Pelancar Roket Air

Salam 1 Malaysia,

Untuk makluman semua saya masih lagi mempunyai 8 set pelancar yang sudah siap dihasilkan dan sedia untuk penghantaran bila-bila masa sahaja. Bagi mereka yang berminat sila hubungi saya untuk tempahan (013-7394353). Harga masih lagi RM150/unit termasuk kos penghantaran.

Siapa cepat dia dapat......tq

azmi j

Bottle Rocket Designs...?

Q: In science class we are using 1.5 liter bottles for bottle rockets. We have to add on to the bottle (nose cone, fins, ect.) to make it stay in the air longer. Any suggestions? And what kind of material should each thing be built out of?


Also, how much water should the bottle be filled with?

Answer
This is fun. I just helped my son with his bottle rocket for science. Two critical areas of the rocket for success are the nose cone/parachute and the stability (getting the center of mass well forward of the center of aerodynamic drag. There is an easy test you can perform to check drag. Of course, fins are one method of moving the aerodynamic drag back and the nose cone moves the center of balance forward.



The biggest advance we found was using a compression plate for the nose cone. We used a cottage cheese container lid glued onto the base of the bottle to set the nose cone into. My son had concerns about the edge of the lip of the lid catching the air and pressurizing the nose cone as the rocket ascended, so we made exhaust holes to match up with the relief between the bumps on the bottom of the bottle. This makes use of the venturi effect to keep the nose cone firmly locked on until the rocket reaches its apex.


The nose cone has to be constructed so that it will tip off at less than a 45 degree tip angle. W placed 6 pennies (hot glued into the lid of the nose cone for additional mass forward and to help tip the nose cone off. His competition required that the nose cone, parachute and all parts of the rocket remain together is less than linear ft of length when deployed. So the nose cone also has a line tethering it to the rocket, as does the parachute. But we used an elastic shock cord to reduced damage to the rocket and parachute. This shock cord is tied through the compression plate.


For the parachute we used the thinnest clear trash bag we could find. Cut a 42" circle with a 2" circular vent in the center. This helps the efficiency o the parachute by keeping air flowing through the parachute but with lots of drag. If you don't have the vent, you can get a pillow of stale air stuck under the parachute and the whole thing comes down too quickly.


For stability, first you want to find the center of mass. Tape the nose cone with the parachute onto the rocket. Take a string and tie it around your rocket. Slide the string toward the nose or tail until the balance point is found and the rocket hangs horizontal to the ground. Mark this point with a permanent marker +M. Now to locate the aerodynamic center of drag. This is a bit more difficult. The rocket needs to be held horizontal over a pivot point. A short piece of wood trim with a 2-3 ft. dowel put in the middle of it forming an upside-down "T" works well. Hang the trim piece by a short string at the end of the dowel. Now you need a large fan. Using scotch tape, tape the rocket body horizontally attached to the trip piece with the location of your best guess of the aerodynamic center of drag located at the dowel point. now suspend the rocket in front of the airflow of the fan 5-8 ft from the fan. The rocket will likely tent to turn in the airflow. If the nose turns to the fan, then reposition the rocket a bit further forward on the pivot. If the tail turns toward the fan, reposition the rocket further back on the pivot. When the rocket is neutral in the air flow and has no tendency to turn toward or away, or just spins freely in the airflow then you have located the center of aerodynamic drag.


This point can be marked with a "+A" The +M should be at least 3-4" forward of the +A for good stability. Adding fins will

move the aerodynamic center of drag to the rear of the rocket. You can now do a quick check of the stability of your rocket. tie the same string you used for the center of mass test at the center of mass so the rocket hangs horizontal. Then put the rocket in front of the same fan you used previously. The rocket should point into the fan in a very stable fashion.


You will likely need to add fins. Be careful a this point. There should be constraints on where the fins can be. Check with your teacher. Thin plastic,as used in these cheap disposable cutting boards works well. Or if you can get thin balsa wood at a craft store you can cut any shape of fin that you want. Keep in mind that you want as much of the area of the fins as far back as possible. Unfortunately, the curve of the bottle near the neck makes mounting the fins challenging. That is why sloped or angled fins may work best. They will mount just forward of the curve of the bottle, but extend well to the rear of the curved part of the bottle all the way to the mouth of the bottle. Again, be careful of the constraints for clearances for the launch pad and pressure fitting. We had to keep out of the curved area of the bottle within the cylinder defined by the rest of the bottle, and the fins could not extend beyond the opening of the bottle.


Adhesive for the fins is critical. You cannot use hot glues or any solvent glues that molecularly bond with the plastic of the bottle. This could compromise the strength of the bottle and cause an explosion hazard on the launch pad when the bottle gets pressurized.

Good luck and have fun!

FLIGHT OF A WATER ROCKET

Flying model rockets is a relatively safe and inexpensive way for students to learn the basics of forces and the response of a vehicle to external forces. A model rocket is subjected to four forces in flight; weight, thrust, and the aerodynamic forces, lift and drag. The relative magnitude and direction of the forces determines the flight trajectory of the rocket.

On this page we show the events in the flight of a water rocket. Water rockets are among the simplest type of rocket that a student encounters. The body of the rocket is an empty, plastic, two-liter soda bottle. Cardboard or plastic file fins are attached to the bottom of the bottle for stability, and a fairing and nose cone are added to the top as a payload.

Prior to launch, the body of the rocket is filled with water to some desired amount, normally about 1/3 of the volume. The rocket is then mounted on a launch tube which is quite similar to that used by a compressed air rocket. Air is pumped into the bottle rocket to pressurize the bottle and thrust is generated when the water is expelled from the rocket through the nozzle at the bottom. Like a full scale rocket, the weight of the bottle rocket is constantly changing during the powered ascent, because the water is leaving the rocket. As the water leaves the rocket, the volume occupied by the pressurized air increases. The increasing air volume decreases the pressure of the air, which decreases the mass flow rate of water through the nozzle, and decreases the amount of thrust being produced. Weight and thrust are constantly changing during the powered portion of the flight. When all of the water has been expelled, there may be a difference in pressure between the air inside the bottle and the external, free stream pressure. The difference in pressure produces an additional small amount of thrust as the pressure inside the bottle decreases to ambient pressure. When the pressures equalize, there is no longer any thrust produced by the rocket, and the rocket begins a coasting ascent.

The remainder of the flight is quite similar to the flight of a ballistic shell, or a bullet fired from a gun, except that aerodynamic drag alters the flight trajectory. The vehicle slows down under the action of the weight and drag and eventually reaches some maximum altitude which you can determine using some simple length and angle measurements and trigonometry. The rocket then begins to fall back to earth under the power of gravity. Bottle rockets may include a recovery system like a parachute, or a simple detachment of the payload section, as shown in the figure. After recovering the rocket, you can fly again.

On the graphic, we show the flight path as a large arc through the sky. Ideally, the flight path would be straight up and down; this provides the largest maximum altitude. But water rockets often turn into the wind during flight because of an effect called weather cocking. The effect is the result of aerodynamic forces on the rocket and cause the maximum altitude to be slightly less than the optimum. The parabolic arc trajectory also occurs if the launch platform is tilted and the rocket is launched at an angle from the vertical.

Sumber : NASA water rocket article.