In our project, we hoped to measure the maximum velocity achieved by a pendulum as a result of the explosion of a balloon filled with a mixture of hydrogen gas and air. Using hydrogen gas and compressed air on the chemistry floor, we filled balloons to a reasonable and consistent volume, with the mixture being close to ½ pure H2 gas and ½ compressed air. After filling the balloon using a specially designed filling/triggering apparatus obtained from the group that did a similar project several years ago, we would transport the balloon downstairs to the GRL where our photographic set-up was located. We would secure the balloon to the table next to our pendulum (which was a stack of washers hanging from a string in its final form), and immediately before triggering, we would pump more air into the balloon using a hand-pumped balloon filler. We are not sure why this was necessary, but we found it to be the only way to consistently successfully trigger the explosions. We used two flashes in the experiment. The first was set to go off at the same time as the spark which triggered the explosion, with the second to go off at an adjustable time interval after the first. We were therefore able to capture images of the pendulum at two different positions during the explosion. Using these images, and the known time delay between the two flashes (obtained by using the spinning clock method with a disc rotating at a known frequency), we were able to obtain the distance traveled by the pendulum in the known time interval, and therefore the velocity at which the pendulum was expelled by the explosion.

	- Sony DKC-FP3 digital camera, with remote and AC power adapter
	- Two Vivitar 283 flash units, with paper clips to short across the auto-thyristor socket
	- Timing box: triggered 1st flash immediately and 2nd flash at an adjustable time delay later
	- Momentary double pull double throw switch
	- 5v power supply
	- Buffer Box: when it receives a 5v signal, it outputs a 120v AC current from a wall outlet
	- Induction coil
	- Spark mechanism: 2 clip leads put through a rubber stopper which held the balloon
	- Second safety switch
	- Panasonic GS-120 digital camcorder
	- Pendulum: Metal washers tied to ring stand with string
	- Other Lab Equipment, eg. ring stand, clip leads, lots of masking tape
			

At the very back of the room, we have the main balloon setup on its own table. A hanging mass is suspended on a ring stand right next to the balloon. The balloon is on a cork with a hole in it for inflation. Also, the cork has two wires through it that are not touching, these create the ignition spark. These wires run to the table in the back and attach to the induction coil and intricate triggering system. 

On the next closest table reside our two flash units and the camera. These are also connected to the back table and controlled remotely so we never have to be very close to the actual explosion. Behind this table is a safety line/piece of tape that we all stand behind before each ignition. Before each explosion sequence we would also don ear and eye protection, give a verbal warning, cover the smoke detector with a can (with permission from security), hit the safety button and count down from five. 

The last table holds all of our complicated electronic equipment. There is one main double pull double throw momentary switch that triggers the whole thing. From the switch, there are two circuits; the first goes through the delay box and then to the flashes. Any time the power is on, the flashes can be tested. The second circuit has a safety button that must be depressed before the connection can be completed. The safety box runs to a box that outputs +5 V. The +5V trigger the power box which runs to the high voltage coil. The coil runs directly to the cork and creates the spark inside the balloon. There is also another remote for the camera so that we can take the picture, trigger the explosion and trigger the flashes all with two simple clicks.

When filling our balloons on the Chemistry Floor, we used a special piece of rubber tubing that connected to the air hole in the cork. We transported the filled balloons on a metal trolley, covered by a metal trashcan to reduce the chances of static electricity accidentally triggering an explosion. Also, we wore our eye and ear protecting to protect a chance explosion during transit. 

Our triggering method was designed to optimize the safety of everyone in the lab. The device itself is a 2-way momentary switch that activates the igniter as well as the flash units simultaneously. The ignition device splits off into a compilation of equipment found in this order:

After the two switches are depressed the 5-volt supply unit is triggered to create a 5-volt surge which activates the buffer box to allow a connection between the induction coil and the wall outlet. Then, the induction coil uses this power supply and boosts the voltage to a high enough point that a spark is created across the ignition mechanism (seen below) to explode the hydrogen balloon.

The triggering device for the flashes is the same initial switch for the explosion, but there is a separate path that this trigger follows:

The switch completes the circuit which shorts the first flash, then the short continues to the delay box and then after a certain delay has been obtained the second flash is discharged resulting in two separate images.

The way we timed the explosions and flashes was quite easy since the same switch accomplished both items. The difficult part was obtaining two images of the pendulum for good analysis and also timing the trigger and camera to create a good image. Both of these problems were solved by taking pictures and analyzing what needed to be done. At first we had a short delay in flashes, but that did not give us the desired images of the pendulum so we lengthened the delay using the delay box and found a good time interval between flashes that produced spectacular photos. The problem with the camera timing was that we were not getting anything but the beginning of the explosion so we lengthened the shutter speed to one second from it’s previous speed and found very analyzable pictures. To aid in our speed measurements we also captured a photograph of a high speed clock in which we will measure the angle between lines and using the frequency at which the clock is turning we will be able to acquire a time increment and thereby an accurate measurement of maximum velocity.

To take pictures we used the Sony DKC-FP3 and set the camera about a meter and a half away from the exploding balloon. There was no worry about the camera being damaged by the flame because the explosion did not produce enough heat to even singe the string that the pendulum was on. Besides taking pictures of the explosions, we also captured a high speed clock rotating at 57 hz to give us a time increment of the flashes for our speed measurements, and also a ruler next to the pendulum to give us a scale factor for accurate distance measurements on our photos.