The last 6 months have really flown by and with a house move in the mix there hasnt been much time for water rockets. We have decided for now to put the water rocket projects on hold.
We dont think we are finished with this hobby as there are still plenty of things to do but we have an exciting new science project to take on this year after 4 years of water rockets. We are going to step up the altitude quite a bit, well a lot in fact, we are going to work on a High Altitude Balloon project.
We are hoping for some similar pics to this one from our project
We are doing our background homework now and as usual will publish our work on a blog website http://hab.hampson.net.au which will start to get some content soon
We will of course keep this water rocket website online as there is lots of good information there for anyone else considering the hobby. We are till happy to answer water rocket questions if you have them.
We have been working on several designs for new water rocket cars over the last 6 months and have decided on a configuration for our next water rocket car. It will affectionately be called Green Hornet II and will be painted it in the now traditional HHWRSA Green and white colour scheme, carry a HHWRSA banner and the Australian flag .
The following are design features of the new water rocket car
Extending the pressure vessel stack from a 3 x 2L bottle stack to a 4 x 2L bottle stack, all stacks are held together with robinson couplings
Increasing the total volume from 6L to 24L – 3 x 4 bottles stacks (2L per bottle)
Increasing the 9mm Gardena Nozzles to 15mm Gardena Nozzles
Increasing the number of nozzles from 1 to 3 (1 per 4 bottle stack)
All new chassis design based on two truss structures and cantilevered pressure vessel attachments to provide improved chassis stiffness to hold a greater volume of water without bending and scraping on the ground
Adding a removable parachute attachment and remote control R/C parachute deployment mechanism
Utilising fibreglass wrapping of the bottles to increase fill pressures
Changing the two rear fins from 45 degrees to vertical and increasing the fin size
Maintain the existing remote control steering
Here are the hand drawn designs for the new car
Green Hornet II - Profile View
Green Hornet II - Top View
To be able to fill the pressure vessel volume we will be using a 5hp petrol powered air compressor, which should be good for approx 120psi. After that we will cut over to the hand pump to increase the pressure beyond that level.
5hp Petrol powered Twin cylinder compressor
We will utilize the same external launch cage as the previous car. The new car design may increase the length of the car slightly, if necessary, we will simply extend the length of the cage and the launch rail to ensure the pressure vessels are maintained within the cage.
We will also need to modify the existing launder to accommodate the 3 nozzles and the bigger nozzle quick release connectors.
This cars main aim is to increase acceleration and velocity over the previous car to hopefully lower the water rocket dragster speed world record. It should also be able to increase the distance record significantly. Based on our calculations we should be able to break and push beyond the 100km/hr barrier with this car.
There is nothing radical in this design, there are a few new things for us to work on and engineer out the bugs, but we expect to have this car operational within a couple of months all things going well. Our more radical design ideas we have left for the following car as these will require a bit longer to work out each of the components.
Keep a watch on our website as we will document our build progress as we go.
We prepared the car with two onboard cameras, one looking forward and one looking sideways. We also prepared our coloured cups to place on the 10m road markers so that it will be easier see the car pass the road markers.
MD80 Camera mount behind the front wheel
MD80 Rear Mounted Camera
We also decided for this launch day to use twitter to provide live updates from the launch day. We setup and tested a twitter client on our iphone and it worked well. Twitter updates are appearing on
We arrived at the launch site at approx 2:30pm and setup the launcher and the cage, at this point we realized we had forgotten our two normal camera to capture the run, so we decided just to use the iphone video camera and ty to hold it as smooth as possible.
We then measured out the course with our 50m tape measure and marked every 10 metres with a solid chalk line across the road. From the northern end we then marked the 45.7m mark with a dashed line. We then put the red cups every 10m, the blue cups every 50m and the green cup at the 45.7m mark.
We did some twitter updates, then turned on the two car cameras, turned on the electronics for steering, filled the car with water and bubble bath and locked it in on the launch rail inside the cage. Heres how our launch went
We were happy that all of the videos were ok. We used VirtualDub to calculate the time it took for the car to reach the 150ft marker. To do this we used the side looking camera and went through the video file until we found the first frame where the car launched, this woudl be our starting time. Virtualdub works out what type of file it is and how many frames per second the camera captured. For the MD80’s each frame was 0.032 seconds.
We then went through the video file frame by frame until we could see the coloured cups in the frame. We then took the used the time from virtualdub for that marker when we saw the white line and the cup one frame past the centre of the frame of the camera. We listed the time to pass each marker then calculated the following
– Relative time to pass each marker putting the first frame as 0 seconds
– Time to move from one marker to the next
– Time to reach the 150ft marker
– Average Velocity at each marker
– Instantaneous Velocity at each marker