Archive for the ‘Development’ Category


Website Back Online

The HHWRSA website is back online. We still have a few small things to fix, but we are back again.

Posted by on August 14th, 2011 1 Comment

Green Hornet II – New Design

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.

Posted by on April 20th, 2011 3 Comments

Rear Exhaust Deflector

One of the things we have noticed after raising the height of the rear of the car to give more ground clearance, is that it looks like some of the exhaust will be hitting the rear wheel supports.

While this may not impact speed or distance greatly, we have added a corrugated plastic deflector at the rear of the car to ensure the exhaust is deflected up and away from the rear wheel supports.

Rear Corrugated Plastic Deflector

The rear deflector is angled up towards the back of the car as can be seen from this picture. Yes the rear wheel attachments are not pretty but they are functional :)

Angled up exhaust deflector

This deflector is only really necessary due to too much  flex in the chassis. This caused us to raise the rear wheels to get the chassis of the ground, that then moved the rear wheel supports into the exhaust plume. So this deflector is a work around, but it will be interesting to see how it performs. It may also give us more downforce over the rear wheels which would improve stability.

The connection to the launcher still fits with the deflector in place and the female Gardena should just flick up over the top of the deflector as the car accelerates away after launch.

Posted by on April 2nd, 2011 Comments Off

Distance Marker Improvements

We noticed that the lines we marked with chalk on the asphalt road didnt come out very well on the onboard video from the last launch day. So we have taken 3 additional steps toimprove this for our upcoming record attempt.

1 – We are using plasterboard (gypsum board, gyprock, drywall etc) which is approx 12mm thick (1/2″) to draw the lines, this is about twice as thick as our previous chalk and initial tests show the lines a lot clearer.

2 – We will put coloured markers on the side of the road at each 10m mark (line).  Each 10m mark will get a “RED” marker and each 50m will be a “BLUE” marker.  We will put a “GREEN” marker at the 150′ mark (45.7m) (for the speed record distance)

3 – We are installing a second camera on the car to look sideways with the front wheel in shot to capture the markers on the video as the car passes them.

A big thanks  for some inspired thinking goes to Lisa  and Spaceman Spiff from The Water Rocket Achievement World Record Association for the  coloured marker ideas.

The markers we will be using will be plastic coloured cups / tumblers, another great idea from Spaceman Spiff, which will save space in the transport vehicle getting to the launch site. We have the biggest, brightest ones we could find so that the cups are still visible even if there is a bit of a  crown in the road.

The ones we chose are 12.5cm (5″) high and have a very vibrant colour. They will also take up to 550ml of water so once in place and full of water they wont blow over.

Here is a quick picture of the cups we will be using

Coloured Distance Markers

Here is a comparison to a normal size plastic cup …

Comparison to normal cup ~220ml

With these three improvements in place the video should clearly show the car passing the marks every 10m from which the cars speed can be calculated and the distance can be validated.

Posted by on March 10th, 2011 Comments Off