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.


This entry was posted on Wednesday, April 20th, 2011 at 7:51 pm and is filed under Development. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.


3 Responses to “Green Hornet II – New Design”

  1. George Says:

    That’s looking great Todd. :) With nozzles that size you will sure get a lot of acceleration. It will be interesting keeping it on the ground! Have you considered using brakes as opposed to a parachute? I guess a parachute is much easier.

  2. todd Says:

    thanks for visiting and leaving a comment George :)

    we did think about using a physical brake but we didnt like the idea of stressing a servo as the brake actuator. Also we would need to fit them to both sides of the car to stop it spearing off in one direction under braking. We think the parachute mechanism should be easier to implement, provide more efficient braking and be able to be removed when we need to save weight and go for distance :)

  3. greg Says:

    i love really long water rockets
    … in my garage