Archive for July, 2009


Water Rocket Car – Static Test

We tried two test with the wrocket car strapped down so it wouldn’t move. We put the camera in place to record how the air and water were being mixed as the water was propelled out of the bottle. Here is the video

First Test – 600ml water and 100psi

This was quite uneventful with practically no water escaping from the bottle, which shouldn’t have been a surprise really. Only a fine mist was expelled. You can see the water vapour condensing to be visible after the air has been expelled.

In the slow motion shot, its interesting to see the bottle shrink back to size after being expanded at 100psi

Second Test – 1486ml and 1200psi

The first jerk you see on the video is me trying to pull the gardena launcher off without getting soaked. This did start a small wave in the bottle. The water level, although not visible in the video, was above the level of the nozzle. Then when the pressure was released there was a bit more water expelled but still not a lot. Again the water vapour in the bottle condenses to be visible as mist.


We didn’t get out of it quite what we wanted but we did confirm that the water itself being accelerated plays a big part in the water being expelled from the bottle. IN really all of our full runs, we have no water left in the bottle.

I guess I am going to ahve to strap the camera to the car to get a true picture of what the water is doing

Posted by on July 18th, 2009 2 Comments

Bike Computer on Water Rocket Car

We wanted to get some stats on how fast the Water Rocket Car was going, so we took off a bike computer we had on my bike and fitted it to the wrocket car. This is just a generic bike computer worth about A$10 on ebay.

It has all the normal bike computer functions

  • current speed
  • fastest speed
  • distance traveled
  • average speed
  • calories burned (probably wont need that one)
  • stopwatch

The ones we are interested in are fastest speed as well as distance traveled. We can reset these after each run.

The computer wasn’t too hard to fit. There are three parts to it, the head unit (computer), sensor switch and the wheel mounted magnet.  The magnet is screwed to the wheel and the sensor is mounted with cable ties to the body in close proximity so that it detects the magnetic field of the magnet as it goes by. The head unit is secured to the body of the wrocket car with a screw under the head unit.

Magnet and Sensor

Magnet and Sensor

Magnet screwed to wheel

Magnet screwed to wheel

Head Unit (Computer)

Head Unit (Computer)

The computer needs to be calibrated to the circumference of the wrocket car wheel. This was measured at 410.5mm. This distance is loaded into the computer so that it uses this distance for calculations every time the magnet goes under the sensor. You can see 0.040km (40m) on the screen. This was after 100 turns of the wheel. So its pretty close .. maybe i didn’t count to 100 properly .. hmmm

For our next launch this should give us some additional data.

Posted by on July 18th, 2009 1 Comment

Website – Attempted Hack – Update

No further hack attempts, in the last 48 hours whch is good, looks like the hackers couldnt get what they wanted and went elsewhere … so no need to worry about the websites security, all good !

Posted by on July 18th, 2009 Comments Off

Website – Attempted Hack

The website was down for most of the day while I investigated a injection attack on the HHWRSA webserver. It appears it was just an attempted attack from an external site in Russia. I can find no evidence of any changes on the webserver. I have re-enabled the server and will keep an eye on it over the next 24 hours.

If you for any reason get redirected to another website or your antivirus software complains while you are on the site, please drop me an email. My email address is in the contact us link at the top of the page

Posted by on July 15th, 2009 Comments Off