Posts Tagged ‘wrocket-car’

 

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

MD80 Camera

The water rocket community is using these MD80 clone cameras more and more as they are cheap, light and provide good video. We decided to replace our heavy onboard  camera with this camera.

MD80 clone camera

Initial tests showed the video quality was quite good and much better than the cigarette lighter camera we tried. We mounted this camera on our water rocket car for our recent test day. The camera can be seen in this launch picture.

MD80 Camera attached to car

We had an issues that one of the launch videos was overwritten when we got home to download the videos, so on advice from other water rocket users of this camera we will need to download the videos off the camera after every launch.  This means we need to take the laptop and a USB cable to the launches to download the videos.

We decided also to mount the camera further back on the car to get a better chance of seeing markers on the road. Here is where we mounted it on the rear guide rail lug support.

MD80 mounted on the water rocket car

This location gives easy access to the underside where the USB cable attaches, as well as not interfering with the on/off switch and the start/stop button of the camera. We can also charge it on the bench in the garage of we need to with a USB cable to a power adapter. Here is the USB cable attached to the car

Camera attached to laptop and downloading video

This  position mounting the camera further back  provides a good view of the water rocket car as well as the ground and the front wheels. This is a shot from the camera mounted in that location.

Video grab from new mounting location

Posted by on February 14th, 2011 3 Comments

Increase Chassis Ground Clearance

We realised that the chassis of the car is scraping on the ground more than it was previously. The cable ties that hold the bottles to the chassis show quite a bit of wear due to the scraping. All the scraping is slowing the car down and reducing the distance the car will travel.

The scraping is probably due to a couple of things

  • the chassis being wet repeatedly and becoming more flexible
  • the long span between the front and rear wheels

When the  approx 2kg of water is added the middle of the chassis will touch the ground. We have a design for a lighter and stiffer chassis but decided to just modify this one slightly so we could submit a record attempt before we rebuild a new chassis.

The simplest way we came up with was just raising the rear of the car slightly . We achieved this by flipping over the L brackets that hold on the rear wheels and putting them ontop of the chassis rather than under it. This raised the rear by about 2cm and the lowest point by about 1cm. Here is a pic of the car with the rear raised.

The additional clearance of the chassis is visible in this wide angle shot

As the rear is now higher a section between the rear wheels had to be cutout to allow the launcher hose to connect to the nozzle. Also the screws used to attach the car to the guide rail had to be adjusted to slide correctly in the rail.

Posted by on February 12th, 2011 Comments Off

Launch Cage Test Day

We were fairly keen to try out the new launch cage so even though it was 33 degrees C (50 degrees C on the asphalt) last Sunday, we ventured out to our local launch  site to test the water rocket car with the new launch cage at launch pressures.

The water rocket car had the reinforced triple stack of bottles attached, which have been tested to 180psi. We also had the upgraded launcher using the high pressure hose, both of which hadn’t been run on the car before.

We were also trying out the new MD80 Camera which is a light camera mounted to the water rocket car.

The aim of the test day was to see how the car would launch out of the cage, if it was sticking in the guide rail or not launching straight. Here is the video of the launch day.

Results
Its not shown on the videos, but we did do a 60pis test and an 80 psi test before doing the 120 psi & 125psi tests. The 60psi and 80psi tests worked fine so we increased the pressure up to launch pressures. We didn’t include the video of these launches as they were not really all that  spectacular :)

We were pretty happy with the results of the cage test. The car on both high pressure launches is leaving the cage straight and there doesn’t appear to be any major loss of speed due to friction using the guide rail. There doesn’t appear to be any recoil of the cage and launcher and the cage held together well on launch. Getting the cage to the launch site also worked well, only issue was some strangle looks we got on the way there ;)

The MD80 camera worked ok, but we still have a few teething issues to work through as the first run didn’t record, or most likely, the second video recorded over the first one. We will work on that and possibly download videos from the camera between runs using a laptop, just to be sure.

The car once it left the cage was turning left, this was most likely just a slightly sticking front wheel, the wheel bearings were not greased before this test as we were not going for distance, which would account for the minimal rolling distance as well as the left turn. This should be easily fixed.

Here are a couple of video images showing the water rocket car launching. One of these is now posted on the dragstrer competition page on www.wra2.org , the page is here

Launch 2 - 125psi, very clean exit form the launch cage

Launch 1 - 120psi, nice exhaust plume when leaving the cage

Posted by on February 2nd, 2011 Comments Off