Welcome to the Water Rocket Forum, sponsored by The Water Rocket Achievement World Record Association.

Since our founding in 2003, we've become the largest, most sophisticated and ground breaking group supporting you, the serious water rocket flyer! Whether you are a beginner or an expert, the WRA2 has something for everyone.

A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.


Hello Everyone. It is that time of year again. Time to approve changes to the competition rules for the new year.

You Can vote at:
viewtopic.php?f=32&p=19486#p19486

Please take the time to vote. TH:

6.75L Water Rocket Car - Wild Bill - Test Day 2

Discussions about water rocket powered cars, sleds or boats.
Post Reply
User avatar
thampson
Current WRA2 Dragster Speed & Distance Record Holder
Current WRA2 Dragster Speed & Distance Record Holder
Posts: 232
Joined: Wed Jul 16, 2008 8:19 am

6.75L Water Rocket Car - Wild Bill - Test Day 2

Post by thampson » Mon Aug 24, 2009 9:32 am

We had another test day on the weekend with the MkVII revision of the water rocket car. We had good and bad results .. Good in that we edged our record distance out to 80m (240ft), bad in that the rest of the time the wrocket car .. now affectionately called "Wild Bill" ... systematcally ripped the front wheels off one at a time ...

roll the video tape ... aaarh you know what I mean ....
http://www.youtube.com/watch?v=aPQ6xP7ArpM

and also on our website..

We spent quite a bit of time on unpowered runs getting the chassis rolling / tracking pretty straight before each powered run.

Our first run of 80psi and 1L of water was the one that made 80m, even then it hit the gutter ... anything above this pressure skewed off to the right or left and into the gutter ...

I think its pretty evident after this many runs and crashes that the fins are not providing enough area to try to correct the wrocket car with the amount of thrust we are now getting and we are just overpowering the chassis.

We have been looking into RC steering control but I dont think even that would be enough to arrest the directional stability problems we are having.

We will put "Wild Bill" out to pasture and work on MkVIII. With bigger wings, a wider track at the front and put in the ground effect downforce pieces. This should generate downforce at the rear and the wings provide better yaw stability ... We had good results with this strategy with the 1 and 2 bottle cars so hopefully we will get some results here as well.

Also we are looking at smaller diameter nozzles again to even out the thrust ......

We have calculate approx 40L of standard pressure air is being squeezed in out 6.75L wrocket car .. which is whats pushing all that water out and giving us so much thrust ....

We will keep at it .. 100m is just teasing us now .... :)

-todd-


HHWRSA
Hornsby Heights Water Rocket Space Agency
http://wrocket.hampson.net.au

Andrew Leigh
Advanced Member
Advanced Member
Posts: 39
Joined: Sat Aug 07, 2010 10:10 am

Re: 6.75L Water Rocket Car - Wild Bill - Test Day 2

Post by Andrew Leigh » Sun Aug 29, 2010 2:55 pm

Hi,

I know this is an old post but I am new to the forum so a couple of thoughts.

- Have you considered a front wing to provide downforce. Once the downforce provided by the propellant is exhausted the rig is as light as a feather so to speak? I think your front wheels have no traction and are then unable to hold direction.
- It would appear as if the straighness of the trajectory is inversely proportional to the amount of water in the bottle, further evidence that perhaps down force is required.
- Have you considered making your front wheels adjustable for camber and tow?

Cheers
Andrew



User avatar
thampson
Current WRA2 Dragster Speed & Distance Record Holder
Current WRA2 Dragster Speed & Distance Record Holder
Posts: 232
Joined: Wed Jul 16, 2008 8:19 am

Re: 6.75L Water Rocket Car - Wild Bill - Test Day 2

Post by thampson » Mon Aug 30, 2010 1:03 am

Hi Andrew,

thanks for the post. We have progressed quite a bit from MkVII version of the water rocket car, we are on MkXI now :) We managed to solve the stability issues by fitting remote control R/C steering to the water rocket car and increasing the grip on the rear tyres. The thrust was just overpowering the rear grip and steering the car on the MkVII version of the car. We also added a bit of toe out on the front wheels to improve it go straight line.

Working on the water rocket car is a very interesting sideline of water rockets as many things that would work for a vertical rocket dont necessarily work for the car, so there is quite a bit of analysis and research to work out how to correct the problems. Also we can pretty much run the car whenever we like even in strong winds or light rain.

There is a lot of information on our website and in the Water Rocket Car forum here on our progress of late if you are interested in the development of the car.

-todd-


HHWRSA
Hornsby Heights Water Rocket Space Agency
http://wrocket.hampson.net.au

Andrew Leigh
Advanced Member
Advanced Member
Posts: 39
Joined: Sat Aug 07, 2010 10:10 am

Re: 6.75L Water Rocket Car - Wild Bill - Test Day 2

Post by Andrew Leigh » Mon Aug 30, 2010 10:17 am

Will check on your progress.

Cheers
Andrew



Post Reply