6.75L Water Rocket Car - Wild Bill - Test Day 2
Posted: 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 ....
[youtube][/youtube]
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-
roll the video tape ... aaarh you know what I mean ....
[youtube][/youtube]
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-