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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.

Launch Cage Test Day + MD80

Discussions about water rocket powered cars, sleds or boats.
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thampson
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Launch Cage Test Day + MD80

Post by thampson » Wed Feb 02, 2011 9:26 am

We were fairly keen to try out the new launch cage so we ventured out to our local launch site to test the water rocket car with the new launch cage at launch pressures.

We were also trying out the new MD80 Clone Camera which was mounted just behind the front wheels and is much lighter than our previous camera.

Here is the video
[ytubehd][/ytubehd]

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.

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.

There is a little more detail on our website for those interested
http://wrocket.hampson.net.au/?p=1364

We are just about ready for a record attempt now, so keep your eyes out, we will hopefully post live updates from the record attempt on our blog and twitter :)

-todd-


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Re: Launch Cage Test Day + MD80

Post by WRA2 » Thu Feb 03, 2011 5:05 pm

Nice video Todd,

The leaves blowing around during the launch was really cool too.

Do you know what else that cage would be good for. Sponsor logos or at least a team logo.

Good idea on downloading the video after each run.

Have you seen the discussion on removing the date from the MD 80 video?

http://www.wra2.org/forum/viewtopic.php ... 1&start=45

Several of our members have come up with some really creative ways to totally remove the date and time without cropping the video.


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thampson
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Re: Launch Cage Test Day + MD80

Post by thampson » Fri Feb 04, 2011 12:10 am

Thanks Lisa,

I did see that thread and I think the date does get in the way of the lovely view from 500' or more. But I dont mind the date being there on the ground, in fact it will support that we did the 2 runs inside the 2 hour window.

I do have to fix the year though DOH:

We might put a Team Logo on the Cage as well, that a good idea. If we can manage some sponsorship then we have plenty of space for that as well :)

-todd-


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Re: Launch Cage Test Day + MD80

Post by WRA2 » Fri Feb 04, 2011 5:28 pm

thampson wrote:Thanks Lisa,

I did see that thread and I think the date does get in the way of the lovely view from 500' or more. But I dont mind the date being there on the ground, in fact it will support that we did the 2 runs inside the 2 hour window.

I do have to fix the year though DOH:

We might put a Team Logo on the Cage as well, that a good idea. If we can manage some sponsorship then we have plenty of space for that as well :)

-todd-
There is nothing in the rules that specifies that you cannot get sponsorship. 8)


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Re: Launch Cage Test Day + MD80

Post by U.S. Water Rockets1 » Sat Feb 05, 2011 9:41 pm

thampson wrote:We were fairly keen to try out the new launch cage so we ventured out to our local launch site to test the water rocket car with the new launch cage at launch pressures.

We were also trying out the new MD80 Clone Camera which was mounted just behind the front wheels and is much lighter than our previous camera.

Here is the video
[ytubehd][/ytubehd]

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.

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.

There is a little more detail on our website for those interested
http://wrocket.hampson.net.au/?p=1364

We are just about ready for a record attempt now, so keep your eyes out, we will hopefully post live updates from the record attempt on our blog and twitter :)

-todd-
Awesome videos, Todd.

Regarding the MD80... you should always download the videos between runs or at least swap out the MicroSD cards. If you have a crash you can lose all of your recorded runs. The firmware is not the most robust bit of programming so a low battery or full card in these cameras can cause the card to get corrupted or the file allocation table can get trashed and you cannot access the files anymore. The best practice is to download every video right away. It is also possible that an empty card has faster access time and therefore less dropped frames.


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thampson
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Re: Launch Cage Test Day + MD80

Post by thampson » Sun Feb 06, 2011 7:44 am

USWaterRockets,

Thanks thats good advice, we will take the laptop along as well on the next launch day, just another thing to remember ;).

The MD80 makes it pretty easy to download the video files, we will mount the camera so we can access the USB port easily on the car so its just a matter of connecting it to the laptop between runs.

cya
-todd-


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http://wrocket.hampson.net.au

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Re: Launch Cage Test Day + MD80

Post by U.S. Water Rockets1 » Sat Feb 12, 2011 11:36 pm

thampson wrote:USWaterRockets,

Thanks thats good advice, we will take the laptop along as well on the next launch day, just another thing to remember ;).

The MD80 makes it pretty easy to download the video files, we will mount the camera so we can access the USB port easily on the car so its just a matter of connecting it to the laptop between runs.

cya
-todd-

If you can't get at the usb port you might be able to mount it so you can pop out the SD card and put it into a card reader connected to the computer.


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thampson
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Re: Launch Cage Test Day + MD80

Post by thampson » Sun Feb 13, 2011 9:05 am

USWaterrockets,

Thanks for that suggestion :D. I was working on mounting the camera in an accessible spot today and looks like i have a good spot where I can access the camera and attach the USB cable between launches to download the videos.
car-camera 015.jpg
The camera view is not too bad as the view shows the side of the car and the front wheel. With any luck this angle will let us see the 10m marks on the road as the front wheels cross them.
car-camera-capture.jpg
-todd-
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Re: Launch Cage Test Day + MD80

Post by WRA2 » Tue Mar 01, 2011 9:36 pm

thampson wrote:USWaterrockets,

Thanks for that suggestion :D. I was working on mounting the camera in an accessible spot today and looks like i have a good spot where I can access the camera and attach the USB cable between launches to download the videos.
car-camera 015.jpg
The camera view is not too bad as the view shows the side of the car and the front wheel. With any luck this angle will let us see the 10m marks on the road as the front wheels cross them.
car-camera-capture.jpg
-todd-
Hi Todd,

That mounting position looks good. It looks like the markings on the track will be seen easily from that viewpoint.

Good luck when you make your attempts.


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Re: Launch Cage Test Day + MD80

Post by Spaceman Spiff » Tue Mar 01, 2011 11:38 pm

thampson wrote:USWaterrockets,

Thanks for that suggestion :D. I was working on mounting the camera in an accessible spot today and looks like i have a good spot where I can access the camera and attach the USB cable between launches to download the videos.
car-camera 015.jpg
The camera view is not too bad as the view shows the side of the car and the front wheel. With any luck this angle will let us see the 10m marks on the road as the front wheels cross them.
car-camera-capture.jpg


Looks good ,Todd.

I just noticed another detail of your car I hadn't seen before. You cut out trangles from the wood structure to save weight. That's like they do when they make airplane wings. I'm sorry I don't know the right name for the holes. Do they have a name or term?

-todd-


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Re: Launch Cage Test Day + MD80

Post by thampson » Fri Mar 04, 2011 10:07 am

Hi Spaceman,

yes i did put the chassis on a diet :) Cutting out the triangles on the chassis reduces the weight without effecting the strength :)

I intend to use this truss like shape for future chassis development as well.

cya
-todd-


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Re: Launch Cage Test Day + MD80

Post by Spaceman Spiff » Sat Mar 05, 2011 12:34 am

thampson wrote:Hi Spaceman,

yes i did put the chassis on a diet :) Cutting out the triangles on the chassis reduces the weight without effecting the strength :)

I intend to use this truss like shape for future chassis development as well.

cya
-todd-
It's a good idea. It reminds me of a tube frame on a real dragster! Good thinking!


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Re: Launch Cage Test Day + MD80

Post by U.S. Water Rockets1 » Sat Mar 05, 2011 11:17 pm

Todd,

Do you have the camera set up as a webcam to get the alignment just right? If you set it up that way, you can frame the video just the way you wanr and make sure it is straight and level and you can see the points of interest like the wheel and the roadway in your case.


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Re: Launch Cage Test Day + MD80

Post by thampson » Sun Mar 06, 2011 8:29 am

Hi USWaterrockets,

They are not running as webcams at the moment (although its a good idea, I might try that, I have the webcam software). I just set it up where I want it, take a 10 second or so video, then just download it to the laptop and see if Im happy with the location and the view it gets. This is how I managed to get the final location after a few different tries.

I just took delivery of a second MD80 clone camera which I will fit to the car as well, so I have 2 cams onboard. I thought I may be able to have the second one viewing sideways just behind the front wheel and place small meterage signs every 10 metres along with the marks on the road to make it easier to verify as the car went over the line markers .. im not sure yet .. I will see how it looks on the video.

One thing we noticed on the last test day with the line marks was that they didnt come out well on the camera at speed.

cya
-todd-


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Re: Launch Cage Test Day + MD80

Post by WRA2 » Sun Mar 06, 2011 4:38 pm

thampson wrote:
One thing we noticed on the last test day with the line marks was that they didnt come out well on the camera at speed.

-todd-
Hi Todd,

Have you tried reflective tape for the marks? Maybe the cameras could see those better.

Another suggestion would be to place "easy to see" markers at each line (sort of like the orange cones used at construction sites) They could be made from bottles painted an easy to see color and marked with distances.


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