Archive for the ‘Development’ Category

 

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

Howto build a Launch Cage with Guide-rail – Part 3

This is the final part of the launch cage construction posts, it  covers the addition of the mesh, the access for the air hose as well as final adjustments. We learnt a lot about applying mesh and have included tips below which should speed up the time to do this task for others.

Attaching the Mesh
The mesh that we used is a zinc coated welded steel mesh made by Whites Wires here in Australia. Its has a 6.5mm (1/4″) square aperture and a 0.6mm wire diameter. This mesh  is usually used for  snake and mouse protection on aviaries.  The welded mesh provides more rigidity to the mesh than twisted wire mesh such as chicken wire.

Closeup of Mesh

TIP 1 : SAFETY SAFETY SAFETY – Anytime you are working with mesh or wire its very very important to wear wraparound  eye protection and gloves  while handling the wire and mesh.  Wire strands can easily get into your eye and you dont get a second chance with your vision. Also the mesh is very sharp when cut so gloves are needed !!!!!!

The initial plan was to use wire to wrap the mesh to the frame. So first a section of the wire was cut to size for one side. This took quite a while with wire cutters, cutting each wire individually.

TIP 2:  USE A ANGLE GRINDER TO CUT THE MESH – Use an angle grinder to cut the mesh. It cuts through it like butter and also trims off the sharp edges all in one go.

Once the wire was cut to size it was placed against the frame. Initially the mesh was cut right up to the edge of the frame. As the frame is 35mm wide, it doesnt need to go all the way to the frames edge as it will expose the edges. Its safer to cut the mesh about 10mm away from the edge.

TIP 3: CUT THE MESH 10mm SHORT OF THE FRAME EDGE to prevent cutting your leg as you walk past it once its on.

The mesh was trimmed then using wire it was strapped to the frame by wrapping the wire around the frame and through the mesh. Basically sewing it to the frame. While this did work and the mesh was tight against the frame, it took about an hour to do one side and left a lot of the sharp ends of the strapped wire exposed .

There had to be a better way….  We did  some research on how  mesh was added to the frames of aviaries. The answer it turned out was universal and quite simple ….  tek-screws !

Tek Screw with Hex Nut

A tek screw has a self drilling point and the ones we used had a hex bolt head that held the mesh tight against the frame. We also used a magnetic hex Tek bit for the power drill which made installing these very fast.

TIP 4: USE TEK SCREWS TO ATTACH THE MESH TO THE FRAME

Once the wire wrapping was removed, the same side section was attached with Tek screws in about 5 minutes. Here is a closeup of the tek screws holding down a mesh section.

Closeup of tek screws holding down sections of mesh

In all we used about 125 tek screws to attach all of the mesh to the frame. Where the mesh needed to be trimmed it was done with the wire cutters but in most cases it was cut to size with the angle grinder before being put onto the frame.

Securing the Access Door
The access door is covered with mesh from the inside, it uses the two wooden stoppers to stop the door falling into the cage and the  sliding bolt to hold the door in place.

Sliding latch on access door

Air Hose Connection
The air hose connection to the launcher is fed through a small hole cut in the mesh. Access  to connect the airhose to the launcher is via the access door. Here is the airhose in place and the accessdoor open.

Airhose connected to launcher with access door open

Final Adjustments
Finally, here is the water rocket car in place on the rail and attached to the launcher. Some small adjustments on the lugs were made to get the exact height correct. Several manually powered launchers were made to check all was working satisfactorily. Some grease will be applied to the rail before a powered test is made. Here are some pics of the final cage.

Finished Cage - Side View

Finished Cage - Rear View

Water Rocket Car attached to the launcher and guiderail

One tip we found after we had already applied the mesh was to paint the mesh itself black. This virtually makes it dissapear to the eye and is usually performed to make viewing birds easier. With the white frame we have, we probably wont bother trying to paint the mesh black :)

Only thing left to do now is some powered tests of the rail and the cage. Hopefully we will get this done shortly, then head to the launch site to try to set some records :)

Posted by on January 25th, 2011 Comments Off

Howto build a Launch Cage with Guide-rail – Part 2

Guide Rail
As we realized in the design stage a guide-rail is necessary to ensure the water rocket car clears the cage without hitting the sides on launch. We use a split tail design on our water rocket car, so for us the best spot to attach the guide-rail to the car is down the centre.

The guide-rail itself is  a metal curtain rod which we have used previously as a vertical launch rail for our vertical water rockets. It also happened to be about 1.5m in length which was a perfect length.

To attach the guide-rail to the cage we suspended a section of timber from the top of the cage along the centre. It was important to make sure this piece was perfectly horizontally  level, otherwise the car may bind up in the rail on launch.

Guide-rail attachment suspended from the top of the launch cage

there is a bit of clearance between the car  to attach the rail itself as can be seen from this test fit picture.

Test fit and clearance of rocket car to rail

The rail was then attached to the suspension section with some blocks to get the rail closer to the car.

Guide-rail attached to suspension section

Here is the car in place under the rail. The alignment looks pretty straight.

Car in place under the rail

Car Rail Lug Attachments
Next the lugs needed to be made up and attached to the car. As the bottles need to be able to be removed from the car, we made up some U shaped attachments. One is placed over the nozzle and the other over the first and second bottle gap. These are spaced to allow the bottles to expand without pressing too hard against either of  them and possibly rupturing or bending the lug attachment.

Guide-rail lugs and attachments

Large screw heads were the right shape and size to use as lugs to slide down the guide- rail, so appropriate sized screws were secured into the attachments. The attachments are secured into the chassis from underneath. Using screws as lugs allows for the height to be  adjusted by turning the screw in or out to fit in the rail correctly.

The U shaped attachments were painted green to match the rest of the car.

PaintJob
The cage was given a coat (or 2 ) of paint to smarten it up a bit. The launch rail attachment was painted green to keep with the Green Hornet theme :)

A coat of paint :)

The last part of this 3 part posting will cover the attachment of the wire mesh, test fitting the attachment lugs and adding the access to the launchers airhose.

Posted by on January 24th, 2011 Comments Off