Posts Tagged ‘howto’

 

How to make a 2L Reinforced Bottle

We are trialing using 2L reinforced bottles to power the rocket car. Here is a brief overview of our process.

We start with 3 bottles

- 1 x 2L bottle
– 2 x 2.25L bottles (although 2L would probably suffice)

Start with 3 bottles

The 2 x 2.25L bottles are cut so that one will go over over the bottom of the 2L bottle and one will go over the top. There is an amount of overlap as well where the top and bottom sections overlap to be 3 layers thick.

Cut out sections + 2L Bottle

Close up of the 2 cut sections

The next step is to shrink slightly the 2L bottle. A big pot is required which can be filled to a depth of 3/4 of the bottle + have spare volume so no hot water splashes out when the bottle is inserted. Be careful of this, make sure the pot is big enough.

Bring the pot of water up to about 75 degrees, you can test this by quickly inserting the bottle 2 seconds or so and see if it shrinks slightly. Dont get the water too hot or the bottle will shrink to fast and deform. Once the water is the correct temperate insert the bottle for 2  seconds and check how much the bottle shrinks. Its better to do it a few times rather than have the bottle too long in the water and deform.

Submerge the bottle to past 1/2 way until the bottom section shrinks, then turn the bottle around and do the top as well. Be very careful with the top, you dont want the spout deforming.  What you should end up with is a bottle that is slightly smaller over the entire area (except the bottle throat and cap section).

The next step is to fit the other two sections. Start with the bottom section first, you will find that as its a close fit it wont slide on easily due to the air trapped in the bottom section.  There are a couple of ways around this. One is to use a wooden skewer or similar and push it between the two bottles so the air trapped in the cutout bottom section can get out, or you can drill a small hole in the base of the bottom cutout (not the 2L) bottle and air will get out this way. As we are going to fit a Robinson coupling anyway this hole wont weaken the second bottle.

You can put a bit of PL premium between the two bottoms of the bottles to hold them together but this is optional.

Once the bottom section is on, put the top section over the top of the 2L bottle, we slide the top section underneath the overlapping bottom section. TO do this its easier if you have a wooden skewer and run it around the bottle while you push the top section in, then just push until the top section is in place. You will find that once in place they really dont move. You can add a strapping of fibre reinforced tape if you wish.

Here is a pic of the bottle when finished. Its has already had a robinson coupling added to it.

Completed Reinforced Bottle - Robinson coupling added

If you look carefully you can see the slightly shrunken inner bottle.

Posted by on June 26th, 2010 1 Comment

How to Make a Robinson Coupling

I have found a supplier of threaded lamp rods, washers and nuts that fits the bottle caps perfectly. If you are in Australia then Beal Pritchett Pty. Ltd. in St Leonards is the place to go :)

I wanted to make sure the parts all fit correctly so I put one set together, it made sense to make a video so it may be of some assistance to others trying to join bottles.

Parts used are

– 1 x 30mm x 10mm OD. threaded lamp rod
– 2 x 14mm OD nuts
– 2 x 18mm metal flat washers
– 1 x bicycle inner tube for 3 rubber gaskets
– 2 bottles – 1.25L in this case
– 1 bottle cap – standard 28mm bottle cap
– Threadlock – (optional)

Tools used
– 2 socket wrenches
– 2 x 14mm sockets
– 1 x shorts socket extension
– 2 x long socket extension
– Metal coat hanger
– Electric Drill
– 3mm & 10mm drill bits
– 10cent coin (22mm diameter)
– Sizzors

The video is below, expert camerawork by Mark :)

Posted by on May 30th, 2010 2 Comments

Small Diameter + Longer Thread Nozzle

After some previous failures at making smaller diameter nozzles, our new solution involved inserting a disc with a small diameter hole between the bottle and the gasket inside the bottle cap.

Unfortunately we were having trouble with leaks when we had a 1.5mm – 2mm disc inserted in the cap. The cap just didn’t have enough thread to make a good seal.

This week George from Air Command posted a video (definitely worth watching) showing how to use different types of bottle caps as nozzles to increase the length of the thread dramatically. This is just what we needed :)

We scoured the house for empty bottles / pump packs and found one that had the same thread as a drink bottle. We decided to commandeer it for testing … luckily the normal drink bottle top fitted the pump pack so no need to waste the contents of the pump pack :)

Pump Pack Nozzle and Normal bottle cap

Pump Pack Nozzle and Normal bottle cap

Its obvious how much longer the thread is on the pump pack .. The pump mechanism was disassembled. Use a pair of long nose pliers to remove the white disk from inside the cap, then bend some of the tabs on the pump section and it will come apart quite easily. It already has a hole ready for the gardena nozzle.

Pump Pack Dissasembled

Pump Pack Disassembled

Here is  a close up of the difference in size of the nozzle and the normal bottle cap

Normal Bottle Cap + Longer thread Bottle Cap

Normal Bottle Cap + Longer thread Bottle Cap

Top View Comparison

Top View Comparison

You can see on the last pic there was a small 1mm ridge that was filed off to make the top of the green cap smooth. This will allow a nice mating with the Gardena launch adapter. The existing hole was just about perfect, we probably enlarged it 0.5mm and the gardena snaped in perfectly.

Next step is to make the reduced diameter disc. Scouring the $2 shop we found some cheap signs that stick to the back of cars. They are 1mm thick plastic which is slightly flexible. A 24mm disc was drawn on one and cut out. A 6mm hole (can vary based on what size reduced nozzle you want to make) was drilled in the centre and cleaned up.

Cap + Gardena 9mm nozzle + gasket + 6mm disc

Cap + Gardena 9mm nozzle + gasket + 6mm disc

We found that the disc needed to be inserted between the bottle and the gasket (see below), other way around caused leaks.

Reduced diameter disc fitted

Reduced diameter disc fitted

Here it is fitted on the bottle

Nozzle Fitted to the Bottle

Nozzle Fitted to the Bottle

Fitted ready to test

Fitted ready to test

The longer thread nozzle clips properly into the launcher and doesnt pop out as George advised us to look out for which is good. See below

We tested up to 80psi with air only on a 1.5L bottle with no leaks. Next test will be with water to see how the disc stands up to the pressure of the water rushing out.

Posted by on September 3rd, 2009 Comments Off

Water Rocket Car MKVIII – How to Make a Rear Wing

Its always good to learn from what other people are doing with water rocket cars … thunderrockets from Belgium .. have been testing a water rocket car with a Top Fuel Dragster style wing on the rear. From the videos it looks like its providing good rear stabilization, so we thought we would give Wild Bill a last lease on life and replace the fins with a rear wing, hoping this will provide more rear stability ….Here is how we did it.

Design Stage

Firstly it was out with the pen and paper to get some ideas of how it should look, then adding some dimensions based on measurements of the existing water rocket car. Here are the initial drafts. YOu will probably need to click on the images for a bigger view of the pictures.

Initial Wing Design

Initial Wing Design

Initial Measurements

Initial Measurements

We are not sure how much down force is required, so we designed in an adjustable wing attachment that allows the angle of the rear wing to be altered.

Build Stage

First the wing mounts were cut out, (all are made from 7mm plywood). Then the adjustable pieces were cut and a hole drilled for the pivot and 5 holes for the variable angle bolt.

Wing Mount + variableangle attachment

Wing Mount + variable angle attachment

Two bolts and nuts are used to secure the wing mount to each variable wing attachment.

Then the wing end plates were measured and cut-out. These wing end plates make the wing more efficient by not letting air spill over the edge of the wing. All air is forced over the entire length of the wing to produce the maximum downforce possible

Wing End plates measured ready to be cut out

Wing End plates measured ready to be cut out

and here they are cut out and sanded

Endplates

Endplates

The main part of the wing was measured and cut out. Practically its a square 200mm x 266mm. The end plates are then glued and bolted to the wing. I used one attachment up and one down to secure it.

Wing with end plates - rear view

Wing with end plates - rear view

Wing with end plates - front view

Wing with end plates - front view

Four small L brackets were bolted to the variable wing attachment. These provide the locations where the variable attachment bolts to the wing itself. Here are the wing mounts + variable attachment and the wing ready for mounting to the water rocket car.

Pieces ready to mount to water rocket car

Pieces ready to mount to water rocket car

The wing mounts were then attached with L Brackets and screws and nuts to the chassis of the water rocket car. These were practically in similar locations the the previous fins. The mounts had slots cut in them to fit around the wheel mounts

Wing Mounts attached - side view

Wing Mounts attached - side view

Wing Mounts Attached - rear view

Wing Mounts Attached - rear view

The wing was placed ontop of the wing mounts and variable attachments, centered, then locating holes marked to be drilled. These holes were then drilled and the variable attachments removed from the wing mounts and bolted to the wing itself.

Wing with variable attachments - side view

Wing with variable attachments - side view

Wing with variable attachments - rear view

Wing with variable attachments - rear view

The variable attachments were then bolted to the wing mounts. The variable attachments are in the middle location (3rd of the 5 holes)

Current wing angle

Current wing angle

Here are some pics of the wing in place

Attached Wing - Front view (no wheels)

Attached Wing - Front view (no wheels)

Attached Wing - Rear view (no wheels)

Attached Wing - Rear view (no wheels)

And with the rear wheels attached

Rear Wheels attached

Rear Wheels attached

Front Bumper

Also to try to minimize the wheels being ripped off during testing, we have added a front bumper, which can take all the punishment of the gutters instead of the wheel mounts .. well thats the idea anyway …

Front Bumper

Front Bumper

Not exactly aerodynamic but we can work on that.

Finally here is a pic of the MkVIII Car ….. Wild Bill + a Rear Wing .. hopefully tamed a little bit …..

MkVIII Ready to test

MkVIII Ready to test

Posted by on September 1st, 2009 1 Comment