Posts Tagged ‘howto’

 

Updated Abort System – High Pressure Components

Abort System Upgrade
Our next launch day of the rocket car will be with the reinforced bottle stack and a launch pressure of approx 150-170 psi. With this in mind we have

– added 5m of high pressure hose to move the abort system back further  from the launcher
– replaced the lower pressure hose with the 290psi high pressure hose
– replaced the plastic T piece with a metal one and metal joiners
– mounted the hose and valve to a piece of wood for better stability when operating

Updated Abort System

The Abort extension hose has the Gardena quick release on the end of it currently as the launcher uses this for its quick release,  this will be replaced with a nitto quick release when the launcher is updated with the high pressure hose and connectors (this is the next planned  update).

Extended Hose and Gardena Quick Release

The T piece has  three 1/4″ BSP threaded male connectors. Each of the hose connections uses a barbed female 1/4″ BSP connector. The barbed section of the connector fits down into the hose and is clamped. The female threaded section screws on to the male connector of the T piece,  teflon tape was used to stop any leaks. The hoses are secured to the board with 15mm saddles .

Metal T Piece and connectors

Accurate Distance Measurement
We would like to get a accurate measurement of the next launch distance as (fingers crossed) it hopefully will be our longest yet. We have invested in a 50m tape measure to mark out the road with 10m increments as accurately as possible.

50m Tape Measure

50m tape measure

Posted by on October 27th, 2010 Comments Off

Water Rocket Mist Attachment – Static Test

An interesting development we saw on www.wra2.org from Jelo and Thunderrockets was a device called a mist rocket. This is an alternate method of mixing the air and water into the exhaust plume which produces a single air/water thrust and not the normal water then air pulse of a standard water rocket. Also when flown vertically there was a distinctive jet sound.

We though we would give this a try for our water rocket car.

The design uses a PVC pipe to funnel water from the second bottle to the nozzle. The air pressure in the top and bottle bottles are equal. The air in the top bottle pushes the water down the pipe and the air pressure in the bottom bottle forces air through two (2) small holes to mix air with the water just prior to escaping from the nozzle.

This is how we built it and tested it.

First we purchased some 20mm electrical conduit and a conduit cap. The 20mm conduit just fits in the 22mm bottle throat. A 10mm hole is drilled in the centre of the conduit cap and a 10mm internal diameter (ID) nut from our robinson couplings is carefully glued (with 24hr araldite) into the base of the cap, making sure no glue gets on the threads.

20mm Conduit Cap with 10mm ID nut - no glue yet

The conduit cap is then glued (24hr araldite again) to a section of 20mm conduit (longer than the bottle at this stage) and left for 2-3 days to set properly. Once this is set, this section should screw easily onto a standard 10mm robinson coupling thread.

Conduit connected to threaded rod (robinson coupling rod)

The next step is to cut the conduit so that it fits just inside the nozzle cap. The section is screwed onto the robinson coupling between two bottles then marked, unscrewed again and cut to size. The conduit shouldn’t protrude past the bottle lip as this will cause the bottle lip not to seat properly against the rubber washer in the nozzle and the bottle wont hold pressure.

Conduit cut to size of bottle

The conduit section then needs 2 holes drilled near the base of the rod. we used 6mm holes, these are to let air from the bottom bottle mix with water from the top, also if any water does get in the bottom bottle it allows it to escape.

Conduit section with cap and 2 holes drilled near the base

The completed conduit (now referred to as mist attachment) is then inserted into the bottle and screwed onto the robinson coupling. Note that about 10mm of thread was needed on the threaded rod to catch on the nut threads.

Robinson coupling ready for mist attachment

Mist attachment connected to robinson coupling

The the nozzle is screwed into place and its ready to test / launch. Here is the pic ready to test

2 Bottles with robinson coupling and mist attachment - Ready to test

The handy thing with this attachment is that it can be added and removed quite easily for test or launch.


Mist Attachment Test

The test we conducted was a vertical static test with 1L of water (no foam) and 100psi. The bottles used are 2.25L bottles. We were interested to see the following

– If we could reproduce the jet sound that thunderrockets produced on launch
– Examine the exhaust plume to see if it generate a good air / water mix
– Examine if there was any distinct air pulse after the water was ejected from the bottles

We did find that filling the top bottle a little more challenging to ensure water didn’t get in the bottom bottle. We used a small section of hose connected to a funnel to get the water past the 2 holes in the mist attachment, then gently pumped the top bottle.  Here is a video of the test

Conclusion

– We didn’t get the jet sound, even after 2 separate static tests – its a possibility that the rocket needs to be flying through the air to generate the sound, or possibly the holes were too big.
– The exhaust plume definitely had a good mix of water and air and produced a spray similar to a foam launch
– There was no distinct air pulse after the water was ejected
– An interesting observation was that there was minimal (a small amount) splash back in the bottle at the end of the thrust phase.

We will try this test again in a horizontal configuration to suit our water rocket car

Posted by on July 27th, 2010 5 Comments

Horizontal & Vertical Launcher Upgrade

Since we have been concentrating on water rocket cars for the last 6 months, our vertical water rockets have been collecting dust in the garage. So this weekend we have upgraded to launcher so it can be used for horizontal as well as vertical water rockets. This way we can launch the water rocket car as well as our vertical water rockets on the same launch day.

To achieve this we have  added an extra splash guard on two hinges which are fixed in the horizontal position by 2 bolts. We will replace the nuts with wingnuts to allow easier removal.

Extra Splash Guard on hinges

The extra splash guard has a slot cut out for the launch string to feed through in horizontal launch mode.

Splash Guard slot

Here is the launcher in the horizontal launch mode with its height adjustable gardena quick connect.

Launcher in Horizontal launch Mode

A support rod was cut and bored through the centre to allow a bolt to fit in it. A correct sized nut was then countersunk and apoxied into the top of the support rod.

Support Rod with nut embeded

The support rod clips onto the launcher when not in use

Support Rod stored while not in use

When the two botls are undone from the bottom of the launcher and the splash guard is moved to the vertical position, the support rod fits into a 22mm countersunk hole in the underside of the splash guard. A screw then holds it solidly in place. Here is the launcher in vertical launch mode.

Launcher in Vertical Launch Mode

The launch string is moved to  accommodate the vertical launch through a 90 degree bend.

Launch string moved for vertical launch

It takes only a couple of minutes to swap from one launch mode to the other. The 20Litre water container is used in both modes and keeps the launcher firmly in place.

Posted by on July 19th, 2010 Comments Off

High Pressure Air Hose – Upgrade (100th Post)

This weekend we have upgraded the air hose on our launcher to the new 290psi (working pressure) air hose.  The air hose had Nitto connectors so we have continued to use these where a connector is needed.

First step was to remove the old coiled air hose and install a Female Nitto quick release to the Air pump hose. The air pump hose has an internal diameter of 8mm, so getting the 10mm barbed section down the middle of the air hose took a little while. Here is the pump with its Nitto quick release installed.

Air Pump with Nitto Quick Release - Closeup

and another pic of the pump

Air Pump with Nitto Quick Release

The Nylex High Pressure Air hose is 15m long and the male end clicks straight into the quick release on the pump.

Pump and Air Hose connected

The next part was to install a male Nitto connector to the abort section of the launcher.

For this we used a small section of the Nylex hose and one of the male Nitto connectors. As the Nylex hose has an internal diameter of 10mm this was relatively easy. The other end of the Nylex hose connects to the abort T piece which has a 12mm barbed section. This took a bit longer to get on, but some hot water and a few expletives later and it was on.

Abort section with Male Nitto connector

The male Nitto connector on the abort section clicks into the female quick release of the 15m air hose.

15m Air hose and Abort section connected

The Gardena quick release is still used to connect to the launcher itself. We will probably upgrade this in the near future now we know the 10mm hose will fit over a 12mm barb. We will also be replacing the plastic release valve with a metal one and increasing the length of hose from the release valve to the launcher.

The Gardena uses standard 12mm fittings, whereas the air hose use a standard 10mm fittings, so there needs to be a conversion at some point. Here is a pic of the pump and abort section all connected.

New Airhose - all connected

A quick test today up to 100psi showed no leaks, we will do a higher pressure test prior to the next launch day.

Also a small milestone, its  our 100th posting on the HHWRSA website and our 2 year anniversary of HHWRSA :)

Posted by on July 18th, 2010 Comments Off