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#230 - Tajfun 2 L2

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#227 - Zip Line

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#225 - Air Pressure Exp.

#224 - Tajfun 2

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#193 - Coming Soon

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#187 - Skittles Part #1

#186 - Level 1 HPR

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#180 - Light Shadow

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#177 - Reefing Chutes

#176 - 10 Years

#175 - NSWRA Events

#174 - Mullaley Launch

#173 - Oobleck Rocket

#172 - Coming Soon

#171 - Measuring Altitude

#170 - How Much Water?

#169 - Windy

#168 - Casual Flights 2

#167 - Casual Flights

#166 - Dark Shadow II

#165 - Liquid Density 2

#164 - Liquid Density 1

#163 - Channel 7 News

#162 - Axion and Polaron

#161 - Fog and Boom

#1 to #160 (Updates)



Each flight log entry usually represents a launch or test day, and describes the events that took place.
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Day 70 - Open Day, Acceleron V, Simple G-switch, FC V1.6 progress
Setting up at the open day. The event took place at a local primary school library.
Heavy duty ERG hardware goes several kilometers high.
More hardware
Mmmmm ...high velocity chocolate ....
Our water rocket stand set up.
Phil demonstrating how to glass body tubes.
Acceleron V is still under construction. It has about ~33L capacity.
Parachute will be located here. Currently it is held by Velcro.
The staging mechanism pod is now smaller and features an upgraded FC.
G-switch components. An RCA plug, an extension spring and a small brass weight.
Cross section of G-switch.
Assembled G-switch
Reverse view.
Components have arrived for the small run of FC V1.6 that will soon be built.

Date:  22nd November 2008
Team Members at Event:
GK and PK

This weeks' update is a bit of a mixed bag of different things we have been up to. Most of the time spend over the last weeks had been getting things ready for the NSWRA Open day.

Open Day

The open day went quite well. Although there were perhaps less people than I had expected but it was actually better because we got a chance to talk to the other rocketeers about their projects. It was interesting to see some of the high power hardware being developed by ERG as well. Phil gave a good presentation on fiberglassing body tubes, and after seeing some examples of the strength and weight of the tubes, we've decided to go to the next level of construction and have a go ourselves at making reinforced body tubes for our rockets. The next day I went out and bought a few things for the process. I'll be adding a few more things to the Christmas wish list.

Acceleron V

We've started re-building the Acceleron booster. Over the past couple of months we've been collecting 2L bottles so that we can splice them together. All up the booster uses about 50 2L bottles to make up the booster segments, transition sleeves and neck reinforcing.

The booster is the biggest we have made to date at ~33L. Previous versions of this booster were 24L and 18L depending on the bottle configuration used. Here each of the three segments is made up of 3 spliced pairs of 2L bottles tornado coupled together. At 130psi the pyro rocket equivalent is an H310. (~250Ns total impulse) with 13mm nozzles it is more like an H500.

The staging mechanism pod is similar to what was done on the previous versions of the booster. The big difference is that it is now smaller and lighter and no longer contains the parachute. The parachute is now stored in the space between two bottles of one of the segments. The parachute is released using the piano hinge mechanism that has worked well for us on a number of our other boosters.

The TDD pressure switch has been reused and the V1.4 FC has been replaced with V1.5 and configured for booster operations.

There are still quite a few things to do on this booster such as attaching fins, reinforcing more bottle necks, attaching the sustainer support sleeve and pressure testing all the bottles.

Simple G-switch

The flight computers/timers we use usually need to be triggered on launch. Over the last couple of years we have tried different ways of building G-switches some worked better than others. So we are adding another one to the design mix. The main reason that we are building our own is that commercial G-switches are around $9. As we ramp up production of FC V1.6 we wanted to be able to bring down the cost of the whole unit.

This version of the G-switch is made from a 50 cent female RCA plug bought from the local electronics store. We drill out the insulating plastic with a Dremmel tool and thread a thin extension spring through the hole and solder it to the center contact. We then solder a small brass weight to the other end of the spring and the G-switch is finished. The RCA plug conveniently gives us the electrical insulation between the two contacts, the solder lugs for the electrical connections, as well as providing a good mechanical mounting point. Because the outer contact is circular, it does not matter which way the G-switch is attached as long as it is horizontal.

The G-switch is tuneable by changing the brass weight, or spring length.

Flight Computer V1.6 Progress

We've now received all of the components to build 20 of the V1.6 flight computers. I'm hoping to finish the PCB shortly and will send it away to have it manufactured. I've been using a new version of Eagle to design the PCB. It took a little time to get up to speed with it and create some custom components, but overall it is a very powerful tool. I like its schematic / PCB layout interaction that basically lets me design the circuit diagram and it maps the nets to the components layout. A quick run of the auto router then generates the double sided tracks with vias. Nice and easy.

The software for the flight computer is mostly finished and has had the user interface simplified. I have replaced the multiplier, offset & delay parameters that were a little harder to interpret by the casual user with direct time setting ranging from 0.1s to 99.9 seconds in steps of 0.1 seconds.

The time can only now be set in the configure mode, meaning that when the computer is turned on, a single button press will arm it. Again simplifying the user interaction with the flight computer.

I may add an option to be able to switch the servo motor timing from 1 - 2ms to 0.5 - 2.5ms as some servo motors need this timing to get full range of motion. So much for standardisation by manufacturers. This request actually came in from the Oberon WR team after they built a version of 1.5 and found that their 180 degree servo did not quite get the full range of motion that it should have. We were able to replicate this issue with one of our cheaper 180 degree servos.

We are just hoping for some nice weather this weekend so we can do some launching.

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