Sunday, 19 February 2017

Making small Parachutes.. some tips.

So I'm working on a rocket that originally I'd started building with the idea of leaving incomplete for the rocket design workshops I've been running... I cracked and ended up putting it all together a while ago! However I realised to fly it I needed a chute size (50cm diameter) that I didn't have in my collection. So I made a couple of small chutes a while back as experiments out of some superlight ripstop nylon but struggled to cut it with an even edge which would then instantly fray as it cut. My remedy before was to turn and hem the edge all the way round. I wasn't too satisified with the results as the hemmed edge added a little weight (pretty negligible) but also added a lot of bulk when the chute was folded. So after some head scratching I did a few experiments in cutting/melting the nylon with a soldering iron.. brilliant results can be had with the cut both cutting and also sealing the edge instantly.

I found my little battery powered soldering iron the best for this with its fine tip.. my larger irons were too hot and caused a wider melt line whereas this one could create a neat cut less than a mm wide.

 I ended up slightly stretching the nylon over a wooden board and keeping it taught ish with some masking tape. This helped me both mark the circle (pen and a piece of cord swiveling around a central pin) and also helped the cut as I'd noticed if you cut an unstretched piece the melt line thickness can vary.

Added some binding tags to attach the shroud lines too. I made the shroud lines 2.25 x the diameter of the chute (50cm)

All packed up and ready to go... just need some weather (and I actually keep them stored unpacked as they can get a fold memory if you leave them packed and may not deploy correctly!).

Friday, 3 February 2017

Madlab Rocket Workshop

 Had a fabulous night in Manchester last night running my rocket design workshop at the mighty Madlab. It was the first time I'd seen the new (soon to be open to the public) Fablab space they have been developing and its a wonderful space filling up with some amazing kit. We had around a dozen attendees with a good showing of members of the Manchester Space Program . It was a good night and the group were really keen and interested and all really motivated to try out rocket stuff. I was also inspired as they were all really explorative and got onto many interesting subjects such as the feasibility of "rockoons"  (launching rockets of balloon platforms) and thrust vectoring and gimbal mounting motor assemblies... I hope they go on to do some experiments as there was a LOT of expertise in the room.
As ever when facilitating my overexpressive hands take over but hopefully I conveyed some decent stuff and I managed to get the group through laying out and simulating a simple rocket design in the brilliant opensource OpenRocket.

There was a lovely bonus for me last night that I got to see this rocket (picture is only half of it!) This rocket was donated to the Manchester Space people and I knew I'd seen the name before... it is Black Streak which has had at least one launch that I know of and its carbon fibre airframe has been up over 20km.... WOW. Very cool to see it in the flesh.

Finally MASSIVE thanks and props to the Madlab team, Claire, Finn, Tim, Sarah and others whose names I've missed.. you made me darn welcome and made everything really easy. Top.

Saturday, 28 January 2017

Workshop Preparation and Rocket Motor mount prototyping

Been doing some prep for the upcoming Rocket Design workshop I'm facilitating at Madlab I wanted to replace some of the images I'd used of motor mount assemblies in a presentation as frankly the old images weren't that great/clear... however I've since put the motor mounts into rockets so had to make a new one! I had a spare estes 24mm motor mount assembly which I've knocked up as an example.

It's been a bit of a motor mount week though as I've also been exploring motor mounting for a high power reloadable rocket motor kit I've bought with which I hope to scratch build a level 1 UKRA certification qualifying rocket around. It is the smallest reloadable motor casing that has options for the H impulse motor power I would need to fly to qualify.

The motor kit is a Cesaroni 29mm 3 grain kit and so I've been tinkering prototyping some mount components, again it's really handy having the small CNC to really accurately cut the centring rings and even cut a hexagonal pocket for captive nuts.. I find a 1.5mm endmill is small enough to not leave a radius that interferes with the nut.

So below is the prototype motor mount for the cesaroni kit!.. definitely a step up in size! When I have fully dialed in my design for the level 1 certification rocket I'll essentialy be remaking this mount assembly but using better materials, ply instead of mdf and some phenolic tubing instead of a (surprisingly accurate to 29m ID) tube from some wrapping paper... and applying the epoxy in a much neater fashion!

Sunday, 22 January 2017

OzQube 1 Pocketqube chassis work

Regular readers (a very elite bunch!) will know that I have been involved for ages with Stuart the brains behind the OzQube-1 pocketqube satellite for a few years despite us being on opposite sides of the planet! I've finally today made a start on a chassis for him from a blank I accurately sized over xmas. Theres plenty left to do and these small 50mm chassis always throw up some interesting stuff/challenges. Pretty much all the PQ chassis I've been involved in or have made always seem to involve tiny brackets which are a pain to make, working on this and the discussions around it have led me to come up with a PQ60 compatible design which doesn't rely on brackets... it's very much on the drawing board phase at the moment but watch this space for my usual snail like progress!

Tuesday, 10 January 2017

Asimov and the Slide Rule Boys

So I am re reading I Robot by Asimov as its a text on an open university module I'm doing. Its great fun revisiting this classic, I love Asimov and enjoy older science fiction as it's always interesting dipping into retro-futurism and comparing it to current technologies and trends.

The first few chapters are told as retrospective narratives by Susan Calvin regarding early issues with robotics.. she is telling stories in 2062 about things that happened to 2 roboticist trouble shooters around now/2017... and of course Asimov imagined this all before publishing in 1950.

So as well as reading what Asimov imagined the future would have created (positronic brains the big one in I Robot) it's interesting to see what technology available in the 1950's he imagined would still be in use in his future world. Enter 'the slide rule boys'. At numerous points the trouble shooting characters, Powell and Donovan, refer to the 'slide rule boys' meaning the engineers and physicists working for USRobotics creating the robots.... and yes.. it's sexist..I know.

For me (and I freely and proudly admit I am a slide rule fan who carries a slide rule every day) I love that Asimov considered the slide rule such an important device that it wouldn't be superseded by an imagined other technology, it is testimony to the device and its standing at the time in the 1950s. Although they have fallen out of popular use, falling prey to calculators and computers, they are fascinating devices and powerful tools for a variety of tasks to this day. The slide rule I carry everyday (as opposed to the larger ones for home use!!) is an Aristo nr89 which can calculate a surprising number of things by manipulating the slides, multiplication and division, tangents and sines, diagonals of squares, inch to mm conversions, circle areas and more and more. Interestingly for me slide rules also gave me a more concrete feel for logarithmic scales... and.. the Aristo 89 has a metric ruler on the edge so is quite handy for ..heck... drawing lines and measurements. :)

Wednesday, 4 January 2017

Are makers a movement?

Image by Andrewrabbott - Own work, CC BY-SA 4.0,

So this post is a response to Adrians post .... short version.. we mostly agree!

As ever feel free to ignore.. although I get involved in maker stuff I don't spend much time thinking about the form it takes so others are much better informed than me and indeed my definitions may be well off the mark. However here is my two penneth worth!..

For me I prefer the term maker culture or maker scene as I feel there is a broad culture of people globally linked by making within which I feel there are movements. For me a movement is when a collection of bits come together to create a unified direction towards a common when 'movement' is used to describe the bits in a clock all working together to make the hands reflect the concept of time. So I think there are lots of movements within maker culture.. but not all makers would align with all movements. So for example;

I see a lot of movement around restart and repair, from the magnificent restart party through to Make's appropriation of the phrase “if you can't open it you don't own it”. This unifies a lot of makers, from circuit bending re-users, to people designing and making ethically sourced repairable embedded systems, to those coming up with ways to reuse plastic bottles.

I see movement around localised production/manufacturing with global design, the fablab idea etc. This movement has a lot going on in it but those makers immersed in areas with lots of manufacturing opportunities might not align with it as a movement as they don't see a need. For example I doubt I'd have thought about PCB fab houses and the ethics and complexity of making at home versus using a UK fab house or euro manufacturer or a far eastern company... if I was a maker based in Shenzen...whereas as a maker halfway up a mountain in rural North Wales I do!

Citizen science, lots of makers I know are involved in citizen science projects and this could be considered a movement within the maker scene, as could many other areas, crypto currency, OSS/FLOSS, renewables, energy monitoring, opendata ...I could go on and on..

However some people are makers purely out of an autodidactic playful trait, in that they tinker with arduinos/launchpads/espxxxx/picaxe/fpga or PCR/geneslicing or CNC/lasers/routers/3dprint or diyspace/satellites/radio/rockets or hand whittle a bowl/spoon just because they want to learn and play with no particular end goal or aim... and this is where making seems more flaneurial than a movement to me.

So why does this subject catch my attention, well the difficulty for me considering the whole of maker culture a movement, is that I feel it could alienate people.. I know plenty of makers who just make. I was chatting the other day with a person who was telling me about their model trains and how they had created a massive logic gate control system for it.... for their own pleasure.. I certainly class this person as an archetypal maker... but part of a movement?... I'm not sure. If movement and common aim becomes the core of maker culture.. do we not kill off its aimless wandering vagabond spirit of freedom?

Thanks for listening. :)

Wednesday, 21 December 2016

OpenRocket 3d print design tip!

So I'm working up some ideas for a high power rocket and aiming to go for my level 1 UKRA certification at some point next year. I'm planning to scratchbuild as much as possible which means it can be tricky to know the exact weights of items you are designing into the rocket.. such as the nosecone which I plan to 3d print.

 I can get a really accurate estimate of what a component is going to weigh by modelling the piece in CAD (I have some code I use in Openscad that generates nosecone geometries based on parameters I feed in) and exporting a .stl file as if I am going to print it.

I then load the stl into the slicer I would use to generate the gcode for my 3d printer "Cura". Rather wonderfully having selected the infill and the material, Cura will give me a weight value of the finished item. I can then jump back into OpenRocket and overide the mass of the component which is then incorporated into the design and adjusts the centre of gravity accordingly. Neat!