Tuesday, 20 September 2016

Making Rulers.. and rocketry tools!

Yes.. I've been making rulers! It started because I wanted to make a tool to give away as a freebie at an upcoming Rocket Design Workshop I'm running for North Wales Tech group. One of the challenges when building small rockets is marking straight parallel lines onto the body tubes to mark fin positions or other attachments. A solution is to use a piece of angled bar as it will always lie accurately along a tube and cannot be off square. So for the workshop I thought it might be nice to knock up a small laser cut keepsake one complete with ruler markings and we'll put the workshop date and logos on etc. The two circle symbols on this one are used in rocketry to represent the centre of pressure and the centre of gravity which we'll be discussing in the workshop too so they act as a nice reminder. I cut these on the laser cutter at my nearby newly established Pontio fablab, which is excellent and its so easy to get good quick results on a laser cutter. However I can only access the space every now and again and wanted to see if I could make some rulers without a laser cutter on my cnc router. It's trickier.. the 2 small key chain rulers here are made on 3mm ply and have been engraved with a fine V bit, they are ok, but its difficult to get the resolution and clean cuts at this scale... I obviously need a laser cutter at home... feel free to send me one if you have one spare! Finally someone asked if I drew all the lines of the ruler sections by hand... there is a brilliant path effect in the mighty inkscape which allows you to create a scale along any shaped path.. brilliant!

Friday, 9 September 2016

I'm accidentally in a SPACERACE (and need your support)

Today I sent another pocketqube satellite chassis I made for Paul over to Germany, I've sent them before but this one was special, it's hopefully a flight model.

So regular readers will know that I am involved with building this for a pocketqube satellite project that's main payload is an experimental propulsion system called an EMdrive. EM drives have been discussed for a long time and have created a lot of arguments about whether they work and/or whether they break the laws of physics.. neither of these debates am I qualified or clever enough to comment on! However recently NASA eagleworks paper on their experiments with EM drives passed peer review and suddenly EM drives are less contentious and are garnering much interest academically.

Shortly after the NASA eagleworks peer review story, Cannae inc began to talk about how they are planning a cubesat launch to test their experimental EM drive system. Now.. I do wish them luck and every success... but part of me hopes that Paul and our EMdrive satellite can get there first! Part of this is ego obviously, but another part of me believes that amateurs/DIYers..MAKERS like us deserve to hold the bit of history of placing the first EM drive experiment on orbit.

The trials and tribulations of amateurs/diyers/tinkerers/mavericks is infused in the origins of EM technology all the way back to Roger Shawyer the innovative British scientist who proposed them. So.. how can you help.. well, put simply, we need funds. For testing and validation and launch we will need to raise around 25k euro.. peanuts to most space agencies but quite a lot to us. Although funding space projects is always high risk (no greater a week to know this after the spaceX rocket RUD) and there are many ways to fail you should be reassured that Paul has experience building, intergrating and launching satellites with his previous pocketqube satellite launch WREN. You can also check out our extensive blogs on this project on Hackaday.io

If you can and want to be part of something that possibly could be a watershed moment for mankind and space propulsion please join the brilliant people who have chucked some money in the fund here.


And if you can't.. help spread the word about our project in the spirit of making, pioneering and adventure :)

Monday, 29 August 2016

Test flights! Rockets and DIY altimeter hardware.

So got a bit of time to launch this rocket. I built it ages ago (it's an Estes Star Stryker kit albeit with an adapted 3dprinted nose) as I wanted to build the smallest payload carrying model rocket and indeed build a diy altimeter to go in it. 

So the launch and recovery went really well, low wind and clear skies I fired it with a B6-4 motor as I quite wanted to get it back! It launched straight and stable, deployed the chute well and was easily recovered (avoided trees).. perfect.

The DIY altimeter (think I'm calling it SIMPalt) seems fine after a reasonable quick decent (I think the 13 gram weight is at the limit of what the star stryker is probably designed to cope with payload wise).  I was primarily interested in whether the SIMPalt hardware would hold together structurally rather than the data as the code for the altimeter is primitive (library based and not calibrated) and at some point will be replaced with some code a much more talented buddy is working on for me. 

However.. just for fun I pulled the data from the SD card and made a quick curve.. this should not be taken as accurate (can't remember how fast this code was managing SD writes on the logic analyser etc...) but I am quite pleased that despite the noise the shape of the curve is pretty representative of the flight, the apogee to chute deploy and then the change in gradient as it's descent is slowed by the chute particularly. 

Tuesday, 16 August 2016

Variable voltage DC power supply

Finished making a little case (well a front and a back!) for this variable power supply that I had worked out and wired up a while back and then had on the (enormous) to do pile! I finally got round to drawing a bit of cad and I cnc routed these panels. The panels are just 4mm mdf with a bit of spraypaint to finish them. The gubbins comprises of a very cheap variable voltage dc-dc board which is a lm2596. They come with a small ceramic pot on the board to vary the voltage but I've replaced that eventually with a 10 turn pot to give me the resolution I need to set the voltage to 2 decimal places! (I say eventually, in testing I used an ordinary pot which proved the concept but was difficult to even hit a value to the nearest volt!!)
 These variable buck dc-dc boards take a voltage input of anything between 4v and 35v and will output a voltage range between 1.23-30v, they seem pretty stable. The display is a 3 digit voltage display like THIS, It is important you get one that is listed as having 3 wires, namely then it takes its power supply from the input voltage and has a third wire connected to measure the output voltage.. there are some that only have 2 wires that just connect across the output voltage which means when the voltage drops below around 3.3v.... they turn off! The 3 wire ones happy measure down to the minimum values. (note neither of the links are traders I've used.. rather just to show the stuff!)

The back panel has the inputs on the right and the outputs on the left all on 4mm banana jacks... I love cnc routing.. it makes you able to get these things really precise.. If I had had to drill those holes manually I would have designed it with more space between them making the entire thing bigger!

Anyway.... nice to finish one thing off the pile!

Thursday, 11 August 2016

A trip to CERN, Science, Innovation and Open Source.

So.. Been on holiday and toured around Europe taking in 9 countries and doing about 2600 miles over 3 weeks.. lovely! One highlight that is geeky enough to warrant a blogpost is I got a quick trip in to CERN just north of Geneva. As I had the kids with me the 4 hour tour was out of the question but the 2 visitors centres (mikrocosmos and the Innovation Sphere) where definitely do able... and they were brilliant. One of my best parts was chatting to an amazing guide ( a particle physicist who did shifts in the visitors centre and was FULL of passion) and in particular we talked about CERN and open source, prompted by me mentioning using Kicad which CERN have used and developed and shared back into the community, he spoke at length about numerous complex high end software/systems that CERN has done this with and affirmed in me that across the vast majority of the huge complex that is CERN and LHC and ALICE and  ATLAS and CMS an open source attitude prevailed. It was reaffirmed later in the trip wen you stand in front of a console that shows in realtime the data flow mapped over the world that is CONSTANTLY being streamed to hundreds of recipients around the world. Inspiring... I used to alway say that the ISS is mankinds greatest technological achievement... but darn... CERN is a close call...

Here are many pictures!....

Cloud chamber (refrigerated alcohol vapours) that captured and rendered visible particles passing through it.. cosmis radiation and muons etc! Kids loved this!

As well as great renderred and interactive diplay activities lots of real time data was on screen from the LHC.

All cryo pumps green!

Great virtual tour where you could steer yourself flowing through the particle accelerator and the 3 main experiments en route.. Photo's don't do it justice!

More live data

Live power use... blimey!

Outside there was a selection of pieces of kit... such amazing engineering and machining in these, beautiful. The above was a big RF chamber

The Gargamelle bubble chamber... revealed to humanity some neutrino secrets.

An amazing piston... about 2 meters in diameter it apparently pumped ovder 300million timnes in its active service at a rate of 3 revs per minute... each stroke delivering 350 tonnes of pressure! 

Ignore the dodgy dude in shorts (me) this sculpture had cast into it details of all major scientific and in particular physics milestones... inspiring.

The science and innovation sphere runs an immersive mapped projection show on multiple screens and surfaces in various languages... it was awesome and the kids really enjoyed the space. 

My daughter was really engrossed in this sphere... love this picture... the seeds of technology.

Thursday, 14 July 2016

Super Cheap Digital Read Out (DRO)

So, a DRO for machine tools (lathes, milling machines etc) is a digital read out that tells you the position of or how far a given axis has travelled. Obviously this useful if you want to make a part or a cut into a component to an accurate size, the trouble is... they can be very expensive! Even a hobby level DRO setup for say a milling machine can run to hundreds of pounds.  One common workaround (apart from using the engraved hand wheels) is to use a Dial Indicator set up to indicate how far a given axis has moved and indeed I've used that technique a lot. (it's a nice technique as it automatically cancels any error due to backlash as it isn't linked to the lead screw and always tells you the exact position of the axis). Still dial indicators and requisite holders/clamps can cost a few quid and can be awkward to get into a good position etc... so when I saw this hack to convert a tyre tread gauge into a micro DRO... I knew it was for me..

So these digital tyre tread indicators are super cheap... I paid £3.99 for one and could have spent less if I was prepared to wait for one to be delivered from the far east. They are essentially a short travel version of the cheap digital callipers that are widely available ( and indeed have the output slot that people have exploited to create data logging calliper )..  So the modification consists of a couple of different things... firstly you need to reduce the drag on the calliper slider which is created by a small steel slip inside the device.. this is for when you measure a tyre tread you can position the indicator then remove it from the tyre to read the result and the slight friction on the slider keeps it in position. For the DRO hack we need it to be as free to move as possible. Once this is removed I turned a small collar for the end of the probe from some Delrin which was drilled to fit the probe end snugly and the other end drilled to house a cheap but powerful 3mm diameter neodymium magnet

For the next part I whipped up a quick drawing to be able to CNC rout a plate for the base that would house the larger magnets. I made the toolpaths tight to the 8mm diameter of the magnet so that they were an interference fit and required pressing in on my small arbour press (also for added security I put a blob of superglue under each magnet). I then glued the magnet base to the base of the unit and hey presto... a portable quick fit DRO!

It works great, I am really pleased with it and will probably for the price make a couple more.. Its also great that the 8mm magnets are enough to hold the device firmly even if only 2 magnets are attached to whatever it's clipped too. The zero function of the device means that even though it only has a small throw (27mm) it is easy to sequentially move the DRO and zero and keep a running count of position over a longer length. 

Saturday, 9 July 2016

Another quick make, Ball and socket joints!

In amongst a busy week I managed to fit a little make in! I was inspired to make these by my twitter buddy Rob Ives ... for the uninitiated Rob is a master maker and what he can't engineer out of paper doesn't leave much! Check out his website for some great stuff and projects to download.. https://robives.com/ 

So anyway.. these ball and socket joints are made from some cheap 12mm nylon beads I got on ebay which I drilled and tapped (awkwardly... the nylon tends to melt when drilling making it tricky) to take some M4 bar.. The wooden sockets are cut on my CNC with the holes for the beads being 9mm diameter. A bit of tension on the bolts and the result is a grippy yet positionable joint. I then turned up a small 8mm lug and tapped it to M4 as well and attached a crocodile clip (with a blob of epoxy) to the other end. Hey presto... another accessory for my ever growing accessory station!