Saturday, 23 May 2020

Living Hinge Hipster PDA

For more years than I care to remember I've been a fan of carrying a stack of index cards. As a freelancer trainer I used to pride myself in being able to whip up an interactive training experience if needed short notice with nothing more than index cards and a marker. I first came across the fact that there were others like me when I saw the Hipster PDA discussion over at 43folders  probably around 2007. I then had a brief peak of use with fans of the GTD productivity methods. Many people got into printing custom cards, calendar cards and more, but for me a plain old stack of cards and a binder clip was the classic. With one fault, after a few weeks of a deck of cards being in pocket they would look decidedly scruffy and dog eared. As such over the years a plethora of ideas to stop that have been deployed. The current one is this living hinge cover I drew up in inkscape and laser cut a few months back at the Ffiws Makerspace in Porthmadog. Cut from 3.125mm ply the hinge won't survive being sat on but is surprisingly robust, the clips work as well as they ever did and I use 4 clips so that some can be used as bookmarks for a current card over multiple projects. Finished with a small bit of elastic its easily pocketable and a good conversation piece when people notice the hinge section. :)

If you have access to a laser during these times (lucky you!) then I've posted the file on thingiverse for anyone to use. 

Wednesday, 20 May 2020

Thermal Insert Rig, modification of Dremel 220

Years ago I bought a Dremel 220 drill stand to help quicken the process of drilling PCB's, there is a lot online about the Dremel 220 already, and most of it is true.. whilst it can be a useful bit of kit if its all you have its wobbly and annoying and although you can get good results, you would be much better off with a small cheap drill press! That said mine has seen some use, often rigged as an extra hand holding the Dremel to use it as a small offhand grinder etc. Anyway, I've wanted to have a better option for pushing thermal insert nuts into 3d prints rather than just a soldering iron in hand and a pair or pliers. I have a plethora of the super budget Makerslife soldering irons (I reviewed them here!) and decided to have an attempt at converting one to fit onto the Dremel stand. 

At first I considered making some kind of adaptor that bolted into the existing mount for the Dremel and even got as fair as modelling the 18mm diameter 2mm pitch Dremel collar thread, but then realised that one bolt removed all the Dremel assembly from the main shaft and that it would be easier to have a soldering iron adaptor that just fitted straight onto the 16mm steel bar that acts as the sliding quill. 

I designed and 3d printed an adapter plate and realised I could unscrew the hot end from the handle of the soldering iron and I aimed to place the 3d printed adaptor in between the end of the element holder and the soldering iron's original handle. Having disassembled I realised I could pass the element and the wires through the adaptor and only needed to cut the ground wire and re solder it together and heat shrink it back together once assembled. 

The first attempted adaptor was too thin and flexed and also showed that, despite the plastic 3d printed adaptor being in the same position as the original handle, it was going to get to hot and begin to soften. I thickened the adaptor design and reprinted it with more infill. I then also reassembled the MKII version with some copper tape acting as a heat sink and also mounting the hot end using some over-size nuts and washers as standoffs to try and promote some cooling. It's worked and I whilst i can use it for a session to fit a few thermal inserts I think continuous use would probably cause the adaptor to soften eventually. I think the next iteration will be to use the adaptor as a drilling template to make a steel or aluminium one!

In testing it's been great, I could do with making some custom tips to mount on the end of the iron for different size inserts and as mentioned earlier probably remake the whole thing out of metal, however the inserts are going in well, and seem extremely strong!

Thursday, 14 May 2020

Record 74 Vice

Ages ago on twitter I noticed a friend of mine Tim asking about vice options and I was very pleased to be able to tell him of my love for Record vice's and the Record No 0 I've had for a long while and the Record Imp tiny vice I restored a while ago. We discussed various models and I sent him down the rabbit hole of the Record 74 swivel vice which is an excellent bit of kit that I didn't own, but shared my admiration of. 

A few weeks later Tim had found one near to him and had gone over and collected it and as it happened the seller had another. Tim was astonishingly kind and picked it up for me and sent it up to me as a thank you for helping him identify the vice he wanted. 

It's so very swish, a lovely bit of kit! I've been waiting to affix it to a workbench as I wanted to save it until a shed reshuffle had taken place, which is slowly happening with a new shed having been erected in the last month or so. The vice looks great and its a real advantage to be able to swing it around and also to be able to swing it out of the way if needed. It's been well restored and cleaned up with a new set of jaws made for it (as well as the originals) and looks fab. I might get rid of the red on the screw guard at some point as I don't think it originally would have been painted, but for now it can be admired and put to use!

Tuesday, 12 May 2020

The Rkub2 Microbit edge connector board

I've been tinkering with the micro:bit a lot more recently having used them for a couple of product reviews and tutorials for hackspace magazine. I was shopping around for an edge connector that I could use as part of a robot build that would break out the pins but also was able to handle voltage from a 3 cell 11.4v lipo battery. This RKub2 board was available on eBay for £4.99 delivered as a solder-able kit so it was worth a go.

It's relatively straightforward to put together with all the components being larger through hole types apart from two power regulators which are SMD but massive enough to be able to handle without tweezers! Once assembled it has all the pins broken out to a header socket row (or you could make this a row of header pins if you wanted to insert it into a breadboard more often). For power input it has a few interesting options. The first thing of note is that it has a connector for 3.3v which can receive the standard micro:bit battery box connector and therefore you can power the bit and have all the extra pins broken out using the standard 2 AAA batteries. On the other side of the board is a barrel jack connector which can receive a 12v input and also next to it are two pads for a 12v input. this is very handy as we can solder some wires with an XT60 connector to it and directly attach out 3 cell lipo battery. When powering the board from either 12v input a connected micro:bit is powered from the on board 3.3v regulator automatically and the whole unit can be switched on and off with the small switch. When powered by 12v (or 11.4v in our case) the board has a section on the lower right with power rails for 3.3v, 5v, and 12v (or the 11.4v input in our case).

For the project we had in mind for this board its been excellent as we were driving some motors with 12v driver boards and this board meant we had all the different power voltages and the micro:bit supply on the one board.

Monday, 27 April 2020

A live stream on Open Research Rocketry and Opensource!

I was really pleased last week to be invited to do a live stream talk facilitated by the amazing A Industriosa makerspace and lab in Vigo Spain. Above is the 1.5hr talk which featured lots of me waffling, a few minutes at the beginning with a few technical issues and a heap of great questions from the viewers of the live stream. Hopefully we have made some new friends who will get involved in emergent Open Research Rocketry opensource projects and perhaps inspired a few people to get involved in rocketry once Covid lockdowns eventually start to be relaxed.

Tuesday, 21 April 2020

Open Research Rocketry, First Opensource project released!

I've been developing Open Research Rocketry for a while and it has many lofty aims for rocketry in the UK. From non profit flights for people to fly small payloads on high power rockets, developing more launch sites and rocketry activity,  policy research and, of course, developing rocketry themed technology. All, of course, opensource. The plan was (and still is) to wrap this up in a not for profit company which has some commercial activities, but all surplus is used to offset and reduce STEM/STEAM activity around rocketry. Hopefully helping develop new rocketry communities, industry and inspiring people into involvement. Many aspect of this road map are currently on hold, including the company set up, until it becomes clearer when activity can resume on rocketry ranges and in education and other sites when counter Covid measures are responsibly eased.

However, some progress continues, I'm really pleased this week that we have released our first opensource hardware project which is a simple small PCB for igniting e-matches that are used in deployment systems in high power and research rocketry. It's a useful little module that may form part of people test set ups or indeed part of a modular flight computer system. It's brilliant that we have begun to have community contributions and merge requests also. Do check out the project here.

And check out the main Open Research Rocketry page and if you have any suggestions for opensource resources relating to rocketry do send them over for our resources page.

Wednesday, 15 April 2020

Fibreglass Rocket Nosecones using 3d printed molds

So the last week or so I have been experimenting with designing and printing small PLA molds into which I can lay up fibreglass to create nosecones for rockets. In this post I plan to share the progress so far. Before we star though I wanted to explain a bit about why I want to create fibreglass nosecones. I have very successfully used 3d printed nosecones in all scales from the tiny ultra lightweight single wall nosecone I printed for my A impulse UK altitude holding record "Imp" rocket, through to larger nosecone for high power rocketry. Fibreglass/composite however is attractive as it is lightweight but also strong, and also only requires a thin shell whereas many 3d printed designs need thicker walls or indeed to be a solid infilled part. I'm also interested in building a minimum diameter 29mm rocket airframe to try and break Mach 1 and so I need a nosecone that maximises strength whilst remaining as hollow as possible to hold avionics inside when space in the airframe is so tight.

So I first created the models for the nosecone I wanted to experiment with first, a 29mm ellipsiod design in OpenSCAD and then created a mold by cutting half the nosecone out of a solid cuboid to create a mold half. Working in this way and casting inside the mold means I made the nosecone void the actual required size of the outside of the nosecone.

I printed a pair of mold halves using 0.2mm layer height and was reasonably pleased with the quality and surface finish of them. For the first and second attempt I did nothing to the 3d printed mold halves and left them in exactly the finish that they came off the printer. Although epoxy doesn't adhere *that* well to PLA I still wanted to use a release agent, but due to current lockdown, I had to try and use items I already had. I'd read online about someone using Glycerin as a release agent. The first attempt therefore I painted a thin coat of Glycerin onto the mold halfs before wetting them with laminating epoxy and adding some very very thin fibreglass cloth I have that is 40g/m weight. Its super thin and as such the next morning the mold halves had cured but the material was to fragile to pull from the mold without breaking it. Also I feel that the glycerin had failed as a releasing agent. I reprinted the mold halves again for a second attempt again with no post production/finishing and the same layer height.

This time I used some neutral shoe polish as a release agent applied by a finger very thinly. I was careful not to allow it to fill the corners where the nosecone shoulder sat and managed to get a neat uniform layer over it all. This time I went with some 110g/m cloth and laid up the mold halves seperately.  Working at this small scale I had decided to try and make a single layer in both halves seperately with a margin of unglassed cloth left over and then I would do a second process to stick the two halves together with more epoxy and tape after trimming (hopefully) the first skin after it had cured.

Success, the next day the second attempt halves demolded pretty cleanly and although still flimsy showed that this could work (see top picture).

I trimmed the mold halves down as accurately as possible and then replaced them in the mold. I added a tiny smear of shoe polish to the mold half faces and then stuck the halves together with tape. At this scale it is pretty easy to get the mold halves to align, if I was working at a larger scale I would probably create keyed mold halves that interlock.

Having clamped the halves I then mixed another tiny amount of epoxy and added a strip of fibreglass cloth around the joint to stick the two halves together. It's difficult to work with such small amounts of such lightweight cloth through such a small aperture, but you don't have to be too precious as this will be on the inside of the nosecone so doesn't matter to much about the finish.

After this cured we could remove the nosecone and check it's fit in a piece of 29mm body tube, it fits perfectly! Once the nosecone is joined you can, of course add more layers internally to stiffen it etc. I added an extra layer inside and still this nosecone weighs less than 2.5g.

As  a next stage I wanted to create a Von Karman Haack nosecone as that is probably the preferred geometry for my mach busting rocket idea. The original ellipsoid nosecone had picked up the details of the inside of the mold and the 3d printing layers were visible. Whilst I am happy these could be removed/smoothed out with sanding, filling, priming and painting it makes sense to minimise this work. As such I printed the Haack nosecone mold at 0.1mm layer height which increased the resolution of the finish and I spent some time sanding the inside of the mold to further enhance the finish.

I also wanted to comment that the molds are definitely reusable, any errant epoxy that sticks to the PLA can be scraped off whilst maintaining the mold surface, I remade another ellipsoid to the same finish using the same mold.

The Haack nosecone having been remolded has shown that printing at 0.1mm and trying to maximise the quality of finish on the mold is definitely worth doing. Whilst some sanding and smoothing will be needed the surface finish is generally very good on this one.

Finally, once I have a slightly larger collection of molds sorted I will release a repo with them all in over on