Recycling 18650 cells into Useful Battery Packs

This has been on my todo list ever since I reviewed the Sunnko 709A spot welder machine in Hackspace Magazine issue number 48 and I finally got a bit of time to play this morning. Making battery packs from recycled 18650 cells, the cells commonly found in older end of life laptops and other devices, is nothing new and there are plenty of technical blog posts and youtube guides out there to explain the process. It appeals to me on a few levels, I like the recycling part but also it's handy to make some battery packs up that can be used to power FPVground equipment or even for use with my Pinecil soldering setup in the field. Of course it's also great practice perhaps for making 18650 packs with brand new cells which I may be tempted to do for long range drone or fixed wing projects as you can pack a lot more capacity into a smaller and lighter battery than a LiPo.   

I recovered these three cells from an old Sony laptop battery someone gave me and whilst I recovered 5 cells, I only wanted to build a 3 cell battery. I spent some time charging the cells to find that they were all serviceable and then made sure to charge these three cells so that their voltages matched pretty closely. This is useful when making a battery which you wish to balance charge as then it doesn't take an age in the first instance getting the pack to balance. The cells as recovered retained the little paper disks on the positive end which afford protection from shorts, It is good practice also to add extra insulation between the 18650 cells to protect from accidents and you can see in the above image I arranged the cells with some barley gasket paper between them. Whilst many people use a jig to hold the cells and then the pack covering to reinforce them, I decided a few spots of hot glue make for a robust structure.  

Next up I cut some nickel strips to make the connections and then spot welded them using the Sunnko machine. For the strips that connect the cells I simply made straight cuts but for the positive and negative terminals I wanted to make tabs with smoothed edges to solder to to avoid them snagging or cutting any insulation or wiring. The spot welder can create really nice joints and it's great to be able to avoid soldering directly to the cells as it puts a heap of heat into them and isn't massively safe.

All that remained was to solder up an XT60  battery connector and also a balance connector and associated wiring.  I made up my own balance connector using a JST XH connector and it's relatively straightforward to wire up, soldering to the new spot welded tags in between the adjoined cells, again, with some decent flux and a hot iron it's much easier to avoid putting too much heat into the pack. Finally a good dose of sanity checking and triple checking with the multimeter that everything is connected correctly and it's happily charging correctly. I've just used some Kapton tape to insulate the pack and hold the wiring in place, a more common approach is to find some large heatshrink which is on the list to pick up at some point. As I'm not too worried about the weight or the ascetics I am tempted to just give it a good wrap of PVC tape. 

Tool Tuesday - Wire Brush

This is a tool that perhaps shows my predilection for rusty projects! The wire brush is an excellent tool for loosening and removing rust or loose surfaces. It's a tool that gets a lot of use on my collection of scruffy vehicles but also has been used to remove flaky masonry paint and more. It's not a refined tool and I tend to go for the budget end if possible as they are almost by definition destined to be abused. 

Bonus content! - Hackspace Magazine Lockpicking Articles

I've recently written a 2 part article in Hackspace Magazine about locksport and lockpicking, the first part (issue 48) covers the basics around lockpicking practice and essential stuff such as the golden rules, never pick a lock you don't own and never pick a lock you depend on. The second part (issue 49) looks at DIY lockpicking/locksport tools where we made some picks, tension tools and a practice board. Occasionally when I am writing this type of piece I have to edit out sections to meet the word count requirements of the article, in this instance I culled a section on how to re-pin a lock. I'm posting it here as it's a really useful skill that can mean you need fewer practice locks and can get multiple setups/pinnings per lock. 

Re-pinning a lock is a useful skill that can enable you to create a new challenge out of an existing lock that you have got used to picking. Essentially you are removing the centre core of the lock and removing the pins and replacing them to make the lock a different challenge. A standard 5 or 6 pin tumbler lock has the core of the lock retained with a C clip in a machined groove and this can be removed with a pair of pliers. Once you have removed the clip, be careful to not pull out the lock core until you are ready as all the pins will fly out and potentially get lost. You can’t remove the core until the lock is in the unlocked state. If your lock currently has a key that fits you can insert the key and then unlock the lock, but only turn the key an eight of a turn. With the key turned rotate the whole lock assembly so that the key is now vertical such that if you removed (but don’t do this yet) the core the key pins would remain sat in the now vertical channels in the core. A plug follower is a dowel, or indeed a 3D print in our case, that matches the diameter of the lock core. These are quite commonly half an inch in diameter. The plug follower allows you to remove the lock core without releasing all the pins at once. Whilst removing the lock core hold the plug follower flush with the far end of the core and feed it in as you move the core out. If all has gone well you now have the lock core, with the key inserted, and all the key pins still in the holes and you have the lock body with the springs and driver pins still in each channel hole block by the plug follower. Cover the end of the lock or place it flush onto a table top and then slowly retract the plug follower from the other end. You should hear each driver pin and spring release and once the plug follower is out you can lift the lock body and find all the springs and driver pins safely on your work surface. Re-pinning the lock reverses this process. Note that if you swap the key pins to different locations, making a new challenge from the same lock, your key will no longer fit or operate this lock. You can, of course, pick the lock into an open position and re-pin it back to work with the key.

To re-pin the lock place the plug follower at the back of the lock and with a pair of tweezers carefully place a spring into the hole furthest into the lock, next grab your driver pin with the tweezers and place that pin over the spring and push it until it is slightly seated into the hole. Next push the plug follower into the side of the driver pin, you should be able to trap the driver pin, binding it on the hole edge and then use your tweezers to push the pin fully down into the hole, you can then slide the plug follower over that pin to secure it and move on to repeat the process for the next pin. Finally once all the driver pins are replaced you can place the core, containing the key pins, back into position, lock the lock by rotating the core and then re attach the retaining C clip.

Tool Tuesday - Bahco Hacksaw

The dedicated reader might have noticed that Tool Tuesday has been quieter of late. I decided that I would move from every Tuesday to a more relaxed every now and again approach, hopefully equating to around one Tool Tuesday a month. The idea being then I also do more blogging on personal projects.... well never say never!

Anyway today's Tool Tuesday is this excellent Bahco hacksaw. Whilst a great step up from a no brand cheap hacksaw, this Bahco sits firmly in the middle ground and is available for around £12-16. It's a very nice frame and handle, comfortable in hand and the blade tension bolt and handle are excellent. The black moulding on the far end works well for a guiding hand and some pressure application and as such it returns very accurate cuts. What really makes this hacksaw shine though in my humble opinion are the Bahco Sandflex Bi metal blades. I've yet to break one and they seem to last a very long time. Mine is due a new blade but I can't remember the last time I opened my spare blade pack to replace one which tells me all I need to know. 

Tool Tuesday - Record Ball Peen Hammer

I mostly associate Record with excellent engineering vices but it's fair to say they have had their branding on a lot of tools over the years. I've had this Record branded ball peen hammer since my mid teens (late 1980's) and it's an excellent bit of kit. Sadly the model number is obscured/worn but reading around a lot of this era Record hammers are actually rebadged "Marples" hammers that are very well regarded. The castings on the head are nicely made and the hickory handle is still the original, despite a fair amount of use and abuse. It's at the lighter end of ball peens but is perfect for small engineering work, stamping and centre punching etc. If you ever see one second hand I'd say grab it for a quality little tool. 

Tool Tuesday - Telescopic Bore Gauges

 

Today's Tool Tuesday is a particular favourite set of tools as they often are my first port of call when beginning to design or build a rocket! I often need accurate measurements of internal tube diameters and the Telescopic Bore Gauges are an excellent approach. 

Each gauge covers a range of internal diameters and features 2 sprung probe sections that can be pushed back into the centre body of the gauge somewhat. In the handle mechanism there is a spring pushed bar which when you tighten a knurled nut at the back of the handle will lock the 2 probes in their current position. To get an accurate result you push the probes into the desired internal bore and hold the gauge at a slight angle and lock the probes to finger tight. You then pull the probes so that they span flat across the bore to bring it to it's final measured size.  You then remove the bore gauge and use an accurate device to measure across the jaws of the probes, a well calibrated micrometer is best but often a vernier caliper across the probes is sufficiently accurate for most needs.  

Building a Doritos STAX rocket!

Photo Credit Peter Barrett

I'd never built an "odd rock"! Odd rocks are a category of rocketry reserved for those who create rockets from odd materials or make odd objects fly. I've seen loads of examples from flying cars to an office fan but it's never been an area I've delved into. At the milder end of odd rocks there has been a long history of people making rockets using confectionery packaging and in particular Pringles tubes. Pringles tubes are a very worthy rocket building material but they have been done a lot and I wanted to do something different. The Dorito's STAX tubes are a pleasing rounded triangular shape and I thought it might be a worthy candidate for a build. 

This build was very quick and dirty and everything was done in between work and other commitments and definitely took a back seat priority wise to other rocket projects. I started by drawing around the tube to get a rough sketch of the tube profile and took a picture of it on my phone. I dragged the image into inkscape and then hand traced to get a vector of the tube shape. The tubes aren't quite an equilateral triangle which adds a bit of faff! I laser cut some plywood centring rings into which I cut a hole to receive the motor mount tube. This was finished off with a PETG 3d printed motor retainer. 

The fins are 3mm balsa laser cut to a shape that kind of looked a bit dorito-esque! I originally planned to put the fins through the wall but ended up just gluing them on. I reinforced the oversize fins with a layer of tissue paper and glue. Due to the shape of the tube this rocket is impossible to simulate using a package such as openrocket. As such I decided to go very large with the fins to try and definitely pull the centre of pressure rearward in the airframe. The nosecone offered some challenges and I didn't really have time to create an accurate fitting cone. As a first attempt I decided to model a shoulder-less nosecone which would overlap the top of the tube somewhat rather than trying to accurately model to the tube. Having my rough nosecone model in FreeCAD to 3d print I then created a stack of lasercut plywood triangles to create a shoulder piece that could be sanded to a decent fit inside the tube. The recovery bridle was some thin kevlar and I flew this using a proven hexagonal annular parachute I'd made some time ago. Finished with a bit of satin black spraypaint and a quick vinyl cut graphic, DSTAX was finished! 

Photo credit Peter Barrett

Due to this not being sim'able, once together I decided to add around 18 grams of nose weight (some small flat lead panels epoxied into the nosecone bulkhead) and this seemed to make the airframe stable when performing the classis "swing test". The swing test is where you attach a string at the centre of gravity (with the airframe loaded with a motor etc) and then swing it in a circle, it should correct itself slightly into the wind and then remain stable, an old school approach that works well to give you some indication of the stability.  The other consideration was the maximum lift off weight limit of the target motor, an estes D12-5, which is 283 grams. All up weight of the rocket came in under the maximum at 224g. 

As you can see in the video the first light was successful albeit with a slightly late deploy of the recovery system. I think it's a little over stable by the way it turned into the breeze but it's certainly within acceptable limits. If I built another I would consider reducing the ridiculously large fin area somewhat!  

Tool Tuesday - Stud Clamps

I've written about stud clamps before, both here and in Hackspace magazine, but, due to their usefullness, they need a Tool Tuesday post of there own. 

The stud clamp allows you to work on bolts or threaded items whilst holding them securely without damaging the thread. Or they can be used to aid removal of threaded studs from assemblies. Essentially they are a piece of material with holes drilled and tapped to receive bolts or threaded bar of the corresponding thread type. They are then carefully cut, either by hacksaw or a slitting saw in a mill and this creates the clamp. Thread your target material in and pinch the clamp shut in a vice or using some other type of clamp, mole grips or a G clamp for example, and your work is held super securely for you to work on. 

Tool Tuesday - Budget EMT Shears

I've become a big fan of cheap EMT shear type scissors. They are widely available and there are super affordable versions if you steer away from the more "tacticool" versions. As a pair of beater scissors they are great and will cut a wide variety of materials. I often use them to trim the edges of cured fibreglass layups etc and they really are tough. Just make sure you don't take them from a first aid kit you may rely on! 

Apply Heat Transfer Vinyl to Tricky Objects

I know, I squandered that career in modelling I was destined for... I like playing with different materials on the vinyl cutter and I've used HTV or Heat Transfer Vinyl a little bit, but usually limited to flat smooth fabric items. At home I've used the domestic iron to apply designs to bags and tee shirts and at the Ffiws makerspace where I work sometimes we have a larger flat plate heat press. However I wanted to experiment with HTV on more awkward surfaces, i.e this baseball cap. I'd seen crafters in the US using smaller irons specifically designed for HTV but I couldn't find them in the UK or running at 240V rather than 110V.  However, another area that uses these irons are aero modellers building lightweight planes which have a heat shrunk covering applied to wings made from balsa ribs and spars. I ordered one to have a play with for less than £20.   

There are commercial hat presses for sale or heat presses with replaceable elements in different shapes for different objects and these obviously apply heat and pressure uniformly and make HTV hats trivial to create. However for small batches the iron works well. After cutting the HTV on the vinyl cutter and weeding (removing the parts of the vinyl that aren't part of the design) I stuck the HTV and the heatproof backing onto the cap in the correct position. Note that if you want to have a go at this you want to find a 5 panel baseball cap rather than a 6 panel baseball cap as a 6 panel has a seam vertically down the front of the cap. The curvature of the hat makes it almost impossible to stick the HTV backing down too, more because of the thickness of the backing rather than the stickiness. You also want to curve the HTV/Backing to conform to the hat rather than making the hat panel flat as that would then crinkle when the hat returns to it's normal state. I used extra kapton tape (heat resistant tape) to hold the HTV panel in place, but neither the tape or the backing adheres that well, it's only when you tack the first part of the design with the iron you can feel assured it won't move.  

My original plan was to stuff the hat with an old towel to try and keep the hat firmly in shape, however I realised that it was easier to cover one hand with 3 layers of the towel and push into the back of the design with one hand and then hit it with the mini iron using the other hand. I set the iron to roughly 160C and applied the iron to each section of the design for around 15 seconds. I made a slight error on the first attempt as I hadn't noticed a bit of kapton was stuck under and lifting an edge of the design, so I opted to cut the black HTV ring around the yellow design and add that as a second layer to cover the slight error! One thing I noticed is that due to the curvature of the cap the HTV backing kind of self releases when the HTV is stuck which is very useful and means you automatically peal the backing whilst it's still hot. I'm pretty pleased with the results and the iron is great and will be useful for this as well as other model making activities. 

Tool Tuesday - RS Pro Flat Nose Pliers

It's pretty fair to say I love all types of pliers as tools. I have a few sets of more expensive pliers but the majority of my collection are pretty cheap and cheerful. One type that I use a lot are flat nose pliers, a sort of thin nosed pliers where the jaws bend away from the grip. The RS Pro flat nose pliers are a reasonable set of smaller ones for not too much money. They are small enough to often be used as a slightly more forceful set of tweezers and I often use them to place small nuts and fasteners where my fingers are too big to fit. I I had one small gripe it's that they aren't particularly precise in closing and the jaws don't align perfectly as you would find in higher quality tools. However they are great for many tasks and are perfect for one of my favourite little hacks, if you place a rubber band around the handles you can use them as a small low pressure clamp holder that's capable of holding the work slightly off the bench. Super handy for soldering, clamping small glued items or I've even used this to create temporary test stands for tiny motors. 

MTV Robot at PiWars!

I LOVE it so much when people make use of something I've shared or written about and I feel really pleased that Calderdale college elected to build their PiWars entry robot based on the opensource MTV Robot platform that I designed and wrote about in Hackspace magazine back in issue 37. The MTV robot is built around a really cheap tracked chassis that can be bought online and a stack of 3D printed parts you can add yourself. 

For those of you who don't know PiWars is a brilliant robotics competition that anyone can enter and your robot has to compete in numerous different fun challenges. It's a really lovely community and even if you don't enter it's a fun group to watch to get interesting ideas for robotic projects! 

The Calderdale college team made numerous changes and add ons to the MTV platform and the team came 5th overall in a beginners class of 15 entries and they even came first in one event "up the garden path" which was a challenge where you had to control the robot with voice commands. Superb stuff! Read more about the excellent Calderdale team/experience on this great blogpost and grab the free PDF of Hackspace magazine 37 to get the links and info for the MTV design files. 

Tool Tuesday - The Digital Multi Meter

 

The Digital Multi Meter or DMM is never far away from my hand and gets a lot of use. I was recently reminded of how it also can make some aspects of electronics more accessible. DMM come in fantastic variety of  flavours and models and are available from around £5 through tow hundreds of pounds. They have heaps of uses and capabilities, measuring voltages, current, resistance, checking capacitors, and much more. I tend to use two functions of mine massively, checking DC voltage level is a popular task and also checking continuity ( a mode where if there is a connection between the probes it will beep) is so useful to check if something is connected. 

Many DMM will check resistance but with some you need to know the order of magnitude you expect the resistance to be. These are selected using the rotary switch. Some DMM are "auto ranging" and as such will switch the units detected to the correct one for the measurement. So when checking a resistor that is 10,000 ohms it will detect and switch to give the value in kilo ohms. I ran a soldering workshop recently and I always give a short example of using the colour codes on a resistor to decode its value. However one of the participants was red green colourblind and would struggle to decode the band colours. Not a problem with an auto ranging DMM! The list of features on a basic multimeter is impressive but the list of all possible features in endless. Whilst for regular mains work I would want to spend more on a quality known brand, it's fair to say that for low voltage work electronics hobby stuff really good auto ranging DMM can be found for less than £20. A useful addition to any bench.

Tool Tuesday - The Breaker Bar

 

This week I've been swapping some wheels around on my old VW Caddy Mk2, well actually on two Caddy's, my one on the road, and my off road spares donor vehicle! It's common for tyre companies or garages to fit wheels using a compressed air impact driver and as such wheel nuts can be pretty heavily over torqued and difficult to undo. The answer is the humble but incredibly useful breaker bar. A breaker bar is a long oversize bar with a socket fitting at one end so it can receive a socket wrench. They are usually none ratcheting as socket wrench ratchets aren't often capable of very high torque. My breaker bar has a 1/2" socket wrench fitting and it lives in my van with a 17mm socket on it at all times as that is the size of my wheel nuts. I also carry a 19mm and a 21mm socket with it in case I can offer help to anyone changing a wheel as these are the other two common wheel nut sizes.

They work very well and definitely make life easier than trying to use the shorter lower quality tools that are often bundled with a a small spider jack in many vehicles. 

Tool Tuesday - Archimedes Drill

The archimedes drill is a very useful tool for making small holes in a variety of materials. At the chuck end they have a floating collar you hold to steady the device and use your other hand to plunge the handle causing the archimedes screw to turn. As such you can moderate not only the speed, but also the downforce. This results in a sensitive drill thats really handy when accuracy and good finish are important. I use mine often to pick up small marks/punching when a centre drill would be too large. I've also used it for PCB drilling when hand etching boards as it gives cleaner results than a dremel type tool. 

Free Flight and tinkering with vinyl cutters and lasers!

 

I've been getting interested in free flight aeroplanes and plane design in general. I really am a newbie though and as such I've been building some simple kits to gather some experience. The BMFA sell a range of educational kits and one of them is recommended as a good starting point for building with balsa. The Gymminie cricket is a simple rubber powered free flight model that is aimed at indoor flying in a sports hall or outdoor flying on an incredibly still day. It's a very affordable kit at £3.50 and gives some decent experience of building lightweight airframes with balsa and tissue. It's a good lesson in delicate working but the stuff/skills that you learn on this applies to any classic balsa and tissue build. 

My interest in the Gymminie cricket design overlapped with me getting hold of a secondhand vinyl cutter, a silhouette cameo mk1. This machine has been great and warrants a post all of it's own at some point, but as a quick overview I have it set up and running being driven from Inkscape with a great opensource plugin extension.  Whilst I've predominantly used the vinyl cutter to cut vinyl stickers (see the next plane in the post) I spent some time dialling in an approach to be able to cut tissue paper. Its definitely possible but is a tricky balance of cutting feeds and speeds, backing board tackiness and general operator competence and patience! The two Gymminie cricket builds have been a great test bed for lots of tissue experiments.

I wanted to jump into trying to design and scratch building my own planes. Starting simple I've been tinkering with an all balsa chuck glider design which I've named "Intuit" because, you guessed it, it's been mainly built on intuition rather than any decent engineering knowledge! Whilst I could have hand cut the balsa with a craft blade I've been cutting balsa successfully on a CNC laser diode engraver rig which I can't talk too much about as it's destined for review in Hackspace magazine. However I can go as far as saying it's nice to be able to cut balsa accurately and this chuck glider is starting to perform well with the various adjustments to trim and embellishments it has. I've certainly learn't loads and it's good to apply bits of reading around general plane principles and aerodynamics to actual things that attempt to fly. On the horizon is more chuck glider designs, I'd like to try a rocket boosted swing glider ( a rocket that deploys glider wings and glides for recovery) and I'm quite interested in using small motors and supercapacitors for electric free flight experiments. More post will follow!

Tool Tuesday - Wera Kraftform Precision Hex Drivers

I have to say I am a Wera tool fan and my fanship mostly centres around the Wera Tool Check Plus which I blogged about a while ago. I still find the combination of the tool check and the Xiaomi/Wiha precision driver set covers most of my needs. However often I need longer tools to access fasteners in recessed pockets often when working on robots or drone projects. The Wera Kraftform Precision range are very nice tools and you can buy them in various curated sets, or, if you are like me, I buy them individually so I have the common sizes I need. Pictured above are my most used ones, the 1.5-2.5mm Hex drivers which are in pretty much daily use. The rotating caps move very smoothly and the tool tips are well made and durable with these showing very little wear after a fair bit of use. 

Tool Tuesday - Bicycle Spoke Key

 

This weeks #ToolTuesday is a classic tool for those interested in maintaining or repairing bicycle wheels. Inspired in part as I bought a fixer upper e-bike project and the rear wheel was in a bit of a state of disrepair! The humble spoke key, or "spoke wrench" for those over the pond, comes in a few variants but we'll look at the classic circular tool. Spokes on bike wheels serve an important purpose, they profile the strength and the load bearing system between the hub and the wheel rim and they also can be adjusted to "true" the wheel if the rim has a slight bend, dink or isn't quite centred. Tightening a spoke is usually achieved turning the "spoke nipple" at the rim end and a tightened spoke will pull the wheel hub slightly towards that point on the rim.

Occasionally spokes may work themselves a little loose. A tell tale sign is you might hear a spoke "pink" as you ride the bike indicating that, as it is passed over, the rim moves ever so slightly. You can check for loose spokes by strumming the spokes with a thumb or finger and detecting ones that create a lower note than the others. 

The spoke key has numerous options for different spoke sizes which are numbered around the tool perimeter and once you have found the correct size for your spoke nipple you can tighten and loosen the spokes like any nut and spanner. A word of caution though, you should only need to make very small adjustments (a 1/4 turn or so) for a loose spoke and if you are adjusting multiple spokes you should try and adjust opposing spokes in turn to keep the wheel rim centred. Wheel truing where you correct alignment issues is a real skill, you can learn it at home, but it's often good to find a local wheel expert who is sufficiently practiced in this dark art!

Tool Tuesday - The Flexible Pick Up Tool

I can't say that this is a tool I use every day, but it's a super handy tool when needed. Squeezing the sprung plunger/handle arrangement and a small set of four spring steel jaws expand out of the other end. This allows you to grab, retrieve or otherwise manipulate small objects. Looking online most are advertising this with an image of it stuck down a sink plug hole, I can't say I've ever done that! However, I can say it has retrieved a lot of dropped parts/nuts/bolts from engine bays or quite often objects that have rolled down the back of a work surface. If you have any sort of hobby which involves fitting systems into tight tubes, as I do with rocketry, this is an excellent and useful tool. In rocketry you quite often have to thread a cord through a eye bolt placed inside the bottom of a 50cm long tube and this tool can really earn it's keep.  

They are a very affordable tool also, in fact mine still has the hardware shop price sticker on it of 99p, that's some years ago though, but a casual search online shows them as available for not masses more. Finally, they also are a fun tool that begs to be used by almost everyone who handles one, my children certainly have both played with it previously setting marble transferring challenges etc! They are quite sharp though, and certainly need to be handled with a little care and don't dream of grabbing someone else with them as they are surprisingly grippy/pinchy!

 

Opening a Tindie Store

 

After years of being a Tindie customer and a recent period writing content for the Tindie product blog I decided it was high time I set up a Tindie store. I've opened the store with a couple of rocket related products but I plan to keep adding random bits and bobs to it as I develop small items. 

First of the two products on there are my rocketry screw switches,  I started making and using these a few years ago but now having a few flights under their belt I am confident in the design. They have copper on both sides to which are soldered wires and the wires only become a circuit when you tighten the switch bolt. They are small and robust and on the product page you can see some photo's of them in different configurations/use. I'm selling them in 2 packs so you can set up 2 separate redundant systems in your rocket. 

The second product people may recognise! It's my Centre of Gravity and Centre of Pressure stickers that I used to sell via the Flame Trench shop. Sold in packs of 10 (5 of each design) they are super handy to mark your rocket airframe and make it easy for you to show the CG CP positions to an RSO!

Tool Tuesday - The Swann Morton Unitool

I need to reinvigorate my blogging rate and I've decided to start this weekly blog I'm calling #ToolTuesday. It's heavily inspired by my great friend @biglesp who for a long time has run the excellent #TuesdayTooling series over at his blog. Les focuses on software and microcontrollers on his Tuesday Tooling posts exploring tools and toolchains to get you up and running doing cool things across a variety of platforms. I've chatted with Les over the years that I should do a similar series but which looks at hardware tools useful in all kinds of making and tinkering and so here it is!

This first post is an odd starting point as I bought a stack of these Swann Morton Unitool multiblade craft knives recently as they are being withdrawn as a product. It's a shame as they are an excellent little tool. The three blades are larger than many of my smaller craft knives/scalpels and are excellent for all kinds of jobs. The very flat edged "D" blade is superb for cutting flat sheet items like balsa or cardboard and I use the angled "A" blade as a de-burring tool a lot as it can centre into small holes really well. The middle blade "B" is slightly odd in my opinion but as such falls into the "blade that gets used for heavy beater work" so I've abused that blade for all forms of carving and even wire stripping etc. 

The blades pivot and are retained with two thumb screws and they stay in place very well, which also leads to another reason I love the design, you can lock the blades away and close the device and the holes in the blades combined with the thumbscrews make it really secure. I've never had a blade come loose or open in my pocket. 

Finally, I love the look, when I was young and building plastic model kits the orange plastic handled single blade craft knives from Swann Morton where the only widely available choice and the Unitools styling reminds me of many happy hours tinkering! Hope you've enjoyed this first post, see you next week!

Chonk Rocket! Build and First Flight

Pre Covid I was mentoring a school team towards taking part in a UK rocketry competition and I'd bought a few bits and pieces on their behalf. Some estes BT80 body tubes, a matching nosecone and some F36 cti motors. Of course Covid scuppered the team and I had these bits sat here looking at me, so I decided to build something. I'd never really designed and built something for the upper end of mid power, I have models that I've designed up to D on 24mm diameter motors and then the bigger HPR stuff. I also realised that a simple reasonably wide airframe mid power rocket is an excellent test vehicle for testing DIY parachute designs and getting a bit of data.

"Chonk" Is quite a straightforward build in essence, I CNC'd some centering rings and CNC'd the through the wall fins. I decided to put a fine layer of fibreglass on the rings but I haven't glassed the fins. I find through wall fins make a very strong fin can and as such I felt with everything stuck to the 29mm phenolic motor mount tube that it was all going to hold together.  Despite being a simple single deploy airframe I wanted to get flight data, where possible, to make it a decent test platform so I performed extensive butchery  modification to the off the shelf NC80b nosecone. 

I used the bandsaw to take off the base of the nosecone and then installed a 2mm threaded rod by pouring around 10mm depth of laminating epoxy into the nosecone tip. I left a nut on the threaded rod in the epoxy to act as a decent anchor. I also CNC'd a plywood ring to sit in the lip of the shoulder and receive the closing bulkhead and later I added a couple of M2 nuts and bolts to further hold the bulkhead and NC all together. I then made a bulkhead with a simple soft retainer and reinforced the bulkhead with fibreglass and a wooden centre washer. Inside the bulkhead I installed some uprights around the threaded bar area and installed 2 altimeters, a perfectflite Alt15 and an Eggtimer Quark the latter of which I had wired up to an openlog board for it to write flight data to an SD card. 

To arm the altimeters I used the CNC screw switches which I designed and built quite some time ago, they worked flawlessly and maintained continuity throughout the flight. As the nosecone is quite heavy it's gets some decent loads/forces on ejection and deployment so it was a good test. A couple more test flights with this design and I might be tempted to make a few and stick them on tindie to sell.  

Chonk flew last weekend in great conditions at Midland Rocketry Club and I'd made a 60cm 10 gore annular chute to fly in it. Chonk was probably slightly over chuted but a very steady and stable descent was made and I do like how people watching react to the annular chutes as they aren't a common sight at UK rocketry events yet! I reduced the delay to 7 seconds, but definitely it was a little late (even better test for the screwswitches!) and if I fly in this configuration again I'd take the ejection delay down to 6 seconds. 

One of the best things that happened at the event was a fantastic rocketeer and accomplished modeller Pete turned up with a downscale micro version of "Chonk"! He'd seen me making Chonk on twitter and decided to make one using a micromaxx 6mm motor! Such good fun and his Micro Chonk flew very well! 

M-Sure 150mm Digital Caliper

A while ago I was sent a set of Moore and Wright Dial Calipers for review for Hackspace Magazine. The company that sent them over was Machine DRO who I'd bought off previously (an excellent digital height gauge still in regular use). I remember at the time one of the members of staff saying that they were working on an in house range of measuring and metrology kit. I spotted the other week that their in house M-Sure range had been launched and quite fancied the look of the digital calipers, my current cheapo set (one in a long line of cheap digital sets) having just died!  Priced at £28 I ordered a set of the 150mm. 

Dispatched quickly they soon arrived well packed with the calipers themselves in the case inside a plastic bag with some protection waxed paper in between the precision ground jaws. A desiccant bag also was added to make sure their was no moisture. Also in the case is a small plastic tool for opening the battery cover, although it's fair to say a coin would do the job if this went missing. I couldn't spot a CR2032 inside the case and was about to start muttering and wading through my draws to find one but I then realised the battery was in the rest of the packaging along with a instruction manual should you need it!

I was pleased to see a small O ring seal in the battery compartment, but do be warned that this isn't fixed in place and sits rather loosely in the groove so can fall out when the cover is removed. The display had a clear plastic film over it but once removed the display is clear and crisp and the refresh rate is very fast, certainly faster than the cheaper calipers I have used. Note in the picture below that there is a seal over the USB connector. If I were to make one of two small complaints it's that the left hand side of this cover sticks up where there is a plug that retains this seal when the USB slot is uncovered. Whilst none of the seals claim to be waterproof it was a bit annoying that the addition of a seal had in fact created a little area for chips/dust/moisture ingress into the case. 

In use the calipers are a very nice experience, the movement is smooth all the way up the scale and is still pleasant up towards the 150mm end. Again I have had calipers that get either floppy and loose or grindingly stiff at the far end of the scale so these are excellent in that respect. 

Under the USB seal is a Micro B USB connector. Data output is common across some of the M-Sure range which includes Digital Micrometers, Dial Test Indicators, Height Gauges, Bore gauges and more. There are some generic "linear gauges" I have my eye on as a potential DRO system for a small milling machine. I haven't tried the data output function on these calipers yet but I'll feedback when I have. Note that some other instruments in the M-Sure range need an additional add on USB interface to enable data capture and there are also extra remote displays available for some devices in the M-Sure range. 

My second small complaint, that really shouldn't detract from an otherwise excellent set of calipers, is that they have some marks and staining presumably from the manufacturing process, most noticeable on my set is a stain under where the PCB sits when the calipers are closed. This is not an issue for me at all, they will be filthy after some time on my desk, in my bag and in the shed, but it's important to mention. The aren't advertised as clean room specified but just in case someone buys them and opens them in their high end metrology lab!

My two little niggles aside these are an excellent buy at a great price. I've always had good customer service from Machine DRO and they were a pleasure to work with a while ago writing up the Hackspace article.