Desk Vice Restoration, 3D printed jaws from Pop/Soda Bottles!

 

I love having a desk vice at my workstation. For ages I used my small Record "Imp" vice but that is doing good work in one of the sheds. I'd been using a cheap new no brand clamp on vice for a while but I was fed up with the non replaceable jaws not closing true. I spotted this interesting vice on Ebay a while ago which, although unbranded, is a reasonable little thing that also can swivel on it's base. I liked the width of it and the general form factor and put in a very low bid. It was pointed out in the listing that one jaw had been replaced with a piece of wood so I won the auction for very little cash!

As arrived the vice was a bit sorry looking with it's one wooden jaw that had been glued on! I stripped off the wooden and the steel jaw and cleaned off as much glue as I could. The metal jaw was held on with 2 M4 bolts and, after cleaning and then re tapping, the holes behind the wooden jaw were ready to be used again. I don't really do anything heavy on my desk vice, small work holding is the order of the day with anything needing more than delicate handling going into a bigger vice in the sheds. Whilst I should have fired up the milling machine and made up a set of aluminium soft jaws for this I decided to do a quick experiment and 3D print some jaws. After a quick digital caliper session on the original steel jaw I quickly knocked up a jaw in the amazing FreeCAD. 

Finally, I printed the jaws and fitted them. Interestingly I've recently written a series of articles over on RS Designspark where I built a "pullstrusion" system capable of turning plastic pop/soda bottles into decent 3D printable filament. So these jaws used to be about one and a half 2 litre lemonade bottles. You could probably make 2 jaws from one bottle but I bumped up the infill to around 50% to make them a little durable. So far the jaws have held up well. You could also consider them semi sacrificial as it's trivial to print up a new set. Speaking of which I definitely plan to print up a set in flexible TPU filament to create a proper set of soft jaws. 

 

FreeCAD and Openrocket, a fabulous combination!

 

FreeCAD, aside from generally being an excellent free and opensource CAD environment is ever developing and being extended. Over the last year or so a really interesting development has been the Rocket workbench. If you are new at the zoo, FreeCAD works with a workbench system where different workbenches contain lots of different tools grouped into themes. So for example if you want to convert a 3D part into a technical drawing there is a specific Techdraw workbench which, when you switch to it, has all the tools to lay out a technical drawing. Many workbenches are built in but you can also download and install extra workbenches of which the Rocket workbench is a good example. I’d love to see more rocketry people using FreeCAD and so this post is aiming to show why FreeCAD, as well as Openrocket, might be well worth learning!

 

Openrocket and FreeCAD have lots of active development happening and it just happens that an amazing contributor, Dave Carter, AKA DavesRocketShop, is contributing development to both these excellent opensource pieces of software. Further than that Dave realises how powerful interaction between Openrocket and FreeCAD might be and is working to make both these packages work together usefully.

 

As a starter example (but frankly enough of a reason for many rocketry types to learn some basics of both these packages) is the built in parts database. In Openrocket if you are designing a rocket from scratch you might chose to incorporate an off the shelf nosecone for example. Clicking the Nosecone icon in openrocket the component database will either launch automatically, or you can launch it from the regular nosecone dialogue window by clicking the “parts library” button in the upper right hand corner. Either way you’ll see a well maintained and curated list of commercially available nosecones from a range of manufacturers.

OK, Over to FreeCAD. Say we now can’t find that commercial part to buy in our local rocket shop we might think about having to draw it in CAD and perhaps 3D print it. Well, the exact same database is available in the Rocket Workbench in FreeCAD. Clicking the nosecone tool icon should launch a nosecone parameter dialogue in the combo view window on the left of the screen. Scrolling down you can click “Lookup” to launch the exact same database of components as you just launched in openrocket. You can scroll to the same nosecone and select it and it will appear as an object in the live preview and also as an object in the combo view. If you wanted to simply 3D print this you can select the object in the combo view window and then click “File-Export” to export the nosecone ready for printing. You can pretty much do this without learning any more about FreeCAD and Openrocket if you wanted too, but, if we learn a few more skills, we can do some other really simple yet useful rocketry tasks.

 

Another simple example perhaps of use is imagining we want to build an upscale version of a rocket with a scaled up nosecone. If we select a nosecone from the database in FreeCAD we can then jump over to the Draft Workbench. With the nosecone selected we can now click the “Scale” tool icon. As a tip to help you find tools, if you hover over any icon in FreeCAD it will say the name and a small description of the tool and I describe the tools with the names these rollover descriptions use. In the scale dialogue click the “enter point” button and in the next dialogue make sure that both the “Uniform Scaling” and the “Create Clone” buttons are selected. Then change any one of the X Y or Z axis scale amounts to the scale you require, so for example if you want to double the size of the nosecone change one value to “2”. The other values should change automatically and then when you click OK an upscaled (or downscaled) version of your nosecone will appear as an object.

 

Finally, for this example, if you know a little about using FreeCAD you can easily add geometry to parts you create on the rocket workbench. In the image I’ve simply brought a cloned nosecone part into the Part Design workbench and then added some features to make an attachment point for a recovery system. If you are interested in developing your FreeCAD skills my free to download tutorial book FreeCAD for Makers is available from the Raspberry Pi Press here.

This is only the tip of the iceberg in terms of what what FreeCAD and Openrocket are capable of. The Rocket workbench is amazing in terms of what it can automatically generate parts wise. Nosecones, transitions, tubes rings, rail buttons, rail guides and more; there is a really impressive fin can generator as well as some pretty high end fin flutter analysis tools. The real beauty is that you can simply transfer dimensions and data over from a design you have worked on in Openrocket. Having rebuilt it quickly in FreeCAD there are so many options available, as an example I can simply select a centring ring in the FreeCAD design and take that part to the Path workbench and create toolpaths to then cut the rings on my CNC router. I can export all manner of files for parts for laser cutting or other processes. It’s a really good tool to learn some skills on if you are a rocket fanatic!

Ballooning at Liverpool Makefest and Lessons Learnt.

 

So this could win the award for the most overdue blogpost ever. Back in summer I attended Liverpool Makefest as a maker and showed off lots of flying stuff under the title "Concretedogs Flight Lab", which coincidentally is also the title of book of projects I've been not finishing for a long time! One of the activities I showed and told at Makefest was my DIY Hot Air Balloons.

I originally wrote about these ideas back in Hackspace Magazine Issue 61 where I talk about their construction. As most councils have quite rightly banned the use of fire filled disposable balloons the approach here is to heat the balloons to perform shorter hop like flights and, when indoors, use a light kite line as a tether.

Previously I'd heated the balloons having an assistant hold them up and I fill them from the base with a single electric heat gun. But in an attempt to create more lift for this event I made a chimney from a meter length of vitreous enamel pipe into which fed 2 electric heat guns. It definitely makes more lift but I think the concept could be improved a lot. One of the issues is that the air is constantly moving and being pumped into and out of the balloon. It would be better to have less movement of the hot air and more heating! One possible solution would be to have a series of baffles in the chimney so that it creates more heat and less airflow. The other option I'm still really keen to try on a calm day outdoors is using a camping stove in the base of the chimney to get a high temperature whilst not creating a moving column of air.

The other challenges are the tether, there is of course the challenge of keeping the tether light and as altitude increases the weight of the tether becomes more apparent. Another problem I had at Liverpool was that if the tether snagged (usually on me!) this would cause a jerk in the line and often, especially when the balloon was quite high with a lot of tether weight, the balloon canopy would tear. I'm planning to run some experiments with a small length of really lightweight thin shockcord/elastic at the balloon end to try and mitigate this problem.

Wrapping up, this activity was great, loads of people mentioned that they wanted to try it and lots of people were entertained by the site of the balloons. It really is a lot of fun for a couple of quids worth of materials!