Friday, 6 December 2019

Flat Pack Workshop Rocket

I have some work coming up that requires me to take a rocket to a workshop overseas in my luggage so I decided I wanted to try and design a rocket that would break down to be easily packed. I wasn't initially concerned with it being a flying model but wanted it to have all the usual parts to act as a decent workshop prop. In case you are wondering the logo adorning the rocket is for a new non -  profit company I am in the process of setting up called Open Rocketry Research. More on that soon!

The hardest bit to pack is the booster section with the fins so I wanted to make the fins removable. I designed a set of conformal fin rails that have a radius on the back of 27.5mm to match a common 55mm postal tube. I've added escutcheons for M2 nuts and bolts to be able to drill and then mount the fins more securely. I printed the fin slot to accept 3.125mm plywood as I wanted to laser-cut the fins from this material, in the end, it doesn't (for workshop purposes) need the fins bolting in as they are a very nice interference fit into the slot. I'm tempted to fly the thing now, it certainly seems strong enough in terms of fin strength!

The conformal fin rails are superglued to the body tube and I've published the stl file and the FreeCAD file to Thingiverse, its trivial (if you know how) to use FreeCAD to change the dimensions for a longer or shorter fin root length (currently 100mm) or to swap the radius to fit a different tube. Get in touch if you need any help adapting this.

Saturday, 5 October 2019

New Sewing Machine! Parachute deployment bag prototyping!

So sadly (and despite replacing the two drive gears for the feed dog mechanism at great effort) the older 80's singer sewing machine we had had some other terminal failures and was beyond economical or technical repair. I'm really lucky to have been long term loaned this new(ish) machine (around 2 years old). It's a Brother FS60 and today I read through the manual and got started with it. 

I LOVE IT! Such a different level of tool compared to the old one, despite only using a basic stitch it has numerous features already that make it excellent to use. It has a mechanism that enables automatic needle threading and a clever system to allow for a more drop in of the lower bobbin and the user not having to "pick up" the thread with the needle. It also ensures to stop with the needle always in the down position that means it is super simple to turn and continue seams etc. 

I've not gone too wild making things today, but I wanted to test how the machine performed on the very lightweight ripstop nylon I use for parachutes and it performs admirably. I quickly knocked up this useful storage bag for the annular parachute using some off cuts of the same material the parachute is made from. I then went on to do a quick and rough prototype of a small deployment bag using some dark blue nomex cloth and some 10mm elastic. Its great to confirm that this sewing machine can work across a variety of materials and deliver good results.... Now, if only the seamstress operating it (me) had some talent!!

Tuesday, 1 October 2019

Thoughts on the TCT show 2019 and picture dump

So yes, got to go to the TCT show last week at Birmingham NEC and see the huge array of snazzy industrial CNC equipment. Lots of 3d Printers and definitely a lot of multi material extruders and systems for tool changing on 3d prints seemed the de rigeur for this year. 

There seemed to be a lot of smaller, but still largely unaffordable outside big industry, SLS type machines capable of sintereing lots of differing types of metals. There was a tantalising machine that doubled a SLS process with a 5 axis CNC mill, enabling,  for every few layers of sintering, a pass with tooling meaning that internal geometries could be finished to a very high standard and tolerance. 

Other stuff that caught my eye was there are some interesting filaments starting to hit the market that are desinged to be used in lost filament types of casting in combination with vacuum furnaces etc. Again its stuff that is not even potentially affordable to academic "maker" spaces, let alone community spaces, yet, as ever, it would be amazing to see these tools given to the really creative end of the maker community to see how far they could be developed and pushed! I live in hope!

Friday, 20 September 2019

ODR Dual Deploy Flight and Test Flight for the Annular Parachute

Last weekend I went down to the excellent Midland Sky rocketry event hosted by the Midland Rocketry Club, it was a fantastic weekend with great weather and lots of flights. I was very pleased to successfully fly the ODR rocket again with the dual deployment working perfectly! The fab Alex Ward lent me an onboard camera and I had a padcam set up so there's a couple of nice videos below.

The other excellent thing was that my friend Charles Simpson wanted to fly my annular parachute on one of his rockets, his "zombie" rocket (as it had been resurrected a few times!) was about 1.6kg and the annular chute gave it a really steady descent rate on a single deploy flight. I would estimate it in the region of 6m per second. I know I am biased but it looked gorgeous in flight! I need to make more!

Tuesday, 10 September 2019

Rocketry Series episode 6, Finishing the Scratch build and maiden flight

Episode 6 (although I keep saying episode 5!) where we finish the scratch build "VR2" rocket and give it a maiden flight.

Saturday, 7 September 2019

Inflating the DIY 1.5 meter annular parachute.

So I have been working on and off on this 1.5 meter diameter parachute for a while now. It's been a great project and I have learnt loads especially about sewing machines! It's designed to be the correct size for my Level 2 certification rocket I am currently constructing. The parachute is designed with 16 "gores" or panels which are hot cut using a soldering iron.

 I made a plywood pattern to cut around and the hot cutting method works well as the edges are all sealed and don't fray. I added enough material to allow for a flat felled seam but cut the inner and outer edges to be the designed size with no seam. I think that this is strong enough but I am interested to make another and experiment with adding binding to the edges as I have seen this done on some ex military parachutes I own.

 After cutting all the panels it took a few sessions at the sewing machine to connect all the gores together, then came the task of connecting all the top lines which are the shorter lines on the inner diameter that connect into (hand sewn into) the main lines, with 16 of each that was plenty of work!
Above showing the stage with all the inner diameter lines sewn in on the machine. I just used 2mm braided nylon for this build as I had some and its quite cheap which is important when you use about 45 meters in this construction. Now that I have worked out some design issues etc I will probably make another at some point and use a higher quality material for the lines. 

Above is the first test inflation on a luckily breezy day. The geometry/shape of the annular design when inflated actually results in a much higher drag coefficient than other parachute designs which seems counter-intuitive particularly when you consider the huge hole that they have in them! Finally, massive thanks to my parachute making mentor BJ Gray of Bama Recovery Systems, who I heartily recommend if you want to purchase a very high quality parachute made by a true master of the art.