Saturday, 28 December 2019

10 minute make; Magnetic Feet

Last week I was using the variable power supply I built some time ago. It's a great and useful little build that replaced a small trimming resistor on the DC-DC LM296 based board with a 10 turn resistor to increase the resolution. It's stood for ages on top of my old lab supply with a couple of small magnets stuck to the machine screws in the frame and the case of the larger supply. It's stopped it getting knocked off a little but becomes detached easily and I have been meaning to attach the magnets to it in a better way. 

So I quickly knocked up a magnet housing/foot in FreeCAD and chucked a couple on the 3d printer. A quick blob of superglue later and the two magnets pressed in and voila! It now stays in place pretty well just on the two feet, however, I might whip up another pair when I get another spare 10 minutes!

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.