These screw switches are designed to act as a robust switch mechanism for power management for rocket electronics. You can wire these inline to the positive power line/wiring and then tightening the screw switch will securely power on your rocket electronics. Simple to do once your rocket is on the launch rail.

They are CNC milled from double sided copper clad fibreglass and have a PEM nut inserted using a 1.5 tonne arbour press to securely place the nut. The inserted nut is isolated from the other side of the copper clad board and so the included wires soldered to each side of the board aren’t connected. The switch is closed when the M2 switch bolt, which has another PEM nut threaded onto it acting as a large pad, is tightened into contact with the front plate. This completes the connection between the front and the back plate and allows the current to flow.

Designed for use in mid or high power rocketry I made these switches as I was concerned with failure rates in cheap keyed rotary switches. I’d had success using 3.5mm stereo sockets and jacks as “remove before flight switches” but with increasing G forces I wondered at what point the metal plates in the stereo socket would open. The screw switch is a better solution and has now flown in numerous mid and high power rockets, including some violent flights with non optimal deployment! (hey it happens to all of us!) I’ve suffered no loss of continuity in my testing, flying with logging altimeters.

The PEM nut on the bolt is secured with a small dot of loctite but can be removed and you can replace the M2 bolt with a longer bolt if required (some people find this useful to have a longer bolt with the pad threadlocked in place at the lower end of the bolt with the bolt head standing off closer to the airframe access hole/port). I’ve flown these mainly with the switch bolt tightened into the on position with a small screwdriver and have not used any threadlocker on the switch bolt threads, you might feel you want to add a small dot to the switch bolt threads. The screw switches haven’t failed for me either way so the choice is yours.

The two mount holes are designed to receive M2 bolts and the upper surface is counter bored a little to ensure the bolt head cannot accidentally create a circuit. You can mount the screw switches in multiple different ways, horizontally, vertically etc. In the product images you can see two switches that have been mounted to a nosecone bulkhead and the switch stands off the surface resting on the press fit PEM nut as one example. Another example shown in the product images is one mounted in a electronics bay destined for a minimum diameter 29mm airframe, the screw switch has been bolted into a specially designed 3d printed sled to sit on a rail system. The press fit PEM nut sits inside a hole so the switch fits flush to the board. The boards (without the small wires added) weigh 1.7 grams including the switch bolt.

I CNC rout the copper clad boards and then hand assemble the rest, each one is tested regarding continuity and operation. I supply them with short (roughly 5cm) wires soldered to each side but these are easily replaced should you need to. I don’t include mounting bolts/screws or hardware. It’s worth removing the switch bolt every now and again and giving the upper face a polish as the copper naturally will tarnish and also will tarnish in the presence of deployment charge gases. Whilst the tarnishing reduces conductivity a little a quick polish with some fine steel wool brings them back to a shiny surface finish quickly.

Whilst these have flown really well across numerous flights, as ever with rocketry products, you buy and use these at your own risk and I offer no warranty or indemnity if flights go wrong. However if there’s a problem with your screw switch, you want something slightly different making or you want to discuss electronics bay layouts etc, do get in touch!