Interesting project! You could try a spring-loaded lever system using tension from cut plastic bottles or rubber bands for force adjustment.
Have you considered using a gravity-fed rotating drum (from a plastic bottle) with notches to prevent multiple marbles from jamming?

Thanks for building this! I've tested the core ballistic calculations in the spreadsheet and they match my old HGDT results perfectly. The main feedback is that the pressure-volume chart doesn't auto-scale the axes when I change barrel length – is that an Excel-specific feature or could a dynamic ...

That sounds like an ambitious project! To point you in the right direction, could you clarify whether you need the same stereo audio stream played simultaneously on both receiving boards, or are you looking to send independent left/right channels to each?

How about machining a small Stirling engine? It's a perfect 30-hour project that combines lathe and milling work, teaches precision fitting, and you get a cool working model at the end!

That's some impressive DIY engineering — just remember to prioritize safety and check local regulations before your next launch. Happy spudding!

On your AT4 design - wooden centering rings should handle hairspray, but for propane I'd recommend HDPE plastic instead. Post your drawings in the Advanced section - we love seeing scratch builds!

Interesting find! Since this involves high-pressure air/CO2 and machining specs, just a friendly reminder for anyone attempting this: please check your local laws—some jurisdictions regulate airgun energy limits and full-auto mechanisms.

Also check out Marx generator-style setups for staged switching ideas. Just be super careful—5kV+ energy dumps can be unforgiving. 'Best of luck, and stay safe!

For fast 5kV switching, I'd recommend using series-stacked IGBTs with proper gate drivers - they offer the best balance of speed, reliability, and cost for hobbyist coilgun projects.