C02 dragster / F1 in Shools launcher

Overview

I designed this as part of a budget F1 in Schools track and timing system back in 2015. The official Denford system is of high quality but very expensive. Beyond the budget for most schools. The original system is seen here (audio mixing warning):

Since publishing that video, I have had several requests to release the source or manufacturing files for the launcher. I think I originally designed this on 123D Design, a defunct CAD program from Autodesk. As such I could never find the files. Recently, I finally found a SAT file of the assembly and was able to manufacture another version. This included some new 3D printed components.

This remake was part of a video on over centre mechanisms:

Source CAD

If you are not an Onshape user, you can still right click on any part and export it in a format of your choice. This can be done without even having an account. If you do use Onshape, you can make your own copy and modify from there.

https://cad.onshape.com/documents/fe6b495b492d21e40f63683e/w/0cd513e0f526e3c35e301f03/e/a7a87de3225f68346b3f7abb?renderMode=0&uiState=6438d80bd694ea1e0266756b

Manufacture

These parts were original designed to be machined from 3mm and 12mm acrylic sheet. This time around, I laser cut the 3mm pieces and 3D printed everything else. When 3D printing, filament choice is not that important, but ensure strong parts by using many perimeters and high density infill. Assembly will be easier but not impossible if the two outer cover are transparent.

Hardware BOM

• Flanged bearing x 2 (5mm ID, 12mm OD / 15mm flange OD, 4mm thickness)
• M5 x 25mm bolt and nut (ground down to be slimline)
• M3 x 50mm bolts x 10
• M3 nuts x 10
• M3 x 30mm bolt, tip sharpened
• M3 washer (rubber or fibrous) x 1
• M3 theaded rod x 55mm
• M3 lock nut x 3
• M3 x 15mm bolt x 2
• Tension spring or rubber band (minimum relaxed length 45mm)
• 12V push solenoid (pin shortened by approx 10mm): https://www.jaycar.com.au/tubular-12v-solenoid/p/SS0903
• M4 theaded insert x 8mm x 2
• M4 locknut x 2
• M4 x 20mm x 2 bolt
• (Optional) rubber grommet

Assembly

Please refer to the following video for step by step instructions:

Troubleshooting

If the hammer will not rest in the primed position:

• Check that the springs or rubber bands are not catching on the M5 bolt in the centre
• Further shorten the solenoid pin slightly

If the pin pushes the canister forward rather than puncturing it:

• Use stronger springs/rubber band
• Sharpen the bolt to a finer point