Quick shift pneumatic system

[porkypig]

Hello, I am a George and I am styding mechanical engineer. It is my second year in my university's fsae team and I have always been the engine guy.
However I have a question about quick shift system. We always used electromagnetical shifting system and I was always wondering how the pneumatic quick shift systems can go from first gear either neutral or 2nd gear, As long as it is only the half distance between first-neutral-second gear compered to second-third-etc gear.
Could anyone answer my question?
Thank you

[Luniz]

There are a few options:

1.) Rebuild the shifter drum in order to move N to the beginning of the sequence
2.) have a second pneumatic cylinder with half the travel specifically for shifting into neutral
3.) The ghetto option: From 2nd, shift into 1st and back up very quickly. The pressure drop from the first shifting action will reduce pressure for the second action, so the shifter will "get stuck" in neutral... sometimes. We did this in 2009.

[porkypig]

There are a few options:

1.) Rebuild the shifter drum in order to move N to the beginning of the sequence
2.) have a second pneumatic cylinder with half the travel specifically for shifting into neutral
3.) The ghetto option: From 2nd, shift into 1st and back up very quickly. The pressure drop from the first shifting action will reduce pressure for the second action, so the shifter will "get stuck" in neutral... sometimes. We did this in 2009.

In 2009 did you used co2 or compressed air?

[Chapo]

Option 4: Have a button that operates your solenoid for a shorter time (one that you have worked out is not enough, through testing, to shift the car into neutral)?

[Luniz]

Again, ghetto here: We used a CO2 cartridge from a Soda maker with a pressure regulator from the hardware store. Heavy but cheap, reliable and durable. One cartridge would last a whole test day, and if it runs out you just get another one from the supermarket. The system pressure was about 12bar/170psi which is more than the rated pressure for the pneumatic components (8bar/120psi) but it worked anyway. The cartridge itself is pressurized to about 300bar/4300psi to liquify the CO2.

[TMichaels]

Option 5)
Use the gear box and neutral sensor and adjust the time that the solenoid is driven based on the current gear. Moving to PWM increases the resolution and makes you hit neutral consistently when needed. Especially if you stop driving the solenoid by triggering an interrupt with the neutral sensor. That is how we did it and it worked pretty well.

[BeunMan]

Used co2, did ms timing on the co2 valves to activate the actuator for the correct duration and used a hal-effect sensor as the gps (gear position sensor) to measure the rotation of the drum. It will attempt 5 1-N or 2-N shifts and adjusts the timing each time to mitigate possible effects of engine heating the tubes and changing the properties of temperature on the co2 in the actuators. If failed, switched back into gear for another attempt. All done within ~3 seconds.
We also did some 'enable co2, close, wait, reopen co2, get into gear' to not force the gear selector into gears too fast. It got better results than a 'open co2, wait until in gear' method but requires quite high update rates of your gps to account for the amount of time to wait before reopening the co2 valve.

If solonoid: Tobias pretty much laid it out for you.