THIS IS WRONG: "The down side to this is that air is lost with each extention of the actuator. Its safer, easier, but requires more frequent gas refills".
3 Ways uses air for both up and down moves.
2 ways uses air only for up move.
So you need twice bigger tank with 3 ways systems. The 2 way is easier, safer, and need less air, you just have to be sure nothing touch the leg and wheel while retracted or the spring has not enough power to unlockThese retracts are well made, showing good craftsmanship. The spring down function works perfect, no hang ups. The oleo affect will soften a bad landing, Robarts are too stiff, these are perfect. Spring Airs hang, up sometimes, these don't.
These retracts are installed on a Cessna type twin EDF jet, 20lbs, two Himax 96mm EDF fans. Reference the Nitro Eagle 100 jet.You can give me more information onto your trains rentrants as the dimensions in thickness and the weight which they can support(bear). Please thank you.