No, no... thank YOU! We had the calculations all done to SAY it would work, and we had some preliminary test data that matched our calculations... but given my marks in thermo and fluids 20 years ago in university, there was... well... probably close to a 50% chance we were wrong (hopefully I've got better since)! As you have been kind enough to share your results, when I compare your observations to what my model predicts (and the demo version of working model won't let me save.. fair enough... or I'd post it here) it validates the model. We will be building this week with far more confidence!
As for the transducers, some digging around on the web shows that T.I. Instruments is now
www.sensata.com Unfortunately they don't show a 5cp3-7 sensor in their product line, but I've dropped them an e-mail to ask if there is a derived or evolved version of it, or perhaps they just changed the part number, which should make it a legal COTS item. I will try to remember to report back here if I find anything useful.
Jason
EDIT: The plan is to design for five of the cylinders, then cut back if we can, either by dialling the regulator back, or dropping one cylinder. The idea behind using more of the smaller cylinders (besides the fact that we've got them...) is that gives us five "tubes" of airflow to keep the pressure up throughout the stroke, while with a larger diameter cylinder we would only have two, or perhaps three. Not that this appears to be a problem. We are also considering setting up the system as Two clippards --- Regulator ---- Valve ----- Two Clippards ---- Cylinders so that there is no bottle neck due to the valve. This will hopefully reduce the amount of pre-load we need, and allowing us to maximize the useful stroke of the 8" cylinders.