Toying with the plumbing at the Electrolab
Tonight at my local hackerspace, Electrolab, I brought the ball valve ordered last week to RS Components. Michel, an old timer of the lab specializing in mechanics, was prompt to drag me to the mech corner of the lab to test various plumbing links. The aim was to find the right links to pair it with the paintball gun tank salvaged in the lab, which will be used to store the oxidyzer in the very first engine tests on the test stand.
Having found the appropriate links, and Michel planning to bring copper tubes of the right size from his stock at home, I then got in discussion with Mickey and Ellyan about the best way to activate remotely the ball valve.
We compared two solutions: a system with a pneumatic jack, and the other with a stepper motor using a reducer gear (the ball valve switches from open to closed in a quarter of a turn).
Thanks to Mickey and Ellyan, I learnt about using a tork wrench, unfortunately the ones available at the lab were too powerful to measure the small tork needed to rotate the valve. We hence moved to the good old method: using weights tied by a rope to the ball valve lever to determine the weight needed to turn it, and calculate from there the force needed to rotate it. The final calculation gave 0.56N/m.
Going back to the automated rotation mechanism, the pneumatic jack solution quickly appeared to become bulky and complex. The stepper motor with the reducer gear seemed a much straight forward solution: the motor, a pinion to replace the valve lever, and we've got it! We discussed printing the pinions on the reprap (3D printer) available at the lab, and though the plastic piece would theoretically withstand the force we're talking about, we prefer going for an off-the-shelf metal piece. The next step is to find the right one and purchase it!
Once again, I'm amazed by the great skills, and great propensity to help others, that I've found in the lab. I'm grateful to all those who helped me along the evening, I'm a little bit less a newbie in mechanics now, and a little closer to building the Alpha rocket!