On Sunday 21 November 2021 02:40:39 John Dammeyer wrote: > Has anyone ever tried any sort of closed loop control of an air motor > similar the one on this butterfly impact wrench. > https://www.penntoolco.com/52-424-9/ > In order to not have both the TTS and R8 collet drop out of the > spindle I'd like to be able to limit the number of turns to 2. > > What I've found however, is that 10mS pulses to the valve supplying > air for CCW rotation barely move it until it's unloaded and then it > immediately spins up very fast and does at least 4 to 8 turns. That's > way too many. > > I've only got a one pulse per rev hall sensor detecting a magnet on > the socket. But I suspect between reaction time of the valve, the > compressibility of air and the rotary inertia of the motor that unless > there is some sort of constant load that control is pretty well > impossible. > > With servos, if the motor is loaded and then suddenly totally > unloaded, it too might turn a number of revolutions before the control > system could bring it back down to the original speed. > > Short of adding some sort of mechanical brake am I trying to do the > impossible? Oh and to avoid another 1000 words to explain I've added > a picture. John
Close to the truth, However there might be a salvation in a viscous greased disk that would absorb the rapid spin, trapped between two other disks. It would allow the initial slow unlocking but seriously impede the following rapid spin. Or an eddy currant brake but that would take burn it up power so it would need to be applied only when the air is applied, and possibly for half a second after the air valve was turned off. I like the suicide braking idea, but there is limited space and it needs more diameter than you have room for. A coil spring anchored to the tool that would allow maybe three turns of the socket before winding tight against the socket OD might be a softer stop. Or a pile of interlocking disks that were screw driven like the rear brakes on an old Schwinn bicycle? That was fairly compact and lasted close to forever. Just tossing out ideas to see if one sticks. Cheers, Gene Heskett. -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author, 1940) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
