Peter and Bud - Upset Circuit

[TConnolly 13]

Tim, what pump pressure are you actually operating at? We used to use a Rexroth servo valve which IIRC had a pressure limitation on the jet pipe/flapper pilot stage. We were operating at 5000 psi but we had a pressure reducing valve on the pilot line to drop the pressure to around 1,000 psi. Your schematic doesn't show a seperate pilot pressure port for the valve (internally piloted) but I am wondering if a similar limitation existed on the original vavle. I'm at home and I don't have my Moog valve data sheets, but it may be the reason for the reducer - a look at the Moog site shows a 3000 psi limit for the smaller servo valves but I don't see any 74 series valves - but what the hell do I know at this time of day, its late and I'm up because I got tired of tossing and turning - figured I would get more rest if I got up.

[TimWilborne 108]

You can stop thinking about this. Try counting sheep. I thought about it all night too and it just hit me. It has to do with the original machines lack of servo controller, or more accurately lack of encoder or linear transducer. I will explain in detail later today. Getting ready for work

[TimWilborne 108]

Originally this machine did not have a true positioning system. It would flash to a switch that began the upset cycle. The upset was set by an adjustable rod on the end of another set of cylinders that opposed Peter and Bud (Upset Cylinders). It would push on these cylinders for about a half of a second then the other cylinders would release allowing Peter and Bud to push further. Both sets of cylinders were 6" bore and the servo did the pushing. The other cylinders pressure was set at 750 psi so the servo had to be set to a pressure lower than 750 psi otherwise Peter and Bud would be able to overpower the other cylinders. The other cylinders are no longer in use so this is not a problem anymore. Does that make any sense?