SPQ13 TRACY

This week was an accomplishing week.  Buttoned up the hydraulic fitting box exercise.  I am quite a bit more familiar with the fittings than before I started them, but without constant exposure I could see myself forgetting specific names and types as there are so many differences.  The biggest lesson I pulled out of that was a familiarity with looking up the fittings and being able to I.D. them in a book.

I was able to hop on the Bobcat mini-excavator today and stack some tires up.  It was nice to become more comfortable with the controls.  I will be practicing that more and more, and even switching up the controls between standard and iso.

 Jeremy, Gary, and I took apart a variable displacement axial pump this week just to see what was all going on.  It was good to be able to actuate the swashplate and see the pistons.

As we were flipping through the service manual, Jeremy and I got a little more than curious on how the Bobcat can helicopter endlessly and still supply oil to the tracks and the blade.  We found a swivel joint out in the shop and took it apart and found that it is simply a large round stock with holes bored out for supply and return that feed into individual ribs on the side.  The round stock rotates inside a case allowing the fluid to travel down and out, and up and out.  8 lines going in and out: 6 that go to the tracks which include forward and reverse for both right and left as well as a drain and pilot (which I understand from looking at the schematic controls the autoshift), and 2 and go to the blade cylinder.  Being able to skim the service manual, find a swivel joint to take apart, and answer any random questions that came up helped to better understand the schematic that was handed to us today.



The schematic still has many parts that I don't fully understand.  Our table has decided to pick apart the slew motor section which includes a brake.  What I have figured out so far is that the motor is an axial piston motor combined with a planetary gear set, and that the motor is an auto brake.  I was able to trace a pilot line from the brake actuator back down to a tee that has a 2-way check valve.  The 2-way check valve moves either direction depending on the direction that the LH joystick is pushed.  This allows flow to move the pilot activated directional control valve to the open position.  Fluid then flows through the pilot activated directional control valve and fills the chamber inside the brake actuator.  When the force of the spring in the brake actuator is overcome, the brake is released from the motor.  As the joystick is let off, the pilot activated directional control valve closes and the spring forces fluid out and through an orifice and a timer valve, and is then sent to drain line to tank.  I'm still not exactly sure what a timer valve does.  My guess is to control the amount of pressure downstream of the timer valve so that the fluid doesn't go back up the drain line and back up into the motor, but rather continues downstream and ends up in tank.

Still a lot of speculations, theories, and assumptions.  I still have to wrap my mind around how load sensing works in all of this, among many other things.  All in all, I feel like my understanding of hydraulic systems is coming along nicely and I look forward to doing more of it in the coming weeks.

Hours:
Week: 35
Total: 215