Auger motor popping hoses

[oldnslo]

Only running at idle, no throttle at all. It's 3500 lb. hose and it blows while mixer is turning and very shortly after it starts turning. Keep in mind that I'm simply plugging two 4 foot hoses with flat faced couplers (1 male, 1 female) into the male/female flat face couplers for the auxiliary hydraulics on the front of the Bobcat. The same place that you would plug in other Bobcat attachments. There is no spool on this side of the auxiliary system. Just whatever attachment you plug into it. I have a backhoe that plugs right in to the two hoses, and the backhoe has it's own spool controls. In the case of the concrete mixer, the other end of the 4 foot auxiliary hoses reach over to the mixer and one line obviously goes to the "IN" side of the Prince RDRS 150-16 flow controller valve, then out from the 'CF' or controlled flow port another short hose goes to the IN port on the motor. There is a 3rd port on the Prince controller that is 'EF' or excess flow. That hose is tee'd into the hose coming from the motor back to tank hose. Hopefully that all makes sense. I had a gauge on the return before and it showed nothing. I assumed it was a cheap Chinese piece which I tossed, but never put one back. I've been away from the project for a few weeks because of the holidays but I'm ready to tackle it again. One thing however, when I took the flow controller off and just ran the auger without it, just straight thru, there was no problem, it's just to fast for a concrete mixer.

If you are blowing hoses while turning with the Prince flow control and not blowing hoses without it I would triple check which port is pressure and which is controlled flow. Flow MUST come from the skid loader into the pressure port on the flow control. The CF (controlled flow) port would connect to the motor. The EF ( excess Flow) port would connect to the return port of the motor and these would go back to tank.

If you have this valve hooked up backwards it will restrict the flow out of the motor and tend to blow things up. I would say you are lucky that you haven't damaged the motor yet. I.e. blown the shaft seal.

For run down on cement mixer you could install a check valve between the work ports on motor. This would allow run down and also possibly allow you to turn the drum slowly by hand if desired.

 

[glastron23]

sort of right... lets start from the pump. oil is taken from the tank by the pump, flow then goes to the valve P port, through the valve to the T port then back to tank. circuit complete.
now lets move a spool to the open position. oil flow is then directed from the P port to the valve work ports (A or B lets say A) oil flows from P to A out the aux hose to your motor, through the motor to the aux return hose to port B then to the T port to tank.
now lets rotate the drum, the drum turns and you want to stop it, you close the valve closing the flow from A to B, BUT the motor will turn because the drum is turning causing the motor to become a pump, the pump(motor) takes the oil from the aux hose connected to the A port and pushes it into the aux hose connected to the B port which is closed to the tank causing the pressure to rise really fast and high (due to the lack of a tank path) causing the hose to rupture.
trying to plumb this to tank is a big job on the skid steers, it would be a lot simpler to add the cushion valve. This valve will allow the excess pressure/flow from the motor to go from the aux B hose to the aux A hose and since the oil in volume will be the same as the oil out volume you will not be blowing hoses.

 

[memphismark]

would you recommend a cushion valve for both in and out ports on the motor, just for heck of it, or just one valve on the motor return

 

[SSdoxie]

Double check the plumbing/routing starting at the front coupler of the machine. When Right Hand trigger is pushed to activate flow, the oil goes out the Female coupler on the 753. Hoses should be from female coupler on 753 to inlet of flow control, CF (controlled flow) goes to inlet of motor, EF (excess flow would go back to return. Return form the motor could be teed into the return with the EF but it would work better if there was a third (case drain) line on the 753 going directly to tank, then either EF or motor return would connect to that and the other would go to normal return. As I stated in prior post, you cannot send all the return oil directly to tank, by-passing the control valve return or the hydrostatic pump will starve for oil.
A quick test to see if oil flwo direction is your problem:
After starting the 753 but before pulling the front Aux. trigger slide the thumb button on that handle to the Right (towards outside of machine) watch the drum turn, it will run opposite direction, while holding the thumb button right pull the detent trigger and let go of both. Auxialiary are now detented in revers direction. If it rusn this way without popping the hose, simply swap the male and female couplers connecting to the machine and use detent trigger in normal manner.

 

[memphismark]

I definitely need to check the flow. I wasn't sure which of the couplers, male or female, were the flow. By the way, I have it all hooked as you suggest with the CF to motor and EF tee'd to the motor return. One question. What is a case drain and how could I do this to get the return back to the tank and by-passing the control valve? Thanks. Mark

 

[SSdoxie]

I definitely need to check the flow. I wasn't sure which of the couplers, male or female, were the flow. By the way, I have it all hooked as you suggest with the CF to motor and EF tee'd to the motor return. One question. What is a case drain and how could I do this to get the return back to the tank and by-passing the control valve? Thanks. Mark

Case drain is the 3rd coupler I asked about. There is a kit that could be purchased from Bobcat for it, but less expensive to make it yourself. Use a 3/8" in coupler and run 3/8" hose back alon the lift arm (following the tube line), down inot frame of machine and around front of the engine and tee it into small hose fitting going into bottom of the hydraulic reservoir. Determine how much Excess flow ther is compared to Controlled flow and connect the smaller flow amount to the Case Drain circuit. Your 753G will flow 14 GPM @ 2450 RPM, if setting the CF flow anywhere over 50% then run Excess flow to Case Drain, If setting the CF to less than 50% run motor return to Case drain. Note: If you are not adjusting the CF and leaving lever in full Max flow or close to it, take it out of the system and just adjust flow with the throttle.

 

[memphismark]

does the thumb button pushed left or right determine the flow direction, clockwise or counter-clockwise in the case of a motor turning? What exactly does the index finger trigger pull do? Also, I have to lower the arm bar from the outside of Bobcat after starting, and reach over and in to activate the auxiliary hydro button on the keypad. Is there a smarter way? I need to be outside the Bobcat to tend the concrete mixer. Thanks

 

[SSdoxie]

Thumb button is proportional flow if you press the Auxiliary button one time, moving the button to left sends flow out the female coupler & return through the male. Button to the right reverses the flow. Pulling and release the trigger without touching thumb button send flow out the female and locks it on, thumb button to the right and pull trigger locks flow in reverse direction. Yes, this will change direction of motor ratation. Any time the trigger is pulled, flow goes to fully on (no proportional) regardless of which selection was made on left panel.
The trigger will work without lowering the seat bar or pressing the Press-to-Operate button. Only have to press the Auxiliary button on the left panel, then pull the trigger to get flow.

 

[memphismark]

since you are the only person who has ever been able to answer this and these questions for me adequately, (answers are not in my manual anyway) what is the purpose of what you are calling "proportional" flow. If the trigger is pulled and this locks the flow on to the auxiliary hydros, is proportional a 'temporary' use? If so, what would that be used for as compared to what you called "full on". I've always pulled the trigger and held it while I pushed the thumb button one way or the other for the log splitter direction. Didn't know there was another use for it. Thanks

 

[memphismark]

would I use an open or closed center motor spool valve to control the auger attachment and Bobcat auxiliary hydraulics connection. I'm thinking this may help and just eliminate the Prince controlled flow valve.