Hydraulic Stall Behavior

[marrt]

On my original Moss Road Vintage (MRV) 425, I don't recall being able to stall the engine using the tram. However, I would usually back off, since this is poor technique and causes pump cavitation, so I can't say for sure. But, my 13 year old vague recollection is the tractor would lug way down but not stall the engine. Perhaps a relief would kick in or something.

When I drove a new 425 at the factory, I purposely pushed the tractor into the famous gravel pile to see if it would spin the tires. The tires didn't really spin much before the engine began to stall and I backed off. I'm quite sure it would have stalled the engine easily though.

So, will the newer 425's stall the engine if pushed against an immovable object?

 

[ponytug]

While in no way meaning to imply anything about the mechanical state of your MRV425, I would point out that warmer oil (less viscous) and a little bit of wear at the pumps and motor would go a long way to relieving the pressure and preventing an engine stall...as would a pressure relief.

During the factor test drive, I remember almost stalling out the 14XX that I test drove on "THE" gravel pile, but I know that I certainly didn't have the engine at WOT. I also had zero technique. I would have been a hazard to all things in the vicinity with the governor at max speed- myself, the warehouse, the trees by the creek, the cows in the next pasture... :drink:

For the record, hot or cold, powering my 1445 at a fixed object will stall the engine. I don't do it often, but every so often, I misjudge how much I can get in the bucket and try to take a bigger bite of something solid, which bogs everything down. My reflexes are getting better, so I don't actually stall it, but it I kept the pedal mashed down, it would stall.

Thanks again to whomever posted the technique of one foot on each pedal- it makes undoing the WOT against a fixed object much faster and easier!

All the best,

Peter

On my original Moss Road Vintage (MRV) 425, I don't recall being able to stall the engine using the tram. However, I would usually back off, since this is poor technique and causes pump cavitation, so I can't say for sure. But, my 13 year old vague recollection is the tractor would lug way down but not stall the engine. Perhaps a relief would kick in or something.

When I drove a new 425 at the factory, I purposely pushed the tractor into the famous gravel pile to see if it would spin the tires. The tires didn't really spin much before the engine began to stall and I backed off. I'm quite sure it would have stalled the engine easily though.

So, will the newer 425's stall the engine if pushed against an immovable object?

 

[KentT]

With 28.3ci wheel motors, my 425 will spin the tires when pushed up against an immovable object... the fun part is trying to figure out which tires are going to spin first. In loader work, I've often discovered that my rear tires have dug holes without the front tires spinning, and I never realized it until I backed up. Using other implements, the front tires will sometimes spin first.. but sometimes not. Basically, I think the wheel with least resistance spins first, regardless...

My MRV original 12.5ci wheelmotors would not stall the engine (even at 250 hrs on the machine when I first bought it), with fluids hot or cold, it would only whine and do nothing... The 21ci CharLynn wheelmotors would often stall the engine, especially if the fluids were cold. The 28.3ci ones spin tires...

 

[cqaigy2]

my 422 will stall when pushed too hard.

 

[J_J]

With two wheel motors in series, how is one tire spinning and the other is not.

The fluid displaced by the first wheel motor is going to power the next wheel motor.

If the one wheel will not move, then the engine should stall.

However one of the wheel motors could bypasses the fluid if worn.

.

 

[KentT]

With two wheel motors in series, how is one tire spinning and the other is not.

The fluid displaced by the first wheel motor is going to power the next wheel motor.

If the one wheel will not move, then the engine should stall.

However one of the wheel motors could bypasses the fluid if worn.

.

In theory, I agree completely, if the system is 100% efficient. But, wheel motors (or any hydraulic motor) will not seal completely like a valve does. They do not truly "dead-head." Internal leakage past the gear or vane is a fact of life -- the only questions are how much and under what conditions.

In operation, even with new wheel motors, it happens...

 

[cqaigy2]

In theory, I agree completely, if the system is 100% efficient. But, wheel motors (or any hydraulic motor) will not seal completely like a valve does. They do not truly "dead-head." Internal leakage past the gear or vane is a fact of life -- the only questions are how much and under what conditions.

In operation, even with new wheel motors, it happens...

Possibly pressure relief in parallel with the motor?

Says the complete hydraulic noob....spell checker fixed hydraulic for me.

 

[KentT]

Possibly pressure relief in parallel with the motor?

Says the complete hydraulic noob....spell checker fixed hydraulic for me.

Pressure relief valves are available options on many (such as on the White CE series used on new PT-425s) but I doubt that they come standard with them from Tazewell.