New BX23 HST problem?

[Rimmer]

I still vote for "normal." I've done it several times: push into a pile of dirt (or whatever) with the FEL, tractor stops moving, transmission whines, engine sounds only slightly loaded. "What's going on here? Oh, yeah ... I'm in high range." When I shift into low, either: (1) the tractor moves, or (2) the wheels spin, or (3) the engine lugs and blows black smoke.

 

[gsxr1100]

Phrede ---I stalled then engine when moving something that weighted more then the tractor and was not in a movable form. Also stalled in high and low.

As noted in the past, weight is a huge issue. If I do not have the BH on the tires spin and nothing. With BH on engine bogs down. I think rimmer stated it like I see it. As the above happens in both gears.

As you stated if you just sit there with no wheels spinning and no load on engine either you have not engaged hydo pedal 100% or you are in high gear (as rimmer stated). I just say that since something needs to give (engine , wheels etc). Power-in equals power-out. It needs to go somewhere (even the whining noise means it is moving). Again as rimmer stated, listen for the whine of death (just a high pitch hyd noise.

 

[chocolatehauler]

My two cents. I think it has to do with peddle position. And/Or inital load. I to have had it not move or load up when trying to move forward under load. And yet when working with the loader it will almost stall. It has something to do with how I approuch a high load situation. It seems if I am all ready moving into a high load situation the engine will load up and if I am starting into a high load it will just sit there. does that help any? All I know for sure is this little tractor compared to other hst types I have owned ford, case is far and away done more than I thought possiable. Have fun /forums/images/graemlins/smile.gif

 

[Phrede]

GSXR1100, What you are saying is entirely different than rimmer. You say you can stall the engine in high or make the wheels spin. Rimmer sez he can not (in high gear).

"As noted in the past, weight is a huge issue. If I do not have the BH on the tires spin and nothing...."

In this case the tires spinning is something and is different than what rimmer sez or what I have. My problem is not losing traction due to light weight and is exactly as rimmer has described.

Chocolatehauler may have something. I have noticed this to happen from being stopped and then trying to move. Maybe something to do with a dead band in the control circuit??

If this is normal I'm OK with it, just use low gear. But if it is not I need to get it fixed. I am wondering about climbing a hill in high, but if the "moving first" theory is correct, hill climbing will not be a problem, unless you stop on the hill. Anybody had any problems on hills in high?

I understand that this is a smaller machine and don't expect too much. I just want to know what it is capable of. I really do expect to do all of the heavy work in low and just forgot to shift when I noticed it.

Thanks to all for your help.

 

[frank_f15]

i don;t know if that is normal or not, i have never stalled the engine on my b2400, usually the wheels will spin, but i never work in high range, but seeems to me , no matter what range u are in if u overload the tractor it should either spin the wheels or stall the engine.

 

[gsxr1100]

Phrede- If you re-read my posts you will see I have stalled, yes stalled the engine moving an item weighting over 3,000 lbs (only about 4 to 6-yards of concrete in one spot with dirt etc). I was in high gear and also tried in low gear. Low worked after the first stall just needed to move the pile in 4x4, about 0.5 mph and locked both rear wheels.

Other times when going into a pile of dirt, rock etc yes I can spin and sometimes not. Again, I agree with rimmer since he stated it is a matter of foot pedal; which in return in fluid flow to hyd.

Also the weight has an impact. Most times (90%) with BH on, the tires will not spin. There is no yes/no answer. The high-pitched noise will tell you.

Lastly, based on what I have seen and what others have read, you are fine.

 

[techman]

Pherde:

What you are seeing is completely normal with a HST. A HST will deliver a fixed amount of torque INTO the final gear transmission. When you hit that torque limit, the oil flows over a relief valve. If the torque combined with the high gear ratio won't allow movement, it aint gonna go. Switching to low gear multiplies the fixed max torque and gives more push.

As for the engine loading, when at the max torque limit, the engine HP is now a function of the oil flow, or in other words, how far the speed pedal is pushed. If you hit the torque limit with a low speed on the pedal, the required HP is low. If you stall and push all the way on the pedal, the engine HP goes up as you press harder.

I have found on my '22 that even at full torque and full pedal, it only loads the engine somewhat, and no where near stalling. In other words, the power capacity of the HST is under the engine's rated power. Most of the engine's power is for the PTO and the hydraulic implement pump. This is also why on a BX 15 or 18, the HST power is a greater percentage of the available HP, and you would notice the engine loading somewhat more.

By the way it is not a good idea to hold the pedal down when movement is stalled. All of the high pressure oil going over the limiting relief valve converts its energy into heat. Even a few minutes in that condition can ocerheat the hydraulic oil and potentially damage hydraulic components by overheating them.

For the more curious, the horsepower in the HST is defined by Pressure x Flow / 1714 (constant for PSI and GPM) = HP. When you stall motion, the pressure is fixed at the relief valve setting (perhaps 2000 or 3000 PSI) and the required HP is now a function of flow, which is determined by the pedal position (it controls the pump displacement, and therefore the oil flow). So the more you push the pedal, the greater the HP needed from the engine. One of the great advantages of the HST is that you can deliver full drive torque at low speeds (flows) and not need a lot of HP, just like a mechanical transmission in a very low gear.

I hope this helps.

paul

 

[Phrede]

Paul, your explanation makes complete sense to me. The weakest link in the drive system must be the input shaft of the final drive and the relief valve is set to protect it. It would not be the output shaft as that load is independent of the gear range.

Based on the advertised max. speeds, I would expect to see about 30% more drive torque available in low range at the same relief pressure. Because of the typical flat torque curve of a diesel engine, a significant drop in RPM may not be seen when near the torque limit of the HST.

Just a couple of more thoughts....
Does this tractor have two pumps, one for the HST and one for the aux. hydraulics?

Is the relief valve adjustable and accessible? If so, where is there a test port for a gauge?

I see a service manual in my future, any recommendations?

Thanks again for all the help

 

[techman]

Phrede:

Yes there are 2 pumps. The HST is a single unit, but it actually has a pump (variable displacement) and a hydraulic motor all in one package. The package also has the relief valves, some check valves and other parts to make up a complete hydrostatic transmission. You can see the HST as it is bolted on the front of the main transmission case. It is highly finned and has the engine shaft, with fan, connected to it. It looks like the reliefs are not adjustable. I guess one could play with them and shim the springs, but I wouldn't advise it.

The second pump is a fixed displacement that is mounted on the top-center of the trans case, pointing rear. It supplies oil for the implements, 3PH and power steering. There is a relief valve for that pump and a test port for pressure. The relief can be shimmed, but normally replaced as it is factory set.

The service manual is helpful, but not "great". Also very helpful is the parts manual for the tractor, which I found and downloaded on the net (as a pdf). It gives a lot of nice breakdown drawings of the tractor.

paul

 

[gsxr1100]

If I had to guess, I would say the relief valve setting is more on the lower 2000 psi end. I remember my old deere 455 was around 1500 psi