How to increase HST relief pressure on a CK30

[tinman955]

How much change in psi can a guy make before any danger, 200psi 500psi 1000psi?

What port can be used to check hst psi?

 

[Tim M]

It's been a few years but, sitting on the tractor looking down at the ports, I believe the left port is the forward pressure. The middle is the charge pressure (not what you want). The right one is reverse. It won't hurt anything if your monitoring the wrong port in the beginning. You'll see immediately which is which when you apply a little pedal.

Here are the details on the plug threads:

http://www.tractorbynet.com/forums/...rostatic-transmission-pressure-port-plug.html

I was able to get a local hydraulic shop to make me a hose for a gauge 0-5000psi.

And for the record to all you gear "snooty snoots" with my modified RV I was able to "spin the wheels to China"!

 

[dfkrug]

I was able to get a local hydraulic shop to make me a hose for a gauge 0-5000psi.

Make sure you get a guage that reads at least 7K psi. AgriSupply has a
10K psi guage for about $15. A 5K psi guage is not going to be accurate
at the extremes of its range.

 

[Tim M]

What would be your guess as to the accuracy it's losing at say 4300 psi?

I think this is the one I have.

Bourdon Tube Pressure Gauge
Industrial Series Liquid Filled
Type 213.40

Products - Pressure Gauges - Industrial Pressure Gauges - 213.40 - WIKA Instrument Corporation

2ｽ? ｱ 2/1/2% of span (ASME B40.100 Grade A)

2% of 5000 is 100 psi.

 

[dfkrug]

What would be your guess as to the accuracy it's losing at say 4300 psi?

I thought you were shooting for closer to 5000psi. I don't know what
the accuracy is of most cheap pressure guages, but in general they
are less accurate at either extreme. I would be more concerned about
EXCEEDING the upper range. A 5000psi guage is prob good enough
for measuring 4300psi, as long as you don't expect it to be much higher
than that.

 

[SSdoxie]

I forgot that I started this thread, TIN.

Kudos to Tim for making an adjustment, and measuring the pressures,
before and after. I have been meaning to get a 10,000psi guage to
measure multiple HSTs.

I may be quite easy to intall the CK35/CT235 RV in a CK30/CT230 as
well. I don't imagine the part costs very much....

The current CK35/CT235 has a slighlty different hydro than the 27 & 30. The drive reliefs have the replenishing check valve incorporated into the the relief on the 27 & 30 the replenishing checks are ported internal. The relief valves will not interchange.

 

[Tim M]

Ok. So what about the rest of the HST internals? Would it be safe to take the CK30 HST relief pressure up over the 3950 psi spec to the CT235 spec of 4260 psi?

 

[SSdoxie]

I don't know what the purpose in design was or is. I suspect it is lower on the 27 & 30 due to HP to help keep the engine from dying when under max load. All 3 models are the same frame (weight) & gear reduction so the lower HP of the of the 27 & 30 may not be enough and you could get more engine lugging especially at lower RPM.

 

[dfkrug]

I don't know what the purpose in design was or is. I suspect it is lower on the 27 & 30 due to HP to help keep the engine from dying when under max load. All 3 models are the same frame (weight) & gear reduction so the lower HP of the of the 27 & 30 may not be enough and you could get more engine lugging especially at lower RPM.

I think DaeDong made the wrong trade-off in the HST design. If they
designed for a higher pressure, the weaker engines would just not be able
to move quite as fast under the high loads and traction. The Kioti HST
is the first one I have used extensively that will go to relief in low range
and high loads/traction, without spinning the tires. My JDs would never
fail to spin tires in low range/hi traction situations. My B21's engine was
low power, and a bit tired. It's HST would not go to relief in low range,
ever. The engine would bog rather than spin tires. A newer B21 might
not do that.

 

[Tim M]

Definitely an under designed HST. I would much rather stall the engine than hit relief.

Let's assume your not comfortable running your CK30 HST relief pressure at a higher than spec psi.

What other options are there?

Can an entire HST unit from a CK35(CT235) be put onto a CK30?

Anybody know how much an HST unit costs?

Can any of the downstream gearing be changed?

Not interested in smaller tires(less ground clearance).

 

[MotorSeven]

I don't think they are under designed since some of our tractors will spin the tires before going into relief, others here with the exact same model will stall out. I tend to think it is the way they were set or adjusted at the factory. Both my HST's - CK30 and now my Dk40 both spin the tires.

 

[dfkrug]

I don't think they are under designed since some of our tractors will spin the tires before going into relief, others here with the exact same model will stall out. I tend to think it is the way they were set or adjusted at the factory. Both my HST's - CK30 and now my Dk40 both spin the tires.

That is one of the reasons I started this thread. Testing your HST RVs
will tell if your unit is in spec. And if your FWD RV is lower than your
REV RV, then switch them. I think that Tim's method of adding a U-shaped
shim is a good work-around to the welded RV that is installed. How much
increase can you safely allow? No easy answer there, but is does seem that
the gearbox and final drive components may be the same. I have NOT
exhaustively compared part numbers to verify that.

BTW, I have not even tested my own HST pressures; it is certainly
possible that the FWD is low. The failure to spin tires that I have experienced
is in such rare circumstances that I am not seriously inconvenienced.

As for lowering the gear ratios out of the gearbox, that would be hard, and
you would need to do that BEFORE the MFWD shaft driven gear. Changing
all 4 tires to a slightly smaller diameter would help, but with a ground
clearance penalty.

Swapping the whole HST is a possibility, but likely a very costly one.

On the other 2 Kiotis I bought new (CK30 and CK20), I have used them,
but I have not tried the low range/high load/good traction test to determine
if the wheels spin or not.

 

[VictorW]

Tim M and Tinman wondered how much hst RV pressure is to much. If you took it to say 5000#, wouldn't that be like having a gear tractor with no RV. A gear either spins the tires or stalls the engine. I would think that every drive part would handle the torque except for maybe the hst unit. So I think the question is how strong is the hst unit. Mine will spin the not loaded R4 tires in fwd, low range, on pavement and fwd, medium range, on dirt. I have stalled the engine at 2400rpm if the tires bite in and I'm in a higher range than low. I haven't checked the pressures so I can't advise when the RVs open. It would be nice to know how much the hst unit can handle.

 

[Tim M]

That's why I asked if the CK35's (CT235) HST internals were the same as the CK30 (other than the relief valve discussed by SSDoxie above).

If they are then one could infer that it would be fine(or reasonably so) to run the CK30's up to 4300 psi.

MotorSeven,

I agree most people probably are not going to hit the relief before they spin. I have a FEL, backhoe and loaded tires. I hit relief in low gear quite often with no tire spin at 3950 psi (Kioti CK30 RV spec). For what I do I can work around it but it would be nice to get more power to the ground.

Is this a design flaw? Debatable, but I think so.

 

[tinman955]

I did find out that the 40-45-50hp hst bobcat tractors have a 5000 psi which you would assume should plenty enough but I dont know what comparable tractors ie deere, bota ect are running psi wise?

Its a fine balance of power to weight and ofcourse the ability or lack of to transfer the power to the ground in an efficent package, I have no idea how well engineered these Daedong family of tractors are when it comes to being efficent in all ways.

I admit what first attracted me to the daedong family of tractors was price, then I seen one in person and realized what a guy gets for his money, so then I found my local dealer great service carried them and I was sold.

I mean how many individuals have owned more than one compact or utility tractor, or have even ran other brands, to know what is right or wrong?

In my opinion my Bobcat's have been very good equipment, with just a few quirks like some of the topics being discussed. Bobcat is in the infant stage of selling tractors but are no rookie to equipment but i assume as a company the tractor business is separate from their other equipment offerings, they just buy a universal tractor paint it white and they are in the tractor business. Time will tell if they move forward or just let it ride...

 

[IndyIan]

I haven't been able to stall out my HST in low range yet. In mid-range I can use the loader to dig loose materials but not tough stuff.
I don't really understand how the torque output changes with output shaft speed as its possible to really make the engine work hard in high range going fast on the road but at slow speeds the HST goes into relief easily?
I'd like to see all the torque curves for engine rpm and output shaft speed as well as the efficiency curves so I know where to try and run the drivetrain.

 

[BigDogues]

Hi Tim,
I came across you thread on RV mod today. I have had a CK25 since 2006 and have always felt it hit PR far too early. I rarely spin my tires and almost never stall. How has this mod been holding up? Do you think this would work for my CK25? Any input as to what i should see for pressure? I always assumed the CK25 and 30 were exact except for the engine in my model year.
Thanks in advance.

 

[Brozum01]

I have a dk40se hst. The hst has always felt sluggish and goes into relief. Does anyone know where the hst forward and reverse relief valves are located and how to access them?