Grading GC1720 - Deadheading hydrostat?

[Nacademus]

Nacademus, what you describe IS too aggressive with scarifiers. Don't use the same angle when using just the back blade as with the scarifiers. Lengthen the top link when using the scarifiers. When they bite in, they will pull the boxblade into the dirt. There is enough pressure that it will cause the weight transfer (think of a weight distribution hitch) to clamp down on the rear wheels, stopping them dead. The angle of the scarifiers is important. The boxblade can be "tuned" so that scarfiers pull the unit into the material, so no additional weight is needed, but still not enough to bring the tractor to a stop. Been there, done that.

Honestly. That makes sense now that you explain it that way-wonderful analogy. In my head, I didn't consider that the 3PT was rigid in position with the lever untouched and only freely travels upward.

The weight distribution hitch analogy is a good one.

What is odd, though, was that these scarifiers are not adjustable and really only contact about an inch, inch and a half BARELY into the soil. I could still almost see the each whole scarifier tooth as it wasn't fully bit in the dirt that much. The box was nowhere near full. It's weird. I should have taken a picture-if I did, I bet most of you would be surprised. Oh, and there are only THREE scarifiers on my BB. Maybe the rear blade hung up on something I just didn't see.

King Kutter 4 ft Box Blade BB 48 XB

I still think it if it was actually hooked and stopped cold, it should have kept eating, digging in. Just sort of petered out on me.

There MUST have been some sort of force, like you said comparing its operation like a WD hitch. I just couldn't identify it at the time.

I built my own hydraulic pressure gauge from parts on Amazon-just haven't gotten around to using it. I will warm the tractor up tonight and check it.

Here is what I used to make my own hydraulic gauge-in case anyone else wants to make one and save some money.

Hydraulic Liquid Filled Pressure Gauge 0-3000 PSI
https://www.amazon.com/gp/product/B019465ZC8/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
$10


3/8" NPT Thread Hydraulic Coupler Set ISO 7241-B (Coupler set with dust caps-assure your tractor has 3/8 or not and get what fits)
https://www.amazon.com/gp/product/B07FVLY3BQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
$19-but a single male can be found for $10


I sourced a small 3/8" to 1/4" npt adapter from a local store (Rural King) ~$5

My total investment was about $35 but could be done for $10 less. I wanted to keep the other coupler in the set as a spare, anyways.

I like to try and make my own things when I can. Gives me a little project and something to look forward to in the mail . ^_^

 

[DMW]

The boxblade/scarifier angle really doesn't affect larger tractors. The SCUTs have smaller tires. The 3pt arms are at the same level as the rear axle (or slightly above). Even if the box is full, my GC has no problems spinning the rears, if they don't spin, adjust the angle, it's easier than trying to maintain a height manually with the 3pt lift lever. Also try pulling in 4WD, it also affects the angle of the boxblade. Fronts will start spinning first as you lose traction when the boxblade loads up.

 

[k0ua]

Honestly. That makes sense now that you explain it that way-wonderful analogy. In my head, I didn't consider that the 3PT was rigid in position with the lever untouched and only freely travels upward.

The weight distribution hitch analogy is a good one.

What is odd, though, was that these scarifiers are not adjustable and really only contact about an inch, inch and a half BARELY into the soil. I could still almost see the each whole scarifier tooth as it wasn't fully bit in the dirt that much. The box was nowhere near full. It's weird. I should have taken a picture-if I did, I bet most of you would be surprised. Oh, and there are only THREE scarifiers on my BB. Maybe the rear blade hung up on something I just didn't see.

King Kutter 4 ft Box Blade BB 48 XB

I still think it if it was actually hooked and stopped cold, it should have kept eating, digging in. Just sort of petered out on me.

There MUST have been some sort of force, like you said comparing its operation like a WD hitch. I just couldn't identify it at the time.

I built my own hydraulic pressure gauge from parts on Amazon-just haven't gotten around to using it. I will warm the tractor up tonight and check it.

Here is what I used to make my own hydraulic gauge-in case anyone else wants to make one and save some money.

Hydraulic Liquid Filled Pressure Gauge 0-3000 PSI
https://www.amazon.com/gp/product/B019465ZC8/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
$10


3/8" NPT Thread Hydraulic Coupler Set ISO 7241-B (Coupler set with dust caps-assure your tractor has 3/8 or not and get what fits)
https://www.amazon.com/gp/product/B07FVLY3BQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
$19-but a single male can be found for $10


I sourced a small 3/8" to 1/4" npt adapter from a local store (Rural King) ~$5

My total investment was about $35 but could be done for $10 less. I wanted to keep the other coupler in the set as a spare, anyways.

I like to try and make my own things when I can. Gives me a little project and something to look forward to in the mail . ^_^

You do know that the pressure generated by your hydrostatic transmission is seperate from the hydraulic pump driven off of the camshaft of your engine that runs your implements like the FEL and 3pt hitch right? Hydrostat pressure's can easily be 5000 PSI and can only be measured at ports on the transmission pump made for this purpose. As for what the PRV should be set for varies tractor to tractor depending on size. As the tractors get bigger the pressures get higher, But 5000 to 6000 is fairly common. In your smaller tractor it may be less. You will need the workshop manual to know where to install it. And of course the PRV for the hydrostat is seperate from the PRV for your loader and 3pt.

 

[Nacademus]

You do know that the pressure generated by your hydrostatic transmission is seperate from the hydraulic pump driven off of the camshaft of your engine that runs your implements like the FEL and 3pt hitch right? Hydrostat pressure's can easily be 5000 PSI and can only be measured at ports on the transmission pump made for this purpose. As for what the PRV should be set for varies tractor to tractor depending on size. As the tractors get bigger the pressures get higher, But 5000 to 6000 is fairly common. In your smaller tractor it may be less. You will need the workshop manual to know where to install it. And of course the PRV for the hydrostat is seperate from the PRV for your loader and 3pt.

No. I did not know. I did not anticipate that. Surely it doesn't feel like its applying all the pressure to locomotion that it can. Thanks for teaching me that-I honestly never thought to check.

It seems that there are actually 2, high pressure relief and low. Are these what specifically govern the functions of the range selector?

 

[k0ua]

No. I did not know. I did not anticipate that. Surely it doesn't feel like its applying all the pressure to locomotion that it can. Thanks for teaching me that-I honestly never thought to check.

It seems that there are actually 2, high pressure relief and low. Are these what specifically govern the functions of the range selector?

View attachment 620959

Your interested in the High pressure relief valve. The low pressure deals with the "makeup oil" coming from the charge pump. Since you don't actually Have a charge pump per se, on the hydro, your tractor uses a circuit from the gear pump up on the engine (your implement pump) for the charge pump function. This is pretty common on smaller tractors.

The "range selector" has nothing to do with your hydrostat. It is simply an old fashioned gear two speed in your case transmission that is behind the hydrostatic transmission. So you have the high pressure hydro pump. that is variable displacement controlled by the swash plate that is attached in your case directly to your pedals, and that is followed by the hydraulic motor driven by this variable displacement pump. The output shaft of the hydraulic motor is attached to the input shaft of the old fashioned non synchronized 2 speed gear transmission. This is your "range" transmission, from there it goes to the final drive reduction near each rear wheel, and there is a "transfer case" like take off to drive the propeller shaft headed up front to the front differential/axles.

 

[Nacademus]

Thanks for the explanation! I am going down a rabbit hole trying to learn all I can. Its kind of fun for me.

I am most familiar with residential lawn equipment and their HSTs - which follow the same principle but obviously differ substantially in overall driveline orientation. I have learned that the transmission in my tractor uses the HST to modulate speed and torque output as it enters a series of gearboxes and gear reductions before the power meets the ground-as well as incorporating various take-offs to run other auxiliary demands (4wd, secondary hydro, etc).

Cheaper lawn tractors tend to shortcut much of the demand for extra utility and robustness by making the HST and its swash plate characteristics more directly a part of the the torque conversion itself and places it more aft in the drivetrain - comparatively, anyway. Since the demands on them are probably much less in these residential cases, they can more directly drive the wheels with maybe only a couple gears assisting with turning the axles via reduction.

 

[k0ua]

Thanks for the explanation! I am going down a rabbit hole trying to learn all I can. Its kind of fun for me.

I am most familiar with residential lawn equipment and their HSTs - which follow the same principle but obviously differ substantially in overall driveline orientation. I have learned that the transmission in my tractor uses the HST to modulate speed and torque output as it enters a series of gearboxes and gear reductions before the power meets the ground-as well as incorporating various take-offs to run other auxiliary demands (4wd, secondary hydro, etc).

Cheaper lawn tractors tend to shortcut much of the demand for extra utility and robustness by making the HST and its swash plate characteristics more directly a part of the the torque conversion itself and places it more aft in the drivetrain - comparatively, anyway. Since the demands on them are probably much less in these residential cases, they can more directly drive the wheels with maybe only a couple gears assisting with turning the axles via reduction.

Exactly. People often think of hydrostats and try to think of them in the same way as an automotive automatic transmission. They aren't really the same at all. And by calling them "ranges" the manufacture doesn't help dispel this notion. Yes the range selector is just a gear shifting mechanism for an unsynchronized gear transmission.

 

[Imold]

Thanks, I am getting edgumakated. I also have limited experience with HST on my Cub Cadet RZT-L54 and Husqvarna YTH24V48.



Jim.

 

[oldnslo]

Nacademus
If I read the description correctly you only have one high pressure relief that works for forward and reverse. If this is try can you tie a chain to a tree and the front axle and see if the tractor will spin in reverse on similar footing?

If same problem then I would invest in the fittings and gauge or if still under warranty talk to your dealer and have them check it out for you.

 

[WranglerX]

You do know that the pressure generated by your hydrostatic transmission is seperate from the hydraulic pump driven off of the camshaft of your engine that runs your implements like the FEL and 3pt hitch right? Hydrostat pressure's can easily be 5000 PSI and can only be measured at ports on the transmission pump made for this purpose. As for what the PRV should be set for varies tractor to tractor depending on size. As the tractors get bigger the pressures get higher, But 5000 to 6000 is fairly common. In your smaller tractor it may be less. You will need the workshop manual to know where to install it. And of course the PRV for the hydrostat is seperate from the PRV for your loader and 3pt.

I believe on MF GC 17XX (05 to 20) series with ISEKI 3 cylinder diesel, all implements are are run off the pump in HST....

Dale