Hydraulic down pressure on 3 point?

[radman1]

I am trying to determine the benefit of hydraulic down pressure on a 3 pt. An aquaintance of mine has a prototype machine in development which is currently designed with 3 point down pressure, category I attachments and FEL. I see it as cross between a skid steer, CUT and utility vehicle. I call it the "Ultimate Crossover Vehicle" (UCV). I have seen the prototype unit and he asked me for suggestions on the 3 point. The potential of this machine is huge. I would sell my skid steer and CUT immediately. I don't own a side by side utility vehicle but with this, I wouldn't need one. I can think of many reasons why down pressure shouldn't be done and is probably a bad idea unless it can also have float capability.
I can see the concept useful for a blade or box blade. Potential stabilizer for a front end mounted backhoe or tree spade. Rear vibratory plow to maintain constant depth. Hydraulic wood or steel post driver? Any other suggestions?

 

[john_bud]

Some older tractors in the CUT size range had down pressure. Very handy for things like PHD's. But, for tillage the downpressure steals traction. That's the trade off.

A 3pt design should have float, position and draft control along with down pressure. Also needs to be able to control drop speed in float mode and hydraulically lock it in place. A white paper design can spec out the cylinders such that full pressure is in the up direction and use a very large ram so the down pressure is limited to 500-1000 pounds. Down force about 1/2 of the measured static weight of the back tires with no implement. Your call on designing it for loaded or unloaded tires (I'd go with loaded tire weight).

jb

 

[radman1]

Some older tractors in the CUT size range had down pressure. Very handy for things like PHD's. But, for tillage the downpressure steals traction. That's the trade off.

A 3pt design should have float, position and draft control along with down pressure. Also needs to be able to control drop speed in float mode and hydraulically lock it in place. A white paper design can spec out the cylinders such that full pressure is in the up direction and use a very large ram so the down pressure is limited to 500-1000 pounds. Down force about 1/2 of the measured static weight of the back tires with no implement. Your call on designing it for loaded or unloaded tires (I'd go with loaded tire weight).

jb

I did mention postion control and down stop on the postion control. They had not considered a postion control. PHD is a good idea but they already have a hydraulic PHD for the FEL. Their current design is weak on 3 point lift capacity. I recommended 2000 lbs measured 24 inches behind the lift arms. (1500 lbs would be my minimum) The pto is hydraulically driven and current design is 23-24 hp. I recommended 30-35. I told him for cat I equipment, draft control is probably not a big requirement. Also mentioned need for rock shaft rate of drop control.
For tillers, mowing, and seeders, down pressure is a very bad idea. Down pressure might be useful with a disc but this is not a common used tool.

 

[john_bud]

You don't have to use a rotating rock shaft deal. External cylinders would solve most issues and it wouldn't take very big cylinders. 1 3/4 to 2 1/2 woudl be my guess. External cylinders would also (if intelligently implemented) yield built in hydraulic tilt. A sales / marketing hook?

jb

 

[radman1]

You don't have to use a rotating rock shaft deal. External cylinders would solve most issues and it wouldn't take very big cylinders. 1 3/4 to 2 1/2 woudl be my guess. External cylinders would also (if intelligently implemented) yield built in hydraulic tilt. A sales / marketing hook?

jb

This unit has a single rear external hydraulic cylinder for the lift. I assume it would require 2 external cylinders for tilt capability. Is that correct?

 

[john_bud]

This unit has a single rear external hydraulic cylinder for the lift. I assume it would require 2 external cylinders for tilt capability. Is that correct?

Yes. One per arm. Challange is to syncronize them for straight up lifting and dropping.

jb