Got a tractor drawbar hp question

[glovemeister]

Suppose a chisel plow is to be used in heavy soil conditions where the resistance is 600 pounds per foot of width. Soil condition is considered firm. What size four wheel drive tractor would be needed to pull the chisel at a speed of 6.0 mph if the chisel is 14 feet wide.

I haven't found a formula for this but the knowns are speed desired 6.0 mph, soil resistance 600 lb/ft of width. Width 14 ft wide. 14X600 = 8400 total resistance. Multiply that by 6 mph to get 50,400/375=134.4 required horsepower. However I am just curious as to if this is correct, and what I would need to do to calculate horse power per ft. if I have that I can multiply it by the width of the chisel to get the total required horsepower.

Thanks a bunch!

 

[OregonFarmer]

Suppose a chisel plow is to be used in heavy soil conditions where the resistance is 600 pounds per foot of width. Soil condition is considered firm. What size four wheel drive tractor would be needed to pull the chisel at a speed of 6.0 mph if the chisel is 14 feet wide.

I haven't found a formula for this but the knowns are speed desired 6.0 mph, soil resistance 600 lb/ft of width. Width 14 ft wide. 14X600 = 8400 total resistance. Multiply that by 6 mph to get 50,400/375=134.4 required horsepower. However I am just curious as to if this is correct, and what I would need to do to calculate horse power per ft. if I have that I can multiply it by the width of the chisel to get the total required horsepower.

Thanks a bunch!

Depth? If it's about 10-12", then at least 150hp, just based on experience, not math. If you are chiseling deeper, find more horses.

 

[Eagleview]

You would not be able to work it out like that , you have no idea as to what gear the tractor would need to be in to achieve 6mph at maximum power in the first place . The higher the gear selected , the less power you have .

Some tractor manuals have a chart on HP and Torque output and a range of gear ratios , final drive ratios and tyre sizes so it can be worked out how much draw bar pull you have .

How did you multiply resistance X 6 mph to get HP ?

 

[art]

There are several things that make differences here. The number of shanks as well as is it drawbar pull? Does it have discs?

Twenty to twenty five horsepower per foot is not unusual!

 

[bigtiller]

Depth and sweep size is important also. Five inch pulls easier than the big twelve inch ones. Are you going 12 inches deep or 16?

 

[SPYDERLK]

You would not be able to work it out like that , you have no idea as to what gear the tractor would need to be in to achieve 6mph at maximum power in the first place . The higher the gear selected , the less power you have .

Some tractor manuals have a chart on HP and Torque output and a range of gear ratios , final drive ratios and tyre sizes so it can be worked out how much draw bar pull you have .

How did you multiply resistance X 6 mph to get HP ?

My question too ... altho units are right. Ultimately comes down to ft-lbs per time. I always forget the HP equivalent and have to look it up. He uses one thats totally unfamiliar. Probably useful to know.

As far as tractor HP @ 6mph you can get pretty darn close by just knowing the PTO power rating and the gear you need to be in to go 6mph at pto rpm. Those are usually available numbers.
larry