How many HP per 16 inch plowshare is needed?


I was just watching the Allis Chalmers Channel posting of the D17 movie and they were saying that it would pull a 5 bottom plow. Am I wrong to think that is a bit much for that tractor. What is the rule of thumb for a HP/share?
They did make a 5-14 fully mounted plow for that tractor. Neighbor had one in early 60s. Light soil. Better match was a 4 bottom in sand, 3-16 in typical heavy clay. We had a mounted 3-16 on a WD45. Traction Booster was a big help.
Thats what I thought. I pull a 3-16 with my 17 in heavy sod and its enough tractor but I would hate to put a 5 bottom behind it.
What soil type? On sand around here probably 12 HP per bottom on average to go 4MPH or more. Heavy clay then you will want to double the horsepower per bottom.
Well-heres my story. Neighbor was plowing up some sod in the fall for wheat. (SW.MO.) Pulling 4-14s with a 7000 Ford. He said it was pulling the guts out of it. I asked if I could try it with my 185 Allis. He grinned and said you can TRY-I went over-hooked up his plow. Put the 185 in 2nd gear. Pulled it fine but blowing black smoke. Plowed a few rounds and stopped-he was standing there his mouth open-said just plow all day if you want. I wouldnt want to have tried with a D-17 let alone 5 bootoms.
Years ago, I always heard a rule of thumb was 15hp/ bottom around here, in silt loam soils. My 2520 was rated at 59 hp, and pulled 3- 16's easily in anything, and 4-16's in previously tilled ground. It would pull 4-16's in alfalfa sod, but could work doing it. But that rule seems to work well; anything for extra hp is a reserve for when you do get into a hard piece of sod.
My Farmall 140 will pull 2-14s at 3.5 mph 8-10 inches deep. I have sandy loam soil. Breaking heavy sod, I have to drop to 7-8 inches to stay at the same speed. That is about 11 drawbar horsepower per 14 inch bottom. My International 464 pulls 3-16s at 3.5 mph (again, in sandy loam). That is about 14 drawbar horsepower per 16 inch bottom. I would say that you need 0.8 drawbar horsepower for every inch of plow width, assuming sandy loam soil and an average depth of 8.5 inches with a speed of 3.5 mph. Based on that, the biggest plow a D-17 can pull is 4-16s in light soil at 3.5 mph (and that will push the envelope significantly).

It's all in the soil and how fast you want to go...

I pull 4-16's with an 806 diesel- that's a little more than 20 drawbar h.p. per bottom, which is pretty much standard in my neighborhood. I plow 8-10 inches deep, can always pull in 3rd low (4-4 1/2 mph.)
If the ground is right, 4th low (5-5 1/2 mph)
I'm plowing clay. 5 miles north, One neighbor tells me of pulling 6 bottoms with a 806 gas when it was new. Totally different soil.
Another neighbor in the same clay I usually plow, he pulled 4 bottoms with his new D17 back in the day.

I also pull 3-14's with my 450D- at about the same depth, but only 2nd gear. (about 3-1/2 mph.) That's only about 13 drawbar hp. per bottom.
The old M pulled 3-14's in 2nd- (about 3 mph) again, approx. 12-13 hp. per bottom.
Some of you guys are blessed. My ground brought a 95 hp 4wd Case to a dead stop pulling 3-16 Kvernlands. Same ground brought a Ford 800 to a dead stop with 2-10's in 2nd gear.

It all depends on the ground.

In the clay here 20hp per bottom is about right also. 2 16's is about all the old M wants when it is tough going. My 40hp Kubota will not handle 2 14's in this ground, but does OK with 1 16. My grand dad ran 2 14's behind his M.
If you google "Moldboard Plow 1-F194 - Info Needed" and click on a certain website dedicated to Farmall Cubs, you will find a lot of information on how to relate Nebraska Tractor Tests to the amount of plow a tractor can handle. I highly recommend it.

At home pull 3-14s with M, but that was when we at least plowed every other year. Had a neighbor plow some afalfa ground with 2-14's and a L Case.Dropped the plow in the ground and the front end come up 4 inched off the ground and stayed there. That Case plow must of been tough.
Thanks for the info...

Force required to pull a plow depends on the size of the plow, working depth and soil conditions. Soil conditions include soil type, and ground cover or stubble type. It will also depend some on operating speed. Approximate force required in pounds per square inch at 2 mph in normal conditions are:
sandy soil 2.5
corn stubble 3
wheat stubble 4
blue grass sod 6
june grass sod 6
clover sod 7
clay soil 8
prairie sod 15
virgin soil 15
gumbo 20
For example, plowing clay soil with a 12" bottom 6" deep will require 8x12x6 = 576 pounds of force. Running faster will push these numbers up some amount.

I was turning virgin/prairie sod and operating at 9 inches. That means I was 9x16x15 at 3 bottoms that is 6480 lbs of force. Max drawbar is 7,061 so that explains why it lugged down my tractor so much.
With heavy ballast, good tires, light ground, certain conditions and a well set plow... yeah. It will probably pull it slowly. It probably wouldn't take much more than a bananna peel under a wheel to bring it all to halt tho...


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