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dsg
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2001-04-18          26866

How do I determine the Drawbar HP. I have a JD 4700 Hst. 48 engine and 40 pto Hp. Thanks, David.

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Anthony M. Parente
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2001-04-18          26869

David,
The JD technical manual does not specify the drawbar HP. However, since the JD4700 is a CAT 1 tractor, the maximum possible drawbar HP is 45. I hope this helps.
Tony
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RickB.
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2001-04-18          26877

Drawbar hp info is most commonly developed as part of a Nebraska Tractor test,which as far as I know, is not required of compacts to be offered for sale in Nebraska as it is for larger farm tractors. PTO hp is more easily measured, especially at the dealership level. Another reason for manufacturers not to advertise drawbar HP is it would point out the gross inefficiency of hydrostatic transmissions as compared to a gear drive. As an example, the IH 1066 was offered as a gear drive tractor developing a maximum 100.5 drawbar HP. The hydro version produced 84.88hp. The relative PTO HP were 116 and 113, respectively. All other factors are equal or very close between the two versions of this '70s farm tractor. Info from Nebraske tests # 1081 and 1083, 1971. I doubt your 4700 develops over 30 drawbar hp, but that is only a guess. ....

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Anthony M. Parente
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2001-04-18          26885

David,
Rick is right on! I calculated the drawbar HP based on the Nebraska tests for gear Vs. HST transmission, (only 76% effeciency)= 29.26 HP.
The real use of drawbar HP is to maximize farm production which envolves tractor speed, load and fuel consumption.
I chose the HST because I use the loader alot.
What are your concerns about drawbar hp?
Tony ....

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Roger L.
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2001-04-18          26890

I agree with Rick and Anthony. As long as there is enough torque available at the rear tire to break traction, drawbar horsepower isn't really very important....and is darned hard to figure. PTO horsepower is probably more useful. ....

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JeffM
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2001-04-18          26901

Anthony and Roger, this thread started because of the thread "Plow or?" in which drawbar hp was discussed as a means to determine how many plowshares a tractor can handle. In that regard, drawbar hp is much more useful than gross engine or PTO hp because it is more indicative of the work being performed. I don't know the conditions for the Nebraska tests, but I'll bet a NH TC25 gear drive with ag tires (25 hp gross, 21.7 hp PTO, 2474 pounds) has more drawbar hp and therefore plow-pulling ability than a Kubota 2710 HST with turf tires (27 hp gross, 20 hp PTO, 1740 pounds). I'd rather mow the lawn with the 2710, though. ....

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JeffM
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2001-04-18          26902

RickB, thanks for the enlightenment on the Nebraska tests. We may not plow much with compacts and therefore the higher drawbar hp losses with a hydrostatic drive are not as relevent compared to the lesser PTO hp losses which predominate uses such as mowers and brush hogs. But there is one situation where I notice the dramatic difference between gear drive and hydrostatic and that is on the road when going up hills, especially with a load. I have not yet been able to do a true apples and apples comparison (for example, a TC33 and a TC33D on the same road with the same tires and load), but my perception driving different machines is that there is a significant difference in performance in this situation between gear drive and hydrostatic.. ....

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Anthony M. Parente
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2001-04-19          26920

David, et al
I use the manufacturer's MAX HP rating when choosing the best implement for my JD4700 HST compact. The implement HP ratings are based on the tractor's max HP and assume 2 wheel drive. The implement HP rating can be reduced by 20% for 4WD. This info was provided by my JD dealer and the Landpride rep. I have not been disappointed to date. My JD dealer will call the JD factory to find out the actual drawbar HP.
Tony
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Bernie Galgoci
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2001-04-19          26922

I hope the copyright police don't come looking for me, but I will give the direct quote for a rule of thumb given in a book I have that deals with farm machinery. I'm sure it assumes a gear, not hydrostatic, transmission tractor. Hope this helps.
"Different ways of rating tractor power and variations in the amount of power needed to simply move the tractor itself through different soil conditions make it difficult to size implements to fit tractors or to size tractors to implements. A rather simple system has been devised by Wendell Bowers, Agricultural Engineer, (Oklahoma State University) to estimate drawbar power under varying conditions if the maximum engine or PTO power are known. The factor 0.86 is used throughout the sequence below. The example given is a tractor with a maximum engine power of 86.5 kW [116 hp]."

a = max. engine power, 86.5 kW [116 hp]
b= max. PTO power = 0.86 x (a) = 74.4kW [100 hp]
c = max. drawbar power (concrete) = 0.86 x (b) = 64.0 kW [86 hp]
d = max. drawbar power (firm soil) = 0.86 x (c) = 55.0 kW [74 hp]
e = usable drawbar power (firm soil) = 0.86 x (d) = 47.3 kW [63.6 hp]
f = usable drawbar power (tilled soil) = 0.86 x (e) = 40.7 kW [55 hp]
g = usable drawbar power (soft soil) = 0.86 x (f) = 35 kW [47 hp] ....

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JeffM
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2001-04-19          26923

Bernie, this is great stuff! Probably not very useful because of all the hydrostatic transmissions on compacts and variation in tire types, but I still love it! I guess if you give us engineers a formula it makes us happy, even if it doesn't mean squat in our situation. :>) Seriously, thanks for the info! ....

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Art White
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2001-04-19          26924

The Nebraska tests are done on concrete as it is the only surface they can use that remains the same. That is unfortunate for four wheel drives which often don't show to gain much if ballasting is done properly. Hydro's do loose more power on a hard pull and weight in the wrong area does little to boost traction and will actually hinder it. All to often I've been able to watch a lighter tractor outpull a bigger heavier tractor in the right situation. There is much that goes on with properly handling loads and getting the most out of your tractor. ....

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dsg
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2001-04-20          27000

GUY's, thank you very much for all the input. This board is truly a wealth of knowlage and I'm sure is what the founder's intent was at starting it. I was just curious as to the amount of land plows I could pull with the 4700. David ....

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Anthony M. Parente
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2001-04-20          27010

David,
My new Landpride Model DH1572 72" disc harrow was delivered today. It weighs 690 lbs. I will intend to use it this weekend, if the weather permits, and the field is dry enough. Maybe the following personal experience with my JD4700 will help you. I removed the brush, including 10' tall by 7' across wild rose bushes, and small trees using the 72" Brush Brute. This week, I removed the subsuface roots using a 72" Scarifier with the 7 shanks set to the maximum depth. I set the engine speed to 2400 rpm and the tractor performed perfectly. I easily ripped out roots up to 3" in diameter. I am accumulating attachments at a rapid rate to take advantage of 4700's power. A 3PT quick hitch is next.
Good Luck!
Tony,

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John Miller, III
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2001-04-20          27012

Rule of thumb:Utility Farm Tractors PTO HP × 0.75 = Drawbar HP
{Research funded by the Nebraska Soybean Development, Utilization and Marketing Board and the University of Nebraska.} For your JD4700, a 2-Bottom Plow would be about the limit. ....

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John Miller, III
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2001-04-20          27013

Anthony,
I think the new JD "telescopic lift arms" would be a better choice than the Quick-Hitch. I have both.{couple tractors} The telescopic's are easier and quicker for hook-ups. Most "top-link" setups are not "standard" on a Cat I implement...that's where the problem comes in when using a Quick-Hitch. ....

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Anthony M. Parente
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2001-04-20          27014

John,

Great suggestion!
How far do the telescopic lift arms extend ?
What do the JD arms cost ?
Tony
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John Miller, III
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2001-04-21          27037

Tony,
I've seen posts with prices from $170-250. for the new JD lift arms. I have a JD5205 and the range is about ~~4"...never measured. You just need a slight range anyways{to cut down on the fiddling of hookup!}...I have the Quick-Hitch mounted to my Satoh{if telescopic arms were avail...I'd have them instead} Lastly, but not least, I have telescoping arms on my MF165, of which design and use I like the best. Good luck Tony. ....

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