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Tractor Horsepower

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pete43011

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For years my moderately tired old 8N has happily managed both a six foot finish mower as well as a five foot bush hog. I"ve been looking some at a new tractor- Kubota mostly. Dilemma is that Kubota, JD & New Holland guys are telling me I need 30+ HP to run the same mowers. Are they trying to upsell me, being conservative (safe) or have horses gotten smaller in the last few years? 8N tested 21 HP at the drawbar in 1950 probably (little over half that left today). PTO HP not tested in 1950, new little guys seem to have 20-22 at the PTO on a 30 horse unit. I"m missing something!
 
compare the torque figures...thats where you'll find the difference...buddy of mine has one of those tinker toy deere's with loader and backhoe...it aint got enuff power to pull hat off my head but he does run a 5 foot shredder on it in second gear.
 

Running a 5 foot bush hog requires a fairly heavy drive train or you might get broken pto shafts and gears. I've never owned a 8n but people tell me they are light for a 5 foot bush hog in anything but small brush. Obviously you got along fine with yours but I would want a new one to be at least as heavy as an 8n and preferrably heavier.

KEH
 
yes, horses are getting smaller. a farmall M new rated 39 hp. when I was in high school, it was 45. how they are rated over 50. ratings have come down continualy over the years. I was at Rollag in 2008. they pulled a 65 hp case steam engine up to the dynamometer. I guessed that by his old rarings he would be puting out about 50 hp after nearly 100 years of wear. by todays ratings he put out 270.
 
You"ll conservatively need 4-5 pto hp per foot of rotary mower. 30 pto HP is plenty for a five foot and you could easily run a six footer.
 
You"ll conservatively need 4-5 pto hp per foot of rotary mower. 30 pto HP is plenty for a five foot and you could easily run a six footer.
 
You"ll conservatively need 4-5 pto hp per foot of rotary mower. 30 pto HP is plenty for a five foot and you could easily run a six footer.
 
I've seen some of these steam HP figures.
There is a world of difference between boiler HP and what the engine is capable of. Vs. if the supply of steam was unlimited and at max pressure and temp.
I've seen steamers on the pulling track do well until the boiler pressure dropped.
That 270HP figure is suspect as well. For reasons unknown most dyno operators failed math in school. They will still read HP from the Dyno's 540rpm scale when the rpms have dropped below 540.
HP=Torque X RPM /5252.

There is no difference of a 50 year old tractor with 40pto HP driving a generator,baker fan, auger etc. Than there is 2009 40HP pto tractor. 40HP=40HP
 
As rrlund stated almost all of the new tractors are rated for engine only HP.. We have always ran a 6ft finishing mower behind a little JD 750.. (rate about 18 PTO hp) a little under powered for really tall stuff, works for amost everything.. (just gear down) Just match up with what you have.. or a little more.. PTO HP...
Watch out for some of the Kabota's.. they don't have much of a torque curve.. more like a drop.. the ones I have dynoed they are at Peak at rated.. its all down hill from there.. (basically if it start pulling down pasted rated rpms, its hard for it to recover.) Most of the other colors seem to do well.
Good Luck in your Purchase..
JDGnut
 
I think they (dealers) are giving you good advice.
Todays ratings don't mean much. Then if you add a hydro tranny you really zap the HP too.
Lawn mowers used to get along fine with an 8hp Kohler. Now you have to have a 20+ hp to do anything. Ratinga are all goofed up.
 
I have a 1996-1715 FWD Ford/New Holand "96 model still uses ford model #" That is rated at 27 HP I belive 25 HP at PTO. I run a 5' Kingkutter in it and a 5' finish mower. with no problem but I don't cut big brush with it. Mine is a std trans 9 speed, and uses less than 1/2 GPH when mowing. I can mow with 5' mower for 8 hours and it will use about less than 4 GAL.
 
Don't worry about it.
My JD 4200 compact (26 HP) runs a 5' finish mower, brush hog and 6' blade with no problems. 5' box scaper makes it work with teeth down.
 
the dyno that they were using was not a new style one but the old drum and band one. weight on a scale along with RPM's and some simple math.
check it out if you are ever there, quite interesting.
 
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