Today's newbie question - Horsepower

[Casimir]

Re: Today\'s newbie question - Horsepower

Horsepower is only one small measure of what a machine will do. How that engine Hp is transmitted to the implement or to the ground is the biggest part of the equation (the complex of gears/hydraulic pumps, etc., that turn the raw Hp into "work"). You have more "power" in lower gears. That's why a 15 Hp CUT diesel engine will move a lot heavier machine and wallk away pulling a 25 Hp lawnmower behind it. /forums/images/graemlins/smirk.gif /forums/images/graemlins/grin.gif Weight and traction from the tread design also contribute to the working ability of the machine. On a mower, the size of the pulleys for the belt translate to gears in a transmission. The lawnmower with the smaller Hp engine may have a belt/pulley arrangement that actually transmits more power to the cutting blades.

 

[MossRoad]

Re: Today\'s newbie question - Horsepower

Maybe this article at www.howstuffworks.com will help.

There are quite a few good articles there. Do a search for torque or horsepower and start reading.

Hope this helps. /forums/images/graemlins/smile.gif

 

[Anonymous Poster]

Re: Today\'s newbie question - Horsepower

1 HP is NOT necessarily equal to 1 HP in application.
Electric motor HP <> Gas engine HP.
Hydraulic moror HP <> gas HP.
2 stroke HP <> 4 stroke HP.

This is true, but should stir things up.

 

[Anonymous Poster]

Re: Today\'s newbie question - Horsepower

Lots of people have weighed in on gas vs. diesel horsepower and I haven't anything intelligent to add to those points. I would like to comment on something that realy surprised me when I converted from a gas lawn tractor to a diesel sub CUT two months ago and that is fuel economy. I'm running for 8 to 10 hours on 3 to 3 1/2 gallons of fuel, something my old 20 hp gas tractor would never do! It ran much closer to a gallon per hour and wasn't capable of the work level that the new diesel is.

Good luck in your quest for a tractor replacement!

 

[frank_f15]

Re: Today\'s newbie question - Horsepower

to help u ans. your own question, go to the nearest sears store and look at one of their 25 hp garden tractors, then go look at a kubota b2410(24 hp) which do u think will have better performance? as bird said a lot more comes into play than just hp!

 

[Anonymous Poster]

Re: Today\'s newbie question - Horsepower

I think the lawn mower gas engine is rated at "peak" horsepower for a very short duration and diesel is rated at "sustained" horsepower. My 15hp diesel will run circles around my 20hp gas lawn tractor and run a bigger mower.

 

[grandad]

Re: Today\'s newbie question - Horsepower

This thread has gone a bit astray on comparing lawn tractors with compacts. Your original post asked about replacing your 55 year old - presumably gas - tractor with something modern, so I'm guessing you have maybe an old Ford or Fergie, etc., not a Sears lawn tractor.

Best I can figure, there's not many tractors being sold new with gas engines these days. The better torque curve, longevity, reliability, etc. pretty much make diesels the way to go in tractors. But if you do some lookups in the forum regarding horsepower, you'll find some threads discussing how some of the old 20 or 30 hp ag tractors compare with newer equipment.

In that context, the new compact tractors generally have much higher horsepower for their size and weight than the older utility tractors. The older tractors were designed for agricultural use, where weight and gearing really count a lot... pulling heavy loads, running ground engaging implements, etc. The modern compact tractor tries to meet a different design goal... and places a premium on a lighter footprint, ease of operation and greater efficiency. 4WD, a range of tire choices and a variety of chassis sizes do make some compacts generally comparable to the older designs, but thinking about the specific tasks you have in mind may help your decision more than trying to match horsepower for horsepower.

But you asked a great question, and should get some interesting replies. Good luck in your search!

 

[Soundguy]

Re: Today\'s newbie question - Horsepower

I think you are on the right track...

My neighbor has one of those new huge huskie riding lawnmowers ( 2999+tax ).. something like 25hp 50" cut....

It just doesn't compair to my old old old 4cyl ( and gas! )8n that was only like 26-27 hp from the factory 51 years ago..... heck..I don't think it compairs to my yanmar 1700 21/17 engine / pto.. hp... deisel, 2 cyl...

And as many others state... it is not necescarilly raw engine hp that you need to be concerned with, but application of it. How is the tranny setup / geared, how is the mower coupled, etc.. and weight. Thje very name 'tractor' conveys the idea of traction.. and that is based ( in part ) on weight and power.

My other neighbor mows his 5 ac pasture with a yanmar 1300 and a 3' hog... That is an itty bitty machine... I've easilly seen bigger riding lawnmowers... but I think if you put them in a tug of war, you would still see the little 1300 towing the big huskie 25hp around the yard while the huskie was spinning tires...

Soundguy

 

[Anonymous Poster]

Re: Today\'s newbie question - Horsepower

wickman: I will second, third, fourth (or whatever) what Bird, Casimere, grandad and others have said. 1 hp is 1 hp is 1 hp. The difference is how it is used. It's torque that makes it go, gearing, tire contact, etc. that determine its efectiveness and so forth. I just purchased a new tractor to replace a similarly sized (weight, cubic inches, etc) 51 year old tractor (Farmall SC) so I have an idea of what you've thinking about.

Regarding the hp issue, let me give you an example. I have a snapper 6 hp lawn mower and a gravely 6.6 hp 2 wheel garden tractor. Both these engines put out almost identical hp. But the newer mower will barely push through thick grass. The gravely (same hp and 35+ years old) will move itself, a 40" mower deck and pull me (on a riding sulky) easily up and down hills (1/2 ton m/l). Why will the same hp, same 1 cyl air cooled type engine, do such a different amount of "work"? The gravely is a lower rpm, high torque life time engine. It even has automotive type oil cleaner, oil pressure guage. It has geared transmission (not belt driven - even the mower deck is driven by a pto shaft out the front), 4 ag type tires (duals). If you put the snapper mower engine (remember, same hp) on the gravely the engine would do more work, but still fall short of what the Studebaker engine does now on the gravely.

I hope the point is made, there's a lot more to compare than simple hp. I suggest looking for your new tractor on the basis of engine size (cubic inches), weight, torque (and what rpm the engine has to run to generate that torque). The diesel will use less fuel (the combustion process uses a much higher percentage of available btu's).

JEH

 

[Anonymous Poster]

Re: Today\'s newbie question - Horsepower

Thanks for all the great replies. I'm realizing that HP is really a small, and potentially deceptive, part of the equation. I have almost zero tractor experience and the idea of plunking down 12k plus on a new one that 'should do the job' is scary. So many variables. I will say that this group pretty much covers all of my questions... except it can't provide that 'hands on experience.'

wickman