PTO HP

[Charliew]

Can anyone tell me what the H.P. is at the PTO of a Agracat 3720. This is supose to be a 35 hp tractor. None of the books I have tell about the PTO H.P.

 

[mscott]

I've been told the Chinese rate their tractors hp by the pto?

 

[exportcn]

If a 30 hp tractor. I 've been told the PTO H.P is 19.8kw(27HP).

 

[SPIKER]

Pretty much every engine manufacture rates the engine at the flywheel. so assuming a 3~5% friction loss then it should be about 32 hp pto. just an ASSUMECTION no dats from that perticular unit.

Mark M /forums/images/graemlins/cool.gif

 

[Chipperman]

Charliew
There are many ways of stating HP. The most common are Gross engine, Net engine and PTO. For comparison PTO is best. Many of the smaller tractors are rated in Gross HP.
Happy Tractoring
Chipperman /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif

 

[johnk]

I have a 22 hp Jinma and my friend up the road has a Kioti 20 HP shuttle shift 3 cylinder. I run my tractor @ around 1200 to 1300 rpm's all the time to do all my work. My friend seen my 2 Cylinder tractor with 5 foot bucket scoop up a bucket full of mud @ 1200 RPM's and it didn't bog a bit. He said his would have stalled out without a doubt. You look at a Crafstman 22 HP garden tractor and say HUH??? How can you have two 22 HP tractors that are so far apart in the apparant power even though rated at the same HP? I know gearing has a lot to do with everything but it just doesn't seem possible to have such a different range of actually feeling the difference of supposedly the same Hrse Powers. What are your opinions??

 

[bluechip]

Horsepower is a measure of work over time. Torque and rpm enter into the equation, which someone smarter than me can post. But in general the engine that makes it power at lower RPM will have more torque, which is the energy that does work. Higher RPM engines can make more HP with less torque (for example, a gas lawn tractor engine)

 

[Soundguy]

Also.. that 22 hp craftsman lawnmower.. might have been rated at 22 hp.. with no driveline or attatchments.. that is.. just the engine setting on a bench.. at max ungoverned rpm.. and it produced 22 hp.. right before the engine detonated..

Soundguy

 

[scrinch]

22 hp is 22 hp. The Craftsman and the Jinma should be able to do the same work when they are putting out 22 hp if they are honestly rated and geared appropriately. But the Sears has a gas engine that probably isn't rated to operate at 22 hp for any significant length of time, while the diesel engine probably is. My guess is that you probably operate the Sears unit at 12-14 hp continuously and the Jinma at 18-20 hp, and that's why they feel so different, powerwise. Of course the weight difference and rpm difference give them a very different sound and feel, too.

 

[johnk]

Thats my point. A craftsman tractor probably weighs 350 to 400 pounds and my Jinma weighs over 3000 w/ loader. Most HP should be used to just get the mass of the tractor moving and the mower spinning for example if using one. With both tractor moving and brush hog going there is no apparant power lag on the Jinma. It would be an effort just to put the brush hog in a little trailer and tow it with the craftsman of comparable Horse Power. Thats what stifles me of these HP ratings................

JOhn

 

[scrinch]

Consider a 180 hp aircraft engine and a 180 hp auto engine. Both of these engines are honest 180 hp engines...both are rated at 180 peak hp at max rpm. The auto engine is engineered for operating all day at 50% of max rpm, occasionally at 75% rpm, and almost never at max rpm. If it is used this way it will last 100,000 miles or about 2000 hours. The aircraft engine is engineered to operate all day at 90% of max rpm (and at 80% power) and occasionally at 100% rpm and power. If it is used this way it will also last about 2000 hours. But if the auto engine is used to put out aircraft engine-like power all day long, it will probably last only 200 hours. So while both engines are honestly rated at 180 max hp, you can get a lot more work out of the aircraft engine if you need to operate at high power settings. (Alternatively, the auto engine has tighter tolerances and can be considerably more fuel efficient.)

I think this is analogous to the situation with small gas and diesel engines. We can operate our diesel engines at high power settings all day long, whereas a gas engine would wear itself (and our ears) out if we operated it near max power for too long. So the hp available for doing work all day long are greater for the diesel because you can operate it at that higher power setting. I think with the proper gearing you could get your bush hog moving and spinning with the gas engine (ask the Power Trac guys what they can do with a 22 hp Kohler), but you just wouldn't be able to keep it running very long if you are doing heavy cutting. Accordingly, a gas engine with a higher hp rating is required to do the same job as a lower hp diesel because it will only be continuously operating at 50-60% load. Looking at it from a manufacturer's perspective, the equipment that is typically built around a 22 hp gas engine is a lot less capable than the equipment built around a 22 hp diesel engine...because the day-in, day-out hp available will usually be considerably lower.

Given the aircraft example, gas engines obviously don't have to be rated for lower power loads, but I think the perception is that they generally are.

 

[scrinch]

General wisdom in the Yanmar forum is that PTO hp is roughly 15-20% less than engine hp, at least in the 15-25 hp range. This is based on the equivalency of Japanese and American Yanmar tractors that were named for PTO hp in Japan and engine hp in the US. For example, the YM240 in the US (24 engine hp) is equivalent to the Japanese YM2000 (20 PTO hp).

 

[johnk]

That was a very good explaination of which was easy to understand and it makes sense. It explains potential to kinetic power in real time terms between the diesel and gasoline engines......Thanks.

 

[Soundguy]

It is not just diesel vs gasolene.. it is design and construction of the engine... My 4 cylinder 11hp 3spd 1966 IH cub will out pull, out lift, and out cut my 1994 12hp single cylinder 5 speed murry riding lawnmower..

Both are gas engines..

Soundguy

 

[johnk]

I think the stroke has more to do with an engine than the bore just in relation to torque. You need the torque to get you going then the HP to keep it moving......The longer the stroke the more torque..............

 

[SPIKER]

The Torque vs HP thing is an OLD argument.

Horse power is a mesurement over time, where as torque is rotational force. HP is defines HOW FAST the work can be done where as torque is HOW MUCH work can be done.

the bore vs stroke does have a lot to do with both HP and Torque, a BIG cylinder with a LONG stroke makes Torque out the yieng yang, mostly because it can stuff MORE fuel & air in there to actually have MORE power available to be used/generated. a SMALL bore & stroke makes lots of HP as it can move up and down the cylinder very quickly. One of the reasons todays 4 cylinder engines displacing 2 liters or less can make as much HP as a 5 liter engine can, but the Torque numbers tell a very different tale, that same Small displacement makes nearly as much torque only at very HIGH RPM. the 5 liter will make more torque down lower in RPM and that is where it is needed to get the vehical weight moving. acceleration at half track is where HP comes in.

that being said, HP = HP and torque = torque, it is WHERE it is made, RPM range, and how much fuel is required as well as Rotational Energy available to be tapped off of the engine. You can PULL harder with the diesle as the compression and explosive force is on usually a larger displacement cylinder with a longer stroke, the fuel produces MORE power per volume so similar volume of fule can produce MORE torque using a longer stroke because the expelled energy can push the piston farther. Also comes in Heavy Crank to help the diesle KEEP the power moving...

ok that is my explanation..

Mark M /forums/images/graemlins/smile.gif