Will 10 Horsepower actually matter on the same size tractor?

[finn1]

Ram pickup engines.

6.4 L gas has 410 HP and 422 ft/lb torque.

6.7 diesel has 370 hp and 850 ft/lb torque.

The diesel has higher towing capacity even though it has less HP.

Try 420 hp and 1070 ft lb for the HO version. That’s over twice the torque of the gasoline engine.

Of course you need to specify the optional transmission to handle the torque.

 

[Cahaba Valley Farm]

Try 420 hp and 1070 ft lb for the HO version. That’s over twice the torque of the gasoline engine.

Of course you need to specify the optional transmission to handle the torque.

If this is possible then why is the PTO hp on all the tractors less then the engine hp?

 

[LD1]

If this is possible then why is the PTO hp on all the tractors less then the engine hp?

Was this being sarcastic or a rhetorical question? Or where you being serious?

 

[finn1]

He’s probably serious.

Answer is friction losses in the geartrain. Meshing gears generate heat, and bearings have drag, and gear lube is viscous. That’s all energy that can’t be used to do work.

 

[Cahaba Valley Farm]

He’s probably serious.

Answer is friction losses in the geartrain. Meshing gears generate heat, and bearings have drag, and gear lube is viscous. That’s all energy that can’t be used to do work.

But in reality PTO hp is just torque correct?

 

[mo1]

But in reality PTO hp is just torque correct?

No. Horsepower is torque multiplied by speed, specifically, (torque*RPM)/5252.

 

[LD1]

No. Horsepower is torque multiplied by speed, specifically, (torque*RPM)/5252.

In a round-about way he is correct. Because PTO HP is always measured at 540RPM.

So a tractor with 50 PTO HP is always gonna be 486ft-lbs of torque.

A tractor with 25PTO HP is always gonna be 243ft-lbs.

 

[RickB]

In a round-about way he is correct. Because PTO HP is always measured at 540RPM.

Except for those that aren't. Tractors larger than those primarily discussed here are usually rated using 1000rpm PTO's. Many of these only offer 1000 rpm PTO.

 

[Cahaba Valley Farm]

In a round-about way he is correct. Because PTO HP is always measured at 540RPM.

So a tractor with 50 PTO HP is always gonna be 486ft-lbs of torque.

A tractor with 25PTO HP is always gonna be 243ft-lbs.

Ooh interesting...I have never had anyone break it down like this before. If you don't mind me asking how do you know this? Could you share the math that was used to reach this understanding?

 

[mo1]

Ooh interesting...I have never had anyone break it down like this before. If you don't mind me asking how do you know this? Could you share the math that was used to reach this understanding?

The formula is in my post, horsepower = (torque*RPM)/5252. Applying seventh-grade algebra, torque = (horsepower*5252)/RPM.

@LD1
The reason I didn't specifically put any RPM value in the equation I posted is that there are actually four standard rear PTO types according to the ISO and ASABE and only one of them spins at 540 RPM. Type 1 is the six-spline 1 3/8" 540 RPM PTO that is on most compact and utility tractors. The other three standards use different, higher RPMs. Type 2 is a 1 3/8" 21 spline PTO spinning at 1000 RPM and is seen as an option on many full sized utility tractors and small row crop tractors. Type 3 is a 1 3/4" 20 spline PTO spinning at 1000 RPM and is on large row crop tractors. Type 4 is a 22 spline 2 1/4" PTO spinning at 1300 RPM. We also have nonstandard mid PTOs spinning at other, typically higher RPMs (generally 2000-2500 RPM). All of those will have different (lower) torque figures for the same horsepower ratings as compared to 540 RPM.

 

[RickB]

The 1300 rpm standard is news to me. Examples?

 

[mo1]

The Type 4 standard is new in the most recent version of the ISO spec in 2014. I haven't seen it on any machinery in the wild but it apparently is a standard. It even got a mention in my tractor's owner's manual in their "don't mix PTOs with different RPMs" warning page.

Here is a link to a full copy of the standards but it is not free to read: ISO 500-3:2014

 

[rScotty]

Here's some more to think about.

Say we have a compact tractor with a standard 6 spline, 1 3/8" diameter that is usually spun at 540 RPM. Many compact tractors have a PTO gear box which gives the ability to spin the PTO at different (higher) speeds while holding the engine RPM & therefore the engine HP constant.

The PTO output torque will vary with the PTO RPM selected. Ignoring internal friction, the PTO output torque will decline by exactly the amount that the PTO RPM is increased by the PTO transmission. That holds true as long as the engine is at the same RPM.

rScotty

 

[mo1]

Here's some more to think about.

Say we have a compact tractor with a standard 6 spline, 1 3/8" diameter that is usually spun at 540 RPM. Many compact tractors have a PTO gear box which gives the ability to spin the PTO at different (higher) speeds while holding the engine RPM & therefore the engine HP constant.

The PTO output torque will vary with the PTO RPM selected. Ignoring internal friction, the PTO output torque will decline by exactly the amount that the PTO RPM is increased by the PTO transmission. That holds true as long as the engine is at the same RPM.

rScotty

Asian compact tractors often do have the ability to run the PTO at more than 540 RPM as outside of the US, the standard 1 3/8" 6 spline PTO can be run at 1000 RPM instead of 540 RPM. Often they have speeds of 540, 700-800, and 1000 RPM. In the US, this is not done, we use the 21 spline 1 3/8" shaft instead for the "little 1000" implements to avoid destroying a 540 RPM implement by running it at 1000 RPM. As an aside, this is one of the "legitimate" reasons Kubota cites for not allowing their Japanese domestic market tractors to be imported into the US.

The other thing to think about is that on some larger compacts and many utility tractors, there are faster PTO gears available but they are restricted to keeping the PTO at a regular speeds but reducing engine RPM for an "economy" PTO. A tractor running in economy PTO mode will make less torque vs. standard mode for the same PTO RPM as the engine is making less power.

 

[Cahaba Valley Farm]

The formula is in my post, horsepower = (torque*RPM)/5252. Applying seventh-grade algebra, torque = (horsepower*5252)/RPM.

Thanks mo it makes sense now.

So just checking my math here: If you have a tractor that produces 30 PTO hp then it makes 291 ft lbs of torque correct?

 

[LD1]

Except for those that aren't. Tractors larger than those primarily discussed here are usually rated using 1000rpm PTO's. Many of these only offer 1000 rpm PTO.

Fair point.

I guess no overlooked the 1000 rpm bigger stuff. Since most of the questions and this post I'm general is dealing with compacts or utility sized machines.

 

[LD1]

Thanks mo it makes sense now.

So just checking my math here: If you have a tractor that produces 30 PTO hp then it makes 291 ft lbs of torque correct?

If you insert "at the PTO" after 291 ft-lbs then yes that statement and math is correct.

 

[Texasmark]

Hi all, I wont lie, I am totally new to the tractor world. Very familiar with cars and trucks, not so much on tractors. But, I have been reading articles, posts, and watching videos like crazy for the past 2 months learning what I can as we shop tractors.

Lets take the Kioti NX4510 and NX5510 for example. Both HST. Same basic tractor, 10 more HP. Otherwise between the 2, its larger (wider) tires, and a better 3 pt hitch, thats it I think.

So does 10 Hp matter, say your using a decent sized PTO Snowblower in what the town plows leave behind after a 12" snow fall, is that 10 Hp noticeable?

What about if your just pushing snow around with a pusher box, will the extra HP and TQ help?

Is there other benefits of more HP other than running the PTO?

Have you ever in your 35 or 40 Hp tractor, wished you had 45 or 50 Hp?

Curious to hear everyone's opinions, thank you!

Yes so I went out and bought one....keeping the smaller one and adding several more over the years. Come haying season I use all 4 I currently have. It did require 5 but my last purchase of the LS does the work 2 used to do.

 

[Cahaba Valley Farm]

It did require 5 but my last purchase of the LS does the work 2 used to do.

That's an unexpected statement as the LS is the smallest of all the tractors you have listed on your profile. Can you explain how this is true?

 

[oosik]

My first tractor - 1982 Ford 1700 4WD at approximately 3000 pounds. In 2009 I upgraded. 2009 Kubota M6040 4WD at exactly 10,072 pounds. The weight is due to HD grapple - Rim Guard in the rears - HD Rhino rear blade.

Did I notice a difference. YES The increased weight gave worlds more traction. More than double the engine HP didn't hurt either. But I do believe the increased weight was the biggest factor.