Torque

[Will]

After 7 weeks of waiting for my B2410 to show up I have read every piece of literature many times and every related post on the subject at least once (and thank goodness no one says that for only $50 more I can buy twice the tractor if I only buy a ...).

I've just found even more information on Kubota engines. Looking at the information there and the torque curve I was trying to figure out what the practical importance of having a flat torque curve. I think that it means that the weight a tractor doesn't depend much on the engine speed, and that all things being equal (like traction) that the B2410 will have the greatest torque and pulling power at 2200 RPM. This seems counterintuitive, so maybe I've got this all wrong.

Will

 

[Anonymous Poster]

will.
A flater torque curve will allow you to do work at variying thotlle setings,a tractor actualy does work more so on torque than hp. take 20hp gas against 20 hp diesel,the diesel most certenly will pull more and run bigger mower ect. A diesel hp for hp will usualy have more torque than hp,wheras a gas motor usualy will have more hp than torque. think of torque this way a 4cyl. car 200 hp,an 8cyl 200 hp off the line i'll put money on the 8,more torque.now at speed they my be equel,thats where hp takes over.torque in a diesel is why gas motors are all but gone in most compact and farm tractors today.Gas dosn't have the abillity to lug through and keep on going like a diesel.torque is very important in a tractor,and the flater the curve the more avalibile at difrent rpms.

 

[Anonymous Poster]

Hi Will,
( We'll need to remember that "horsepower" is a measure of "work-done-in-time" or "rate of work". 1hp = 550 lbs. lifted 1 ft. in 1 second. )
A one-horsepower hummingbird and a one-horsepower elephant were going to load sand into a truck. /w3tcompact/icons/shocked.gif
Each one had a shovel appropriate for his size.
They were the same horsepower, because they both could fill the truck with the same weight of sand in the same time.

The difference was that the hummingbird, with his little shovel, moved very fast, and used a million of his little shovelfulls to get the truck filled, in the time allowed. But the elephant moved so slowly, with his giant shovel, that he only needed ONE huge shovelfull, to fill the truck with just-as-much sand, in just-as-much time!

Which one of these equal-horsepower shovelers do you think you could STOP the easiest, in the middle of any one stroke (shovelfull)?

If you said the hummingbird, it's because you intuitively know that the elephant has a lot more TORQUE than the hummingbird. (or you /w3tcompact/icons/laugh.gif !!)

The elephant had a flat torque-curve, because he could lift the same heavy shovelfull of sand more slowly, and still have no trouble doing-it. His "horsepower" would be less, of course (he wouldn't fill the truck as fast as before) but he could still lift the same weight 1/2-as-far in the-same-time (=1/2 the work-done, = 1/2 the horsepower, ... but the SAME torque!)

The humminbird's torque-curve had a "peak" because if he didn't fly nearly-as-fast as he was before, he couldn't develop as much lift with his wings, and so he COULDN'T lift the same weight as-before, in each shovelful, at the slower speed.

So in half-the-time, he would move LESS-THAN half the sand. (over the full distance =less-than 1/2 the work-done, = less-than 1/2 hp.)

The "torque-y" elephant could work as efficiently at any speed; full-speed = full-power(work done), ... half speed =half-power(work-done).

The low-torque hummingbird could only be as efficient at top-speed (full-speed = full power),... half speed=LESS-THAN half-power(work done).

SO /w3tcompact/icons/wink.gif ... if you want a variable-speed animal-tractor, that will be efficient at any speed, and last a long time, use an elephant. The hummingbird will only be efficient at the high-speed stuff, and that will soon wear him out. (but he might be better for for working around flowers!!

/w3tcompact/icons/laugh.gif

Larry

 

[hayden]

Excellent analogy

 

[RobS]

Another nifty feature of ag type diesel engines is "torque rise". Often the torque curve will increase a little as engine speed SLOWS from operating speed. I discovered this last fall pulling a disc and really challenging my tractor. As the load increases it tends to pull the engine speed down. With a gas engine this tends to be a death spiral ultimately resulting in a stall but with torque rise, as the rpm drops the torque actually increases a bit keeping things moving. It was a pretty unique feeling at first, considering this is my first diesel /w3tcompact/icons/smile.gif