POLL: Is Torque Important?

[rbattelle]

Jet,



Negative work is generally defined as work done on a system. Positive work, then, defined as work done by a system.



Could you please also explain what's mathematically wrong about work being a dot product of a force and a displacement?



Again, I apologize if I'm spreading any false information. I mean no disrespect to anyone.



-Ryan

 

[DPelletier]

Jetenginedoctor,

You are right, of course, as far as the physics go. I can tell because of the years I wasted in a college classroom. I had recognized that Ryan had made some errors, but didn't bother pointing them out. I do think that you could have been a little more tactfull responding to Ryan's posts. He didn't purposely mislead anyone and was honestly trying to express his thoughts on the subject. If he were a teacher in a Physics class I paid to attend, I'd likely have a different point of view. I have read many of his 2,720 posts and he remains a valuable contributor to these forums IMO. I would be disappointed if responses such as yours dissuaded him from expressing his opinion in the future. The tone of your response would have been justified if he had responded angrily to your corrections, but he did not. Anyway, moving on.....



The physics lessons aside, torque is a more valuable measurement of an engines usefullness for a towing or other HD application. You could more accurately express it as HP at a lower RPM, but it just confuses the issue. You can have an Acura, a CTD pickup and a Class 8 tractor all making 300 hp (at wildly different RPM's, of course) yet it's the vast difference in peak torque ratings that tell you the real story. If this wasn't the case, we'd all be better off towing with a hemi powered truck (or a turbocharged street bike for that matter!)



Dave

 

[Sled Puller]

SO... ... IS TORQUE IMPORTANT???????

The physics lessons aside, torque is a more valuable measurement of an engines usefullness for a towing or other HD application. You could more accurately express it as HP at a lower RPM, but it just confuses the issue.



Dave

ANSWER: YES.

 

[rbattelle]

Here's that page I scanned.

Fundamentals Of Physics Volume 1

Halliday, Resnick, Walker

Copyright 1993 by John Wiley & Sons, Inc.

 

[Sled Puller]

.







Cool, another farmer! Torque does twist the shafts, this is true. However, if torque is being applied to the axles but the wheels aren't turning, fields aren't getting worked. As soon as the torque is enough to make the tractor and implement move, work is being done, and there is (by definition) HP exerted.







.

Now, is that a cut on farmers, or are you a farmer , also? It is so hard to tell, from your, uh, "STYLE" of posting.



Don't forget, the sammiches that the college boys was eating, while they were busy blowing up space shuttles, were brought to you courtesy of a farmer!



I'll go back to my job, now, which happens to be putting in sewer line, (ironic timing)these days, and leave you guys to formula a simple question to death!!!!!!

 

[Wiredawg]

Good Info; Not so good approach

Jetenginedoctor:



I post on the TDR lot and read lots of posts here. We all present our views and most of us respect each other in the process. For my part, I would only ask you to consider other folks feelings in the process of making a point or disputing a point.



Wiredawg

 

[jetenginedoctor]

Now, is that a cut on farmers, or are you a farmer , also? It is so hard to tell, from your, uh, "STYLE" of posting.



Don't forget, the sammiches that the college boys was eating, while they were busy blowing up space shuttles, were brought to you courtesy of a farmer!



I'll go back to my job, now, which happens to be putting in sewer line, (ironic timing)these days, and leave you guys to formula a simple question to death!!!!!!

I grew up in NW Kansas, spent many hours behind the wheel of tractors and combines, ate a lot of dirt, and have killed more deer with farm implements than I might ever hope to with a rifle. . . . .



I am. . . . a Kansas redneck farmer. . . . sorta.

 

[jetenginedoctor]

Jetenginedoctor:



I post on the TDR lot and read lots of posts here. We all present our views and most of us respect each other in the process. For my part, I would only ask you to consider other folks feelings in the process of making a point or disputing a point.



Wiredawg

I'm very respectful of other people's feelings. But how respectful of MY feelings is it when Sleddy and others try to kick me in the teeth while not really even understanding what it is they're trying to argue with me about? If you knew me in real life, you'd have a very different opinion of me. But in the realm of the internet and all the BS that gets flung about as supposed fact, I take a decidedly direct and perhaps un-padded approach to dealing with garbage directed toward me on online forums. Sorry if you have a problem with that.

 

[Sled Puller]

rabattelle wasn't kicking anyones teeth, and I don't believe this thread had one negative word in it, up to page 4!

 

[AKAMAC]

J. E. D.

You make valid points. I think that application is the key question.



Our co-gen facility runs 12 cyl. naturally aspirated methane engines. The engines run at 1200 rpm and produce 325 kW. The same diesel variation in 773 haul trucks run at 2200 rpm. Peak torque is the requirement for our application. It is the flat line bias of torque that the alternators produce the correct HZ with changing load.



At Vandenberg AFB there are gas turbine gens that are rated in the mega watt capacity. The developed HP of the gens are, as you stated, gear reduced. This reduction multiplies the torque. This reduction gives a window of usable rpm that uses the 3000 HP produced to a load controllable speed.



Remember the VW and the Cadilac comparison in physics class. Both stopped at the top of a hill. Negating wind or rolling resistance, which will reach the bottom first? FORCE!



I love a good debate!



Mike

 

[jetenginedoctor]

J. E. D.

You make valid points. I think that application is the key question.



Our co-gen facility runs 12 cyl. naturally aspirated methane engines. The engines run at 1200 rpm and produce 325 kW. The same diesel variation in 773 haul trucks run at 2200 rpm. Peak torque is the requirement for our application. It is the flat line bias of torque that the alternators produce the correct HZ with changing load.

In order to produce 60 Hz power, the generators must run 3600 RPM with two poles, 1800 RPM with four poles, or 1200 with six poles. If your engines run at 1200 RPM, you are likely to either have a six pole generator or a gear overdrive to drive a two or four pole generator at their necessary shaft speed. Its easiest and most efficient to use a generator that will make 60 Hz 2-phase power at the same shaft speed as the prime mover, so 1200 RPM and a six pole generator makes good sense. Running the engine at 1200RPM makes better sense than 1800 RPM in terms of heat rate (fuel efficiency) and longevity. A gen-set like yours will run hours or days or weeks or even MONTHS at a constant speed, where the similar engine will run at that 2200 RPM speed for a far shorter time and recieve periodic maintenance far more frequently. The difference between the two is more a matter of duty cycle than anything else.



As another note, I'm curious how much variation in load your plant can deal with and maintain emissions compliance, etc. For example, I was an operator at a 1300 MW simple/combined-cycle combustion turbine powerplant in North Carolina. We had GE Frame-7 turbines that ran 3600 RPM on hydrogen cooled two-pole generators. Each of the CTs would make 192 MW without inlet cooling, and better than 200 MW with the inlet coolers on. Burning natural gas, we came into emissions compliance (mode 6Q) at around 50 MW going up in load, and fell out of 6Q at around 38 MW (if memory serves me. ) Our machines utilized the GE DLN (dry low NOX) system rather than water or steam injection to control NOX emissions. Burning deisel, we came into compliance at a lower load because we ran water injection for NOX. Anyway, we could change load nearly 150 MW without falling out of compliance, just curious what load swing you can pull and stay legal. Sorry for straying from the subject a bit. . . .

At Vandenberg AFB there are gas turbine gens that are rated in the mega watt capacity. The developed HP of the gens are, as you stated, gear reduced. This reduction multiplies the torque. This reduction gives a window of usable rpm that uses the 3000 HP produced to a load controllable speed.

That's because they are using an aero-derivitive CT, probably a GE LM-series plant. Smaller turbine engines must operate at higher shaft speeds in order to produce the desired pressure ratio across the compressor. The Frame-7 machines I used to run have huge compressors, and tip speeds exceed supersonic if the engine runs at speeds much over 3600 RPM. The large and small engines operate at different angular velocity, but they are both bound to the laws of physics with regards to the range of speed they can safely make power in.

Remember the VW and the Cadilac comparison in physics class. Both stopped at the top of a hill. Negating wind or rolling resistance, which will reach the bottom first? FORCE!



I love a good debate!



Mike

Not trying to debate. Just trying to set things straight. Who else here has any power generation background????

 

[RustyJC]

Not trying to debate. Just trying to set things straight. Who else here has any power generation background????

Among the power generation units our company has built:



Cooper-Bessemer LS, LSV, KSV engines used primarily in municipal power generation, large cogeneration facilities and as emergency standby gensets in nuclear power plants. 6 - 20 cylinders, up to 6. 3 MW.



Superior Model 40 and Model 60 engines used primarily in municipal power plants and cogeneration facilities. 6 - 16 cylinders.



Enterprise R-4 engines used primarily in municipal power plants, large cogeneration facilities and as emergency standby gensets in nuclear power plants.



Coberra (Cooper Bessemer Rolls-Royce Alliance) gas turbines used as peak loppers, for offshore (oil and gas platform) power and in large cogeneration facilities. Rolls-Royce Avon, RB211 and Trent gas generators, up to 50 MW.



Rusty

 

[53 Willys]

From Encarta

Torque, in engineering and mechanics, a twisting effort applied to an object that tends to make the object turn about its axis of rotation. The magnitude of a torque is equal to the magnitude of the applied force multiplied by the distance between the object's axis of rotation and the point where the force is applied. In many ways, torque is the rotational analogue to force. Just as a force applied to an object tends to change the linear rate of motion of the object, a torque applied to an object tends to change the object's rate of rotational motion.



Microsoft® Encarta® Encyclopedia 2003. © 1993-2002 Microsoft Corporation. All rights reserved.



Horsepower, unit of power in the English system, for measuring the rate at which an engine or other prime mover can perform mechanical work. It is usually abbreviated hp. Its electrical equivalent is 746 watts, and the heat equivalent is 2545 British thermal units per hour. One horsepower was originally defined as the amount of power required to lift 33,000 pounds 1 foot in 1 minute, or 550 foot-pounds per second.



Scottish engineer and inventor James Watt established this value for the horsepower after determining in practical tests that horses could haul coal at the average rate of 22,000 foot-pounds per minute. He then arbitrarily raised this figure by a factor of one-half to establish the current value. In the metric system, 1 horsepower is sometimes called force de cheval or cheval-vapeur and is defined as 4500 kilogram-meters per minute, which is equivalent to 32,549 foot-pounds per minute, or 0. 986 of the English horsepower unit.



Three different horsepower values are used to quote the performance of an engine: (1) Indicated horsepower is the theoretical efficiency of a reciprocating engine, which is determined from the pressure developed by the cylinders of the engine; (2) brake or shaft horsepower is more commonly used to indicate the practical ability of the engine, or the maximum performance, which is the indicated horsepower minus the power lost through heat, friction, and compression; (3) rated horsepower is the power that an engine or motor can produce efficiently for sustained periods of time.



Electric motors are capable of surges of power far in excess of their rated horsepower . British automobile engines are classified in rated horsepower, but their brake horsepower may be four to six times the rated horsepower. The power output of American automobile engines is quoted in brake horsepower, most being rated between 60 and 200 horsepower.

 

[rbattelle]

JED,



Was wondering if you have any comments on the page I scanned.

Also, could you please explain what's mathematically wrong about work being a dot product of a force and a displacement?



Respectfully,

Ryan

 

[Ol'TrailDog]

jetengineerdoctor actually said

"explaination"

Shucks, even an ol' tree chopping mule skinner like me knows its "explanation". :-laf :-laf :-laf Spat, so there. Now that kinda felt good, give that fellar a dose of his own medicine.



Actually, I feel privileged to hang around a bunch of knowledgeable folks like you'all. Doesn't this also have something to do with the "over square" design of the inline 6? I'm thinking leverage applied to the crank type stuff - but will confess ignorance up front before I get a drubbing. Enjoyable thread.



My real world example would be how everyone around here despise how the 04 Duramax six speeds have a hernia trying to get an eight horse slant load started and have to resort to using granny. Whereas, the Cummins's will walk off with the trailers.



Personally, I prefer mule power over horse power for most work anyway.

 

[GBechtold]

In regards to rbattelle's illistration instead of picking the cat up and carrying it across the room and setting it down wouldn't it be easier to just throw it :-laf

I thought it was funny but seriously torque is very important you can have all the HP in the world but with out TQ you aren't going anywear in a real knock down drag out fight stock for stock if you take two diesel engines both with the same CID both with the same amount of fuel & air ratings and the same HP rating but one of them is a V8 and the other is a I6 the I6 is going to move the load alot easier than the V8 Because the I6 has more TQ MHO.

If I want Big HP and slightly lower TQ I'll pick a big block mopar if I want big TQ and slightly lower HP I'll choose a CTD in other words TQ rules just look at all of the OTR trucks very few of them have V motors in them.

 

[Big_Daddy_T]

Jetenginedoctor. I too had it explained to me as rbattelle had posted. Granted Im a backwoods bumpkin with very little education. But, if told proper I never get it wrong again.

There are several engineers in my family. I have had some of the very basics explained because I was interested in the truth behind the discussion. Your explanations were very good. But no better than the wrong explanations Ive had in the past. So Im only as good as the info I receive.

Thank you for the more in depth explanation.

 

[Big_Daddy_T]

Actually gbech. Hp is an expression of torque. Just over time and distance. Work. So with all the hp in the world you could do a lot of work. You would just need to gear it differently. 2lb ft of torque will do a lot of work at 1 million rpm. More, in fact, than our mighty cummins. Excluding frictional losses from gearing. All the force in the world aint gonna do you no good if you dont do any work.



Whats important is where the torque is. Its about the torque curve. Also bore and stroke will also be a big deciding factor on wether or not its a good tow rig. Low rpm torque is good for low speed manuevers and starting from a dead stop. High rpm torque is good for racing. Not all v8s are slouchs at low end torque. Not all inlines are the best at low end torque. Its all in the design. Just because its an inline doesnt naturally make it a torque monster. The cummins has the longest stroke of an american production engine(at least that Ive found). This makes for a lot of inertia for a 10 lb conrod and piston. It has to reach higher peak speeds to travel the length of the bore. So the shorter stroke v8 will have better transient response time. The only hobble I see for a v8 is the heavy counterweights on the crankshaft. Only I dont know how heavy they are. Id like to find the weight of a cummins crankshaft compared to a 6. 0 powerstroke crankshaft and a duramax crankshaft. Anyone know?

 

[Big_Daddy_T]

Doesn't this also have something to do with the "over square" design of the inline 6? I'm thinking leverage applied to the crank type stuff.

You mean undersquare. Undersquare engines, in my experience, tow much much better than oversquare. Must be why most engines used for towing are undersquare. The duramax is the exception to the rule. It does well in unloaded races but throw a load on and you can tell whos got the stroke.



An inline undersquare engine has an advantage in leverage on the crankshaft. Better angle of attack. Makes for great torque and towing ability. Not so good for high rpms.

 

[Big_Daddy_T]

Its late and I had a thought. If you push a boulder up to the tippy top of a mountain. It takes a lot of energy to push that boulder to the top. Where did the energy go? Its still there as potential energy. When the boulder rolls back down the hill. It releases that energy as kinetic. When the boulder is back at the bottom the net result is 0 energy(stored?) It released all the energy. You spent the energy. Then it was undone. Not that no work was done. Just that the work was undone.



The change in the kinetic energy of an object is equal to the net work done on the object.



Its not that you didnt exert energy to do work. Its that the end result is no potential energy is stored.