Torque VS. Horsepower

AndyMA · Apr 6, 2004

( A weird thing about that chart is that the units for torque don't make any sense. I thought that torque is Newton-meters, not kilogram-meters.
)

There are many possible ways to specify torque: Some of them with conversion factors are listed below:

Conversion Factors for MOMENT OF FORCE or TORQUE

dyne centimeter (dyn·cm) to newton meter (N·m) multiply by 1.0 E-07
kilogram-force meter (kgf·m) to newton meter (N·m) multiply by 9.806 65 E+00
ounce (avoirdupois)-force inch (ozf·in) to newton meter (N·m) multiply by 7.061 552 E-03
ounce (avoirdupois)-force inch (ozf·in) to millinewton meter (mN·m) multiply by 7.061 552 E+00
pound-force foot (lbf·ft) to newton meter (N·m) multiply by 1.355 818 E+00
pound-force inch (lbf·in) to newton meter (N·m) multiply by 1.129 848 E-01

Have fun :confusing:

Andy

AndyMA · Apr 6, 2004

( but as a rule of thum torqure will rise with hp. Not always true but its the rule in general. diesel to diesel, gas to gas. if you compare diesel to gas the diesel will usualy have more torque for same hp. )

I take some issue with these facts and wanted to set the record straight.

HP and torque are directly related by a linear equation that is always true.

HP is not measured directly, it is simply calculated from torque. However the HP to torque formula is useful to figure out how much torque the engine is making at peak HP

This is true for any type engine. Much of the information that has been posted on this board and other places is just plain false.

Remember that the magic number 5252 works only with torque in ft-lbs units. Torque in other units such as Newton Meters or kg-m require a conversion factor..

- HP = torque * RPM / 5252
- torque = HP * 5252 / RPM
- torque = HP at 5252 RPM

Hope this clarifies a few things.

Andy

mahlers · Apr 6, 2004

Yeah - what got me was that they didn't make any distinction between kilogram-mass and kilogram-force. That was one of the things that used to drive me crazy back in the engineering days - it's bad enough that the english system is totally bass-ackwards, and then they have to apply some of that to the SI system. I worked in the Aerospace arena (specifically helicopters), and it was a combination of older engineers who only used the english system and younger engineers who learned on the SI system. When some of those projects spanned a couple of team's careers, it was a nightmare to sort out the unit inconsistencies. You'd always be getting things that were off by a factor of 9.81 or 32.2 and you generally wouldn't find the problem until the control system drove the thing completely unstable for no obvious reason. Sorry for the rant...

AndyMA · Apr 7, 2004

Isn't that what happened to the Hubble telescope. Somebody used the wrong units and they had to send up a giant contact lens to fix it I knew the engineers who designed the new lens /forums/images/graemlins/cool.gif I'm one of those engineers whose carer spanned both systems- I can't keep either straight. /forums/images/graemlins/confused.gif How's the TN doing? We should get together, I could rant for days..../forums/images/graemlins/grin.gif

Andy

KiotiJohn · Apr 7, 2004

You guys are welcome to rant all you want, but can any of you answer Don's questions? I don't see any real answers here at all, just rants. I can't answer the question, but maybe you ranters can! LOL /forums/images/graemlins/grin.gif John

AndyMA · Apr 7, 2004

( At rated speed, the 30hp has about 8 and the 25 hp has about 6.2 kg m of torque.


Is that going to be a noticable difference putting the power to the ground? Would that be an average or better than average torgue increase going from 25 to 30 hp. If the torgue is a substantial increase....How much would it be worth in dollars. $500, $1000, $1500?

Don )

Ok Don sorry for the rant. Just trying to correct a few things. Since hopefully above we have shown that hp and torque are linearly related, the 30 hp engine will put out 20% more torque through out it's power range. I think that is a fair amount of additional torque (and hp) and it would be worth a fair amount to me. Putting a $ sign to that depends on your use. Ground engaging imlements take a fair amount of torque, mowers take power to run. Loader work and backhoe work really don't take that much power except I suppose when your're trying to dig into a pile. If you can afford it go for the power, you won't regret it. (just remember I love power /forums/images/graemlins/grin.gif )

Andy

KiotiJohn · Apr 7, 2004

So which one Don? The CK25 or the CK35? /forums/images/graemlins/grin.gif John

mahlers · Apr 7, 2004

( Isn't that what happened to the Hubble telescope. Somebody used the wrong units and they had to send up a giant contact lens to fix it I knew the engineers who designed the new lens /forums/images/graemlins/cool.gif I'm one of those engineers whose carer spanned both systems- I can't keep either straight. /forums/images/graemlins/confused.gif How's the TN doing? We should get together, I could rant for days..../forums/images/graemlins/grin.gif

Andy )

Actually, the Hubble problem was even dumber from what they tell me. They ground the lens here on earth, and didn't properly take into account the distortion that gravity was causing. Once it got into orbit and gravity went away, they realized that everything was screwed up. A Mars mission blew-up because of the unit-conversion thing. Different contractors were using different unit systems and, when one of those contractors designed the re-entry control system, they designed it with an inconsistent unit set. When the control system tried to control the descent into the Mars atmosphere, the gain on the control system was off by a factor of whatever the unit conversion was, and it basically vaporized the whole thing. Duh... I was working at JPL when that happened, and to be honest I can see how something like that happened so easily...

The TN is doing great - of all the tractors I considered, it's definitely the best choice and I'm very happy! Too bad we're on different sides of the county - ranting is always fun. I used to be in your neck of the woods a lot when I was helping Sikorsky and Kaman out with some of their design work - but that was years ago, and now that the Commanche project got killed, Sikorsky is a sad place to hang out.

Bird · Apr 7, 2004

How long ago were you involved with Sikorsky? Was it long enough for you to remember the Sikorsky/Winnebago RV? You could go camping in comfort anywhere you could land it. /forums/images/graemlins/laugh.gif