Weight VS Horsepower on grades?

[Gary - K7GLD]

For some of you guys towing differing weights up grades:

IF, for instance, I am pulling 6,000 lbs up a 7% grade at 60 mph max, what will DOUBLING my load to 12,000 do to my maximum speed. all things being otherwise equal?

I know it takes substantially more power to get a load MOVING, but once in motion, with a grade tossed into the mix, what can be expected?

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http://community. webshots.com/user/davison71 Early '91 250, 727 AT, 307 rear... Banks Stinger exhaust, intercooler... US Gear OD... Tweaked pump, upgraded radiator... MORE than a match for every new PS Ford encountered so far...

"Dura" WHAT? NOW I know where all those recycled beer cans go...

 

[Guest00]

THE MATH< THE MATH ---- All thoes calculations, the computations, the commutations, the logritmic interpolations. #ad


Gary Your making my head hurt,
#ad



[This message has been edited by JNutter (edited 05-06-2001). ]

 

[Bill Stockard]

Gary,

Here goes from an old retired "truck peddler". We had computers that figured this up for us, but here's a formula you can use to get approximte values you are needing to figure your question. I had to go back to one of my old Sales Manuals to get the info.

Grade Resistance HP=Gross Weight(37,500)xMPH x %of Grade

See if this works for the power needed. To get the speed, you will need to figure gradeability which requires the engine HP ratings at different RPMs. This is all in theory since air reistance plays a big factor in your speed.

International(Navistar) and Cummins both had very good computer programs that would figure in all these factors and were quite accurate in comparison to "real world" results.

Bill

[This message has been edited by Bill Stockard (edited 05-06-2001). ]

 

[willyslover]

Gary. . Nice first generation rig !!
I have always liked that body style

 

[klenger]

Can you add some altitude into that equation for us that are closer to the sun? It seems that gearing would need to be considered also.

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Ken Lenger
2001. 5 2500 QC 4X4 SWB SLT, ETC/DDX 5 Speed, 3. 54 (no LSD), camper group, trailer folding mirrors, RBR CD/Radio, LT265/75R16E AT OWL tires, trailer tow group, Patroit Blue / Agate, Westin CPS Step Bars, Jordan Utlima Brake Controller, Weather_Guard 664 tool box
Trailite 21' Travel Trailer, ~4000 lbs loaded.

 

[Bill Stockard]

Gary,

Yep, you got it!! We’re talking rear wheel HP here so that’s a lot of power needed to climb the grade at 60 MPH.

Now throw this into the HP required:

Air Resistance Demand HP=MPH3(375)xFAx0. 0018

MPH = Miles per Hour Cubed
FA = Frontal Area in Square Feet For Example Your trailer is 10’ high and 8’ wide = 80 Sq. Ft.

Now combine that with your HP necessary to pull that grade and see how much it takes and that’s with NO wind!! Again this is rear wheel HP.

Bill

 

[illflem]

How about if you are going with(west) or against(east) the rotation on the earth? #ad

 

[Gary - K7GLD]

Thanks a bunch Bill!

This may be VERY helpful for some quick calc without access to a dyno. I'm not REAL sure about the "cube" bit - seems it's a number times itself 3 times? If so. with all the equations, my setup in calm air is delivering somewhere in the vicinity of 300 hp... Seems a bit high unless I made a mistake in my math somewhere, but I won't complain. NOW, just wait 'til I get my propane injection installed... #ad
#ad
#ad


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http://community. webshots.com/user/davison71 Early '91 250, 727 AT, 307 rear... Banks Stinger exhaust, intercooler... US Gear OD... Tweaked pump, upgraded radiator... MORE than a match for every new PS Ford encountered so far...

"Dura" WHAT? NOW I know where all those recycled beer cans go...

 

[Gary - K7GLD]

Bill, not sure if I fully understand your equation - here's how I figure it (not sure what the number in parenthesis for, or how it is to be used, but ASSUME it is to be divided INTO the gross weight?):

Using round numbers, 6000 lb truck, 6000 lb trailer -

Gross wt is 12,000, divided by 37,500 = . 32 times 60 = 19. 2 times 7 = 134. 4 hp?

Using that same equation for doubling the towed weight (18,000 GCVW) gives 201. 6 hp, 67. 2 (50 %) MORE hp needed?

HMMmm - seems rather LOW in hp, but possibly close since wind resistance is not covered in the equation, but the 50% hp INCREASE required with the same 50% increase in GCVW seems plausable - or did I do it completely wrong? Math was NOT my best subject in school! #ad


Like JNutter, my head hurts #ad


Willyslover - thanks!

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http://community. webshots.com/user/davison71 Early '91 250, 727 AT, 307 rear... Banks Stinger exhaust, intercooler... US Gear OD... Tweaked pump, upgraded radiator... MORE than a match for every new PS Ford encountered so far...

"Dura" WHAT? NOW I know where all those recycled beer cans go...

[This message has been edited by Gary - KJ6Q (edited 05-06-2001). ]

 

[Champane Flight]

I told the doctor "My head hurts when I turn it like this"! The doctor said "Don't turn your head like that"!

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95 Dodge 2500 Luverne grill guard,headache rack,running boards and Amzoiled. Soon to be mildly bombed. 84 Dodge d-150, 318 Hooker headers,Edelbrok intake,mallory ignition,Carter Afb,Accel coil,and Custom dual exhaust. Boat,fifthwheel,motorcycles,and shop. 72000 as of 3/1/01,not even broke in yet. Old Dodge 126000 miles and running better than new.

 

[Bill Stockard]

Gary,

Thats right. Cubed is the number time itself 3 times--3 cubed is 3x3=9x3=27.

One more factor is important in your calculations and that is Rolling Resistance. According to my charts, using your 12,000 lb total weight at 60 MPH, the rolling resistance on concrete pavement will take an additional 22HP. If you are driving on asphalt pavement on a hot summer day, the HP demand could double.

This is what keeps a truck salesman's day interesting!! Sell a customer a fleet of 20 trucks at $100,000 each and they won't pull the load, it will ruin your day!!!!

Bill

 

[rickhans]

I know this is a minor technicality and I hate to be picky, but having studied math for a number of years, I have to make a correction. A number cubed is a number multiplied by itself twice, not 3 times. 3x3 is 3 squared or 3 times itself one time. 3x3x3 is 3 cubed or 3 times itself twice.



[This message has been edited by Rick Hansen (edited 05-08-2001). ]

 

[Doc Tinker]

Way da go teacher(s), I'm beginning to learn something. Environment does make a difference! Easy to learn when you're having fun. #ad


Doc

 

[Bill Stockard]

Rick,

You're right--my English and math didn't agree.

I see you're from Dallas and if you have the time, drop by Bic's Coffee Shop for breakfast and visit with us at the Big D Dodge Diesel Club this next Sat. May 12 at 9 AM. It's very informal.

We meet the second Saturday each month at Bic's. If you need directions, send me an e-mail.

Bill

 

[Gary - K7GLD]

YUP Rick - we all MEANT the same thing - I just expressed it poorly!

Pretty interesting stuff tho' - I am AMAZED at the numbers I am ending up with in terms of required HP to get a load up a grade, wind or NO wind! As far as *I* am concerned, THESE numbers mean lots more than dragstrip, dyno or sled pull numbers - they relate to real life, and what the ORDINARY truck owner can and will be doing with their trucks.

Thanks again Bill!

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http://community. webshots.com/user/davison71 Early '91 250, 727 AT, 307 rear... Banks Stinger exhaust, intercooler... US Gear OD... Tweaked pump, upgraded radiator... MORE than a match for every new PS Ford encountered so far...

"Dura" WHAT? NOW I know where all those recycled beer cans go...

[This message has been edited by Gary - KJ6Q (edited 05-08-2001). ]

 

[TowPro]

Gary, check out this URL,
click here
Down at the bottom is another link that says something like How much HP does it take to tow your RV, click on it! I can't remember where I got this stuff from, but its got all kinds of math in it!

Will



[This message has been edited by TowPro (edited 05-08-2001). ]