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what is the expected pulling power of a loco?

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  • Member since
    July 2009
  • From: lavale, md
  • 4,678 posts
Posted by gregc on Tuesday, January 7, 2020 4:46 PM

dbduck
locomotives will easily pull up to 30 free rolling

loco weight?

greg - Philadelphia & Reading / Reading

  • Member since
    December 2004
  • From: Louisville
  • 588 posts
Posted by dbduck on Tuesday, January 7, 2020 2:18 PM

Not familar with all the math & physics involved..but I do know that most, if not all, of my HO Athearn & Atlas 6 axle locomotives will easily pull up to 30 free rolling , truck tuned, properly weighted cars by themselves on level grade. Meaning most single loco trains are about 18-24+ ft long depending on car type...auto racks, 50' box etc

These are straight out of box locos with no modifications or added weight

  • Member since
    January 2017
  • From: Southern Florida Gulf Coast
  • 18,255 posts
Posted by SeeYou190 on Tuesday, January 7, 2020 2:05 PM

I have always had small layouts in HO scale, longest trains are 12 cars, no grades anywhere, dead flat.

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I expect all locomotives to pull a 12 car train, and so far, all have been able to do it.

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A double headed pair of powered Stewart F3s can simply walk away with a 12 car train with ease. I am satisfied.

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I think each person's expectations will be different.

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-Kevin

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Living the dream.

  • Member since
    January 2009
  • From: Bakersfield, CA 93308
  • 6,526 posts
Posted by RR_Mel on Tuesday, January 7, 2020 2:01 PM

I’m just finishing up four custom E7s, Cary bodies on Athearn SD40-2 frames with dual Mabuchi SF266 motors.  All four weigh in at 35 ounces and the drawbar at wheel slip is 10 ounces each on all four locomotives.
 
About 28%.
 
All four draw 630ma each at 12 volts at wheel slip.
 
 
 
 
Mel
 
 
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
 
 
  • Member since
    July 2009
  • From: lavale, md
  • 4,678 posts
what is the expected pulling power of a loco?
Posted by gregc on Tuesday, January 7, 2020 1:40 PM

on another forum, someone asked what locos pull more than expected?   what's expected?

i estimated that the pulling power of a loco is 20-25% of its weight and that the effect of gravity going up a 1% grade is approx that percentage of a car's weigh -- the grade requires 0.04 oz to pull a 6" car weighing 4 oz.

so 50 4oz cars adds 2 oz of resistance to be pulled up 1% grade which is 20% of a 10 oz loco and the # of cars the OP on the other forum said his loco could pull

i've gone thru my trucks, measured the grade they roll freely on and after tuning the worst truck would roll freely on a 2% grade.   some rolled uphill :).     But Armstrong's chart indicates the full cars roll more freely than empty cars and I would expect better performance with a weight car body.

is 1% of the weight an accurate estimate of the resistance of model cars on level ground?

greg - Philadelphia & Reading / Reading

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