Page 1 of 2 12 LastLast
Results 1 to 20 of 23

Thread: Loco Pulling Power

  1. #1
    Join Date
    Nov 2012
    Location
    Lancaster, SC
    Posts
    808
    Blog Entries
    4
    Thanks
    346
    Thanked 1,126 Times in 471 Posts
    Mentioned
    33 Post(s)
    Tagged
    0 Thread(s)

    Default Loco Pulling Power

    I discovered yesterday that my Atlas GP38-2 won't quite pull 9 cars and a caboose up the 2.5% grade going west out of Newton. This is steeper than the actual grade on that line, but necessary to get the separation I need to transition to the two level section of the layout. Guess I'll need to look at putting two locos on that job.

    On the other hand according to my 1974 employee timetable, a GP38, GP35, GP30. or U23B was rated at 1350 tons between Spencer and Old Fort, which includes all of the section that I'm modeling. That's 9 cars with gross weight of 150 tons each. The RS3 was rated for 1100 tons, or a smidge more than 7 cars. That doesn't look so bad after all.

    I'll need to do some testing so that my Spencer yard master can get consists set up to handle trains across the line.
    Tim Rumph
    Modeling the Southern Railway in N-Scale

  2. The Following 5 Users Say Thank You to Tim R For This Useful Post:


  3. #2
    Join Date
    Mar 2007
    Posts
    547
    Thanks
    7
    Thanked 944 Times in 339 Posts
    Mentioned
    40 Post(s)
    Tagged
    0 Thread(s)

    Default

    There's a bunch of comments to make on that. I started obsessing on tractive effort issues when I first got a new Atlas SD24 and it was surprisingly anemic compared to the older locomotive it was replacing. I started measuring locomotive weight vs. tractive effort in grams and discovered that the coefficient of wheel/rail friction varied greatly between manufacturers and wheel types, but that weight matters. So the more you loose through cutout frames for DCC, sound, etc. lower-weight non-lead alloys, etc., the less it can pull, and add 'slippery wheel syndrome' on top of that - my label for the much harder/slicker metals used on some power, including Atlas.

    So it's not your imagination. I've measured and tested about 50 different locomotives. I have 2.5% grades and 13" mainline curves, and pulling long trains is no joke. I'm still DC. PM me with your email if you want my calculations & results spreadsheet, but suffice it to say that on my own layout, the 'new' Atlas GP38 is in the display case and the 'old' Kato GP38 is still in service - and it outpulls the Atlas by almost 3:1.

    My typical road freight is 3 six-axle units and about 35 cars on the layout.
    Randgust N scale kits web page at www.randgust.com

  4. The Following 4 Users Say Thank You to randgust For This Useful Post:


  5. #3
    Join Date
    Feb 2013
    Location
    Sequim WA
    Posts
    3,579
    Blog Entries
    1
    Thanks
    12,066
    Thanked 5,664 Times in 2,180 Posts
    Mentioned
    144 Post(s)
    Tagged
    0 Thread(s)

    Default

    Curious. ...I wonder if this "different wheel material" has also manifested itself in other Atlas locomotives?

    My new SD-9 is just not up to snuff compared to its older brother from 2010.
    Paul Schmidt

    Shasta (2008-2020) -- All good dogs should live forever

    Southern Railway's Slate Fork Branch

    Check out Appalachian Railroad Modeling!

  6. #4
    Join Date
    Jul 2012
    Posts
    1,114
    Thanks
    43
    Thanked 425 Times in 241 Posts
    Mentioned
    16 Post(s)
    Tagged
    0 Thread(s)

    Default

    That's why I use tungsten moldable weight. It can attach to almost any surface, and get into tiny crevices as well. Just be sure you prevent the stuff from getting in between the chassis frame halves. I did this with my Bachmann GP-40, and it pulls like a horse.

  7. The Following 2 Users Say Thank You to gatrhumpy For This Useful Post:


  8. #5
    Join Date
    Jun 2014
    Posts
    780
    Thanks
    161
    Thanked 920 Times in 415 Posts
    Mentioned
    27 Post(s)
    Tagged
    0 Thread(s)

    Default

    weight is your friend when it comes to pulling.

    moldable tungsten is a good idea. I aim at filling the cab first then battery boxes.

    one of the more interesting things I've decided about traction
    is that one axle or two drivers with an ounce on them do seem to be able to pull more than
    2 axles or four drivers with an ounce on them.

    this is the reverse of what works better for electrical pick-up...

    I mention it because the n-scale SD units are not able to haul as much as the GP versions
    I don't think it is your imagination the SD is slippery.

    add weight...

    victor

  9. #6
    Join Date
    Apr 2014
    Location
    southeast michigan
    Posts
    1,223
    Thanks
    692
    Thanked 1,604 Times in 599 Posts
    Mentioned
    50 Post(s)
    Tagged
    0 Thread(s)

    Default

    There have been a lot of threads on this topic in the past. I was disappointed when I converted my locos to DCC and found they couldn't pull as many cars up the big grade due to the weight loss, and I too ended up weighting down several locos with tungsten putty to help make up for it.

    One thing I'd like to point out which may not be obvious is you want to concentrate adding weight on the lighter end of the loco, ideally, or in between the trucks. You can actually make things worse by adding weight on the heavy end past the truck bolster. Here is why.

    Your loco has 8 or 12 wheels, each of which provide traction. Lets suppose for illustration purposes that on an 8-wheeled loco each wheel is able to provide 1 gram of pulling power before slipping, meaning that at 1.01 grams it will slip. When one wheel slips the other wheel on the same axle will of course do the same. And that means that all those other 6 wheels suddenly have to shoulder the traction load that the slipping wheels provided, e.i. 1 and a 4th gram. And that of course instantly cascades into all of them slipping. So like a chain being only as strong as it's weakest link, a loco can only pull as much as its slipperiest wheel; once that wheel gives things fall apart.

    If you put weight out at the end of a loco, the loco will like a seesaw pull up the other end and take weight off the far truck. If the wheels on that end already have the least weight on them, you just made them slip quicker than before. And once they slip your added weight, unless it is really heavy, won't add enough friction to the heavy truck's wheel's to overcome the loss of traction from the other truck.

  10. The Following 2 Users Say Thank You to NtheBasement For This Useful Post:


  11. #7
    Join Date
    Mar 2007
    Posts
    547
    Thanks
    7
    Thanked 944 Times in 339 Posts
    Mentioned
    40 Post(s)
    Tagged
    0 Thread(s)

    Default

    Victor, I've observed the same phenomenon with 4-wheel vs. 6-wheel trucks in testing. The 4-wheel trucks almost always have a higher coefficient of friction (pull/weight in grams). And it's completely counter-intuitive. Lots of factors in play, the only real way to prove it is to have a chassis that you could swap out trucks on, but I've also seen it where one of the axles is either an idler or elevated and non-load-bearing. An example of that is the Trix U28 which was a pretty good beast for its era. Concentration of weight on the minimum number of wheel/rail points seems to increase grip.
    Randgust N scale kits web page at www.randgust.com

  12. The Following 2 Users Say Thank You to randgust For This Useful Post:


  13. #8
    Join Date
    Sep 2014
    Location
    Alberta
    Posts
    1,394
    Thanks
    4,037
    Thanked 1,331 Times in 768 Posts
    Mentioned
    45 Post(s)
    Tagged
    0 Thread(s)

    Default

    Quote Originally Posted by randgust View Post
    Concentration of weight on the minimum number of wheel/rail points seems to increase grip.
    Is that not prototypical?

  14. #9
    Join Date
    Jun 2014
    Posts
    780
    Thanks
    161
    Thanked 920 Times in 415 Posts
    Mentioned
    27 Post(s)
    Tagged
    0 Thread(s)

    Default

    Quote Originally Posted by Scotian_Huntress View Post
    Is that not prototypical?
    ... weeeeeell...
    it is much like prototype, yes.

    the ...erm... issue may be a little tough to resolve into n-scale.
    I believe that a gp7/9 does weigh less than the SD equivalent... I recall reading something about
    adjusting the ballast of an SD unit to track limits ( to go where a GP dare not tread...)
    I also think the extra axles are to allow extra motors to avoid slow speed overheating.

    In our models we do not really have the option to add much extra weight.
    so the extra drivers remove friction to rail or so it seems.
    N-scale does not have effective suspension AND we are not even close to
    'wheel on rail weight limits'/ 'axle load limits' , this kinda points at
    the problem for getting a driver to pull...lack of weight on driver.

    when you want PULL! from an n-scale loco, your job
    is to think how can I get all the weight onto a pair of traction tires.

    Katos's FEF and gs-4 are a study in the concept.

    victor

  15. The Following 2 Users Say Thank You to victor miranda For This Useful Post:


  16. #10
    Join Date
    Dec 2014
    Location
    FL
    Posts
    242
    Thanks
    45
    Thanked 345 Times in 105 Posts
    Mentioned
    20 Post(s)
    Tagged
    0 Thread(s)

    Default

    No reason to make the traction tired driver the sole “puller”.
    It has friends there that can help.
    For me I balance the lokie, regardless of TT or not.
    I prefer even weight distribution across all drivers and all wheels on diesels.
    Works for me YMMV.
    When a driver slips, the TT is done.
    Don't load them that heavy.

  17. #11
    Join Date
    Jun 2014
    Posts
    780
    Thanks
    161
    Thanked 920 Times in 415 Posts
    Mentioned
    27 Post(s)
    Tagged
    0 Thread(s)

    Default

    hmmmm...

    hi Donzi,

    I can state without qualification even weight across all wheels doing electrical pick-up service
    is better than any alternative I have seen.

    as such is is a good idea for any loco...

    the atlas GP-7/9 locos I have are all good in that regard.

    frankly a couple of Diesels on a train look proper, should you want more pull.

    This is not as true for steam engine modeling.
    To look proper, you need one engine pulling a train.

    you can set springs on the drivers of a 2-8-0 and get good pick-up.
    that same loco will not pull more than carefully lifting the middle two drivers off the rails.
    ...and the electrical pick-up suffers.
    Traction tires... will get you more pulling... but they work far better if they are not sharing the weight.

    victor

  18. #12
    Join Date
    Nov 2017
    Location
    Ariege, France
    Posts
    735
    Thanks
    3,204
    Thanked 1,707 Times in 490 Posts
    Mentioned
    91 Post(s)
    Tagged
    0 Thread(s)

    Default

    Quote Originally Posted by victor miranda View Post
    This is not as true for steam engine modeling.
    To look proper, you need one engine pulling a train.
    The Canadian Pacific is an exception to this. About a quarter of all the photos I have are of double heading and in one extreme case, six 4-6-0's pushing a snow plough As I model the mountain sud-division I run most of my trains double headed, often mixing steam and diesel. The steam always behind the diesel to prevent the diesel taking damage when the steamer scours her pipes !! The 0-6-6-0 Mallet I built was designed exclusively as a 'pusher' and I don't think the prototype ever pulled a train !!!

    Lots of fun and endless possibilities for playing trains
    Thanks, Tom

    Expect nothing except the opposite of what you expect, and then expect it to be something other than that ! Then that's about what it will be

  19. The Following 2 Users Say Thank You to tomcook For This Useful Post:


  20. #13
    Join Date
    Jun 2014
    Posts
    780
    Thanks
    161
    Thanked 920 Times in 415 Posts
    Mentioned
    27 Post(s)
    Tagged
    0 Thread(s)

    Default

    yeah, I figured some one would pull a "Actually, Victor"

    this is a question by how often or policy of the road it takes to be true.

    the PRR used double heading on named trains over the hills in Pa.
    the PRR definitely did not want that because
    one loco is less expensive than two even if the one loco is very large and expensive.
    (think PRR T1)

    If you are doing a helper district, the usual 'help' goes on the end of the train first.
    so even then you have just one on the front.

    two on the front usually is a special case because of how hard it is to remove the extra power.
    snow storms and plows being a pretty common reason.
    so if you want to tell me it is common on the CP I will believe you.
    it also means that CP was wasting a lot of money on the practice.
    with those two items in mind, please don't be surprised If I tell you it is news to me.

    the note is putting on an extra diesel loco is rather common.
    the opposite is true with steam...

    victor

  21. The Following User Says Thank You to victor miranda For This Useful Post:


  22. #14
    Join Date
    Nov 2017
    Location
    Ariege, France
    Posts
    735
    Thanks
    3,204
    Thanked 1,707 Times in 490 Posts
    Mentioned
    91 Post(s)
    Tagged
    0 Thread(s)

    Default

    Quote Originally Posted by victor miranda View Post
    If you are doing a helper district, the usual 'help' goes on the end of the train first.
    so even then you have just one on the front.
    Not wanting to be awkward but the majority of CP's Doubles were head ended !!!

    Here's a couple of nice photos.

    http://www.trainweb.org/oldtimetrain...renton/910.htm

    http://www.okthepk.ca/dataCprSiding/...901/foto01.htm

    Sorry @ Tim R for hijacking your thread and to victor miranda for being a stick in the mud !!!
    Thanks, Tom

    Expect nothing except the opposite of what you expect, and then expect it to be something other than that ! Then that's about what it will be

  23. The Following 2 Users Say Thank You to tomcook For This Useful Post:


  24. #15
    Join Date
    Jun 2014
    Posts
    780
    Thanks
    161
    Thanked 920 Times in 415 Posts
    Mentioned
    27 Post(s)
    Tagged
    0 Thread(s)

    Default

    you have no idea how exceptional you are.

    :-p pbbbbbbbbbbbbbbbbt

  25. The Following User Says Thank You to victor miranda For This Useful Post:


  26. #16
    Join Date
    Sep 2014
    Location
    Alberta
    Posts
    1,394
    Thanks
    4,037
    Thanked 1,331 Times in 768 Posts
    Mentioned
    45 Post(s)
    Tagged
    0 Thread(s)

    Default

    To my understanding, in the steam era and even today, passenger trains on long grades would be double-headed (or even triple headed - provided the draw weight on the couplers would allow this), particularly at night, when there would cars in the middle of the train being jostled back and forth. For freight trains on long grades the preference was to add pusher engines on the back to evenly spread the tractive power, or even a mid-train helper if the tonnage was required. Canadian Pacific would cut helpers in front of vans (cabooses) as a rule, although early operations 1885 to the 1920s? could see them on the rear. On short grades e.g. the Don Valley, Ottermouth Pass until 1900? both passenger and freight trains could be double headed as they could be switched off more easily than rear pushers in front of a van (caboose).

    Canadian Pacific faced extreme grades, over the Kicking Horse Pass on the "Big Hill" from 1885-1909 with a maximum of 4.5% grades: "[t]he railway had to ascend 1,070 feet (330 m) along a distance of 10 miles (16 km) from Field at 4,267 feet (1,301 m) climbing to the top of the Continental Divide at 5,340 feet (1,630 m)." Until the Spiral Tunnels were driven in 1909 doubling the distance reducing the grade to a more manage 2.2% which still required helpers.
    Kicking Hose Pass.pdf
    See:http://www.okthepk.ca/dataCprSiding/...01/month00.htm

    Crossing the Selkirk Mountain Range through Rogers Pass was another difficult route, with helpers required from both sides, based at Rogers Pass Station, the "surface route" was operated from 1885-1916 and involved 2.2% grades though avalanche territory
    Rogers Pass.pdf
    with significant snowsheds
    Rogers Pass Snowsheds.pdf
    the snowfall and avalanches led to the Connaught Tunnel being driven in 1916.
    See: http://www.okthepk.ca/dataCprSiding/...11/month00.htm
    Last edited by Scotian_Huntress; 24th Jan 2020 at 12:56 AM. Reason: broeken link

  27. The Following 3 Users Say Thank You to Scotian_Huntress For This Useful Post:


  28. #17
    Join Date
    Sep 2014
    Location
    Alberta
    Posts
    1,394
    Thanks
    4,037
    Thanked 1,331 Times in 768 Posts
    Mentioned
    45 Post(s)
    Tagged
    0 Thread(s)

    Default

    Quote Originally Posted by Scotian_Huntress View Post
    the snowfall and avalanches led to the Connaught Tunnel being driven in 1916.
    Apparently this was intended to double track Calgary to Vancouver for a capacity expansion - before the avalanche in 1910, from the additional research referenced in the article.
    see: https://open.library.ubc.ca/cIRcle/c...tems/1.0095109

  29. The Following User Says Thank You to Scotian_Huntress For This Useful Post:


  30. #18
    Join Date
    Mar 2007
    Posts
    547
    Thanks
    7
    Thanked 944 Times in 339 Posts
    Mentioned
    40 Post(s)
    Tagged
    0 Thread(s)

    Default

    Wow, extreme thread drift.

    My frustration and obsession with pulling power is partly my own doing, but rooted in the 70's and 80's before DCC and sound ever gained a foothold on us. I had a first-line fleet of eight Trix U28's - some hidden under various shells, but still those mechanisms, and they were all worn enough on the wheels down to brass that they had no difficulty at all on my layout lifting 30 cars up a 2.5 percent hill and around a 180-degree 13" radius compensated curve at the top. Easy-peasy, three units could easily deal with it without slipping at all and there was power left over.

    My 'secondary power' was a mish-mash, but included a Trix F-unit, Kato GP38, a couple Rapido GP's heavily rebuilt, and an early Atlas GP7 on a cast-lead N Scale of Nevada frame under a GP30 body. All of those were heavy pullers. Two of them could handle 20 cars no issues.

    Time marches on and I'm upgrading power; Trix all retired and replaced with Kato six-axle chassis without penalty. One of the GP's gets retired for a 'new' Atlas SD24. Out of the box it's running fine, polished down the wheels during break-in (blackening came off) and suddenly the train is now sitting on the hill, spinning. I'm baffled. And that starts it. I made a dynamometer car out of a spring scale, had a gram scale for weight, and started testing everything.

    Years later...it's getting harder and harder to upgrade without also loosing the ability to pull a train. I tried 'upgrading' my RSD15 rebuilds with an Atlas chassis and it failed miserably in the tractive effort department; I'd need to replace four locomotives with six or seven. I tried upgrading my Kato GP38 to and Atlas GP38 and it came out even worse. But I upgraded my Life-Like SW8 to a Kato NW2 chassis and it was dead-even in pull, even though there was no cab weight in the Kato. Hmmm. Testing then proves that different locomotives of the same weight don't pull the same, and it's not traction tires, either.

    My record for the most extreme loss of pulling power is still the Kato to Atlas GP38; the old 1982 Kato outpulls the newer Atlas by 3:1 in the same locomotive profile. That's as extreme as I've seen and enough to result in parking the nice, quiet and reliable Atlas to keep the oddball and sometimes balky old Kato running in MU service, even though the pickup design on it periodically requires a complete cleaning.

    Recently picked up a vintage Life-Like PA1 and that thing is just a BEAST for weight. Unbelievable. It weighs more than my reweighted FP45 on a Kato SD40 chassis..... And my single-locomotive record is absolutely held by the GHQ L-1; all pewter boiler with the traction tire on the rear driver. It's got so much grip it will overheat the motor if you're not careful. Meanwhile the original Life-Like 2-8-4 is absolutely terrible.

    Prototype tractive effort is supposed to be 25% steel-on-steel without sand; automatic wheel slip control and AC can theoretically get that higher but that's a good working number. But 'really good' in N scale is about 22% for beat-up brass wheels with no plating left at all, and down as low as 11-13% with some of the harder-alloy Atlas wheels and typically runs about 18% on Kato wheels. Recent Atlas wheels are better than some of the early ones like on my SD24. That and the Alco C630-series were some of the absolute worst, MP15 is in the same class.

    You'd think that traction tires would make more of a difference than they do, it will take a lousy 11-15% and take it up, but it still doesn't get you up higher than the 22% margin or so, it's not a miracle cure, and after they pick up grime and dirt they loose some effectiveness as well.

    And, now make the frames lighter with no-lead alloys, cut them out for sound and DCC and wonder why you can't pull a train anymore.... Which if you don't mind buying extra locomotives and not having any grades isn't an issue, more power to you, but this isn't all THAT hard to figure out. The wheel material issue is more subtle. I do think that 'harder' wheels likely work better for DCC pickup and have better electrical characteristics on a lighter locomotive, but it's a measurable impact on tractive effort.
    Randgust N scale kits web page at www.randgust.com

  31. The Following 4 Users Say Thank You to randgust For This Useful Post:


  32. #19
    Join Date
    Apr 2014
    Location
    southeast michigan
    Posts
    1,223
    Thanks
    692
    Thanked 1,604 Times in 599 Posts
    Mentioned
    50 Post(s)
    Tagged
    0 Thread(s)

    Default

    I have experienced similar issues in the last 20 years. Would be interested in knowing the weights of your locos and whether or not that is directly related to pulling power, particularly how much the U28s weigh. According to @Spookshow's site the U28s may be the best running engines of that era.

  33. #20
    Join Date
    Nov 2017
    Location
    Ariege, France
    Posts
    735
    Thanks
    3,204
    Thanked 1,707 Times in 490 Posts
    Mentioned
    91 Post(s)
    Tagged
    0 Thread(s)

    Default

    Quote Originally Posted by NtheBasement View Post
    U28s may be the best running engines of that era.
    Better than the Trix F-units ?
    Thanks, Tom

    Expect nothing except the opposite of what you expect, and then expect it to be something other than that ! Then that's about what it will be

Similar Threads

  1. Replies: 51
    Last Post: 24th Feb 2016, 05:10 PM
  2. Engine with most pulling power
    By dave92029 in forum General Rail Discussion
    Replies: 16
    Last Post: 31st Mar 2011, 02:57 PM
  3. Kato C-11 Pulling power
    By absnut in forum Steam
    Replies: 6
    Last Post: 23rd Jun 2005, 09:27 PM
  4. Pulling Power
    By fifer in forum General Rail Discussion
    Replies: 18
    Last Post: 15th Nov 2004, 09:24 PM
  5. Pulling power of Kato E8
    By brokemoto in forum Diesel
    Replies: 2
    Last Post: 6th Oct 2004, 04:52 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •