To Push or To Pull, That is the Question

Discussion in 'FAQs' started by TrainClown, Nov 23, 2003.

  1. TrainClown

    TrainClown Member

    I'm building a Climax out of some junk bits I resurrected. So basically, there are two trucks. One is powered and the other is a dummy that basically picks up power from the other rail. So when I build these into the engine, should the powered truck push the dummy or pull it? For best performance, you understand. For all I know, there is no difference but there just might be. Can anyone shed some light on this for me?

    Scratching his head,


    P.S. Here is a pic of the trucks:

    Attached Files:

  2. penngg1

    penngg1 Member

    The powered truck should be pulling. the unpowered truck will follow. It is heavier and will track better. Thats why front wheel drive cars easier to control than rear wheel drive, besides how many times have you seen a horse push a wagon. :confused: :thumb:
  3. Tyson Rayles

    Tyson Rayles Active Member

    :confused: Did they ever make a 12 wheel Climax?
  4. TrainClown

    TrainClown Member

    Thanks Bud, that makes sence.

    Tyson, aint you ever herd of a three truck shay? ;) Well I can dream can't I? So I dreamed up a hemo Climax. :thumb: I want to put my own spin on it, and, bet it will be the only one. :D

    But you still have a good point. :rolleyes: :D

  5. cidchase

    cidchase Active Member

    Hi TrainClown,
    This is the kind of puzzle I like!:)
    I think that from a mechanical viewpoint, rear wheel drive
    will provide more potential tractive effort.
    The torque reaction tends to lift the front truck
    and transfer a higher percentage of the vehicle weight to the
    rear truck and a lower percentage to the front truck.
    It's why a scooter does wheelies.... :D :D

    (other ideas welcomed):)
  6. zeeglen

    zeeglen Member

    I have to agree with Cidchase. Bikes have rear wheel drive. The reverse happens when braking, that's why the front wheel brakes are more effective than the rear wheel brakes.
  7. Chessie1973

    Chessie1973 Member

    Well from my experience with Model Railroad Locomotives in the past with powered trucks like this the truck should acrually be pulling not pushing.

    I have had a few of the Cheaper Locomotives powered with trucks similar to those you have and every one that had the powered truck in the rear had a lot harder time not spining it's wheels when pulling a load that the ones with the front truck powered could pull.

    Ususally what would hapen is the rear truck would actually rise out of the rails from the wieght transfer and begin to spin because the traction surface wasn't making as good a contact with the rails. Most locomotives have thier wieght very low in the center of the loco and it helps to remove the overall wieght shift to the rear for the front wheel drive from what I have seen.
  8. zeeglen

    zeeglen Member


    Maybe it depends on the weight distribution and the way the truck is mounted to the frame, if it can swivel may change all sorts of things.

    TC, could you make it so that the trucks are swappable back and forth, at least for some initial trials before the final work is done? Then test to get an answer. And please let us know, this is a very interesting question.
  9. wendell

    wendell Member

    I don't think it will matter climaxs and shays were more likely to push the loads than pull beacuse they did not have always have a run a round track or turntable so it would depend if you were going to push up grade and then back down grade
  10. krokodil

    krokodil Member

    Hi TrainClown

    I would not use on any own construction such drive mechanizm as on your picture. Especially not on the Climax, where you have large empty spaces below boiler but your drive mechanizm will fill them.

    Im also building my own Climax, in the next days I will place some pictures about the drive train.

    Your mechanizm can easily disturb the overall view and performance of the wonderful Climax locomotive.

    Much more easier and simpler solution is the NWSL Shay drive mechanizm used also in my small Shay locomotive.

    Sorry for my English


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  11. Ray Marinaccio

    Ray Marinaccio Active Member

    The Tyco locomotives that used that type of power truck had the powered truck in the front. I'm not sure if it was in that possition for traction reasons or for other reasons such as clearence issues with the narrow hoods or the fact less wire was needed for wiring the headlight.
    A simple test could be preformed with an old Tyco loco. Pull a string of cars behind the loco , adding cars untill the wheels spin. Then turn the loco around and try to pull the same cars from the front coupler.
  12. TrainClown

    TrainClown Member

    After reading your replys I am going to put the powered truck in the front of my climax. I managed to salvage a couple of mounts that allow the trucks to swivell and I have already glued them together, with a bit of scrap plastic, to get my frame. I'm not to concerned with the fact that the trucks have six wheels and a real climax only has four. Lets just say this was a special order ;)

    I bought some scale lumber for the rest of the body and made a swell lamp for the boiler. I also got some decent bells on my last LHS trip and that, strange as it may seem, really makes me happy. :D

    Back to the boneyard,

  13. Bill Stone

    Bill Stone Member

    Actually the reason most cars (except for Cord, DKW, Citroen, Saab and a few others) prior to a few years ago had rear wheel drive --- and bicycles for the same reason --- was due to the difficulties and complications of steering and driving with the same wheels, not because of any other real benefits.

    But I have to suspect that although (in theory) the weight does shift toward the rear in forward acceleration, there would be no real --- measurable --- difference in a model railroad locomotive, particularly in the small scales.

    It's sort of like the old argument between proponents of understeering (front heavy) cars and oversteering (rear heavy cars, such as Porsches and other rear-engine makes.) Yes you had to drive them differently (if you were pushing the edge) but what was the real difference? If you lost it on a curve, the understeering car went through the fence front first, the oversteerer went through tail first. You were, in either case, going through the fence.....

  14. TrainClown

    TrainClown Member

    Good point Bill. I don't think weight transfer for an HO model train would be a significant factor, because the train picks up speed rather slow.

    As for mid engine cars. Its a matter of ballance. I heard the mid engine cars had better traction because the weight was distributed more evenly over the 4 tires. (do we have to worrie about this in model trains?)

    Just a few thoughts. I don't want you to take a-fence.:eek: :D ;)

    (sorry about the bad pun, but a clown can never resist a straight line!)


  15. krokodil

    krokodil Member

    The CLIMAX #30 of FLRR

    Hi everybody,

    there are 3 photos from my new scratchbuild Climax in HO.

    Please comment.

    Attached Files:

  16. krokodil

    krokodil Member

    The Climax #30 of FLRR

    The view of almost ready locomotive (the boogie sides are still missing incl. few more details).

    The engine runs quite well.

    Attached Files:

  17. krokodil

    krokodil Member

    The Climax#30 of FLRR

    An the last overall view.

    Attached Files:

  18. Bill Stone

    Bill Stone Member

    That's beautiful, Krokodil.
    It looks like you turned the boiler on a lathe. Right?
    And, I cannot tell from the photos, how are you getting power to the trucks?
    Please keep us posted with more pictures, as you finish this little beauty.
  19. krokodil

    krokodil Member

    Hi BillS

    yes, the boiler is partially turned from a metal (brass) pen. The rings are soldered copper wire and filed down to flat (in the lathe).

    All wheels are driven as well as the steam engines (unfortunatelly because of the available space and gears, they do not turn prototypically - in the same direction).
    The drive mechanism is very close to the prototype only in the bogies I use worms and gears.
    The cab is etched brass. The steam engines are made from a single piece of solid brass rod on the lathe and filed and milled.
  20. Gary Pfeil

    Gary Pfeil Active Member

    That is just fantastic work Krokodil!


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