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  • Topic: USA SD-70 MAC

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    • November 4, 2017 11:10 PM EDT
      • Cleveland, , Mississippi
         
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      USA SD-70 MAC

      I would like to add a newer locomotive to pull the double stack train. I was wondering if any of you have a SA-70 from USA. I think that is the latest locomotive on the market. My question is: Is the trucks on this locomotive sprung like the rest of the USA locomotives? The GP-30's and GP-38-2 has springs on the end of each axle allowing it to ride the rail no matter what inconsistencies in the track. The Aristo-Craft trucks were molded as one piece and did not give with the track like USA trucks does which caused problems. I wondered if any of ya'll could give me some info. Thanks.

    • November 5, 2017 2:14 PM EST
      • Belleville , Illinois act
         
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      Ron, the side frames are solid and attached to the motor block, not to the wheels.

    • November 5, 2017 4:35 PM EST
      • Pittsburgh, Pennsylvania
         
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      Yea, but are the wheels/axles sprung?

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    • November 5, 2017 9:36 PM EST
      • San Mateo, California
         
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      The USA Trains SD70 motor block is comprised of two components.  Main propulsion is provided by essentially a two axle motor block with the third axle being the "floppy" axle that can move independently and is sprung from the chassis.  
      The main two axle component has its axle tips supported by the side frames, whereas, the floppy axle is not.  The two axle motor component of the block "floats" in that it is not directly attached to the "A" frame that pivots on the chassis, but is supported by the sideframes that attach to the "A" frame. The journal boxes that the axle tips penetrate do have springs that function as a suspension, but they are very stiff.

      Shown below is an excerpt from my vignette about the SD70 that serves to illustrate - though it's purpose was about lubrication.

      SD70 Motor Block Assy

      I hope this helps,
      -Ted

    • November 9, 2017 10:09 PM EST
      • Cleveland, , Mississippi
         
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      This is basically the same arrangement of Aristo Craft six axle locomotives. Two of the axles were stationary and one would toggle back and forth. The problem was that the trucks were one piece and not too forgiving on unlevel track. 

    • November 10, 2017 6:11 PM EST
      • romeoville, illinois
         
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      They are good running and pulling locomotives Ron . I have a couple of them and they track very good over my uneven and overgrown tracks.

    • November 10, 2017 10:58 PM EST
      • Ottawa, Ontario, Canada
         
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      The axle of the pilot truck and trailing truck on the SD-70s is driven by a plastic drive shaft. If you ever have to work on a truck, put a piece of corrugated cardboard between the frame and bottom of the two pieces of the motor block. If not the drive shaft may disconnect, and it is a PITB to reconnect.

       

    • November 13, 2017 10:14 PM EST
      • Carlsbad, CA
         
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      Ron, quite different... The Aristo 3 axle block has 3 identical gearboxes that pivot along the long axis of the motor block... So, if you have cross level problems, this helps, but there is NO springing or suspension fore and aft... you crest a sharp grade suddenly and one of the end axles leaves the rail head... this is why you will see really deep flanges. Basically a crappy system, it's only compliance is when you have crappy cross level! The USAT 3 axle systems are really a 2 axle motor block with some suspension and a 3rd "floppy" axle that moves more like a pilot or trailing truck. Once this pivoting system is properly lubricated (and it is not from the factory) these trucks are very compliant on trackwork. Greg

      Ron Hill said:

      This is basically the same arrangement of Aristo Craft six axle locomotives. Two of the axles were stationary and one would toggle back and forth. The problem was that the trucks were one piece and not too forgiving on unlevel track. 

       

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