AC-12 SPEED IMPROVEMENT

Randy Clark Jan 4, 2019

  1. Randy Clark

    Randy Clark TrainBoard Member

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    Has anyone ,like Carl, come up with a method to remote the Intermountain Cab Forwards?

    It is a beautiful loco but the top end is at best a jog. I am tempted to contact Intermountain and see if they can do anything to tune it up.

    The decoder is a Digitrax with 16 bit sound. Would a Tsunami do any better?

    I am sure 14 vdc would wind her up but I almost never switch back and forth.

    I would bed happy with 55 to 60 scale mph if I could get it.
     
  2. WM183

    WM183 TrainBoard Member

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    I don't believe I have ever heard anyone want their steamer to run faster before! Do you know if it has a reduction gearbox on the motor?
     
  3. Randy Clark

    Randy Clark TrainBoard Member

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    Normally I would agree but this loco barely crawls at wide open DCC throttle. I mean barely crawls. Maybe 15 to 20 mph.

    I am looking at a mashima that runs 17,000 rpm at 12vdc. Most run around 8,500 to 11,500 at 12 vdc.

    With 1/2 mile long straightaways 40 to 50 smph would be good.
     
  4. dualgauge

    dualgauge TrainBoard Member

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    Changing the speed values might work. Or is something binding. I do not have one so don't know how fast should run.
     
  5. NtheBasement

    NtheBasement TrainBoard Member

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    Spookshow's review mentions the slow speed, but he measured 44 mph. http://www.spookshow.net/loco/imac12.html
    I would start by resetting the decoder to make sure there's nothing funny with the settings. Personally I wish my locos had lower top ends.
     
  6. WM183

    WM183 TrainBoard Member

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    I wonder what causes the low speed? Gearing or just a low rpm motor?
     
  7. SVRailroader

    SVRailroader TrainBoard Member

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    I've wondered about increasing the speed as well. Mine hasn't experienced any great slowdown after I placed a TCS decoder inside, but I always felt the top end speed was a bit slow. As the Spookshow review linked above indicates, the "default" top speed from Intermountain was 44mph. While that might be a good average for the real-life engines, I believe they topped out closer to 70mph. Probably one would have to remotor the engine, and I'm not willing to risk taking it apart for that.

    And I agree with WM183's initial response, it's rare to hear anyone wanting to speed up a model. Usually we want to slow them down (especially the Kato ones; wasn't the MR review of the new U30C titled "A Day at the Races"?)
     
  8. Point353

    Point353 TrainBoard Member

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    The following review of the HO version mentions that reducing the tension of the wheel wiper electrical contacts apparently decreased their drag sufficiently to raise the top speed into the 55-63 MPH range.
    Perhaps the same would apply the N scale version?
    http://spcascade.com/AC12/AC12_notes.html
     
  9. Randy Clark

    Randy Clark TrainBoard Member

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    I am checking what max volts Tsunami and lol sound decoders will take safely and what if anything I can get out of my NEC Procab.

    Just a couple more volts to the motor would be nice.

    You can always slow a motor down but getting the revs is another thing.
     
  10. JMaurer1

    JMaurer1 TrainBoard Member

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    I complained about the SLOW speed since they first came out. While I respect that they made a slower running steam loco, the cab forwards DID go much faster than the 44 smph (they were limited to 75mph but could go even faster in real life but were very hard on rail at speeds above 70). Funny, I was just thinking this weekend about trying to remotor one of mine with a faster motor. Running one on the NTrak layout just takes WAY TOO LONG for it to make it around (at public shows).

    If anyone has any thoughts about how to speed them up, I'm game and very interested. Is there any info about how many RPM the current motor turns at full speed?
     
  11. Onizukachan

    Onizukachan TrainBoard Member

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    This was one of the things that kept me from going all in and buying one myself. Those things hustled in real life when they were in general freight service.
     
  12. Randy Clark

    Randy Clark TrainBoard Member

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    I was never happy with the top speed either so I am going to bite the bullet and take it apart and see if the Mashima 17K motor will fit. I have re-motored a few Atlas diesels and Fox Valley Locos with Kato motors. More than doubled my available RPM. If you don't need or want the excess speed just turn the decoder CVs down.

    I have a Brass AC 12 and she will really "haul the mail". Unfortunately it's not DCC and the axle bearings are worn out from running so many miles.
     
  13. JMaurer1

    JMaurer1 TrainBoard Member

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    Randy: I'm very interested in how it turns out.
     
  14. DCESharkman

    DCESharkman TrainBoard Member

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    Just drop a few uppers in the stack to speed them up. Mine does 65 smph. It is from the second run.

    Mine has the ESU LokSound decoder in it.
     
  15. Randy Clark

    Randy Clark TrainBoard Member

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    Unfortunately I skilled getting a second one when that run came out. Now they are nowhere to be found. I'll keep lookin if I don't get mine remotored first.
     
  16. Randy Clark

    Randy Clark TrainBoard Member

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    Back in the box and off she goes. Sending my unit back to Intermountain for some maintenance. Somehow, it managed to get out of quarter the other night. Sending her back to the factory for "refurbishment. Hope she comes back like new.

    You have to love the people at Intermountain. They never question what happened, how it happened, just no worries.

    When the next run is confirmed, you can bet I will be on the list.
     

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