Locomotive gearing for similiar speeds.

Gats Jul 5, 2000

  1. Gats

    Gats Staff Member TrainBoard Supporter

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    Ok, here's a bit of research for those interested...

    There has been plenty of mention in various topics of the difference between the speeds of different locomotives at the same throttle position*.
    Has anyone actually looked at the gear ratios and into the possibility of swapping out gears between the brands that have the same truck set-ups? I mean between Kato, Atlas, and the newer LL (GP20 and SW) units with low-friction trucks.
    I recall an article or two in a couple of early N Scale magazines regarding this, but that was with the available locos in the late 80's and early 90's.
    I realise this could go as far as the differences between the motors themselves - different windings = different speeds at the same voltage - so maybe someone has done a motor swap between the brands since the units mentioned above are of similar design.

    Just a thought...

    Gary.

    *NOTE I'd like to keep this a non-DCC specific question. No need to add "with DCC you can..." discussion as we mostly know that you can tune the throttle response with DCC. [​IMG]

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    Gary A. Rose
    The Unofficial TC&W page
    N to the Nth degree!
     
  2. DaveD

    DaveD TrainBoard Member

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    I checked into this a little once. I contacted Northwest Shortline and a few others, and they said it would be very hard to re gear, plus they didn't even sell anything like that in N.

    But, I'm thinking that maybe the entire truck could be changed in some cases. I was just recently corresponding with Joe Cox regarding his excellent CF7 model that he made. http://cencalrails.railfan.net/cf7.jpg He said he swapped LL trucks in a GP20 for Kato ones I think it was.

    As far as I'm concerned, the lower the ratio, the better. N has such little mass, so next to nothing will make them sputter. The more RPM the motor builds up, the smoother it will be. Of course you trade off quite running for that though.

    Even if you designed your own gear set though, there's a limit to how far you could go, because the cog that transfers from the shaft to the axles could only be so small on the axle part to change the ratio. At some point, you would have to make them metal so that you could make the teeth finer, and cog smaller. Kind of like a watch.

    Dave D.
    Los Angeles, CA
    The Elgin, Joliet & Eastern Photo Archive & E-Mail List: http://eje.railfan.net
    The Ashley, Drew & Northern Railfan Page: http://eje.railfan.net/adn
    Southern California Trains: http://eje.railfan.net/socal
     
  3. Alan

    Alan Staff Member TrainBoard Supporter

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  4. Eagle2

    Eagle2 Staff Member TrainBoard Supporter

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    Well, here I go opening my mouth without knowing what I'm saying, but...

    How much of the speed thing is weight and not gearing? I ask this because I've got a Kato U30C and two Kato SD 40-2's. The U boat is considerably heavier, and considerably faster. Now, I admit that it's also a good bit older, but I have to wonder, based on a small amount of anecdotal evidence, whether the weight is the major factor.

    Jenks - the REAL Big Blue!
     
  5. Gats

    Gats Staff Member TrainBoard Supporter

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    <BLOCKQUOTE>quote:</font><HR>Originally posted by Eagle2:
    How much of the speed thing is weight and not gearing? I ask this because I've got a Kato U30C and two Kato SD 40-2's. The U boat is considerably heavier, and considerably faster. Now, I admit that it's also a good bit older, but I have to wonder, based on a small amount of anecdotal evidence, whether the weight is the major factor.

    Jenks - the REAL Big Blue!
    <HR></BLOCKQUOTE>

    I don't think weight is much of a factor at all. The difference between the same locomotive with 2 (light/heavy) weights would be nominal on speed. The weight difference will come into play with better rail contact and pulling ability with a heavier mechanism.
    Using the U30C as an example, it might be best to look at the locomotive made around the same time. If I recall correctly, the Atlas (Kato-built) SD7/9 was from the same time frame. I know they use the same axle gears as I have replaced one in the U30C with the SD7/9 gear. They had the same diameter and number of teeth and the SD gear was much cheaper and more readily obtained than the Kato equivalent. What I can't recall is if they ran at, or near, the same speed.

    Dave brings up a good point with the truck swap for the CF7. The LL GP20's run slower than the 'equivalent' Atlas GP7/9. Taking the mechanisms are identical (ignoring motor characteristics) the gearing must be different. Time to pull apart a couple of locos and do some side by side tests. [​IMG]

    Gary.


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    Gary A. Rose
    The Unofficial TC&W page
    N to the Nth degree!

    [This message has been edited by Gats (edited 06 July 2000).]
     
  6. Maxwell Plant

    Maxwell Plant TrainBoard Member

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    The motor, shafts and worm gears are the same. It's the gearing and the trucks that are different. Take a LL truck and an Atlas truck out of the frame but leave them assembled. Roll them on a flat smooth surface and you'll see the difference. The Atlas truck will roll of the table and the LL will stop almost instantly. The LL truck is not a free rolling "frictionless" truck, where as the Atlas is. Pop a set of Atlas trucks under your Life-Like GP20's and see how much better they perform. I was amazed!

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    RAILROADING-TO-THE-MAX, Burlington Northern/Santa Fe Style!
    Brent Tidaback, Member #234
     
  7. DaveD

    DaveD TrainBoard Member

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  8. DaveD

    DaveD TrainBoard Member

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    Alan... I believe it is the same guy, because I think he did sign as being in Texas. He told me he might send me a pic of the chassis. I looked on the JnJ page, and they don't show a CF7 shell. So I'm not sure what that means. He basically explained to me what he did, and it sounded pretty involved. He cut the chassis from a GP20 in half and shortened it, then glued it back together with epoxy. But he did say that he thought JnJ sold a chassis made for that, and also for their GP15.

    Maybe you could talk him into doing a photo web report on the whole thing though if you are friends. Everybody I have shown that picture to loves it.

    Dave D.
    Los Angeles, CA
    The Elgin, Joliet & Eastern Photo Archive & E-Mail List: http://eje.railfan.net
    The Ashley, Drew & Northern Railfan Page: http://eje.railfan.net/adn
    Southern California Trains: http://eje.railfan.net/socal
     
  9. Alan

    Alan Staff Member TrainBoard Supporter

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  10. Gats

    Gats Staff Member TrainBoard Supporter

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    Well, guys, been doing some experimentation this end with an Atlas GP7 and a Life-Like GP20. I have stripped trucks, counted teeth, reassembled, swapped around, tested, swapped motors... a few interesting bits have shown up - enough for me to do it again with a sample of 3 of each unit.
    One point I found interesting was the motors are totally interchangeable between the units and have different electrical properties that has a greater bearing on the speeds than just the gearing issue.
    Too much information to place here, so I will attempt to create a page with some details by the weekends end. I am also building a test track for continuing this. Dual track (about 1.5 mtrs) side by side with a small panel I can hook meters into and be able to independantly switch the track power. This will give as close a controlled environment as possible.

    Gary.

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    Gary A. Rose
    The Unofficial TC&W page
    N to the Nth degree!
     
  11. Maxwell Plant

    Maxwell Plant TrainBoard Member

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    I await the results! Post them here if you can Gary!

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    RAILROADING-TO-THE-MAX!
    Brent Tidaback, Member #234 and a N-Scaler to boot!
     
  12. Gats

    Gats Staff Member TrainBoard Supporter

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    Slight delay on the page, guys. Socialising needed to be done, and work commitments. [​IMG]
    I will be expanding the comaparison to 3 each GP7/9 and GP20 just so I have good representation of the units. Also, I plan to add a GP30 and 35 to the mix initially, then increase it to the 6-axle units over time.
    Hopefully, I can come up with a good compromise.

    Gary.

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    Gary A. Rose
    The Unofficial TC&W page
    N to the Nth degree!
     

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