Bachmann N Scale GP7 Truck Mount Fix Opinion Wanted

Mark Ricci Dec 3, 2021

  1. Mark Ricci

    Mark Ricci TrainBoard Member

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    Purchased a N scale GP7 in August and its creep speed was exceptional but did exhibit the significant vibration problem noted by others. Last week noted that the loco lost all its great creep and would stall intermittently. Upon inspection, the front truck fell out and a wheel contact was bent. Bachmann sent out replacement and when attempting to install, noticed that one end of the matching plastic mount piece inside the loco where the truck tabs are held cracked off. (top half shown) .

    Also, the gap between the 2 half frames seems kinda big? Heard that the vibration issue with these is related to defective motor mount and without experience, unable to tell whether gap is too much and is part of the vibration issue.

    Questions,

    1-The Bachmann truck parts received included what appears to be the internal cracked piece. Seeking an estimate to the level of difficulty in replacing or on how much of the loco needs to be disassembled to replace?

    2-Do you think in the replacement of the truck mount will also enable motor mount repair without further disassembly?

    Thank you
    IMG_2212.JPG
     
  2. Sumner

    Sumner TrainBoard Member

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    I've got two of these but haven't had to have them apart. Take a look at Spookshow's description and see if that helps but would get the shell off and then you will probably have a better idea as to the difficulty....

    http://www.spookshow.net/loco/bachgp7.html

    When I got back into this I was hesitant to dive into a loco but will now pull anything apart. I've learned to work away from the edge of the work service in case something decides to get lost and take your time and if not sure of remembering how things came apart take pictures with your phone. I'd like to know the outcome in case this is something that I'll face in the future.

    Sumner


    Sumner
     
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  3. Mark Ricci

    Mark Ricci TrainBoard Member

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    Thank you Sumner for the info. Saved the link in August when you helped before. His guidance on shell removal seems good.

    Have you ever replaced that sort of bracket in other loco's? If so, how would you rate the difficulty in general?

    The loco is under warranty. Bachmann quoted 6 weeks plus shipping time but was hoping that I can do with some research so it can run during Christmas. I haven't even removed the shell in fear of cracking it (the CNJ road name is the theme of my layout) since its very tough on that model but would consider attempt if didn't have to significantly disassemble the loco. Of course I don't even know the correct sequence of disassembly after shell is off.

    Thanks again, will advise upon outcome.
     
  4. Sumner

    Sumner TrainBoard Member

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    Not really sure exactly what broke but maybe the following will help and you can explain what did break but I think i know after tearing the loco down.

    [​IMG]

    The shell fits the frame very tightly. I tried the trick of placing the front and rear steps (one at a time) on the edge of a jewel case and dropping it to separate the shell from the frame. That didn't work. Tried prying the shell apart at the fuel tank but that didn't work (found out why when I did get it off). Finally was able to pry the shell up at one end with a small screwdriver placing it on the ledge above the truck.

    If I was to do it again I'd try and get tooth picks in at one end of the shell on both sides where the dimples are. Hopefully then the shell would come off the dimples easier maybe even using the jewel case trick.

    Also check out Spookshow's site ( HERE ) for more info on this and the GP7 in general.

    [​IMG]

    To make it easier to put the shell back on and remove it in the future if needed I filed the dimples a little flatter and tried slopping them a bit on the side that contacts the shell first on reassembly. I also used the rounded side of the shell to round the shell where the dimples first connect it. I showed both of those mods above.

    [​IMG]

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    [​IMG]

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    [​IMG]

    I didn't go any further with the disassembling of the loco so don't know how hard it is to get the towers off that locate the trucks.

    [​IMG]

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    [​IMG]

    If you are under warranty still that might be the best option as taking those truck towers off might or might not be tricky I didn't do it but would if I really had to and the loco was out of warranty.

    The loco might not have quite the detail that the Atlas GP7/9's have but I don't notice much difference in them and this one is already DCC equipped and runs really nice with exceptional slow speed creep if that is important to you. Again read Spookshow's review ( HERE ).

    I need two 'identical' coal trains with identical engines and cars for a project I hope to finish at one point. It is described ( HERE ). I have about 6 Atlas GP7/9's that I'll equip with ESU decoders. I'd like three engines running in consists for each of the identical trains. If I can match the Bachmann's to the ESU Atlas locos I might use that combo but will probably use 3 Atlas loco's in both trains as they should be easier to speed match all being the same.

    Also have the info above on my site here...

    http://1fatgmc.com/RailRoad/Locos-1/page-8.html

    Sumner
     
  5. Mark Ricci

    Mark Ricci TrainBoard Member

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    Thank you Sumner!
    The tab on the truck is fine but right above where the yellow points to horizontal section is broke. The pic I posted is the bottom view of that horizontal section. It appears that just about the entire Loco needs to be disassembled.

    upload_2021-12-4_4-40-57.png

    [​IMG]
     
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  6. Mark Ricci

    Mark Ricci TrainBoard Member

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    Bachmann sent 2 replacement trucks. A black truck and a grey truck. Grey truck appears to include the section that is mounted inside loco. Just a little disappointed that I have the part but way too involved. Thank you again and going to pack it up and send back to Bachmann today. DSCN4999.JPG
     
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  7. Hardcoaler

    Hardcoaler TrainBoard Member

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    It's probably my lack of skill, but Bachmann is one of those brands that almost dares you to attempt a repair. They seem to be put together in such a way that defies disassembly.
     
  8. Sumner

    Sumner TrainBoard Member

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    Mark I added the following to the page on my site as I think it gives more clarity to the whole deal. Hope it is ok that I used the picture you posted.

    [​IMG]

    For the parts Bachmann sent you shown above my guess is that if the block shaped tower above the truck isn't the broken part but the tab at the top of the left truck is broken then use the left truck. It should slide right into the existing tower.

    If the top tower is broken where the tab clicks into it then use the right truck with the tower. Looks like it is a matter of sliding the old one off the driveshaft and sliding the new one on. The block like tower slides into the two frame halves making that part easy. If sliding the tower off and into the drive shaft is easy then this is an easy fix.

    [​IMG]

    On the one I took apart shown above I didn't try to separate the tower from the drive shaft. Now I wish I would of. One thing I noticed is that the driveshaft connection to the tower shaft looks different now that I look back at the picture.

    Other than struggling with the shell to get it off it only took about 5 minutes to get it apart and another 5 minutes to get it back together if I discount the time to file the dimples and the shell and putting the frame nut back on in the right direction. In some aspects it is easier to work on than some of the Atlas, Kato and Life-Likes I've dealt with and harder in other areas.

    Sumner
     
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  9. Hardcoaler

    Hardcoaler TrainBoard Member

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    @Mark Ricci, if you file down the dimples to make access easier next time, don't do what I did on one of my Life-Like units and that's to take too much off. :( I shaved off an excessive amount on one of the four dimples, going from "perfect" to "too much" with just a few swipes of the file.
     
  10. Mark Ricci

    Mark Ricci TrainBoard Member

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    Absolutely no problem with pic. You have given me so much great help and insight to a variety of MRR ?s and issues! Feel free at anytime.

    It is definitely the top tower and not the tab. Close inspection of the pic initially posted shows the bottom view of the tower where the tab from the truck clicks into has partially cracked off so the respective tab has nothing to "clip" into..

    In the end, Sent it back to Bachmann first thing yesterday morning. Really wanted it on the layout over the holidays but that's not going to happen. They quoted 6 weeks. oh well?

    Thank you for all the great info on the GP7. I love the loco and want it to be a permanent part of the fleet.

    A couple of questions...
    Do you think the motor mount issue resulted in excessive vibration, heat and or stress that ultimately led to the tower cracking?
    Also wondering if the motor mount issue enhanced or detracted from the excellent slow creep?
     
    Last edited: Dec 5, 2021
  11. Mark Ricci

    Mark Ricci TrainBoard Member

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    Thanks, liked to do that once loco is returned and it is still hard to remove.
     
  12. Mark Ricci

    Mark Ricci TrainBoard Member

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    Yes, it was a concern of mine too. However, it is by far the best creeper I own and or have ever seen in operation anywhere, Youtube or other. If it gets repaired, and continues to function over some reasonable time, will be very happy. Mentioned to Bachmann person that if they ever come out with another creeper like this with no defect and in CNJ green, I'd be first on the list.

    Curious, have you ever measured the time your best creeper? I'm asking because wondering if my expectations are too high? I would like to know from those who have been in the hobby.

    Also, would like to know other locos that can approach the GP7 performance or at least the F3. Specifically looking for creeping ability of the Atlas's VO1000 or H15-44 since both were made in CNJ green,

    With the 3 loco's owned - Out of the box Non-Stutter from beginning outer leg of Kato double crossover to end of inner leg of double crossover
    Bachmann GP7 BLI F3 5 min 8 sec!!
    F3 1min 14 sec
    SD35 not even worth measuring

    Around 2 concentric ovals (11 and 9 " radii crossover ) on a 2' x 4' layout.
    Bachman GP 1 h 7 min!!
    F3 23 minutes
    SD35 2 min

    The GP7 creep is just a beautiful thing!
     
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  13. Sumner

    Sumner TrainBoard Member

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    Sorry, don't know about any of that as mine hasn't exhibited those symptoms. In the picture you posted further up the distance between the frames looks pretty close to mine. The motor and those towers index into the frame and if any of that isn't right and has been forced I could see that creating a problem thought.

    I built a wheel cleaning station ....

    [​IMG]
    http://1fatgmc.com/RailRoad/Locos-1/page-2.html

    ... and after using it on one loco ....

    [​IMG]

    ... the slow speed really improved. Not sure how the the 6 seconds from tie to tie relates to your speed but that is more than slow enough for me. I've had a number of other locos that seem to be in the same range. I got one of the last release DCC Bachmann Doodlebugs the other day and it wasn't 6 seconds between ties but still slower than I'll end up running it. The U30C above ran slow on the DC but can't remember if it was the same on DCC. I ran the Doodlebug on DC first as I was unsure of the DCC address for it and it didn't do as well on DC as DCC once I was able to run it that way.

    For DCC I was running the older DCC++ on an Arduino but now run the much improved DCC++EX on an Arduino and use either JRMI's throttle on the monitor with a mouse or ...



    EngineDriver on an Android phone that I really love now that it is possible to run a 'physical' throttle knob with it and get easy step by step speed controll...

    http://1fatgmc.com/RailRoad/DCC/page-3.html

    Sumner
     
  14. Mark Ricci

    Mark Ricci TrainBoard Member

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    Wow, that tie to tie speed is outstanding! Was curious to approximate creeper speed in MPH. According to scarm, the length of both ovals and related track in path is approx 1060 yards or .5 mile. So the best non-stutter stall time here guess is about 1/2 MPH.

    Agree 100%. Actually at that speed its kinda painful to watch the turtle pace for an extended period but we can always run faster. F3 not bad but will look at slowing it down.

    Like the cleaning station. Have you experienced any wear off of metal coating on wheels?
     
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  15. Sumner

    Sumner TrainBoard Member

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    Not on the few that I've done and only did those once. I'll be cleaning more if I ever get more built than the test track I have now. I really can't image it wearing the metal though as it is hard to get that aggressive with it. One could change the pad material also,

    Sumner
     
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  16. Shortround

    Shortround TrainBoard Member

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    Perhaps you could try micro-cloths that are used to clean eye glasses and other delicates. They do take off the crusty stuff well without damage. Wash cloth sized are available.

    Rich
     
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