Bachmann "Plus" F7a

Discussion in 'N / Z Scale Model Trains' started by kettlestack, Apr 15, 2002.

  1. kettlestack

    kettlestack Member

    Having had so much success recently in getting ALL my HO locos running smoothly I decided to start tuning my N power pool.

    I seemed to recall the Bachmann F7a ran a bit noisy out-of-the-box. So it was first on the list for tuning. The design is first rate with split frame just like the LL switcher.

    Well, having lubed it and running it back and forth for half an hour on a 36" length of track it freed up quite a bit and is very quiet.
    It still must have friction there somewhere coz it doesn't like starting and the motor was quite warm after the half hour running-in session

    Has anyone else experienced warm motors in this model after at least half an hour of running?

    Errol
  2. Tyson Rayles

    Tyson Rayles Active Member

    Are you sure you don't have too much oil on it? Does it have flywheels?
  3. kettlestack

    kettlestack Member

    Yep, flywheels are fitted. I left some of the original grease between the large gears and the truck fram as i figured it would reduce friction over such large areas. Maybe I should remove it and use thin oil. Also more running in wouldn't do it much harm.
    I use the minimum oil that can appear on the end of the LaBelle oiling blind needle.
    The motor wasn't hot it was just warmer than I would have expected.

    Errol
  4. Tyson Rayles

    Tyson Rayles Active Member

    I'd check the inside of the body shell to see if the flywheels or armature is rubbing.
  5. nmtexman

    nmtexman Member

    The new F7's don't seem to be that much different from the old ones, internally that is. The shells look much nicer. I finally took one of my A units apart and it took me the longest time to figure out how they transferred power from the rails to the motor!

    I also came up with a copper spring that I can't figure out where it came from. The light bult has the filaments looped and bent to the side. My guess is that it picks up power from the frames in one of the little indentations. I also remember why I hate Bachmann's now!

    Taking it apart wasn't difficult. I hope I can get it back together again properly :D. The B unit shouldn't be that much of a problem. Looks like MT 1131 is the proper MT coupler set for these, although it uses 1128's for the B unit and the rear of the A unit, and 1130's for the pilot. The 1131's are really only the replacement coupler boxes.
  6. kettlestack

    kettlestack Member

    Bob, power is picked up from all wheels via a thin metal shim between the wheels and the truck sides. The upper part of the shims (bent at 90 degrees to the truck sides) presses against their appropriate weight blocks. This is what is described as a split frame chassis for power. The bulb leads are fed from the blocks.
    You are correct about the MT couplers.

    My problem was friction causing the motor to get warmer than it should.
    I found that the axle box moulding has tiny nipples which were designed to act as the lower bearing on each axle. As the silver paint (I have the AT&SF F7a) is thicker than desirable it built up those nipples to the extent the axles were being pinched. I ground them off and things are a bit better now. However, the gears are rather free to move sideways on their spindles which accounts for a lot of the noise these locos make.
    I'm still thinking about various solutions to this cause of noise.
    Overall the design of the loco, mechanism etc is excellent but the finish of the various small parts leaves something to be desired, an improvement in quality control is really all that Bachmann needs.

    Errol
  7. nmtexman

    nmtexman Member

    Thanks for the tip, kettlestack. I did finally figure out that the block is providing the "wire" for the current to go from track thru wheels to motor. And I had also figured out that the light bulb gets power the same way. What I haven't figured out is what the little spring is for!:confused:
  8. kettlestack

    kettlestack Member

    Bob, as far as I can make out the only springs on this loco are in the rapido couplers.
    Don't worry about it, I also usually finish up with bits left over after reassembling things :D
    Just ocurred to me, if it's a really really tiny spring, check out the way the motor brushes are fed from the weights, it might belong there to make good connection with the block.

    Now, what did I do with that beer I had here? :)

    Errol
  9. nmtexman

    nmtexman Member

    Hah! After taking apart 4 A and B units (and putting them back together again!!!), I have found out where the spring goes now. The spring goes in the left-most weight/frame. There is a little indentation there and the spring goes in, end-wise, to make the connection to the motor from the left hand frame. The right hand frame has a direct connection to the upper part of the motor.

    I also bought an extra set of grain-of-wheat bulbs at Radio Shack to put in the B units. I'm hoping that will drop the speed down some in order to get a better match with the A units.

    In addition to all of this, I ran across an old Bachmann F7A in one of my drawers. I can now tell you truthfully, the new ones look much, much better!:rolleyes:

    So, with the new and old, I can now put together an A-B-A-B-A lashup!
  10. kettlestack

    kettlestack Member

    Way to go Bob... Happiness is success! :D :D

    Errol
  11. nmtexman

    nmtexman Member

    Or is it success = happiness?:D

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