Bachmann 4-8-4 2nd run Banana loco

[kiwi_al]

So I saw this Bachmann 4-8-4 on Trde Me for 35.00 NZD and pounced. The vendor said it didn't run and buyer beware. All good. I bought it mainly for the shell but I got thinking (I shouldn't do this) what if I could make it run and use it to test some Chinese motors I have accumulated - sort of a test sled.
I put it on some Kato unitrack and yep it didn't run. I took the shell off and applied DC power to the motor and felt a little resistance but no movement - no there was no smoke!!
I then completely stripped it down to the last screw a bit like Victor Miranda does. I took the motor and applied power - yay it runs - yes it's a straight wound 3 pole, you know the ones.
I put 2 drivers back n the mechanism, with the worm gear, shaft and cup gear along with the motor and screwed the bottom cover on and the top weight as well. I applied power, it ran a little and stopped. The cause is the top weight which forms the top part of the mechanism is bent like a banana so I slackened the screws off a bit and I could go from slow to fast.
So some progress was made.

Now comes the next bit - I unscrewed the bottom plate and added the rest of the drivers and hooked up the siderods etc. (I hadn't taken these apart. I connected only one side up and applied power to the motor, all drivers turned. I hooked up the other side and it jammed - out of quarter or the rods and linkages are wrongly connected.

Now the thing that puzzles me is how in the world this would ever work, Only one side of the drivers pick up current and the opposite side in the tender picks up current. I did a continuity test on the driver wheels and got nothing - this version does not have the side pick up plate of the earlier or later (white Box ) versions.

To make matters worse when I check Marks website (spookshow) his 2nd run version has more wires than I have got.
Anyone got a diagram of a second run 4-8-4? I can make it work but it's got me curious.

Here's what it looks like:



And the mechanism with only 2 drivers fitted.

[daniel_leavitt2000]

It looks like the wires to the headlight were pulled. Where does the top motor contact connect to?

[kiwi_al]

The only wires are to the front light, there aren't any others, I've looked at the photo from Marks website (spookshow) it looks like there should only be those two wires (to the light). There's no wires to the motor. I guess the frame is supposed to be live

[cjm413]

Check here for diagrams

https://hoseeker.net/nscale.htm

[peteski]

Seems likely that before you got it someone has dicked around with this model.

[kiwi_al]

Seems likely that before you got it someone has dicked around with this model.

Yep that's very likely, just about any secondhand steam for sale over here has been messed with. At the worst case i can use most of the spare parts for future kitbashes, which is basically what i bought this for but I get sidetracked easily. 

[SkipGear]

The only wires would be to the headlight. The loco drivers/frame pick up from one rail, the tender picks up from the other and that is transmitted through the drawbar. The post for the drawbar on the loco is insulated from the loco frame is connects directly to the brush hood on the motor.

[kiwi_al]

The only wires would be to the headlight. The loco drivers/frame pick up from one rail, the tender picks up from the other and that is transmitted through the drawbar. The post for the drawbar on the loco is insulated from the loco frame is connects directly to the brush hood on the motor.

Thanks Tony,  it's starting to make sense now. I'll have a play with it tonight I have to find another screw for the leading tender truck - that was missing.

[SkipGear]

Thanks Tony,  it's starting to make sense now. I'll have a play with it tonight I have to find another screw for the leading tender truck - that was missing.

This version was one of the first steam loco's I owned, 12 years old and my Dad brings home a 9x6 layout he bought from an older gentlemen. They had to cut it down the middle to get it out of the guys attic train room. I was left to reassemble it. Once I got the layout together and running, my dad and I went to the hobby shop and picked up the 4-8-4 as my first new loco.

[Boilerman]

Bachmann also made a later version that had flanges that will run on Atlas Code 55 track, I have one that I have one and installed a decoder in it and just doing that made a great difference in how it ran, way smoother and the unit would pull fairly well up a 2% grade with 12 cars.

[kiwi_al]

I've replaced Bachmanns motor, had to mill the frame a bit. This now runs smoothly but not on the track. If I connect power directly to the motor in situ it all runs smoothly. If I put it on the track and use an alligator clip / wire connected to the drawbar post I get nothing. It appears the positive power isn't getting to the motor. I'm assuming that the positive side gets to the motor through the motor case. It could be that the case isn't conductive. But that's as far as I have gotten.

[kiwi_al]

Well it seems the motor case is not conductive. I'll have to directly connect it - go figure

[peteski]

Well it seems the motor case is not conductive. I'll have to directly connect it - go figure

Well, that is not a 100% accurate statement.  The metal part of the motor frame is conductive, but the plastic end piece that holds the brushes is an insulator (for a very good reason - so the motor is not one giant short circuit).    But seriously, if the motor's metal frame is used as one of the conductors, then there usually is a small springy contact connecting one of the brush holders to the metal motor frame.  Rivarossi used this type of design in their steam locos, but I can't recall  Bachmann doing this.

[dem34]

Well, that is not a 100% accurate statement.  The metal part of the motor frame is conductive, but the plastic end piece that holds the brushes is an insulator (for a very good reason - so the motor is not one giant short circuit).    But seriously, if the motor's metal frame is used as one of the conductors, then there usually is a small springy contact connecting one of the brush holders to the metal motor frame.  Rivarossi used thus type of design in their  steam locos, but I can't recall  Bachmann doing this.

As I recall the open frame motor of a Metroliner model does this.

[kiwi_al]

Well, that is not a 100% accurate statement.  The metal part of the motor frame is conductive, but the plastic end piece that holds the brushes is an insulator (for a very good reason - so the motor is not one giant short circuit).    But seriously, if the motor's metal frame is used as one of the conductors, then there usually is a small springy contact connecting one of the brush holders to the metal motor frame.  Rivarossi used thus type of design in their  steam locos, but I can't recall  Bachmann doing this.

You'd be right. On closer look at the motor the brush caps are in plastic so when I apply power to the motor case nothing happens. I should have realised - doh!! The old motor has a solder tag I can steal to make it work. My eyes aren't what they used to be