Disassembly of 4-8-4

[Mike K]

I am recently returned to model railroading after a 15 year absence. I decided to start building a new layout with DCC control. At the same time, my brother gave me an older Bachmann 4-8-4 without DCC. I purchased a decoder for it, but, since I have never had this type of engine, I don't know how to remove the shell. I tried various things without success and I am looking for advice on how to disassemble this.

[ABC]

I am certain that your loco is not DCC-ready, that is it doesn't have an 8-pin socket in the tender. So in order to install DCC you would need to wire the tender for power and the wheels on the tender because DCC is really finicky if you don't have enough pick-up, then you can go about hard wiring the decoder into the loco. And are you trying to remove the shell of the loco or the tender?

[Chris350]

The decoder will go in the tender.  I add this because you weren't clear on what end your were trying to disassemble.  What does the tender look like?  Is it your basic coal tender or a Souther Pacific style oil tender.  There is a different approach to each.  Once inside, you will (hopefully) see a circuit board where the decoder can be installed.  If the engine is old enough that there is no board the install becomes more involved. So if you can add some additional details about the engine, we can help more.

[Mike K]

The engine is #3781 AT&SF part number 41-580-02. I don't know how old, but certainly pre-DCC. The electric pickup is with brushes on all 4 wheels of the trailing truck of the engine. The tender seems completely independent and has no electrical connection to the engine. I believe I have to remove the shell of the engine and hope that there is room above the diecast chassis for me to place and wire in the decoder, which is a wire harness type, not a plug in to a socket.

[Chris350]

yep no tender harness, then not DCC ready.  You may find that there is precious little space under the boiler casting on that engine. There are a couple of diagrams here  for newer 4-8-4's that might give you some idea about how to proceed in disassembling your model, http://www.bachmanntrains.com/home-usa/references.php
  Another option might be to pick up a newer DCC ready tender, and then figure out how to add the connections to the engine, or place the decoder in the tender you have and add the needed wiring.  8 pin sockets and wire harnesses are available separately, for cases like this.

[ABC]

You will have poor results if you just add the decoder to the loco and do not add electrical pickups for the tender. You are better off doing one of the following: using the engine as plain analog/DC, using it for static display, selling it and buying a newer version that already has DCC or at least tender pickup. Additionally, even if you add DCC to this engine as prescribed, it will perform a great deal worse than when it was DC. It isn't worth adding the decoder to this engine, it will not get you anything, but an engine that will run poorly.

[pdlethbridge]

Another thing to consider on an old 4-8-4 is the possibility that its an open frame motor that can't be made to run in DCC

[Jim Banner]

Mike,
I do not have a Bachmann Hudson so I cannot tell your how to take the shell off.  But I can make a few suggestions about adding DCC to it.

Once you have the shell off, take a look at the motor.  If it is a can motor (enclosed motor with the shaft running lengthwise in the locomotive) then your locomotive may well be a Bachmann Plus version which is well worth converting to DCC.  If the motor is a "pan cake" motor with the shaft running crosswise in the locomotive, you have an even older version and it may or may not be worthwhile to convert.

The key is how well your locomotive runs on dc.  If it starts smoothly without a huge leap forward, and runs smoothly both slow and fast, then it is worth converting.  If it just sits there as you turn the throttle up slowly, then suddenly takes off at a good clip, try lubricating it.  If you are not sure how, ask.

I have installed decoders in several old pan cake motor steamers that had been well worn in and ran well for their age and they ran even better with the decoder, once it was properly adjusted.  These locomotives were noisy the day they came out of the factory and never did quiet down, but the noise is no worse with a decoder than without.  The owner, who had inherited several locomotives with pan cake motors, was well aware of their limitations and was ecstatic with how they ran, particularly at low speed.  I was less enthusiastic about them, but the owner was right - low speed running, even if a bit erratic, is better than no low speed running at all.

Had the fellow's locomotives been the Bachmann Plus version, they would have run as well as a Spectrum.

As far as power pickup goes, I suspect ABC missed where you said that all four trailing truck wheels had power pickups.  Adding those to the pickup through the drivers to the split engine frame, that would be 12 wheels picking up power, 6 on each rail.  That is 50% more than the typical brass Hudson which has four tender wheels picking up from the left rail and four drivers picking up from the right rail.  If you had an 0-6-0 switcher, then tender pickups by all means, although you still would not have as much pickup as you do with your Hudson.  I have a Bachmann Plus Northern with just the drivers picking up power and it was a very reliable running for many years until a pinion hardened and split.

You did not mention what type of decoder you had for your Hudson.  But I have long been of the opinion that if you are going to make silk purses out of sows' ears, you had better use the best scissors and needles and the finest thread.  Or in model railroad terms, if you want your old locomotives to their best, use the best decoders.  Save the low cost basic decoders for your finest locomotives that already run well.  Perhaps that is why all my conversions run as well as or better than the locomotive did on dc.


One thing that makes a decoder good for this type of conversion is BEMF control.  Properly adjusted, a BEMF decoder will force a locomotive to run at low speeds, whether it wants to or not.  No, it won't make an old pan cake motored locomotive into a Spectrum, but it will reduce the starting speed so that there is no large leap when it first starts off.  The process isn't perfect - when adjusted for the lowest possible speeds, the locomotive may hunt or be erratic at those low speeds.  To get the smoothest running at low speeds, the jump start may be worse (but still a lot better than without a decoder.)  However, once you have worked out a balance that makes you and your locomotive happy, it will run better at low speeds than it ever did before.  At higher speeds, BEMF control has little effect.

Bottom line, go for it.  The absolute worst that can happen is that you are less than completely happy with the results.  Then all you have to do is return the locomotive to dc operation and save the decoder for your next project.

Open frame motors can be a problem.  They take more power than can motors which generally means you need a physically larger decoder to handle the load.  If necessary, open frame motors can be replaced, even though pan cake motors cannot.

Jim 

[ABC]

Ignore all those links, they don't work as Jim pointed out, my apologies.
Does your box/loco look like any of these?
http://cgi.ebay.com/ws/eBayISAPI.dll?VISuperSize&item=370289386709
http://cgi.ebay.com/ws/eBayISAPI.dll?VISuperSize&item=120488710055
http://cgi.ebay.com/ws/eBayISAPI.dll?VISuperSize&item=280421460192
http://cgi.ebay.com/ws/eBayISAPI.dll?VISuperSize&item=120490228333
If so, you have a standard line Bachman 4-8-4, and it may not be worth converting.
If it looks like the following images, you have the Bachmann Plus version...
http://cgi.ebay.com/ws/eBayISAPI.dll?VISuperSize&item=230399102379
Note that the top of the box will say "Bachmann Plus." If you have this version, then like Jim said you can give it a shot.
But I suspect you have a standard line 4-8-4, but I don't think the plus version had tender pickup either.

[Jim Banner]

Arrgh,
I've got Hudsons on the brain this morning.  Spent yesterday working on Hudsons, today I am referring to 4-8-4's as Hudsons.  Sorry for the confusion.

However, the good news is, I have a Northern (4-8-4).  When I dug it out to take its picture, I found not only the Northern but also the digital camera, case, battery, and two memory cards that have been on the missing list for more than a year.

So here is the scoop.  Mine is a Bachmann Plus Northern with pickups on the wheels of the trailing truck as well as all the drivers.  It has no tender pickups.  And here is how it comes apart:



The red arrows point to the three screws you need to remove from the bottom cover.  The rearmost one is not the screw that holds the draw bar but the one behind it.  Click on the link below for a larger photo.  If my locomotive looks odd, it is because the wheels and axles are still out waiting for a gear.

http://members.shaw.ca/sask.rail/4-8-0-001

With the three screws out, you can slide the bottom cover rearward, up, and off.  Be careful not to lose the two springs under the third axle.  And watch out for the two wires near the rear.  Then you can lift out the split frame, motor and all.  The photo below shows the top of the split frame with the signature Bachmann Plus can motor and large worm gear/flywheel. 



There is lots of room for a decoder on top of the split frame, just behind the smoke unit.  Unless you have a pressing need for smoke, I would take the smoke unit out.  You don't need the extra heat next to a decoder.

If you are unfamiliar with working on split frame locomotives, take a look at this link:

http://members.shaw.ca/sask.rail/dcc/tmaster/tmaster.html

I have my fingers crossed that you have basically the same locomotive as it runs very nicely.

Jim

[ABC]

I have my fingers crossed that you have basically the same locomotive as it runs very nicely.

The Bachmann Plus Northern's are pretty decent, but the older standard line Northerns are junk compared to Bachmann's new Spectrum Northerns, which in my experience are very nice locomotives. I have a Santa Fe Northern, a Southern Pacific Daylight GS4, a New York Central Niagra, and 3 Norfolk & Western Class J's (1 passenger w/aux tender, 1 freight w/aux tender, & 1 railfan). They all run great and the only problem I had among them was the light in the back of my ATSF northern never worked, that's not bad though 5 out of 6 (84%). I added sound to the passenger version Class J, and it syncs up really nice.

[ABC]

Lets try this again with the links to the actual item pages...
Does your box/loco look like any of these?
http://cgi.ebay.com/Bachmann-HO-Northern-4-8-4-with-Tender-660_W0QQitemZ280421460192QQcmdZViewItemQQptZModel_RR_Trains?hash=item414a6be8e0
http://cgi.ebay.com/BACHMANN-HO-NYC-6008-NIAGARA-4-8-4-52-TENDER-IN-BOX_W0QQitemZ370289386709QQcmdZViewItemQQptZModel_RR_Trains?hash=item5636f7a4d5
http://cgi.ebay.com/BACHMANN-HO-N-W-Norfolk-Western-4-8-4-J-Loco-Set-OB_W0QQitemZ120488710055QQcmdZViewItemQQptZModel_RR_Trains?hash=item1c0dafcfa7
http://cgi.ebay.com/BACHMANN-HO-SOUTHERN-PACIFIC-GS4-4-8-4-48-TENDER_W0QQitemZ390035791831QQcmdZViewItemQQptZModel_RR_Trains?hash=item5acff1dfd7
If so, you have a standard line Bachman 4-8-4, and it may not be worth converting.
If it looks like the following image, you have the Bachmann Plus version...
http://cgi.ebay.com/Bachmann-Niagara-4-8-4-w-smoke-NYC_W0QQitemZ230399102379QQcmdZViewItemQQptZModel_RR_Trains?hash=item35a4db4dab
Note that the top of the box will say "Bachmann Plus." If you have this version, then like Jim said you can give it a shot.
But I suspect you have a standard line 4-8-4, but I don't think the plus version had tender pickup either.

[ABC]

Good news folks those links actually work 

[Mike K]

Thanks to all of you who have replied. I will try your suggestions and let you know how it works out.