DCC-ing the dreaded Bachmann Split Chassis!

Discussion in 'Workshop Benches' started by Keith M, Mar 22, 2017.

  1. Keith M

    Keith M Staff Member Moderator

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    Probably a good few folks first reaction to the offer of a cheap split chassis loco would be to run away and hide, especially if you've a DCC layout, but to be honest, it's no great problem, and there are some great bargains around, decent loco's too, and here's the lowdown on "How-To".
    I've just bought the intended victim on Ebay, quite cheaply, in excellent condition with the extra handrails and vac pipes still sealed in the bag. It's a Class 04 Diesel shunter in BR green (my chosen modelling era), originally by "Mainline" but remarketed under the Bachmann name after being taken over, quite a well detailed model and perfectly suited to my layout, so here goes.
    Upending the loco, two screws, one each end hold the hook and loop couplers and body to chassis, so out they come, and the pic below shows what you have.

    Attached files [​IMG]
     
  2. Keith M

    Keith M Staff Member Moderator

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    First job is to remove the two screws holding the wheelset in, on this shunter, there are also two more screws holding the counterbalancing drive weights in position under where the cab fits, so remove these also.

    Attached files [​IMG]
     
  3. Keith M

    Keith M Staff Member Moderator

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    The two chassis halves are held together by three countersunk screws at one side and three plastic square headed 'nuts' at the other. These 'nuts' are part of the insulation between the chassis halves, so don't lose them! As you part the chassis halves, you will find three insulated spacer washers between there, these go onto the aforementioned 'nuts'. Now you can see the motor, how it fits into the chassis and more importantly, where and how the motor collects it's current from the two chassis halves. What we need to do now is to isolate (and insulate) the motor entirely from either side of the chassis, otherwise, it'll be "POP goes the decoder!

    Attached files [​IMG]
     
  4. Keith M

    Keith M Staff Member Moderator

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    Now it's 'surgery time' so we need to cut or file away two small areas of metal to make sure that there is no possibility of either motor terminal contacting either side of the chassis. The two shiny metal areas in the pic below is where I removed metal to ensure no contact between motor terminals and chassis. The area to remove may vary depending on the model you have, but the idea is the same, no contact between motor terminals and either chassis half. I don't have machining facilities or indeed the experience to use them if I had, so junior hacksaw/file or whatever you have is needed, but in this case, the pic shows what I mean.

    Attached files [​IMG]
     
  5. Dave Marson

    Dave Marson Full Member

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    I have one of these Keith :)
     
  6. Keith M

    Keith M Staff Member Moderator

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    Surgery completed, I now removed the copper terminal tag from the innermost contact and filed the brass connection end to leave a good surface to solder to. At this stage, you'll need to decide exactly where the decoder is going to go, and as this model is tight for space, it had to fit at about 45 degrees in the cab end, fixing the decoder with "Kapton" tape, which is a high quality insulating tape. Decoder wiring has to be kept as short as possible as there ain't much spare space, so cut as necessary, and solder the grey and orange wires to the motor terminals, using heat shrink sleeving to cover where possible. The 'pickup' wires are probably best connected with a soldered loop at the ends, and fixed under one of the insulated 'nuts' at one side, the other under it's opposite number screw head in the same manner, once again keeping the wiring as short as practicable. As this is another 'cheapo' loco, I've again used a 'LaisDCC' decoder because it's small and cheap. It's actually a full 4 function decoder, but as I've no plans to fit lighting in this loco, I've removed unneccessary wires for space and simplicity.

    Attached files [​IMG]
     
  7. Keith M

    Keith M Staff Member Moderator

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    Now we can fit the two chassis halves together, so fit the 3 'nuts' first, slipping one of the insulating washers onto each 'nut' before assembling the two halves together. It's easier if you fix two of the three screws into the 'nuts', then finally fitting each 'pickup' wire under the remaining nut at one side, other lead under the screw head at the other. It doesn't really matter if on testing, the loco runs the wrong way, as it's very easy to change this in the "CV" values as you program anyway (For those 'not-in-the-know', bring up CV29 which usually has a value of 6, just add 1 to whatever value is shown, then enter it, this reverses direction). Once the chassis is back together, refit the wheelset and cranks, fixing the decoder in final position before testing. Pic below shows how to connect one of the 'pickups' with a soldered loop under the fixing screw head.

    Attached files [​IMG]
     
  8. Keith M

    Keith M Staff Member Moderator

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    I've again used "Kapton" tape to fix the decoder, and with wheels refitted it's now time for testing and programming. Once all is well, all that remains is to refit chassis to the body, although in my case, I also had more work to do to fit "Kadee" couplings, making a slot immediately below each moulded hook on the loco, and using Kadee 148's, secured as before with the body/chassis fixing screw at each end. With this done, all that remained to do was to fit the handrails and vac pipes from the sealed 'bag of bits' included with the model. Final pic shows all finished and ready to go.
    Keith.

    Attached files [​IMG]
     
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  9. paul_l

    paul_l Staff Member Administrator

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    Nice work Keith, maybe a J39 might appear on the wish list, at some time soon for Viccy Rd.

    Paul
     
  10. SRman

    SRman Full Member

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    Nicely done, Keith.
    I have done a few of these split chassis conversions, including the 04 diesel, plus a pannier tank, two Ivatt 2-6-2Ts, and two Lord Nelson 4-6-0s. As long as people do it methodically just as you have, all should go well. The most difficult parts are finding somewhere to attach the wires to the chassis halves, and finding somewhere to fit and hide the decoder.

    My advice is if you have a very sweet running split chassis locomotive, it is worth converting; if it doesn't run well to start with, don't bother. My early Standard 4 4-6-0 fell into that latter category - I decided it ran too poorly to bother with converting to DCC. A pity, as I did what I think was a good job of weathering it.
    :)
     
  11. Colin_W

    Colin_W Full Member

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    Nice job Keith, off to Elgin show this weekend I may be looking for something like this, so the split chassis holds no fear for me now. I can send it to you !!:twitch:
    Col
     
  12. Jim Freight

    Jim Freight Full Member

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    I've done a few split chassis including the Bachmann J39's, they are not too much of a problem but you do need to be sure that the loco is a good DC runner first.

    Mainline locos in particular can have two significant failings, split axle tubes (including early Bachmann versions) and disintegrating plating on steam loco driving wheels.

    Axle tubes, including gears are typically available new as 3rd party spares. e.g. Peter's Spares, but driving wheels need a scrap donor loco.

    Split tubular nuts not uncommon too, so salvage these from any locos that are otherwise a lost cause.
     
  13. AJS is a Red

    AJS is a Red Full Member

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    Hi Keith.

    Really useful how to guide. I’ve been given a DCC controller and will soon be converting my DC stock.

    One of my locos is an A4 “Sir Nigel Gresley”. This is a Bachmann model of the split chassis variety, it runs superbly on DC and had only been on display with it’s previous owner and therefore should be fine to convert.


    I must admit though that I’m absolutely petrified of dismantling it in case it doesn’t go back together right It’s my favourite Loco.:facepalm:



    I think I’ll tackle some of my Hornby locos first and come back to Sir Nige when I’ve honed my skills a bit more.

    Andrew.
     
    Last edited: Feb 9, 2020
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  14. Jim Freight

    Jim Freight Full Member

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    Unfortunately axle tube splits can occur whether used or not, a first clue is if a driving wheel rotates a little out from where should be and the valve gear starts to lock, split gear tubes can result in the same plus motor jam if the split goes all the way to the gear teeth which it did on one of mine. Luckily there are some 3rd party spares available, if you do need them beware that spares for Mainline and Bachmann versions of Mainline locos can be very different (axles cylindrical or square and numbers of teeth on the gears), Peter of Peter's Spares can advise.
     
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  15. AJS is a Red

    AJS is a Red Full Member

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    Thanks Jim.

    I’ll keep that in mind when I get around to doing the conversion.

    Andrew.
     
  16. Andy_Sollis

    Andy_Sollis Full Member

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    I’ve still got the 04 to do... blew the decoder last try... biggest issue is getting the red and black wires on the chassis.
     
  17. Jim Freight

    Jim Freight Full Member

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    I also use the screw tube head at one end to trap the wire against the chassis like Keith shows above for the screw end. Two points, I bare the metal of any blackening to expose the chassis metal and at the square tube end put a small notch in one face of the square head to pass the wire by it as clearance is restricted. Wire is made into a complete loop around the tube. Worked well for me and saves the difficult job of drilling and tapping a screw thread into the chassis metal or attempting to solder to it, which is very difficult without the correct solder and a high powered iron.
     
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  18. Andy_Sollis

    Andy_Sollis Full Member

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    The latter is probably where I went wrong!
     

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