Split chassis - what is it and why is it best avoided>

I was reading a model guide yesterday and it was singling out engines with split chassis as best avoided (with some, such as the Bachmann Lord Nelson, being decent despite said chassis).

Could anyone explain in what sense the chassis is split and why this is a bad thing.

(You can probably tell that my models have been gathering dust in the attic for the last fifteen years).

 

Split chassis are basically Bachmann models of a certain type where the 'metal block' containing the motor, gears etc can literally split in half when undone to gain access to the said parts.

I've heard people say they can be right bugger to fit DCC to (i only run DC), personally i find split chassis types to be BETTER runners than more recent 3 Pole jobs which tend to be jerkier in my experience.

 

I thought a split chassis was one where the left hand side of the chassis is electrically isolated from the right. It entails having axles that are in two halves and electrically isolated from each other. It does have the virtue of doing away with reed pick-ups at the expense of additional complication. Split chassis also have the disadvantage of being impossible to make with hand tools.

Regards

 

Orion is right. If the OP goes to the Servic section of the Bachmannn web site, he'll find a selection of the service sheets / exploded diagrams for various locos. Look at those for the Manor and Lord Nelson, both are split chassis and the diagram illustrates what a split chassis is perfectly.

 

Split chassis means what it says, a chassis in two halves, each half is insulated from each other and provides pickup for the motor. The motor sandwiched in between usually has two little springs on the contacts for providing power from both sides of the chassis.

Conversion is generally simple except for the Bachmann J39. The J39 split chassis takes up the whole loco body and you have to either put the decoder in the tender and have the thing permanently coupled or cut a pocket out of the metal at the front of the loco. The mazac metal Bachmann use will destroy hacksaw blades, drill bits, dremel cutting discs and more so it can a real pain to fit a DCC decoder to this loco.

Split chassis locos are best avoided because they can be a real pain to put back together at times. You can pretty much guarantee to get the odd one that will be a real pig to reassemble.

The fun comes when you put the thing back together after conversion the square spacers can be little so and so's to get to stay put in their holes and you usually find the insulating washers in between the two chassis halves have a habit of dropping out just as you are doing the screws up. Reassembly can cause some naughty words to be said. I had to make a jig up to get the spacers to stay put during reassembly.


If you haven't got the patience of a saint, then avoid a split chassis loco for DCC conversion like the plague.

 

Ive never had a problem with split chassis models, in fact when Mainline first introduced them in 1979 everyone hailed them as the best thing (far better than Airfix, Lima or Hornby).
Since then Bachmann (with Replica) continued with them.
With all Chinese made models (which now most of them are)... the problem isnt the chassis or the motor.. it's the quartering of the wheels.. if they are not sat right, the engine will subtly sway side to side.. and eventually at high speed the connecting rods with make contact... and the inevitable break occurs... but thats not unique to any one company.

Bachmann (or kader who makes them in China) is pretty unique in split chassis models most European and US models use a mainframe chassis with either a pod motor or a can motor.

 

Sounds like you have been lucky ADB988008.

Split chassis locos can be real pains to get back together after DCC conversion, plus the chassis problem with the J39 where you have to cut out a section of chassis to make a decoder pocket to fit the decoder into the body. The plastic used for the axles was also a problem as well particularly on the J72 with the driving axle being prone to breakage with age as the plastic used wasn't that good a quality for these in Mainline days.

I agree with you about quartering on them too.

Had quite a few of them in my old shop over the years when it was open.

If your looking buying a split chassis loco for DCC conversion, as a rule pass it by is my advice.

Thankfully Bachmann have taken note of the problem and a lot of older split chassis locos in their range are slowly getting new DCC ready chassis but there are still some in the range including the B1 which need updating to the modern era of DCC Ready.

 

With split chassis the easiest is to hack a bit out then use a bit of card to sit in the space and place the DCC Chip to sit on this, black tape around the motor to separate the "live" connection and run a wire from the chassis to the DCC and the DCC to the motor.. all in a days work.


In history my worst two ready to run models for trying to dissasemble and rebuild are both Airfix.. the Airfix Royal Scot splitting the motor to parts fully and trying to reassemble required the skills of a contortionsist's fingers.. and second to that is the Airfix 14xx.. those sprung pickups were just a step to far for their day... though Ive had some interesting days with some kit built stuff too. Hornby's pacer wasn exactly a nice one for harmony when produced I got a knack of through wiring these and removing a useless motor (I'd re-use them in Airfix kit railbuses).

 

I totally agree the conversion is easy, but hacking the metal out on the J39 is a real pain, the metal blunted two junior hacksaw blades and broke a cutting disc on the last one I did. There is a space at the front of the chassis where you can create a decoder pocket, once you have got the metal hacked out the rest is easy peasy apart from putting it all back together that is.

After removal of the motor springs that make the contact for the motor to the chassis, I run the two motor control wires to the motor contacts, these are insulated by heatshrink from the chassis and adjusted a little to fit the chassis, a channel is cut so the wires can exit the chassis, the power feed wires to the decoder are soldered to the chassis at the front of the decoder pocket cut out using a 140 degree melt solder and a beefy iron.

Easy bit done, then you then spend a couple of hours swearing as the thing refuses to co-operate in reassembly...lol.

It's just the cutting of the chassis metal on some models and the reassembly on split chassis locos that is a real pain.

The Airfix Royal Scot is indeed fun to put back together that's for sure ADB68008. Funny you should mention reusing the motor of a Hornby pacer in the Airfix Railbus, I have just fitted a Hornby class 58 motor which is more or less the same to my ex-Airfix Railbus, they are perfect for the job.

Split chassis locos are best left on the shop shelf or toy fair stall in you want DC. The patience of a saint at times is required.