Hello All,

Until today, my understanding is that 3 rail must be AC, and 2 rail is DC. But today, I just learn that there is 3 rail DC as well. I know this from an ebay seller, I bought his Roco loco (my first purchase of non-Maerklin loco ), and he told me that this is 3 rail DC, and converting to AC is easy to do. I googled and found this https://www.marklin-user...operation/OP3raildc.html , but unfortunately, it is for analog operation, while my layout is digital.

So I would like to ask following question.
1. If I buy non-Maerklin loco, how do I know that this is 3 rail DC or 3 rail AC? what to look? what differences?
2. How to convert from 3 rail DC to 3 rail AC? well, the train is on long journey via DHL, so I guess it is hard to answer this question without some picture...
3. Can I run directly 3 rail DC loco (without any modification) on my digital layout using CS2?

BTW, its Roco 63422. From googling, I know that this is DC/GS loco.

Thank you.

BR,
Sony

to convert a loco from 2 rail into 3 rail is much easier, whether its AC or DC. for instance I sometimes buy 2 rail DC loco for my layout, instead of having wires coming from the wheel set (+ and - ) you combine these wires (track current) the free soldering pad is now going to be used for your either middle contact and overhead pantograph.

When buying a second hand loco be careful it has a DSS (digital circuit board) and it has either an eight pin plug or a 21 pin board, all you have to do is plug the digital decoder into it if it has already a decoder and it suits you you can leave it in.

Most Roco locos come either in 2 rail or 3 rail and you can recognize them by their number e.g. 62..., 63.., 72... or 68...,69..., 78.... buying a second hand 2 rail loco make sure they also make it in 3 rail and than you have to get the bottom assembly to convert it into 3 rail or you wait until a suitable 3 rail loco comes along instead of converting it and buying extra bits for it.

Also with Roco locos (with these numbers above and there are some who had a DSS before the numbers 62 and 69 came along e.g. 43...
the benefits are: new motor type, DSS and ready to be converted to your liking with minimal fuss.

buying Roco steam locos is a different challenge, (most electric or diesel locos can out pull a Märklin loco because of its driven axles on both bogies), the driving force is in the tender and sometimes 2 or 3 axles are driven, the weight ratio motor-weight of tender is to minimal to pull a descent load and one loco I have BR 18201 I've used 2 motorized tenders.
comparing a Märklin Steam loco with a Roco steam loco and if you want to get onto equal footing you most probably need 2 Roco steam locos for 1 Märklin one.

I've bought a diesel loco which to date hasn't come out in 3 rail [there is no assembly for to convert it into 3 rail (wiper)] but here one has again options, you can add a 4 pin Roco electrical coupling on one end and use a Märklin carriage (with wiper or the possibility to add a wiper) also converted it with a 4 pin electrical coupling.

there are a lot of people (manly ignorance and people who never owned a Roco loco ) who think Roco locos are inferior because of the fact the housing is plastic but there is one particular loco which has a metal housing on both ends, the Swiss Crocodile, the middle housing is plastic.

When buying a Roco loco always make sure how many axles are driven, there are exceptions whereas the loco only has on bogy with driven axles

John

Hi Mike,

3-rail DC is misunderstandable. On one side there is the TRIX-EXPRESS-System which is a 3-rail-DC-system using one outer rails to supply one loco and the other for a second loco. The center-rail is common ground. This system also used special wheels which are not compatible.
On the other side there is also another 3-rail-DC-system which was used for example in France: Two outer rails for ground and the the center-rail supplies the loco. This system was also popular in Germany before the digital era. TRIX made special versions for this system with Märklin-style wheels and a DC-motor. On loco which were originally delivered for 2 rail-system you must just mount a pick-up shoe and insert a rectifier and a pole reversing switch between the transformer and the layout and you can use DC-models and traditional Märklin side by side.

Regards

Markus