What chip to use? And how to wire the pantograph?

[Multiple identity account]

Hi,

What is the best DCC chip to use for an O scale locomotive? The model is to have 2 motors (from abcgears) and needs to have individual functioing (raising and lowering) single arm pantographs. So which DCC chip is best suited for this?

Also is there a "How to" document anywhere to help assemble a working pantograph?

Cheers!

[Adrian Wintle]

Initially wire the loco for DC operation.

 

Start by working out how much current the motor(s) draw under load and at stall*. This will give you an idea of what current capacity the decoder will need. Then determine how many individually controlled lights you will have and add two (for the pantograph controls). This will give you the minimum number of functions you will need. This will give a much better idea of what decoders will be suitable.

 

* Put an ammeter in line with a DC feed. Set the controller to 12V, Run the loco. The value on the meter will be the normal operating current. Then push down on the loco so the wheels momentarily stop turning and watch the meter at the same time. The peak reading on the meter is the stall current.

 

Adrian

[Dagworth]

Pantographs (pans) need a wide range of vertical movement to enable them to follow the wire height (high->low, station->over-bridge) and the same applies (and to an even greater extend) to models of them. The up-movement is fairly simple and follows prototype practice: a spring raises the pan to the wire. Getting it down requires a different approach: in order to retain the flexibility there must not be a direct mechanical link between the pan and whatever operates it. The only thing this operative must do, is force the pan down on command. The easiest way to do is by servo: it has 2 defined end positions, one for raising the pan and giving it the freedom to move and the other will push the pan down. (no pull, pulling implicates the forbidden direct mechanical link!) Alternative methods include, but not limited to, a 'walking nut' style motorised control system and memory wire. Theoretically a single-coil solenoid can also be used, but that is "quite brutal" in the movement of the pan.

Alternatively you could use a linear servo and arrange it such that the spring that raises the pan is attached to the servo so that when the servo goes to the raised position it brings the spring into tension to raise the pan.

DCC mobile decoders are now available that will control servos onboard locos.

 

That said, this is done with memory wire

https://www.youtube.com/watch?v=wqV7Q16DiSs#t=67

 

Andi

[Phil S]

LGB electric locos have often included working (as in remote controlled / automatic raising and lowering of the pantograph head - optionally with the rearmost or both raised (for example - when shunting, having it 'automatically' on the rearmost pantograph results in a constant swapping over!!

Those I have examined have used a single motor per head, which is basically, as per prototype, sprung to raise itself 'as far as possible' - the motor effectively controls the 'limit' of how far it is free to rise .... from 'not at all' to 'full height'.  Motor drive for up and down required opposite polarity drive during the move.

 

I have created my own version of these, for some other LGB locos which had only 'manual' pantographs - by using 'surplus' Fulgarex Slow Motion Point motors - as these contained both the required geared drive and integral end-off switching  ( as an add-on to the Manual LGB components ).  The Fulgarex mechanisms might be a bit too large for 0 gauge though.

 

The Roco DB E10.292 H0 electric loco matches LGB in having operating pantographs with sound - obviously on a servo-controlled system which models the 'bounce' of the contacting pantograph.

 

As, in digital oepration, the Catenary will NOT be powered - its not technically required in tunnels or storage areas.  In the garden, the wires would create a problem when cleaning the track / accident hazard.  In this case, and in all scales where overhead wire is discontinuous, it can be advantageous to physically limit the pan height to just below 'the wire' height - we do this with thin cord such as used for stringing beads - but a servo-controlled assembly could have this programmed in.

 

Many people run with the pantographs down - and this applies even to still photographs in Railway Modeller !! - there is always an increased risk of 'accident' with them raisd from unexpected overhead obstructions causing trains to come to a sudden stop - usually ripping off or damaging the pantograph itself.