Calculating Cable Size
 

I am getting confused with regard to chosing cable for the bus in a dcc
model railway. Single strands of 1mm lighting cable with insulation
removed are what is used I understand. I have looked on the RS site and
they do tinned solid copper wire which is used for rewirable fuse links
which would also be ok for the bus so according to my calculation 29swg
is the nearest to 1mm.
Now apart from RS qoting the cable in AWG which would mean that I would
have to go to 25awg if my conversion is correct, I am confused because
the spec shows 29 swg having an operating current (at 35C) of 1 amp or
a fusewire rating of 10 amps.
What does that mean exactly? I had assumed that 1mm cable is good for
6amps so why is 29swg have an operating current of 1 amp or am I
failing to understand something here.

Kevin

Calculating Cable Size
 

Kev wrote:
I am getting confused with regard to chosing cable for the bus in a dcc
model railway. Single strands of 1mm lighting cable with insulation
removed are what is used I understand. I have looked on the RS site and
they do tinned solid copper wire which is used for rewirable fuse links
which would also be ok for the bus so according to my calculation 29swg
is the nearest to 1mm.
Now apart from RS qoting the cable in AWG which would mean that I would
have to go to 25awg if my conversion is correct, I am confused because
the spec shows 29 swg having an operating current (at 35C) of 1 amp or
a fusewire rating of 10 amps.
What does that mean exactly? I had assumed that 1mm cable is good for
6amps so why is 29swg have an operating current of 1 amp or am I
failing to understand something here.

Kevin


What causes a cable to be unusable is excessive voltage drop, or such a
high power to distance factor that it physically melts.

They are not the same thing at all.

I am not sure what a DCC model railway is, or what you use a bus for,
but I'd be inclined to wire the thing up with the fattest cable you can
lay your hands in that is physically possible.

Calculating Cable Size
 

The Natural Philosopher wrote:
Kev wrote:
I am getting confused with regard to chosing cable for the bus in a dcc
model railway. Single strands of 1mm lighting cable with insulation
removed are what is used I understand. I have looked on the RS site and
they do tinned solid copper wire which is used for rewirable fuse links
which would also be ok for the bus so according to my calculation 29swg
is the nearest to 1mm.
Now apart from RS qoting the cable in AWG which would mean that I would
have to go to 25awg if my conversion is correct, I am confused because
the spec shows 29 swg having an operating current (at 35C) of 1 amp or
a fusewire rating of 10 amps.
What does that mean exactly? I had assumed that 1mm cable is good for
6amps so why is 29swg have an operating current of 1 amp or am I
failing to understand something here.

Kevin


What causes a cable to be unusable is excessive voltage drop, or such a
high power to distance factor that it physically melts.

They are not the same thing at all.

I am not sure what a DCC model railway is, or what you use a bus for,
but I'd be inclined to wire the thing up with the fattest cable you can
lay your hands in that is physically possible.

DCC is digital command & control. basicly 16v ac is applied to the
tracks permanently and a signal is sent to a controlling chip in each
loco. I think that each loco is typically 1 or 2 amps.
The bus is the feeder to the track. A loop of two cables runs around
the underside of the model railway then every metre or so you connect
the bus to the track.

Uninsulated cable tends to be used because you can solder feed wires
wherever you like.

Kevin

Calculating Cable Size
 

Kev wrote:
The Natural Philosopher wrote:
Kev wrote:
I am getting confused with regard to chosing cable for the bus in a dcc
model railway. Single strands of 1mm lighting cable with insulation
removed are what is used I understand. I have looked on the RS site and
they do tinned solid copper wire which is used for rewirable fuse links
which would also be ok for the bus so according to my calculation 29swg
is the nearest to 1mm.
Now apart from RS qoting the cable in AWG which would mean that I would
have to go to 25awg if my conversion is correct, I am confused because
the spec shows 29 swg having an operating current (at 35C) of 1 amp or
a fusewire rating of 10 amps.
What does that mean exactly? I had assumed that 1mm cable is good for
6amps so why is 29swg have an operating current of 1 amp or am I
failing to understand something here.

Kevin

What causes a cable to be unusable is excessive voltage drop, or such a
high power to distance factor that it physically melts.

They are not the same thing at all.

I am not sure what a DCC model railway is, or what you use a bus for,
but I'd be inclined to wire the thing up with the fattest cable you can
lay your hands in that is physically possible.

DCC is digital command & control. basicly 16v ac is applied to the
tracks permanently and a signal is sent to a controlling chip in each
loco. I think that each loco is typically 1 or 2 amps.
The bus is the feeder to the track. A loop of two cables runs around
the underside of the model railway then every metre or so you connect
the bus to the track.

Uninsulated cable tends to be used because you can solder feed wires
wherever you like.

Kevin

In which case if this is actually distributing 'loco power' I'd make it
as big as you can get it.

16 gauge (1.6mm appx) tinned copper, or strip out some cooker cable,
whichever is cheaper.

Especially if simulating Hatfield with multiple locos :-)

Voltage drop goes down as the square of the diameter..

I assume you can hide it under track ballast an the like?

My, toy trains have come on since I played with them..sounds a lot of
fun.:-)

Calculating Cable Size
 

I assume you can hide it under track ballast an the like?
Normally the power distribution wires are attached to the underside of
the basebaord, and short 'dropper' wires run through holes in the
baseboard to the rails.

My, toy trains have come on since I played with them..sounds a lot of
fun.:-)

Indeed, even Hornby are joining in this DCC malarkey now ( see link) ,
those so inclined can hook up their DCC system to a PC and automate the
whole setup. Or go the whole hog and use Microsoft Train Simulator or
Trainz. ( but then you don't get to indulge in power tool therapy ;-)
)

http://www.hornby.com/pages/newreleases2007685_3.aspx