Live catenary



cosmetic.
To be honest I think it is rather helpful. It is one of those things that sounds like a good idea and makes a great intellectual challenge to work out how to do it, But in reality you can not see electricity flowing though the pantograph. No observer would know how a model is powered from just looking at it. Yes, you will know it is really working and probably feel proud of what you have achieved but ultimately it will be more work than the end result justifies. So just go with a cosmetic system and don't worry about it.
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Gandalph wrote:

To be honest, it's not.

You can't see electricity flowing through the wheels either. If what you could and couldn't see mattered, nobody would have used that new fangled electricity in the first place when modellers already had clockwork and steam.
Cheers David
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David Bromage skriver:

Yes it is.
If you want the loco to detect what rail (left or right) is used with the voltage an the catenary on a analog set you need to detect either a short circuit og on the voltage.
If you like to detect a short circuit (this short circuit is between the catenary and one of the rails, unless you want to drive it by 2 seperate transformers). This detection circuit needs a power supply - and can be done by mounting a battery inside the loco.
You can allso detect on the voltage, but if you like to run the setup with 2 different transformers for either catenary and "2-rail" it is impossible to do. If you only run on 1 transformer for alle it is not quite impossible, but again the "detection circuit" needs to be powered somehow.
To power the detection circuit (unless you want batteries) you need the pantographs to be the one og the supply lines and one of the tracks to be another. So you mount 2 resistors between the wheel pickups, the resistors should be big enough (ohms) to not load your trnsformer to mucht, but small enough to still be able to power your circuit. When the power for the circuit is done it needs to be rectified , stabellized and regulated to a low voltage. On this low voltage you hook up a uP that detects where the power is coming from and controls a "switch" that chooses which wheel pickup that sould power the motor.
Klaus
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"Klaus D. Mikkelsen" skriver:

-cut-
David - any comments ?
Klaus
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David Bromage skriver:

David...................
Klaus
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David Bromage wrote:

Hi David,
Quick first thoughts: Yes, it should be possible. What would the on board electronics detect: - left rail to right rail: Traction current A. - left rail to overhead: Traction current B. - right rail to overhead: Nothing or A+B or A-B. (0v to 24v)
Obviously "common return" wiring isn't going to be feasible because no one of the three conductors is common. Both rails would have to be cut for each block and both would need to be switched . (Double pole switches rather than the normal single pole)
You'd need two in-loco modules/relays that connected the motor (to rail) when rail to overhead current was detected, probably a relay with a capacitor to give some delay to allow for intermitent current collection. A second relay contact would cut out the other relay coil so both relays couldn't be on together. The whole module would cost less than 5 pounds per loco, but you'd face the expense of the double pole switches compared to the single pole block switches normally used.
I think that covers it all.
Greg.P. NZ
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Greg Procter wrote:

A small but vital point, I use PWM controllers, so there's always 12 volts available in combination with a capacitor for lights, or in this case the relays.
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wrote:

I've got a Hornby class 86 locomotive with pantograph which can run from catenery or the rails. There's a slide switch in the roof to select which power source to use. I've never tried overhead power through as I could never find a supplier of a kit (and didn't fancy building it all myself from scratch!)
I'm sure you could do something clever with electronics to automatically detect which power source to use but as others have suggested much simpler solutions I wouldn't go down that route unless you fancy doing it for the sake of it.
peter
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On Wed, 6 Feb 2008 20:34:22 +0000, naked_draughtsman wrote

Was this model comptemporaneous with Hornby's own catenary kits?
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wrote:

I would keep the catenary cosmetic and go DCC much easier. I use Lenz and it is not reccomended to feed decoders via a pantograph and catenary as there could be a voltage spike resulting in a fried decoder. On the real railway current is returned via the running rails to the feeder or sub station. You cannot replicate this with variable polarised DC model railway current. regards, Steve
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May I ask why not. The only benefit i can think of is having sparks flying off as loco goes round. May be better to work out how to get sparks seperately whilst using track for motive power.
Cheers, Simon
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If you do that, you need to put 25kV onto your overhead........But don't touch the wires when your trains are running..
Bevan
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