Forum Options

« Back to Engines and Rolling Stock Topics

Sign In above to begin adding replies.
 

External electric power

HauteSaoneFrance

Joined: 2-01-14

Topics: 27

Replies: 91

Posted: Thu 10th Jul 2014, 7:03pm
External electric power

Having spent some time cruising Inland waters in France (my other love)I have often come across electric locomotives used for hauling barges through long tunnels though those loco's now seem to be no more than exhibition pieces, I'm not sure how they received their power possibly overhead? The thought did occur to me if it was possible to do a 'third' rail for power to 7.1/4 like the London underground which is often 'overground' too plainly not at high voltage but would say 24 volt be possible, has it ever been tried and is it feasible? Hope this is not too silly a question
 

Replies To This Post

Peter Beevers

Joined: 9-10-01

Topics: 3

Replies: 134

Posted: Thu 10th Jul 2014, 10:15pm

London Underground is not 3rd Rail, it has 4. One (I never remember which) is +450v, the other -150v giving a PD of 600 volts. Doing it this way (rather than just a 3rd rail) saves any issues with immunisation against track circuits.
 

WembleyLion

Joined: 1-01-87

Topics: 2

Replies: 34

Posted: Fri 11th Jul 2014, 8:02pm

Peter,

After poking the outside rail with a damp stick when I was a kid I can confirm from the shock I received that the centre rail is the return rail and the outside rail is the live. You will notice that on the over ground sections the live rail changes from the left hand side of the track to the right hand side in the stations (the live rails from both tracks being side by side in the cess)

To answer the original question the only problem I see with using an overhead power supply on scale locomotives is getting the NHS to drill a hole in your chest to get the cable through.

John
 

colinedmondson

Joined: 9-08-09

Topics: 3

Replies: 82

Posted: Sat 12th Jul 2014, 6:45pm

Paul Middleton of Ride-on-railways is doing quite serious development on the use of supercapacitors. Weight for weight I don't think they have the same capacity as lead acid batteries, but they can be charged at very high rates. This lends itself to having a third rail just in the station, so that the capacitors are charged as the passengers are detraining and loading.
 

Richard_Langford

Joined: 1-01-70

Topics: 10

Replies: 37

Posted: Sun 13th Jul 2014, 8:20am

Interesting to hear what Paul is doing. It is an idea i like (super capacitors). Computers have been using caps instead of batteries for the bios memory for a long time now with a fantastic success rate.

 

George

Joined: 27-01-10

Topics: 0

Replies: 20

Posted: Sun 13th Jul 2014, 6:00pm

Hi Richard,
I don't if you've seen it on the Ride on railway website (newsletter), but the capacitors in the loco are, in my maybe not so humble opinion, are incomparable to the tiny thing used in a computer. Also quite visible in the pictures are the safety precautions. Batteries can be dangerous with the amount of current they can deliver, but the instantanious current of a capacitor is even higher. That being said I think the idea is marvelous. However I wonder what would be needed in a seven and a quarter loco of the size of a Titan (not RoR) with 2 750 Watt motors on a track about a mile long with 4 cariages and a compressor for airbrakes. And what of a resistor to keep the start of the load current in check?
Many regards,
George
 

George

Joined: 27-01-10

Topics: 0

Replies: 20

Posted: Sun 13th Jul 2014, 8:33pm

Hi Richard,
I don't if you've seen it on the Ride on railway website (newsletter), but the capacitors in the loco are, in my maybe not so humble opinion, are incomparable to the tiny thing used in a computer. Also quite visible in the pictures are the safety precautions. Batteries can be dangerous with the amount of current they can deliver, but the instantanious current of a capacitor is even higher. That being said I think the idea is marvelous. However I wonder what would be needed in a seven and a quarter loco of the size of a Titan (not RoR) with 2 750 Watt motors on a track about a mile long with 4 cariages and a compressor for airbrakes. And what of a resistor to keep the start of the load current in check?
Many regards,
George
 

Richard_Langford

Joined: 1-01-70

Topics: 10

Replies: 37

Posted: Mon 14th Jul 2014, 11:27am

Hi George. I realise that the size and power of the caps will be vastly different from those in PC's. I was just using the example as they have been such a success on PC's. So much so that i have never had to deal with a faulty cap on a PC but have binned plenty of motherboards because of damage caused by leaky batteries.
 

George

Joined: 27-01-10

Topics: 0

Replies: 20

Posted: Tue 15th Jul 2014, 6:32pm

OK Richard, in that comparison your quite right. In my profession though with the same kind of capacitors I have seen plenty fail. And they to can make quite a mess. My earlier question regarding charging still remains. Maybe I'll try on Facebook. I've seen a posting there to.
Many regards,
George
 

ivanhewlett

Joined: 1-01-85

Topics: 8

Replies: 53

Posted: Tue 15th Jul 2014, 7:01pm

Hi All
I think capacitors are an interesting technology, but having witnessed large electrolytics explode in the past I would like to see them in use for a while before trying them myself.
However on the subject of a third rail, I know I have seen a photograph of what I think was a 10 1/4" line, perhaps in Essex, that was running in the 1980's apparently using a side rail pick up shoe. There is a post on miniaturerailwayworld.co.uk somewhere about this, so it is possible. And of course there is the chap who runs electric trams in 7 1/4 I think on the Isle of Wight using an overhead supply (and no holes in his chest to my knowledge) there is an article in an old News about this somewhere too.
All things are possible ;-)

Cheers, Ivan
 

HauteSaoneFrance

Joined: 2-01-14

Topics: 27

Replies: 91

Posted: Tue 15th Jul 2014, 7:42pm

Hi Ivan, Being a 'Newbie' on here and not technically qualified I didn't dare to question the 'thread drift' away from my original question i.e, is it possible to power loco's with an electrical supply picked up from the rails rather than onboard? I'm quite intrigued as to how the French tunnel hauling locos received their energy, I think it was by overhead pickup? I'm assuming that such as TGV's nowadays gain their power from a single overhead very high voltage ac supply (from the National grid) and then invert to DC onboard? My real question was whether it is possible to run 7.1/4 with a system similar to London underground but for safety only 24 or 36 volt, or even have an overhead supply but also operating at a safe voltage?
 

ivanhewlett

Joined: 1-01-85

Topics: 8

Replies: 53

Posted: Tue 15th Jul 2014, 8:41pm

Hi HSF
Yes threads do tend to drift on this site, the absence of moderators probably playing a part.
I am sure that either third rail or overhead is perfectly possible - though I have never tried either personally. But why not ? 24 or 36 volts is reasonably safe, there is no reason why the supply line cannot be protected with an MCB of course.
The third rail pickup would need some careful thought to achieve the flexibility needed to follow the rail, but overhead could - and I believe is - achieved using trolley pole style collectors. Perhaps someone else can shed more light ?
Cheers, Ivan
 

WembleyLion

Joined: 1-01-87

Topics: 2

Replies: 34

Posted: Tue 15th Jul 2014, 9:47pm

Ivan,

The 10 1/4" line was at Maldon in Essex near to the riverside boating lake/paddling pool.
There are 15" gauge, I think, trams running at Betwys Coed and Cardiff alongside their 7 1/4" gauge tracks; I think they run on 50 volt dc.
The 2ft 3" gauge Volks Railway at Brighton, Sussex runs on 90 volts dc 3 rail and has done since 1896.
Most, if not all, fairground Ghost Trains run on 3 rail track at 110 volts dc.
Plenty of voltages here to chose from and with a Residual Current Device in circuit, should you use alternating current with any of these voltages, all should be relatively safe.

John
 

ivanhewlett

Joined: 1-01-85

Topics: 8

Replies: 53

Posted: Wed 16th Jul 2014, 8:31am

Hi All

Thanks John, you pointed me in the direction of this link:
http://s9.zetaboards.com/MRW_Forums/topic/97874/1/

A couple of pictures here, showing the third rail pickup, and a bit of history too, it seems it was 110V third rail - exciting stuff :-)

Cheers, Ivan.
 

WembleyLion

Joined: 1-01-87

Topics: 2

Replies: 34

Posted: Wed 16th Jul 2014, 8:11pm

Ivan,
Pleased to be of help.

Just a thought, using a higher voltage would help overcome any problems caused by dirty rail or pickups; remember the problems with 12 volt O gauge tracks in the garden.

There are plenty of 110 volt ac motors that can be robbed from old construction site equipment and isolating transformers to be had on eBay for not a lot of money. If these were used with a Residual Current Device this would probably be the safest and should give the least contact problems between rail and conductor.

I have corrected my previous post as RCD's don't work on dc circuits. (I think I am right in saying that)

John
 

George

Joined: 27-01-10

Topics: 0

Replies: 20

Posted: Wed 16th Jul 2014, 8:18pm

Ok, back on topic. A friend of mine here in Holland had a very small there and back in his garden with an overhead line. However he didn't ride behind it rather more like model railway where he controlled from the side of the line. So yes it is possible
With what you describe a third and maybe fourth rail should be your best bet. With the amount of power required the higher the voltage the better, however with higher voltages comes more danger. You will need quite a bit of current, to avoid large losses I would advice a good conductor. With copper being far to expensive for something like this you could look at aluminium. I do wonder if what you have planned is really feasible. With the power requirements and safety issues it is starting to sound daunting to me.
Best of luck.
George
 

WembleyLion

Joined: 1-01-87

Topics: 2

Replies: 34

Posted: Mon 21st Jul 2014, 8:47pm

The conductor material is important but even more important is the transmision losses over the length of the cable; commonly known as 'Volt Drop'.

The longer the cable and the higher the current the greater the volt drop.There are tables that can be used to determine the losses of standard electric cables. They are quite easy to use, the basic formula being 'Volt drop = IR' I being current through object measured in amps multplied by R being resistance of cable in ohms.

To find current simply divide watts by volts to give amps. Resistance tables for common cable sizes can be found on the internet.

To give some idea of what is involved I will show an example and I will use 16mm/2 cable.
This stranded copper cable is just under 5mm in diameter and has a resistance of about 1 ohm per kilometer.

A 1 horsepower motor, regardles of the voltage, is 750 watts; divide by 110 volts = about 7 amps; divide by 12 volts gives nearly 63 amps

Using a cable 100 meters long and assuming that the loco is at the end furthest fom the supply and that it needs the full 1 horsepower to get the train started then it will see a drop of around 1.5 volts for the 110 volt supply and around 13 volts for the 12 volt supply; clearly 12 volts is totally unsuitable.

I have not seen any info. on the electrical resistance of steel cable or bar so I can not comment on the use of steel as a conductor.

Another thought; 110 volt isolating transformers have a centre earth which means that voltage from conductor to earth is 55 volts but between conductors is the full 110 volts; if an RCD is fitted any shock received will only be for 30 milliseconds.

Hope this helps.

John
 

WembleyLion

Joined: 1-01-87

Topics: 2

Replies: 34

Posted: Wed 20th Aug 2014, 8:02pm

You might be interested in this YouTube video of narrow gauge electric locos in a Chinese coal mine. There's some sparkling video here; note the pantograph pick-up (in the first minute), no Nanny State H&S regulations here .

http://www.youtube.com/watch?v=WEpeQiKOjfs

John
 

WembleyLion

Joined: 1-01-87

Topics: 2

Replies: 34

Posted: Wed 20th Aug 2014, 8:50pm

And you don't even need a pantograph pick-up in Albania or a speed control, for that matter.

http://www.youtube.com/watch?v=unhXEQQk8G8

John
 

philashworth

Joined: 1-01-93

Topics: 0

Replies: 4

Posted: Mon 25th Aug 2014, 8:41am

Just came across this thread so excuse me if I am teaching grandparent persons to evacuate ovoids....

This has effectively been done fifty years ago with the Triang Minic railway system 10.25" gauge , some of which were used commercially. It was , in effect, an up-scaled version of 00 gauge picking current up from the track.

There is great interest in them now and although some have been modified to run off on-board batteries I did drive a track supplied orignal and there is certainly plenty of power there.

"Track power is supplied by a 35v 20amp trackside transformer and with attentions turning to the commercial market, the twin motored locomotive, with internal (T.M.N.R.3) and external (T.M.N.R.4) control was developed giving 1½ hp supplied by a 35v 40amp transformer. "

For more info...
http://www.tmnr.co.uk/his.htm

 

George Coles

Joined: 4-08-09

Topics: 19

Replies: 90

Posted: Mon 25th Aug 2014, 3:43pm

Hello Phil

Re: TMNR. There were some interesting responses after I posted a picture. Go to http://www.sevenandaquarter.org/forum/?/Miscellaneous+Topics+/Modelling+in+N+gauge+or+00+gauge/&cat=7&topic=464&action=view_topic
and scroll down the page.
Best wishes
George Coles
(running the TMNR track as it was designed - no jumpers; no wire brushing!)
 

George Coles

Joined: 4-08-09

Topics: 19

Replies: 90

Posted: Mon 25th Aug 2014, 7:55pm

Hello Phil

Re: TMNR. There were some interesting responses after I posted a picture. Go to http://www.sevenandaquarter.org/forum/?/Miscellaneous+Topics+/Modelling+in+N+gauge+or+00+gauge/&cat=7&topic=464&action=view_topic
and scroll down the page.
Best wishes
George Coles
(running the TMNR track as it was designed - no jumpers; no wire brushing!)
 
 
« Back to Engines and Rolling Stock Topics

Web design by Slingshot