| Re: OTD - 27th January (1910) - Trams not able to run because of snow Posted by stuving at 18:54, 27th January 2022 |      |
This G-B system was the one where the studs were flush with the road until the magnet pulled them up, making them live via an internal switch. So when the alarm bell rang to indicate a stud was still live behind the "skate", the driver was meant to bop it on the head with a rubber mallet. Being London, there is more about this then other installations - such as this quite detailed report.
That's wrong - one merit of the system was the greater ground clearance of its skate, and the studs were at or below ground level, but didn't move. The skate was made of a row of blocks hung from springs and were pulled down onto the stud. A rubber hammer was still involved, to make the the armature under the stud pull back into its "off" position.
| Re: OTD - 27th January (1910) - Trams not able to run because of snow Posted by stuving at 12:48, 27th January 2022 | |
The stud contact system was also used to power trams in London.
It was expensive and unreliable.
It was expensive and unreliable.
The main ground pick-up system used in London was conduit - lots of it, in use through to closure. Studs were chosen where the local council refused to allow overhead wires, because it was much cheaper than conduit. There were several systems, and while others were given limited trials (e.g. off-road) in London, only the Griffiths-Bedell system was chosen for a real installation on the Mile End Road. It worked for 23 days - so not a success, but politics had almost as much to do with that as practical experience.
This G-B system was the one where the studs were flush with the road until the magnet pulled them up, making them live via an internal switch. So when the alarm bell rang to indicate a stud was still live behind the "skate", the driver was meant to bop it on the head with a rubber mallet. Being London, there is more about this then other installations - such as this quite detailed report.
From my copy of Simmons's book, the main systems used in Britain were:
Lorain (Brown) - Wolverhampton
Dolter - Paris*, Torquay, Hastings (plus Mexborough and Swinton)
G-B - Lincoln, London (briefly)
*Diatto was the main Paris system, and Simmons may have got that wrong. I think it was used in Brussels too. But both had mainly conduit where wires were not allowed.
On conduits, Brittannica (1911) says:
Overhead conductors will not be tolerated in some cities, and to avoid the use of them open conduit and surface contact tramways have been introduced. In the conduit system the conductors are carried in a conduit or tube beneath the surface of the track, and the electric current is picked up by means of a plough carried by the cars.
Modern conduit tramways are divided into two kinds: those which have the conduit at the side under one running rail, and those which have it under the centre of the track. The only example of the former to be found in England is at Bournemouth, but it is used at Vienna, Brussels, Paris, Berlin and Budapest. Centre conduit construction has been adopted in London, Nice, Bordeaux, New York, Washington, &c.
The advantages of the side slot system are the reduction in the amount of metal in the roadway, less breaking up of the pavement, and slightly cheaper cost of construction. lts chief disadvantage is the difficulty it introduces in' connexion with points and crossings. It is also objected that if the side slot is made the same width as the rail groove it becomes a danger to narrow-tired vehicles. The difficulty in regard to points and crossings is overcome by bringing the slot into the centre of the track at junctions and turn-outs.
Modern conduit tramways are divided into two kinds: those which have the conduit at the side under one running rail, and those which have it under the centre of the track. The only example of the former to be found in England is at Bournemouth, but it is used at Vienna, Brussels, Paris, Berlin and Budapest. Centre conduit construction has been adopted in London, Nice, Bordeaux, New York, Washington, &c.
The advantages of the side slot system are the reduction in the amount of metal in the roadway, less breaking up of the pavement, and slightly cheaper cost of construction. lts chief disadvantage is the difficulty it introduces in' connexion with points and crossings. It is also objected that if the side slot is made the same width as the rail groove it becomes a danger to narrow-tired vehicles. The difficulty in regard to points and crossings is overcome by bringing the slot into the centre of the track at junctions and turn-outs.
| Re: OTD - 27th January (1910) - Trams not able to run because of snow Posted by grahame at 06:40, 27th January 2022 | |
We have been here before you know - most recently when "here" was Nice. I thought there were some other places the topic had come up - either for trams alone or the same idea on trains - but can't find any now.
Thanks for that linkage - there is indeed "nothing knew" and the knowledge and memory of our members is so valuable in joining up our knowledge base!
| Re: OTD - 27th January (1910) - Trams not able to run because of snow Posted by broadgage at 05:32, 27th January 2022 | |
The stud contact system was also used to power trams in London.
It was expensive and unreliable.
A magnet mounted under the tram turned on the power to each stud. The power was collected via a skate supported on springs under the tram so as to make a sliding contact.
Sometimes the power was not turned on and progress thereby delayed.
Sometimes the stud remained live which could kill pedestrians or horses. To reduce the risks, an extra "detecting skate" was fitted at the rear of the tram, if this passed over a still live stud a warning bell alerted the driver who was instructed to stop and affix a rubber cover over the still live stud. By the time the driver reacted, stopped, and alighted to affix the insulating cover, the tram would have moved some yards. Any pedestrian crossing the road behind a departing tram was at risk. In wet weather the road surface near a live stud reached a dangerous voltage. A following tram was liable to dislodge the insulating rubber cover, with potential fatal results for horses and persons. Surviving humans and horses learned to avoid stepping on the studs.
Unreliable and dangerous, soon replaced by overhead wires.
I doubt that anything similar could be used on conductor rail routes. Too complex and expensive, and still some risk of electrocuting trespassers.
Better in my view to use battery power for short gaps in existing conductor rail electrification, and 25 KV overhead for longer gaps. Dual voltage stock is readily available.
| Re: OTD - 27th January (1910) - Trams not able to run because of snow Posted by stuving at 00:34, 27th January 2022 | |
We have been here before you know - most recently when "here" was Nice. I thought there were some other places the topic had come up - either for trams alone or the same idea on trains - but can't find any now.
| OTD - 27th January (1910) - Trams not able to run because of snow Posted by grahame at 20:20, 26th January 2022 | |
From Wikipedia and https://www.tramwayinfo.com/trampostcards/Postc102.htm
The town council of Torquay did not want their seaside resort disfigured by the poles and overhead wires of a conventional electric tramway and so invited the Dolter Electric Traction Company to construct a tramway using their stud-contact system.
A conductor cable was laid in a trench between the rails. At 9-foot (2.7 m) intervals a box was fitted between the rails that contained a stud (which protruded about 1 inch (25 mm) above the road) and a bell crank. A magnet on a passing tram attracted this crank which then moved to make contact between the conductor cable and stud; once the tram moved away the crank dropped away and the stud was no longer connected to the cable. A long skate was suspended beneath each tramcar which was magnetised by electro-magnets and so both operated the cranks and collected the current that both moved the tram car and powered the electro-magnets. A small battery was carried to charge the electro-magnets should the power be interrupted. The negative return current passed through the rails.
[snip]
On 27 January 1910 a snow storm stopped all the trams as they couldn't make contact with the studs
A conductor cable was laid in a trench between the rails. At 9-foot (2.7 m) intervals a box was fitted between the rails that contained a stud (which protruded about 1 inch (25 mm) above the road) and a bell crank. A magnet on a passing tram attracted this crank which then moved to make contact between the conductor cable and stud; once the tram moved away the crank dropped away and the stud was no longer connected to the cable. A long skate was suspended beneath each tramcar which was magnetised by electro-magnets and so both operated the cranks and collected the current that both moved the tram car and powered the electro-magnets. A small battery was carried to charge the electro-magnets should the power be interrupted. The negative return current passed through the rails.
[snip]
On 27 January 1910 a snow storm stopped all the trams as they couldn't make contact with the studs
Wikipedia goes on to talk about the various issues with the system, but could this not provide a future solution for the people of Bath, even though they had trams with overehead collectors in the past? Is there scope for third rail lines to be only energised as trains pass over them, and could that somewhat help the safety case for (for example) electric trains from London to Salisbury?
