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Just did a search on trams in Paris and found this excellent series of artticles about compressed air trams https://www.tramwayinfo.com/Defair.htm . I had come across references to compresed air trams in early days(efg Wantage) but had not realised Paris has so many,and their relative success at the time.

As there are some drawings I may be tempted to do a 3D printed model, but main reason I dis initial search was that I wanted to do a 3D perspective model with Paris theme, and a metre gauge tramwould feature. Bending history a bit so I can have a 4 wheel tram and more modern bogie commuter trains in same model.

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Mékarski system. There was another site (that I can't find at the moment) that gave some excellent information including drawings showing the location of the compressed air stations and network of pipes. There was one in the rue Chanez in the basement of the block of flats next to our block. They were the only trams unaffected by the great flood of 1910.

 

The 'bouillotte' to warm the air back up was an interesting concept particularly as it was next to the conductor. Warm in the winter and extra-warm in the summer!!

 

Cheers,

 

Philip

 

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I had come across these trams but not such a large system as in Paris.  Compressed air was used a lot in small industrial locos, such a in coal mines, but wonder if it could make a come back for trams and trains. There are prototypes for compressed air cars, and from a safety angle would have thought compressed air was safer than hydrogen fuel cells.

What was the range for compressed air. I can see than leakage would have been a problem,less so thes days, and if it needs warming up, ther are probably some ways to do that easily these days.

Part of my philosophy is to build models of items from the past which might still be used today, in a slightly revised form.

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I don't know if you saw on the site (unless I recall incorrectly) the Mékarski tram weren't bi-directional. I don't remember the range or whether there was enough ummph to do from the Porte d'Auteuil to the centre of Paris, for example, and back or had to be recharged at each terminus. The French were very much into pneumatics as there was another system using air where clocks were kept to time from one central station in Paris.

 

I'm not sure whether such a tram system could make a come-back - electric is probably the way to go at the moment certainly in major areas - OLE  notwithstanding.

 

Cheers,

 

Philip

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They were not bi-directional and there were turntables at each end. There is a photo showing a tram being turned, using horse power.

As for compresed air now, there is work being done for cars. Problem with just using electrics is that it is not suitable for every location. Batteries are better than they used to be, but there is ronmfor alternatives. As with hydrogen fuel cells the cost of producing the compressed air has to be taken acount of.

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14 hours ago, Philou said:

 - electric is probably the way to go at the moment certainly in major areas - OLE  notwithstanding.

 

Cheers,

 

Philip

OLE need not be an issue. In central Seville, there is only OLE at each tramstop. The pantograph is raised automatically and recharges the battery. Then pantograph down as the tram restarts along a stretch of track without OLE. A very elegant solution for city centres.

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I think the link mentioned one set of bi-directional cars but they needed to duplicate the equipment that heated the air at each end.  

 

Possibly with modern insulation technology there would be better ways to keep the air warm than having to take on hot water or have a small coal fire in the cab.  

 

A salt mine in Cheshire has been converted into a large-scale compressed air energy storage, so it's competitive for some applications although obviously very different from a tram.  

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Duplicate post - please ignore.  

Edited by Edwin_m
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@Joseph_Pestell I had forgotten about Seville - saw that in October 2019 and it had completely slipped my mind. I was quite surprised at seeing it for the first time there. As you say - an elegant solution. In my home town of Cardiff, they've been trialling a similar thing using an electric bus (Volvo) that at recharging points, drops a 'pantograph' into a cut-out on the roof. The panto is doubled as there is no return to earth, the bus being on tyres. A fleet of 30-odd have been ordered following its success.

 

In China, where trolleybuses have returned, they run 'under the wires' in suburbia and on battery power in town avoiding knitting therein.

 

Cheers,

 

Philip

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8 minutes ago, Philou said:

 

 

In China, where trolleybuses have returned, they run 'under the wires' in suburbia and on battery power in town avoiding knitting therein.

 

Oddly enough, the reverse of the usual European practice which is to have wires for the busy urban stretches and run on batteries in the remote areas where wiring seems like an expensive option.

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The Irish battery train developed in 1930s using battery technology designed by Drum used a similar idea for recharging, but it took too long at intermediate stations,so tended to only be used at end of journeys. It took about a minute to recharge for each mile required. The Drum battery design evolved into what we now have.

There has been quite a lot work done using induction charging. OK when you can determine where the vehicle will stop, so easy for trainsand trams , but difficult for buses. Also finding space for batteries can be a problem in British buses, an I think was a small problem with the new Birmingham trams.

Just because an idea is old does not make it old fashioned . Think 20-30 years ago and tell people trams, and trolleybuses would make a come back, and they would not believe you. Compreseed air engines are being developed for cars, not sure how succesful, but should not be dismissed.

Edited by rue_d_etropal
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I think most of the battery charging in Seville is probably on the longer suburban sections,. the procedure at the city centre stops being just a top-up.

 

And then there is the Bordeaux system (stud contact in the city centre) which seems to work well now after initial teething problems.

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2 minutes ago, Joseph_Pestell said:

I think most of the battery charging in Seville is probably on the longer suburban sections,. the procedure at the city centre stops being just a top-up.

 

And then there is the Bordeaux system (stud contact in the city centre) which seems to work well now after initial teething problems.

again it is old ideas and methods that are being re-introduced.

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55 minutes ago, Joseph_Pestell said:

I think most of the battery charging in Seville is probably on the longer suburban sections,. the procedure at the city centre stops being just a top-up.

 

And then there is the Bordeaux system (stud contact in the city centre) which seems to work well now after initial teething problems.

 

1 hour ago, rue_d_etropal said:

There has been quite a lot work done using induction charging. OK when you can determine where the vehicle will stop, so easy for trainsand trams , but difficult for buses. Also finding space for batteries can be a problem in British buses, an I think was a small problem with the new Birmingham trams.

Just because an idea is old does not make it old fashioned . Think 20-30 years ago and tell people trams, and trolleybuses would make a come back, and they would not believe you. Compreseed air engines are being developed for cars, not sure how succesful, but should not be dismissed.

Another problem with induction charging is that it's not particularly efficient - not a problem for your toothbrush or phone but for a bus or tram it's quite significant.  The APS system as in Bordeaux actually has a live rail but it is split electrically into short sections, each of which is energized only when there is a tram sitting on top of it.  

 

Trolleybuses occupy a niche between motor buses and trams, but in some ways that niche is getting smaller and may be non-existent in many places.  At high passenger numbers they use more energy than a tram, with more obtrusive overhead, and cost more because they are smaller than trams.  They also have particulate emission from tyres, increasingly seen as a problem.  At low passenger numbers hybrid and battery buses are starting to get the same advantages of performance and no emissions (except tyres) on sensitive parts of the route, without the cost of overhead line.  My own belief is that the trolleybus is a technological dead end, except perhaps in very hilly cities.  

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There are experiments in catenary and pantographs on lorries to charge whilst moving on motorways in Germany. In effect an updated version of the trolleybus, which could work for a passenger vehicle, ie a trolleybus or trolley coach,maybe on short stretchs, or at stops.

Induction charging works well with cookers, and that must pull quite a big punch for power. Only negative is the effect it has on people with pacemakers.

Tyres and their wearing downis an issue, but lot of work is being done on 3D printed wheels and tyres. Thee is always going to be some eco impact, just have to get it as small as possible. Even walking wears down soles of my shoes, and there was one exhibition layout which was so long, the operators (jokingly) suggested putting in a claim for shoes wearing down!

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2 hours ago, Edwin_m said:

 

Another problem with induction charging is that it's not particularly efficient - not a problem for your toothbrush or phone but for a bus or tram it's quite significant.  The APS system as in Bordeaux actually has a live rail but it is split electrically into short sections, each of which is energized only when there is a tram sitting on top of it.  

 

Trolleybuses occupy a niche between motor buses and trams, but in some ways that niche is getting smaller and may be non-existent in many places.  At high passenger numbers they use more energy than a tram, with more obtrusive overhead, and cost more because they are smaller than trams.  They also have particulate emission from tyres, increasingly seen as a problem.  At low passenger numbers hybrid and battery buses are starting to get the same advantages of performance and no emissions (except tyres) on sensitive parts of the route, without the cost of overhead line.  My own belief is that the trolleybus is a technological dead end, except perhaps in very hilly cities.  

 

San Francisco now has bendy single deck trolley buses that hold a lot of people. 

 

Andy

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Compressed air is generally a very poor system for energy storage, because a lot of energy is expelled during compression (bicycle-pump effect - notice how hot one gets if you pump hard) and energy has to be input to prevent icing from atmospheric moisture during decompression (spray-can effect, and why the bouillette was necessary in the Mekarski system)

 

There are ways of capturing the losses during compression, but even the best aren’t mega-efficient, and there are always challenges around dehumidifying the compressed air.

 

All of which is why CA locomotion tends to be confined to very specialist applications, where CA is being made and used for other purposes, notably hard-rock tunnelling.

 

Its use as a transmission medium in vehicles comes with similar challenges, which is why hydraulic drives tend to be more popular in places where first inspection might suggest CA.

 

Deutz conducted a very good set of trials in the 1890s, comparing vehicle transmissions to go with internal-combustion engines, wherein they identified the flaws in using CA as a transmission for a locomotive, despite a very clever design that attempted to trap as many of the losses as they could, but that hasn’t stopped optimists trying it again periodically.

 

Storing energy for use on vehicles is probably best done at the moment using capacitors (short-term) and batteries (medium term), but there are several other technologies, flywheels etc, and a very interesting 10.25” gauge experimental loco was built a few years back by a team of trainee engineers, using hydro-pneumatic short-term storage.

 

CA or hydro-pneumatic storage can work-out as a way of buffer-storing energy in some applications however - things like wind or photovoltaic, where the demand is offset in time from the generation and losses are tolerable because the energy is ‘free’. In those circumstances it can sometimes work-out better than battery (no chemistry, and fewer rare materials involved), or pumped hydro storage (which itself isn’t always efficient or simple).

 

 

Edited by Nearholmer
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@Joseph_Pestell @rue_d_etropal I'll try not hi-jack the compressed air thread too much, just to say I'd been on the Bordeaux system in May 2019 and indeed the 'third rail' pick-up did work well. Nothing mechanical to be seen on the surface (quite safe to walk-upon - unlike some earlier stud-contact systems of the late 1800s/early 1900s - somewhat electrifying) other than there seemed to be a 'flap' at every alternate 1.5m section. I know not what it was supposed to be. I assumed (I haven't looked at the technical specs) that the section is energised only at the moment the tram passes over - much as the old stud system was energised by magnets as the tram passed over, raising the studs to make contact - trouble was the studs didn't drop back sometimes :blink:. Nice had that as a system that went as far as Monaco along one of the Corniches (the inter-urban stretch was by conventional overhead).

 

For a slightly whacky system : Line T6 just outside Paris (Chatillon - Viroflay) is a tram on rubber tyres - yes really - it's French of course. Single overhead wire with return via a steel wheel (un galet) running in a steel channel. This guides the tram (haven't been on it so I can't say if there is a conventional steering wheel or not). However, they spent an enormous sum on diverting services under the carriageway on the 'tram' alignment and narrowing the carriageway from four lanes to two to create a segregated corridor. They spent even more on a mile-long tunnel (tram only) going from Meudon to Viroflay which was unnecessary as the tyres would have coped with the hilly terrain. All because they didn't want to pay for the rails, they could have saved a good half of the money and had a conventional trolleybus by providing twin overhead and forgetting any diversion costs as the trolleybus is a good hill climber, completely flexible AND will work off battery power too. It really was a waste of public money in this instance. Moi!! Cross?! Non!

 

I was living there at the time and sent a written statement to the public inquiry expressing concerns over what they were doing and the (seemingly) unnecessary expense. I don't think it's been repeated widely in France as it has been proven costly to maintain, plus no environmental gain as a whole.

 

Cheers,

 

Philip

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5 hours ago, rue_d_etropal said:

 Also finding space for batteries can be a problem in British buses, an I think was a small problem with the new Birmingham trams.

 

The batteries are on the roof of each end car where one assumes supercaps are normally fitted for catenary free running.

IIRC the West Midlands Metro was the first occasion that batteries rather than supercaps were fitted to the Urbos 3 type of tram.

It seems to work well. Climbing Pinfold Street which I guestimate has a peak gradient of 1:7 seems effortless.

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2 hours ago, Andy Reichert said:

 

San Francisco now has bendy single deck trolley buses that hold a lot of people. 

But if you can make a trolleybus that size you can also make a diesel or battery bus the same, less only the marginal extra space needed for engine/batteries which can be above or below and many trolleybuses have that anyway.  Trams can be much longer (depending on route issues such as distance between traffic lights) and a bit wider.  Hence why a tram is more appropriate at high passenger numbers and has little advantage over engine/battery buses at lower numbers.  

1 hour ago, Philou said:

For a slightly whacky system : Line T6 just outside Paris (Chatillon - Viroflay) is a tram on rubber tyres - yes really - it's French of course. Single overhead wire with return via a steel wheel (un galet) running in a steel channel. This guides the tram (haven't been on it so I can't say if there is a conventional steering wheel or not). However, they spent an enormous sum on diverting services under the carriageway on the 'tram' alignment and narrowing the carriageway from four lanes to two to create a segregated corridor. They spent even more on a mile-long tunnel (tram only) going from Meudon to Viroflay which was unnecessary as the tyres would have coped with the hilly terrain. All because they didn't want to pay for the rails, they could have saved a good half of the money and had a conventional trolleybus by providing twin overhead and forgetting any diversion costs as the trolleybus is a good hill climber, completely flexible AND will work off battery power too. It really was a waste of public money in this instance. Moi!! Cross?! Non! 

This is the Translohr.  I sampled another route in northern Paris and I think there's a third one somewhere.  My impression was it was very cramped and rough riding.  A trolleybus might have been better, perhaps with electronic guidance, but an asphalt road carrying identical large vehicles following exactly the same path is prone to rutting so concrete tends to be used for any guided vehicle.  A proper high-capacity transport system also need segregated roadspace, probably with physical measures to prevent use by other vehicles, so the ability to change lanes is also less of an advantage than it first appears.  

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22 minutes ago, Edwin_m said:

 

This is the Translohr.  I sampled another route in northern Paris and I think there's a third one somewhere.  My impression was it was very cramped and rough riding.  A trolleybus might have been better, perhaps with electronic guidance, but an asphalt road carrying identical large vehicles following exactly the same path is prone to rutting so concrete tends to be used for any guided vehicle.  A proper high-capacity transport system also need segregated roadspace, probably with physical measures to prevent use by other vehicles, so the ability to change lanes is also less of an advantage than it first appears.  

Surely a guided battery/electric trolley bus would be a better bet as it could run off wire/off guide outside the central area like an ordinary bus?

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1 hour ago, Edwin_m said:

But if you can make a trolleybus that size you can also make a diesel or battery bus the same, less only the marginal extra space needed for engine/batteries which can be above or below and many trolleybuses have that anyway.

 

SFO currently runs both (D & E) with apparently similar bodies below the roof.  I think the trolley buses have a considerable power (and zero exhaust ) advantage on the very steep hills. I personally would not want to continue to purchase diesel technology, given the emissions issues.

 

Andy

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As an aside, ICL built a prototype line printer in the late 60's using low pressure air steering logic. The steadily falling prices of silicon chips made it redundant.

 

Andy

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Andy, that printer sounds interesting. I wonder if it survived. There is a new computer museum being set up in Manchester .

I used to work in IT, and came across a few old pieces of computer hardware still being used. By early possibly start of the 70s ICL had lost its print software team who had set up their own company in Oxford. They then wrote most of the print software , probably still being used as they were way ahead of anyone else. I worked for the company for a few years, but they were too far ahead of hardware development and that led to problems. Now hardware has caught up, but software has not progressed as much.

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