PatB Posted February 1, 2018 Share Posted February 1, 2018 OK, yes, I should have said ambient rather than atmospheric. Sloppy. However, pretty much every document I worked with where pressures were relevant stated, somewhere, whether figures were absolute or gauge. Nearly always gauge, but it wasn't universal as far as I can recall. Link to post Share on other sites More sharing options...
Jeff Smith Posted February 1, 2018 Share Posted February 1, 2018 If you are concerned about pressure vessel safety then gauge pressure is all you need because it indicates the differential between atmospheric, whatever that happens to be at the time, and the pressure in the vessel. Link to post Share on other sites More sharing options...
Pacific231G Posted February 1, 2018 Share Posted February 1, 2018 If you are concerned about pressure vessel safety then gauge pressure is all you need because it indicates the differential between atmospheric, whatever that happens to be at the time, and the pressure in the vessel. But safety valves are kept closed by springs acting against the internal pressure of the boiler or whatever so, depending on the design, wouldn't they tend to be actually measuring an absolute rather than a relative pressure even though they'll be set against gauge pressure? In practice differences in atmospheric pressure at or near sea level are likely to be at most a few percent compared with typical pressures in a boiler or pressure vessel. Anyone know enough about pressure gauge design to say whether or not they allow for changes in atmospheric pressure? Link to post Share on other sites More sharing options...
Jeff Smith Posted February 1, 2018 Share Posted February 1, 2018 But safety valves are kept closed by springs acting against the internal pressure of the boiler or whatever so, depending on the design, wouldn't they tend to be actually measuring an absolute rather than a relative pressure even though they'll be set against gauge pressure? In practice differences in atmospheric pressure at or near sea level are likely to be at most a few percent compared with typical pressures in a boiler or pressure vessel. Anyone know enough about pressure gauge design to say whether or not they allow for changes in atmospheric pressure? True enough but safety valves are presumably adjustable and can be set up to gauge pressure. As you say atmospheric pressure probably does not vary enough for a basically sea level operated loco to need constant re-setting. I have heard that railways operating up to considerable altitude, I'm thinking of the Andes in Peru, were operated much more efficiently with steam than diesel which requires some form of supercharging to get enough air into the cylinders. Link to post Share on other sites More sharing options...
RJS1977 Posted February 1, 2018 Share Posted February 1, 2018 But safety valves are kept closed by springs acting against the internal pressure of the boiler or whatever so, depending on the design, wouldn't they tend to be actually measuring an absolute rather than a relative pressure even though they'll be set against gauge pressure? In practice differences in atmospheric pressure at or near sea level are likely to be at most a few percent compared with typical pressures in a boiler or pressure vessel. Anyone know enough about pressure gauge design to say whether or not they allow for changes in atmospheric pressure? Presumably though atmospheric pressure will be acting on the other end of the spring in some way (unless it's in a vacuum). Link to post Share on other sites More sharing options...
RMweb Premium Andy Hayter Posted February 1, 2018 RMweb Premium Share Posted February 1, 2018 But safety valves are kept closed by springs acting against the internal pressure of the boiler or whatever so, depending on the design, wouldn't they tend to be actually measuring an absolute rather than a relative pressure even though they'll be set against gauge pressure? In practice differences in atmospheric pressure at or near sea level are likely to be at most a few percent compared with typical pressures in a boiler or pressure vessel. Anyone know enough about pressure gauge design to say whether or not they allow for changes in atmospheric pressure? The maximum extra pressure differential on a spring safety valve would be around 1 bar and then only if you sent the boiler and its safety valves into space - where I dare suggest the safety valve setting might be the least of your engineering problems. I would suggest that any safety system of this sort that became critical within a +/- 1 bar margin is probably not a safety system but rather a safety placebo. Link to post Share on other sites More sharing options...
RMweb Premium 45156 Posted February 2, 2018 RMweb Premium Share Posted February 2, 2018 (edited) Aren't we drifting a bit Edited February 2, 2018 by 45156 Link to post Share on other sites More sharing options...
Guest Posted February 2, 2018 Share Posted February 2, 2018 Aren't we drifting a bit Uh huh. The thread has pretty much drifted off about two days after each episode has been shown. I guess folk are just marking time until the next episode when we get the answer to the really big question... does Dick trim his moustache? Link to post Share on other sites More sharing options...
Hobby Posted February 2, 2018 Share Posted February 2, 2018 Or grow a beard... Link to post Share on other sites More sharing options...
Administrators Phil Parker Posted February 2, 2018 Administrators Share Posted February 2, 2018 Let's bring it back on track (Boom, tish) with a press release from the 16mm Society: Loco from “Britain’s Biggest Little Railway” TV series on display at National Garden Railway Show – April 7th Filmed during June 2017, “Britain’s Biggest Little Railway” aired on Channel 4 during January and February 2018, and in a series of five programmes chronicled the adventures of Dick Strawbridge and an army of volunteers as they built the World’s longest model railway, from Fort William to Inverness along the Great Glen in Scotland. The series used 16mm scale live steam motive power and we are delighted to have the star of the show - the “Silver Lady” locomotive built by Roundhouse Engineering, on display at the National Garden Railway Show along with some examples of the track used, and an exhibition of behind the scenes photographs. Some of the volunteers who built the line will also be on hand to talk about their experiences. The National Garden Railway Show presented by the Association of 16mm Narrow Gauge Modellers is the biggest event of its kind in Europe and is back at the Peterborough Arena for a seventh year with another packed programme demonstrating once more how the garden railway hobby continues to develop. Along with layouts new to the show and some favourites from the past, the show is particularly known for its strong trade support. Over 90 traders are expected including a number that are new to the show, and several that don’t trade online, so it’s the event where both experienced and new garden railway modellers can see and buy new products from their dream loco to that elusive component. Buy tickets online at www.nationalgardenrailwayshow.org.uk before April 2nd and save 15% on the on the door price of £10 for Adults. Under 18’s are free when accompanying an adult ticket holder. There is ample free car parking on site at the Peterborough Arena, and a shuttle bus from Peterborough BR Station – Adult £5 return, also available from the online ticket office. The National Garden Railway Show Saturday April 7th 2018, doors open 09.00, main exhibition 10.00 – 17.00 Peterborough Arena East Of England Showground (just off the A1) Peterborough PE2 6XE www.nationalgardenrailwayshow.org.uk www.16mm.org.uk 6 Link to post Share on other sites More sharing options...
RMweb Premium Mallard60022 Posted February 2, 2018 RMweb Premium Share Posted February 2, 2018 I'm glad all that talk of pressure has eased off as my bladder was starting to suffer. Sort of interesting but............. P 1 Link to post Share on other sites More sharing options...
hayfield Posted February 2, 2018 Share Posted February 2, 2018 For a program (which I really enjoy) which is designed for light entertainment viewing, which aimed at the masses, its quite interesting how seriously some are taking it Its not aimed at entertaining hardened railway modellers, just the average person seeking a bit entertainment at the end of the week, A program in lovely countryside and not seeing any one shot, blown up, or violated in any other way, or being indoctrinated by those with political or social views, in short a bit of harmless fun before bed What is interesting is seeing the pleasure/joy this little loco gives those who unexpectedly come across it, their faces just light up. 6 Link to post Share on other sites More sharing options...
Grasshopper John Posted February 3, 2018 Share Posted February 3, 2018 For a program (which I really enjoy) which is designed for light entertainment viewing, which aimed at the masses, its quite interesting how seriously some are taking it Its not aimed at entertaining hardened railway modellers, just the average person seeking a bit entertainment at the end of the week, A program in lovely countryside and not seeing any one shot, blown up, or violated in any other way, or being indoctrinated by those with political or social views, in short a bit of harmless fun before bed What is interesting is seeing the pleasure/joy this little loco gives those who unexpectedly come across it, their faces just light up. Very well put John. Link to post Share on other sites More sharing options...
hayfield Posted February 3, 2018 Share Posted February 3, 2018 Very well put John. I think sometimes we can either take our hobby too seriously or just think too much into things, when in fact like this program is designed to appeal to the greatest number of viewers with just some light entertainment As I said before I enjoy the programs Dick is in where he seems to overcome problems quite often very simply. The other thing about this show I enjoy is how problems are solved (usually by non railway modellers) which sometimes flies in the face of conventional railway modelling. 5 Link to post Share on other sites More sharing options...
Hobby Posted February 3, 2018 Share Posted February 3, 2018 The other thing about this show I enjoy is how problems are solved (usually by non railway modellers) which sometimes flies in the face of conventional railway modelling. Probably because the programme is more about "engineering in miniature" than "railway modelling"... Before I get shouted down, if you look at the programme from a distance, rather than with a RM hat on you will see it's all about getting a miniature steam engine from A to B with challenges thrown in to liven it up. All the solutions have been taken from the Real World and adapted down to size and location, just like any engineer would do, even the spiral which has it's origin in many Real World examples, from Swiss or Welsh railway spirals to multi storey car parks... The only MR bit are the stock and (possibly) the track... 3 Link to post Share on other sites More sharing options...
Titan Posted February 3, 2018 Share Posted February 3, 2018 I think 16mm narrow gauge marks the cross over point between model railway and model engineering. It is quite possible to have a small electrically operated scenic layout that you take to model railway shows just like any other model railway, and yet also a beautifully engineered live steam locomotive chugging around an extensive garden railway, both of which are to exactly the same scale/gauge or any other parameter you care to choose. Hence the case for both sides of the argument is equally valid. 3 Link to post Share on other sites More sharing options...
RMweb Gold Huw Griffiths Posted February 3, 2018 RMweb Gold Share Posted February 3, 2018 Uh huh. The thread has pretty much drifted off about two days after each episode has been shown. I guess folk are just marking time until the next episode when we get the answer to the really big question... does Dick trim his moustache? Or grow a beard... There's nothing wrong with beards ... . As I said before I enjoy the programs Dick is in where he seems to overcome problems quite often very simply. The other thing about this show I enjoy is how problems are solved (usually by non railway modellers) which sometimes flies in the face of conventional railway modelling. Probably because the programme is more about "engineering in miniature" than "railway modelling"... Before I get shouted down, if you look at the programme from a distance, rather than with a RM hat on you will see it's all about getting a miniature steam engine from A to B with challenges thrown in to liven it up. All the solutions have been taken from the Real World and adapted down to size and location, just like any engineer would do, even the spiral which has it's origin in many Real World examples, from Swiss or Welsh railway spirals to multi storey car parks... The only MR bit are the stock and (possibly) the track... I couldn't agree more - however, once Channel 4 started showing this series, my gut feeling about it was that it's really a programme about engineering, which just happens to feature some model railway kit (rather good model railway kit, as it happens). This was why I earlier made a reference to The Great Egg Race (one of my all-time favourite TV series). For me, this perception is reinforced by the people fronting the series - although they've got a range of backgrounds, Dick Strawbridge, Claire Barratt and Hadrian Spooner are all engineers. In the programmes, we are also introduced to a number of other engineers - again with varying backgrounds - a number of them volunteers (some of whose "back stories" we've also come to hear about). As I've already commented, I'll be sorry to see the end of this series tomorrow. I hope that Channel 4 - and Love Productions - are working on a sequel. Huw. 5 Link to post Share on other sites More sharing options...
Robin Brasher Posted February 3, 2018 Share Posted February 3, 2018 I have read a couple of articles about the Biggest Little Railway in the World. The first was in today's Bournemouth Daily Echo about Model Railway Solutions. This is a local firm that specialises in building baseboards. The TV programme featured a model helix produced by this firm. The other article is Sarah Palmer's article in the February Railway Magazine Guide to Modelling. She makes some valid points. She suggests that the series is more about team building and problem solving rather than railway modelling. She suggests that if, according to the show's presenter, Dick Strawbridge, railway modelling is the country's second most popular hobby then perhaps we should dispense with calling us geeks. She goes on to say that she would like to know more about how the track was designed and the route was planned. I don't think that railway modelling is anywhere near the second most popular hobby now. It may have been the second most popular hobby in the 1950s but I think far more people watch television now or operate their mobile phones or laptops. Here in the Isle of Purbeck we rarely get more than ten people at our model railway club meetings whereas we get over 50 people coming to talks and slide shows about trains. These people are more interested in full size railways rather than models. I think that it is the people that call us geeks who have something missing from their lives. 3 Link to post Share on other sites More sharing options...
Hobby Posted February 3, 2018 Share Posted February 3, 2018 "The TV programme featured a model helix produced by this firm." The impression given by the programme was that the helix was built by the team who were there, like the bridges... So who's telling the truth? Or did they have the firm as "consultants" to show their design which was then built by the team on the ground? Link to post Share on other sites More sharing options...
Mike Storey Posted February 3, 2018 Share Posted February 3, 2018 If modelling in 16mm in the garden is really model engineering, then I am totally f**ked, and have been for the past 20 years........ Link to post Share on other sites More sharing options...
Administrators Phil Parker Posted February 3, 2018 Administrators Share Posted February 3, 2018 "The TV programme featured a model helix produced by this firm." The impression given by the programme was that the helix was built by the team who were there, like the bridges... So who's telling the truth? Or did they have the firm as "consultants" to show their design which was then built by the team on the ground? The programme showed a model helix, produced by the firm to explain to viewers what they were talking about in a quick and easy to understand way. Using a helix is nothing new though, the prototype beat modellers to it by a long way. I doubt a firm was brought in to show the team on the show what one was and they had to use a very different design of supports to cope with the terrain anyway. Link to post Share on other sites More sharing options...
Administrators Phil Parker Posted February 3, 2018 Administrators Share Posted February 3, 2018 If modelling in 16mm in the garden is really model engineering, then I am totally f**ked, and have been for the past 20 years........ Surely ALL modelling incorporates a bit of engineering. If you've made baseboards and legs, you are part of the way there. Only those desperate to categorise everything into very tiny and very separate boxes will care about the distinction ultimately. Link to post Share on other sites More sharing options...
Mike Storey Posted February 3, 2018 Share Posted February 3, 2018 Surely ALL modelling incorporates a bit of engineering. If you've made baseboards and legs, you are part of the way there. Only those desperate to categorise everything into very tiny and very separate boxes will care about the distinction ultimately. My point exactly......thanks. Link to post Share on other sites More sharing options...
RMweb Premium Andy Hayter Posted February 3, 2018 RMweb Premium Share Posted February 3, 2018 (edited) The programme showed a model helix, produced by the firm to explain to viewers what they were talking about in a quick and easy to understand way. Using a helix is nothing new though, the prototype beat modellers to it by a long way. I doubt a firm was brought in to show the team on the show what one was and they had to use a very different design of supports to cope with the terrain anyway. Would you like to say that in English please. I am now more confused that I was when Robin posted. Edit to add: Yes I do understand that the helix concept is neither new nor something that cannot be found in the real railway. The rest makes no sense to my addled brain. Edited February 3, 2018 by Andy Hayter Link to post Share on other sites More sharing options...
RMweb Premium PMP Posted February 3, 2018 RMweb Premium Share Posted February 3, 2018 "The TV programme featured a model helix produced by this firm." The impression given by the programme was that the helix was built by the team who were there, like the bridges... So who's telling the truth? Mr Brasher is telling the ‘truth’, and the tv show had a factual account (telling the ‘truth’) of the team building a helix without any assistance from MRS. Simples. Link to post Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now