I am currently completing an undergraduate thesis involving wind tunnel testing on a model steam locomotive (which I am trying to build roughly by hand and is NOT by any means exactly to scale!). This will determine the effectiveness of smoke deflectors in lifting exhaust away from the cabin. I plan on simulating the exhaust flow by running a tube from one of those smoke machines you find at discos; through the chimney of my model, and observing the flow of the smoke as the air from the wind tunnel forces it across the model. I will compare results with and without deflectors and will also compare the drag force. Hopefully drag at least remains the same, if not decreases due to the deflectors.
I have read all the threads involving smoke deflectors and so far, you guys have given me far more info than anything else I have found on the net! So my question is, does anyone know of any FREE online journal articles, or studies involving smoke deflectors, wind tunnel testing on smoke deflectors or flow visualisation techniques involving locomotives? Any images showing locomotives without smoke deflectors having smoke blown across the cabin, would be excellent.
Finally, can anyone clarify that smoke deflectors were often used in colder climates when steam began to condensate upon exit from the chimney, making the exhaust even denser and harder to see through?
I am by no means an expert on the mater, but i believe that the deflectors were mainly used on articulated locomotives, two of which come to mind are the UP’s Challengers and Big Boys - and these were mainly used in Wyoming - well, the Big Boy’s were, I’m not entirely sure about the Challengers…
Smoke deflectors tended to be used mostly on psgr engines. The UP put them on their Northerns and on (only) psgr Challengers. I think the reason was that the vacuum effect along the side of the boiler was most pronounced at high speeds w/ the engine drifting (when exhausting under pressure the smoke would be lifted away from the boiler by the pressure of the exhaust). The NYC had somewhere in the nieghborhood of 300 Mohawks but only the dual service L-3s and L-4s got the elephant ears. The SP put them on thier Northerns (except the GS-1) and Mountains. Then there are the interesting little anamolies, like why did NYC put them on psgr Mohawks and Niagaras but not the Hudsons and why did SP not put them on more than a handfull of Pacifics?
A true academic eh? Not a lot of call for smoke deflectors in the wide world these days, more’s the pity.
You wrote that you had read all our scribblings. There was a good one a little while back in which a guy named Mark Newton wrote in some good thoughts. Did you read that one? Mark’s opinion is that it is not so much the smoke they want to get rid of. See if you can find that. It was in the Prototype for Modellers forum somewhere.
ninja600 wrote: <“I plan on simulating the exhaust flow by running a tube from one of those smoke machines you find at discos; through the chimney of my model,”> I seriously doubt that this will effectively simulate the exhaust plume. In a locomotive the exhaust steam is still under pressure as it leaves the blast pipe orifices. It is this back-pressure, in combination with the venturi effect of the blastpipe and petticoat, that creates a partial vacuum in the smokebox that in turn provides draft for the fire. Modern front-end design was all about reducing back-pressure to the minimum, while still providing adequate draft. This lead to locos with very soft exhausts, which then needed smoke deflectors to prevent the exhasut steam and conbustion gasses trailing. If you are really interested in learning about the fluid dynamics of front-end design, you need to read up on Chapelon, Porta and Wardale. http://www.trainweb.org/tusp/porta_biblio.html <“Finally, can anyone clarify that smoke deflectors were often used in colder climates when steam began to condensate upon exit from the chimney, making the exhaust even denser and harder to see through?”> First I’ve heard of it. It could be plausible, but then it would make me ask why so many engines in the USSR and other places that are bitterly cold don’t have deflectors. Cheers, Mark.
Nothing online, but the NKPHTS archives at Cleveland State University does contain the NKP’s test results of their 4-6-4 smoke lifter tests.
BTW: the lifters on the NKP Hudsons were installed to improve engine drafting, NOT in keeping smoke off the train. I think you’ll find that to be more common than you think.
'T’aint necessarily so. In Japan, virtually every locomotive (except for some truly ancient foreign-built examples) was fitted with elephant ear smoke deflectors. Some were low-drivered types that never achieved their rated maximum speed of 70 KPH. The wartime-austerity series 3 D51 class 2-8-2’s were originally fitted with wooden elephant ears!
Smoke deflectors (including those “dustpan around the stack” types found on SP skyline casing locos) were needed when the locomotive was fitted with a low back pressure exhaust system. On the NYC, the Hudsons and earlier Mohawks were “barkers,” and could throw their exhaust well into the sky. The later Mohawks and Niagaras were “chuffers,” which meant that the exhaust needed additional assistance to clear the cab roof.
Of course, the Western Pacific put elephant ears on SP-designed 4-8-4’s with skyline casings - a “belt and suspenders” approach if there ever was one!
Chuck (who runs a variety of steam locomotives, most of which have smoke deflectors)
I seem to recall reading that the CNR and the National Research Council did extensive tests on smoke-lifting devices back in the 1930’s. There may be data somewhere pertaining to those tests. Supposedly, wind tunnel testing was used to aid in the design of shrouding for the CNR’s U4a Northerns (6400’s). The design was supposed to improve the flow of exhaust over the boiler top, but apparently had little or no effect, as many locomotive crews noted that they were among the dirtiest engines to run, with smoke being constantly sucked down into the cab. The CNR applied various types of smoke lifting devices to most of their Northerns, along with many Mountains, Hudsons, Pacifics, and even a few Mikados.
Virginian wrote: <“To the best of my knowledge there were no concrete results back in the day.”> Not really true for the US, and certainly untrue for Europe. Much work on European steam was carried out on front-end improvements, and included smoke deflector trials where quite definite results were obtained and published. Cheers, Mark.
I completely agree with what Mark has said - there was a lot of science involved in locomotive design for most of the last century.
If you can get hold of a copy of “La Locomotive a Vapeur” by Andre Chapelon, I’m sure that will helpful.
When fitted to locomotives, the Kylälä and Chapelon “Kylchap” exhaust system often required smoke deflectors to be fitted because of the softer exhaust. An excllent example of this was the Gresley designed A3 class, which when originally built had a single chimney and I believe a plain blastpipe. This would give a sharp exhaust that would lift the smoke, but was not terribly efficient. On the other hand the Kylchap exhaust was very efficient, but wouldn’t lift the smoke, leading the railway to fit the German style smoke deflectors after a few months or years. This was recently demonstrated when the only surviving A3 - “Flying Scotsman”, which has the Kylchap exhaust fitted - was recently run with the smoke deflectors removed for aesthetic reasons. The visibility was so poor that within a week the smoke deflectors were put back on.
I did my MA research on the River Kwai Burma Thailand Railway and then decided to model a freelance post-war version. As well as steam engines from Japan, the IJA confiscated a large number of the Federated Malay States Railway locomotives.
One website, that is unfortunately now gone, had a large number of photographs of the Federated Malay States Railway steam engines. Several classes of the steam engines did have smoke deflectors, all appear, from what info I have available, to have been manufactured in the United Kingdom. But this is certainly not a reflection of the UK clime…one of the companies involved, Kitson (name went through several incarnations), specialized in made for export locos which ended up all over the world One history of the FMSR notes that the traditional British wooden “goods wagon” did not survive in the tropics and were replaced by metal wagons of similar design. It may be, therefore, that the contract for made for export locos also specified tropical specific requirements and if the locos had smoke deflectors there must have been a reason for it.
You should check out the site Images of Rail http://www.users.e-comnet.net/~nlawrence/pages/cdrom.htm
which has collections of steam engine images on CD from around the world. The one from Southeast Asia, which I have, is Tiger Steam. That will give you an idea of how widespread (or not) smoke deflectors would have been.
If you want some specific academic references on FMSR and BT railway, contact me by e-mail.
I happen to now own one of the NKP HO brass 4-6-4’s with deflectors.
When the engine moves forward air will be forced to the side displaced by the engine, the deflectors grasp that air and force it up.
I am not sure if there are very much concise wind tunnel tests done on steamers, your little test will certainly help reveal the secrets behind the deflectors, so shoot video and post your results here!!!
The only thing is your model wont have exhaust coming out of the stack, but maybe you can fit a model smoke device on it.
I really do not care about smoke deflectors or lifters because neither N&W or Virginian used them. If there were truly accurate tests, then I wonder why there was such a diversity of opinion among different railroads as to their effectiveness. I am not saying “tests”, but “accurate tests”. Inductive reasoning definitely extends to testing. Putting smoke deflectors on a loco and running it, and comparing before and after ‘results’, is insufficient in and of itself. I am well aware that among fans of lines that used them there are numerous anecdotes about how well they worked, but being an engineer, and having done a little with fluid flow over the years, I have never seen how they could work worth a hoot, particularly at low speed when they would be most needed, or really much at high speed, but they may do something in a cross wind, I don’t know. I am not about to go cranking numbers or building models or a wind tunnels, but if someone else does I would love to see the results. And, I do not necessarily believe smoke coming from the stack itself is an issue. If it can be shown that airflow relative to the stack is or is not definitively effected, that would be very informative as far as I am concerned.