SOME THINGS YOU NEED TO KNOW ABOUT MODEL STEAM ENGINES - IN THE WORKSHOP

in the workshop some important things that you really do need to know about steam engines and to illustrate these important points i need to connect a large engine such as the stuart 5a to a much smaller boiler this is my 504 test boiler it's gas-fired and it makes a lot of steam but the amount of steam that the boiler makes is relative to its size and also the amount of heat that you can apply to the boiler i'm just setting up for a steam test i don't need to use this displacement lubricator because the engine i'm using has a mechanical lubricator but i thought it would show how to drain it down there isn't much in the way of pressure in the boiler all the taps are open and the only way it's draining currently is by gravity i don't like these glass displacement lubricators but at least you can see the level inside while i'm waiting for the boiler to raise some steam i'm lubricating every part of the engine this is standard lubricating oil that i get from a company called halletoil.co.uk most miniature steam engines use a total loss oil system this one is not so miniature but it's not very big either steam engines are not internal combustion engines generally speaking modern internal combustion engines have a built-in lubrication system that circulates the oil through a filter unless it's a two-stroke then you just mix the oil with the fuel but with these things you have to give them some attention from time to time this small pump that sits on an oil tank at the side of the engine feeds oil to the cross head just one stroke of the pump is enough for quite a long run 10 minutes or so into the steam raising and there's now some pressure in the boiler not much but enough to force the water out of the lubricator and this clip shows how refill it with steam oil this is not ordinary lubricating oil it's steam cylinder oil i also buy my steam oil from the same company halotoyle.cod.uk halotoyo's web address is currently on screen this boiler is heated by quite a substantial gas burner but compared to a coal fire it's not very much really after a while there's about 30 pounds per square inch of steam in the boiler so it's time to open the tap and let some of the steam through the steam engine to warm it up and this is a very messy job i've opened the drain and as you can see steam's coming out of the top one and this serves to warm up the cylinder a little bit don't forget the first steam that reaches a cylinder condenses immediately to water so you end up with a cylinder full of water and this isn't too bad on a small engine but once the cylinder sizes get bigger and the corresponding engine also gets larger you can seriously damage the engine if you get a hydraulic lock at each side of the piston by using the drain after a while all of the water is cleared from the cylinder that is most of it anyway it's best to initially run the engine for a while with the drain open to clear the water when you see a video or film of a steam locomotive often you can see steam gushing out of the front of the cylinders and that's usually as it's leaving the station what that's doing is clearing any water from the cylinders because on a cylinder of the size of the one you find in a steam locomotive severe damage will be done if it's hydraulic locked keep your eye on the pressure gauge in no time at all the pressure drops to virtually zero so i've closed the regulator valve and now i have to re-pump up the boiler i let the pressure get to about 20 pounds per square inch then i opened the regulator valve and it was immediately flattened again and the engine ran badly i fitted the pipe to the exhaust so i could show you this i'm holding this silicone rubber tube in my hand and i shouldn't be able to do this because the steam should be too hot and normally as shown here i would have to wrap a cloth around the tube otherwise i would just burn my fingers and that's not a good idea you can also see there's an awful lot of water coming out of the exhaust pipe this should not be happening either and that's why the engine is knocking take a look at this clip from a while back i was running this very same engine in the garden using a castle steam boiler this is a proper boiler coal-fired and produces lots of steam and even on the pressures down in this clip the engine is still running very well the 5a steam engine with its two and a quarter inch bore cylinder will only run with the steam from this boiler for a very short time here i'm pumping some more water in i'll shut off the engine and let the pressure build until the safety valve blew but almost straight away the pressure in the boiler dropped the engine is making a really horrible knocking noise the timing on this 5a is slightly but normally it runs very well valve timing is very important with regard to a steam engine as it is with an internal combustion engine ideally the steam needs to be admitted to the cylinder early to cushion the moving parts in order to cushion the moving parts though you do need some pressure and there is insufficient pressure coming from the boiler it just drops down to zero as this engine is fitted with a mechanical lubricator i don't need to use this displacement lubricator here once again i'm just blowing everything out of it using what's left of the pressure in the boiler and as you can see it doesn't exactly empty quickly to make matters worse it's time to pump some more water into the boiler which is further going to reduce the pressure i pumped in plenty of water this time and as you can see on the gauge it's nearly to the top the video in the next clip is running very fast it's running at 20 times normal speed i did this just to show the gauge moving i let the pressure rise until it got to about 50 pounds per square inch and then i open the regulator valve you will notice now that the engine isn't knocking quite as badly but as soon as the pressure drops down to about 20 pounds per square inch it does start to knock and this gets worse as the pressure drops as i mentioned earlier this stuart 5a has a cylinder that is two and a quarter inches in diameter and my old stuart 504 test boiler has a boiler diameter of only three and a half inches watch what happens when i open the drain the knocking stops because the water that's been pushed into the steam chest from the boiler is very saturated and wet so at each end of the piston is a pool of water and that's what the knocking is catch 22 with the drain closed it runs for a bit longer but it knocks badly because there's a partial hydraulic lock occurring with the drain open well there's just not enough steam and the engine stops to sum up it is obvious that the heat source on this boiler is inadequate the boiler's capacity is inadequate for an engine of this size and that's why i'm encountering problems and once again here's all the water coming out of the exhaust a steam engine is supposed to run on steam it is not a water engine and unlike an internal combustion engine the steam engine relies heavily on its boiler or steam source the temperature of the steam supplied by a boiler is relative to the pressure inside the boiler watering a domestic kettle boils at 100 degrees centigrade and that's at atmospheric pressure the higher the pressure in the boiler the hotter the steam gets i mentioned this in a video a couple of years ago the toll i got was some fool who wrote in to tell me that no this was not the case and it was this and it was that and it was this and that but take it from me as the pressure rises the temperature rises a kind viewer who's a bit more sensible read this comment and he sent me a link i don't normally include links but i've checked this one out and it's at the beginning of the video in the text as you click on it in this clip i'm pulling some wd-40 through the engine as i always do after a run this will dispel the water i'm also spraying the cast iron parts as well as a rust preventative measure watch and listen to this next clip i'm blowing some wd-40 through the cylinder and as you can hear there's no knocking anymore unfortunately though my compressor is very small and in no time at all the pressure drops and very soon the knocking starts again this has nothing to do with water nothing to do with temperature steam it's all down to the capacity or volume of the air or steam that can be applied to the engine if you don't have sufficient volume what's going to happen is nothing's going to cushion the parts as they move from end to end that model is covers it a steam engine is an external combustion engine and its combustion needs to be good even though it's not in the cylinder like an internal combustion engine just to recap you need a boiler with a good volume relative to the size of the engine a powerful heat source and the steam needs to be dry water is the enemy of a steam engine if it's coming in with the steam supply and that's about it some important things that you do need to know if you mess about with steam engines although it doesn't apply to small steam toys because they run unsaturated steam generally anyway and finally that concludes the episode i'd just like to say stay healthy thanks for watching and i hope you found it useful please take the time to visit my main steam models website and click on the section of the website that says video playlists and by doing that you can find other videos that you may like to watch and by using the playlists you can actually watch the videos back to back making it unnecessary to comment that the videos are too short

Channel: Keith Appleton

Views: 102,504

Keywords: Steam Engine Physics, Steam Temperatures, Live Steam, Model Steam Engines, Stuart Turner, Stuart Models, Stuart 504 Boiler, Stuart 5A Steam Engine, Keith Appleton, How To, Howto, Tutorial, Help, Information, Model Engineering, Model Engineer, Saturated Steam, Temperature Vs Pressure

Id: nJm3CU7873Y

Length: 10min 57sec (657 seconds)

Published: Mon Feb 15 2021