Model smoke and steam

Discussion in 'Resources' started by Dan Randall, 16 November 2016.

  1. SteveB

    SteveB Western Thunderer

    Hi Dave

    It's a 1ltr bottle and if I had drunk all of it in one go then I probably wouldn't be writing this post.:)

    I have thought about putting decoders into the tender but there's an awful lot of wires. Each smoke unit has four wires, two to the motor and two for the heater. I know I could use common return (which I do already) when there are multiple units but nevertheless its still a lot of wires. Wouldn't it make the flex between the loco and tender too rigid?

    I know what you mean about trapping wires, its happened to me more than once. Its easy (for me at least) to do. I'm just playing around and experimenting, so nothing is too permanent yet. There is actually a small piece of vero board under the decoders where multiple feeds have been taken. I've put a small plug and socket on that so I could easily isolate the decoders from each other.

    Any chance you could put some photos up of what you've done, so I could get some inspiration?


    Last edited: 16 January 2017
  2. adrian

    adrian Flying Squad

    Inspirational work - thanks for posting.

    How do you go about refilling the smoke units when they are all fitted?
  3. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    Hi Steve

    Firstly, these are the components I use:

    I tend to use these plugs and sockets as I can cut them to length to suit the wiring loom I require. One shows a piece of rod to create a pin if the wiring demands.
    Wire 20.jpg

    Wire 11.jpg

    The sockets can me mounted in various ways.
    Wire 16.jpg

    Or horizontal. I've deliberately left the near end one unsoldered to show how it is mounted.
    Wire 17.jpg

    Side view if the horizontal mount.
    Wire 15.jpg

    This shows both mounting methods I utilise. The veroboard is 25mm wide and of course can be cut down.
    Wire 12.jpg
    End of part 1. Now a short intermission.....
  4. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    Part 2. My installations - apologies for not being smoke and steam.

    Ok, confession time now, they are in a US diesel where there is a bit more space but not much. However this is to show my approach to wiring looms.

    Front lighting board top (headlights, rotary beacon and number board lights). The sockets with the resistor are all the same polarity.
    Wire 07.jpg

    Wire 10.jpg

    Rear Lights
    Wire 06.jpg

    Wire 19.jpg
    Part of the wiring loom
    Wire 01.jpg

    If you buy artists paint brushes for weathering etc then the brush protector tubes are worth retaining as they make good wiring conduits if space allows and I've used these as seen above.
    Wire 14.jpg
  5. SteveB

    SteveB Western Thunderer

    Thats excellent Dave, thank you for taking the time to do the photos and posting them. Now where do you get those connectors from? I'm using something similar but they're quite a bit longer and I think bigger in diameter.


  6. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    Hi Steve

    I purchased the connectors on ebay. They are usually described as SIL Socket Strip Turned Pin.

    In respect of your 8F could you place the motor control decoder in the tender and leave the accessory decoder in the loco or do both decoders operate the fans and smoke?
    SteveB likes this.
  7. SteveB

    SteveB Western Thunderer

    Hi Adrian

    'Chuff' smoke (annoyingly, I can't think of another easy description for it!) is literally down the chimney. The safeties and drains are done by removing the two safety valve bodies and squirting the fluid through the holes using a syringe. The wadding used to soak up the fluid goes between the SV & CD units. There's a PTFE dam above the wadding that is supposed to separate the two chambers and stop the fan driven air from going from one chamber to the other. That's only been partially successful because they both leak a bit. I'll take some photos of the inside when I take it out next, probably after Bristol show. I have to guess how much to put in each chamber, and there has been a couple of times when I've flooded the motor but surprisingly they don't seem to mind.


  8. SteveB

    SteveB Western Thunderer

    Thanks Dave, I'll have a look. At the moment the motor controller does the sound, motor and chuff smoke. The function decoder does the other two and will do a servo when a suitable decoder is delivered. I believe it may be possible, to get the function decoder to do the synchronised chuff smoke as well, but I haven't tried it. I see where you're coming from and it would certainly help. Thanks for your suggestion. There are also three nano fuses and three zero cross over relays under the two decoders.


  9. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    Despite modelling in O scale or larger we're forever trying to get quarts into a pint pots :mad:. It's the same with diesels as I've found out with my GP9.
    SteveB likes this.
  10. Scale7JB

    Scale7JB Western Thunderer

    Hi Steve, brilliant stuff!!

    Particularly the safety valves. Inspired!

    With regard connectors, I use VGA connectors with the metal outer frame cut off.. these give you 15 terminals in quite a small block..

    SteveB likes this.
  11. SteveB

    SteveB Western Thunderer

    Hi Everyone

    Here’s my latest attempt with smoke and steam. I bought a small tripod to help with my camera technique, but I got one that doesn’t pan!

    I’ve only just noticed when I checked out the link that the forward/reverse servo went a bit berserk for a moment, not really sure what caused it, it didn’t happen on all my trial runs! The first sequence shows the blower working. The Zimo decoder does have a facility to run the ‘chuff’ fan at standstill but its controlled by CV’s and can’t be linked to a separate sound affect so it’s not very flexible. I therefore put a small SPDT relay in the supply to the fan which does give control over it. The sound affect for the cylinder drains doesn’t loop very well, so I’ve used the safety valve sound and just quietened it down a bit. I’m using an MX645 for the motor control, sound, chuff and blower steam and an LED for firebox glow. An MX687 controls the forward/reverse servo, safety valve and cylinder drains.


    The basic smoke generator enclosures. All made from PTFE. The round one is for the smokebox and the rectangular one is two units. One for the safety valves and the other for the cylinder drains.


    The heater elements fitted.


    The start of the wiring. You can see the small SPDT relay on the left of the shot. The Vero board is used for multiple connections. For example, one 5V wire from the decorder that needs to go to several items. You can also see the two nano fuses hopefully giving some protection. I haven’t had one blow yet.


    The underside of the main unit showing the SPDT blower relay and the three zero cross over relays for the heating elements. You can also see the two motors.


    You can see the amount of wires involved. I have been able to improve the neatness compared to my 8F, thanks to a large extent to ‘Yorkshire Dave’.


    I’ve also put the two decoders into a box rather than on a shelf, as on the 8F and that hides most of the mess.


    The main unit installed.

    I think I should start thinking about building a small diorama, I’m sure the engines would look better surrounded by a decent scene rather than my crude test track. I just enjoy building locos too much. There’s just not enough hours in the day.


  12. adrian

    adrian Flying Squad

    That is very impressive, not only the smoke effects but the fitting of the units in the body look to be a very professional job.

    I hope you don't mind me saying but I think the final pièce de résistance would be to have some constant draft through the chimney. The quantity of smoke in the "chuff" is impressive but at the end there seems to be a bit of a vacuum and the last wisps of smoke are sucked back down the chimney. On the full size loco I think there would be a constant draft over the fire and through the chimney so a constant flow of air through the chimney would complete the illusion for me.
    Dan Randall and Len Cattley like this.
  13. Cliff Williams

    Cliff Williams Western Thunderer

    Stunning work Steve!
  14. SoundsLoco

    SoundsLoco Member

    We're working on that aspect. The small back pressure occurs when the temperature in the chimney drops as heated vapour flow reduces.

    Kind regards,

    Len Cattley and adrian like this.
  15. InvernessTMD

    InvernessTMD Western Thunderer

    How did you make the PTFE enclosures? Were they printed or machined?
  16. SteveB

    SteveB Western Thunderer

    Thanks for your comments, I appreciate them. I agree with what Adrian says. When the locos going slow, it’s likely to be in full gear, so more steam per stroke compared to when its notched back. The chuffs do get a bit better if the loco is run a bit faster. Trouble is I’ve only got a 6ft length of track! I only have experience with Zimo decoders and they are generally very flexible and easy to program but they don’t have many options when it comes to tailoring the smoke effects. The larger decoders MX695 and MX696 have an electronic brake on the chuff fan which stops the fan after each chuff, this is not adjustable though. The MX645 doesn’t have the brake and the fan freewheels after each chuff (I really wish I could think of a better word than chuff!) The problem with this is that the chuffs blend into each other at quite slow speeds. All I’ve done is to put a small ‘O’ ring over the motor shaft so that the fan touches it which introduces a bit of friction to limit the freewheeling. Unfortunately its not very adjustable.

    I’ll done a couple of videos to show the difference between the ‘O’ ring fitted and therefore fan braked, and another one where the fan freewheels. I would appreciate your comments on them.

    The first one is with the fan braked by the ‘O’ ring.

    This second one is without the braking.

    This is actually the first time I’ve run the smoke unit un-braked inside a loco. Its actually much better at slow speed than I expected. It doesn’t take much of a speed increase though until the chuffs blend into a constant stream.

    I’ve been in contact with Paul Chetter (its his sound project being used) and he’s being very helpful. According to the Zimo manual, the sound project does affect the fan operation, so maybe there may be more scope here. I suspect there will always have to be some compromise.

    There is a facility to ‘fire’ the chuffs using a cam rather than from the sound project. Maybe this would be more controllable. Certainly the cam profile could be modified from sharp corners to almost round which would affect the pulse duration. Maybe, there would also be the chance to put two cams in, one for slow speed and one for fast. I’ll have to think about that, I’m not sure its worth the effort.


  17. SteveB

    SteveB Western Thunderer

    They’re all machined from solid. I chose PTFE because it machines fairly well, has a high melting point and very low thermal conductivity. I’m very fortunate in that I have a cnc mill. Its a fairly old one but it does everything I want and a bit more.

    Knowing what I know now, I don’t see any reason why the enclosures couldn’t be 3D printed especially if some of the higher melting point plastics are used. I don’t actually know what temperature the heaters run at but it doesn’t seem that high as long as there’s plenty of fluid to help keep them cool.

    I would be very happy to let someone have an appropriate 3D file if they want to have a go at 3D printing. I would even throw in a motor and a couple of heating elements.


    InvernessTMD and Len Cattley like this.
  18. SoundsLoco

    SoundsLoco Member

    More than most,and more than you have described.

    You can vary the density of the 'smoke' so that it is less dense whilst standing, highest possible when accelerating, something in between when cruising and just a wisp when decelerating. That's just by varing the heater temperature.

    You lose this variable control when using an on/off relay to switch the heater, for obvious reasons.

    Additionally, the speed of the fan is automatically varied to suit the sounds playing.

    Wait and see! LOL
    Very worth while, but I use the 'sync-discs' from Paul Martin at NGTrains. easy to fit if the correct axle size is available. Never goes out of sync, neither the smoke effect nor the sound. Looking at your skills, you could probably make your own. 4 magnets and a reed switch.

    Here are a couple I fitted to Brassworks 0 gauge loco's, 2MT and Manor



    Kind regards,


    Edit by S Cook to clean up quoting - hope you don't mind Paul!
    Last edited by a moderator: 11 February 2017
  19. SteveB

    SteveB Western Thunderer

    Hi Paul

    I’ve played around a bit with varying the heater temperatures using CV137, 138 and 139 but I must admit, not much. I’ve got to be careful here because I don’t really understand what I’m doing but despite the heaters going through a relay they do seem to respond to changes to these CV’s. The relays are solid state and I guess CV’s 137 to 139 change the voltage by PWM. My very basic and crude understanding of this is that it turns the relay on and off (at high frequency). Regardless of whether my understanding is accurate, they do change things. I also monitor the power consumption, just to make sure I’m not cooking anything, and I can see and power reduction when I reduce the value in the appropriate CV.

    Do you think I would be better off using sync discs? I’ve just ordered some from NG Trains so I can have a play with them.

    Do you happen to know if CV60 would affect the voltage on F04 when this is being used fan sync?


    Last edited: 11 February 2017
  20. Scale7JB

    Scale7JB Western Thunderer

    Very impressive again!

    Very quickly, the reason for the servo going mad on the reverser is I believe interference.

    I had the same on my reverser and brakes servos but fitting the correct value capacitor to the the control wire of the servo helps it. There should be reference to it in the Zimo manual.