Model smoke and steam

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

  1. Dan Randall

    Dan Randall Western Thunderer

  2. Dog Star

    Dog Star Western Thunderer

    Thank you Dan, neat addition :thumbs: .

    Is that really a white cat on the tender of the first engine?

    If so - Heather, a new detail for you to offer to customers ;) .
    Ian@StEnochs likes this.
  3. Heather Kay

    Heather Kay Western Thunderer

    Hmm. Not sure about that. I think I'll stick to hanging a pushbike off the back of a tender.
  4. adrian

    adrian Flying Squad

    It's interesting to see how these effects are developing.

    My youngest lad plays rugby and I got chatting one morning to one of the parents about his e-sig because it was generating clouds and clouds of smoke. I have no intention of smoking or vaping but it was a whole new world to me. There is a whole sub-culture of what I can only call modding of e-sigs, i.e. they are basically over-clocking boosting their e-sigs to maximise the vaping effect. He was buying in wire and winding his own heating elements and they are all experimenting with different winding configurations, size, shape etc.

    They even have max cloud "kits", cloud tanks etc,
    25w Max Cloud Kit
    Max Cloud Tank
    to "enter the world of cloud chasing" - I sometimes wonder if this could flow down into the modelling world!
    BrushType4 and Dan Randall like this.
  5. markjj

    markjj Western Thunderer

    Dan Randall likes this.
  6. adrian

    adrian Flying Squad

    Thanks for the link and interesting - but I do think some of the e-sig developments could be small enough for o-gauge . Certainly technology to watch.
  7. SteveB

    SteveB Western Thunderer

    You might be interested in my very amateurish video. Its an MOK Std4 tank done in S7. My first attempt actually at anything this size. I’m used to much bigger stuff normally. I started building it when Adrian was still doing his thread, so I pretty much copied him, including the CSB suspension. It’s a shame that he hasn’t finished it (yet).

    I’m using a Zimo MX696 decoder with two home made smoke units. The MX696 is quite big and only just fits inside. I did try using the much smaller MX645 but despite the heating elements getting their power from the track rather than through the decoder it only lasted about an hour before it decided to give up. Shame really, because with the smaller size, I was able to get a third unit inside to simulate the steam from the cylinder drains.

    The choice of fluid used for the smoke effect is very important. The best I’ve found so far is the stuff sold by ESU. It dissipates very quickly, so even when its been running for 10 minutes or so, the atmosphere in the room is still quite breathable.


    chrisb, Kimbo, Stumpytrain and 23 others like this.
  8. Dikitriki

    Dikitriki Flying Squad

    That is very impressive Steve, perhaps the best smoke effect I have seen in 7mm scale. Now if it could be blackened a little bit.......

    Stumpytrain and Jordan like this.
  9. David Varley

    David Varley Western Thunderer

    That just brought a big silly grin to my face :D
  10. BrianG

    BrianG Member

    Steve, that's really quite spectacular. I did dabble with the smoke some years ago but it was fairly uninspiring as it would not produce a decent 'puff' of smoke. Would you care to provide details of your home-made units?
  11. john lewsey

    john lewsey Western Thunderer

    Hi I've just been looking at some of this on u tube vert vert impressive
  12. Mudhen

    Mudhen Western Thunderer

    That's really good Steve. I'm in the process of building one of these locos and am interested as to where you sited the speaker and zimo chip.
  13. Ian G

    Ian G Western Thunderer

    Is it possible for someone on here to show how to fit smoke units to Diesels please.

    Ian G
    BrushType4 likes this.
  14. adrian

    adrian Flying Squad

    I know I wished he'd hurry up and get it finished as well - it seems he's too busy having fun galavanting around with the 2mm mob at the moment. I believe that there has been some limited movement seen on the 7mm front ( Siphon F - JLTRT bogies - Cherry Clan ) because there's a MOK 8F waiting in the wings and a V2 is due to arrive in a few months so some space needs clearing out in the erecting shop.
    Stumpytrain likes this.
  15. SteveB

    SteveB Western Thunderer

    I’m quite inexperienced when it comes to forum posting, so please accept my apologies for all the blunders I’m bound to make. I’ve been lurking on this forum for around a year now and I have to say that I’ve learned a tremendous amount, so it about time I made a contribution.

    Now if it could be blackened a little bit.......

    If only. I’ll just have to pretend they’re using really good coal on a really cold day and its being fired by a really good fireman! Can’t have everything.

    The smoke units are really simple; the only problem is the enclosures. The heaters are two 15ohm heaters wired in parallel. They get their power direct from the track via a zero crossover relay. I also put a 2amp nano fuse in-line, just in case. I don’t understand electronics, but I’m told the zero cross over relay is needed to avoid excessive voltage spikes, which I dare say wouldn’t be too good for the decoder. The relays are available from

    I started off using the Peter Clark Smoke Units

    but these seem to be primarily aimed at diesels or at least larger steam locos. I cut off all the electronic stuff and reduced the size of the fan and chamber. I replaced it with a brass unit but I guess I could have just cut down the original mazak arrangement.


    This was fine for the Safety Valve Unit and the next couple of photos show how I mounted it in the Firebox.


    Trying to get a square assembly into a round smokebox wasn’t going to work very well, so I machined up a special round unit.


    The material is PTFE. It machines quite well, has a very low thermal transfer rate and quite a high melting point. Having made the round unit I thought I might as well make a ‘proper’ one for the Safety Valves.


    If anyone is interested, I would publish my drawings for the two units.

    I’ve put two identical speakers in the loco, one at the front as shown in the photo, and one in the coal bunker.


    Both point down to the track and are ‘in phase’. I came across an interesting article regarding speaker and sound.

    Well worth a look. I carried out some trials myself as I didn’t really believe that a speaker would actually be better when it’s not mounted in an enclosure, but it’s all true.

    Remember that my loco is S7, so I’ve got a bit more room between the frames. I think it would still be possible to put the same speaker in a ‘normal’ loco but it would have to be cut down to fit.

    I can’t take a photo of the bunker speaker because the body is back with Warren Haywood. Warren painted it initially and did an absolutely superb job. Unfortunately, when I was doing a bit of maintenance work on the chassis, I caught the side of the body and it fell of my workbench onto the floor! OMG, I can tell you it’s not a pleasant feeling when you pick it up off the floor and examine the damage. The roof had sprung off, the bunker was folded up towards the firebox and the rear steps were very badly bent. Anyway, it’s now repaired, albeit, nowhere near as good as it was originally and it’s back with Warren for him to produce another miracle. I’ve shown a photo of the coal which covers the bunker speaker. Although it does muffle the sound a bit, it’s quite surprising how much it lets out.

    IMG_0619.jpg IMG_0622.jpg

    Where you put the decoder is very dependent on what decoder you fit. This photo shows the size difference between the larger MX696 and my failed MX645. The ‘package’ for the MX696 also includes two zero cross over relays and two nano fuses.


    The only place for the MX696 is in the boiler which is why I’ve cut it way so much and fitted a much lower profile motor/gearbox than specified by MOK. When I originally used the MX645 I fitted it in between the frames under the cab. Quite a good arrangement, so it’s a shame that I had to change to the larger version.


    I'm about half way through my next engine which is an MOK 8F.


  16. Mudhen

    Mudhen Western Thunderer

    Thanks for all the info Steve, much appreciated.
  17. BrianG

    BrianG Member

    Thanks Steve. That answers a lot of questions, which in parallel I was following up researching modern smoke units on the web (see what you started!) Obviously the rapid-response fan is the key to getting a good 'puff' at low revs, which was not possible with piston-driven smoke units in days of old.
  18. SteveB

    SteveB Western Thunderer

    You're both welcome. If you would like any more information then just ask. This forum has been very helpful to me so if I can pay a bit back then I would be pleased.


  19. SteveB

    SteveB Western Thunderer

    I’m not really sure where the best place to post this. As its about model steam and smoke then I guess this is the best place. Following on from my 2-6-4T, I’ve been working on an 8F. Its still quite away from being finished not the least because my chosen prototype is 48706 which, in the period I’m modelling (1960’s), had a part welded mk1 tender and thats the one that MOK don’t do!

    This time I’ve used a Zimo MX645 for the motor control, chuff smoke and sounds whilst the safety valves and cylinder drains are handled by an MX686. I was intending to get the MX686 to handle a servo as well for the weighshaft but fortunately I found out that the English version of the manual is wrong. It says that the 5V output will handle 200mA but in fact it will only handle 20mA, nowhere near enough for the servo. The German manual is correct! Am I the first to have found this? I have let Zimo know and they have said that they’re going to update the English version but they didn’t say when. I’ve ordered an MX687W which will handle the servo but they’re not normally available in the UK, so it’ll be a while before it turns up.

    For someone who can’t even work his mobile phone properly, dealing with ‘bits, bytes, CV’s, long addresses, secondary addresses, pseudo-programming etc has been quite a challenge. I actually got is right first time but due to a broken fuse, I didn’t think I had, so I spent hours and hours, checking and re-checking, changing CV’s until I eventually checked the fuses. They were brand new, so they should have been okay, it just goes to show that you shouldn’t take anything for granted. Perhaps if I had been a bit more confidence about my ability with the CV’s, then I would have checked them all earlier. Oh well, I did feel pleased when I found it so I celebrated with a very large single malt.

    Sorry about the quality of the video, it’s not that easy to do, I was holding the camera with one hand whilst trying to keep it pointed at the loco and pressing buttons on the controller with my other hand.

    I’m not sure what I think about the cylinder drain steam, it’s a lot of additional effort and its not easy to squeeze everything in, even with the small decoders. I think its best to only use two of the generators at a time, otherwise with 3 amps going through the wheels and split axles there might be a risk of melting the plastic in the wheels! There doesn’t seem to be much, if any, residue left on the track after using them. I’ve tried putting down a tissue and then a mirror and neither showed anything.


    This is the unit that makes the steam for the safety valves (left fan) and cylinder drains (right fan). It looks a bit of a mess really. I'll tidy things up a bit when I get the new decoder but I think it'll still be a mess! Just too many wires really.


    This is the 'chuff' steam generator. IMG_0005.jpg

    The whole set up on trial before putting it inside the boiler.


  20. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    All 75cl of it....? :D

    Just looking at your photographs of the 8F installation could the decoder(s) be mounted in the tender and carry two or three wiring looms to them?

    Or mount all the sockets on a piece of PCB to reduce the wiring. This is something I now do to reduce the chances of any wires becoming accidentally trapped/caught or broken.