Repairing Tri-ang/Tri-ang-Hornby/Hornby Smoke Unit Elements

[Crofty58]

 Thanks. I'm surprised that there is resistance in the brass end caps though . I'll give it a go with some UK type old fuse end caps and make a ceramic core..I have plenty of resistance wire from old Hornby resistance controllers ...so that could be another option .I agree 30-33 ohms that my existing elements read. What I've experimented with is using  DCC with a bridge rectifier then a 12v fixed regulator purely for the smoke unit...works fine although some heat is lost in the regulator which gets warm of course. I have some 33 ohm, wire wound in ceramic , 5w power resistors which I had thought about...just a tad too big without altering the chamber size and they make break-down possibly . Saying that ,the maximum power draw ( in-line watt meter ) is only 2W at 0.2A  though with the Hornby elements on this set up.

Don't forget there is some resistance in the end caps, it maybe the fuse wire I used has some resistance as well, in which case a fine resistance wire may well be an alternative.  The elements read 33 ohms when new.

 

 

[Crofty58]

 

Sorry ..didn't know your message would be attached to the immediate end of my reply...will have to get to grips with how to do this...it's an age thing  😢.

 

[96RAF]

I suggest you ignore the blue button with the white arrow as it just repeats the wuoted post in toto, then you have to escape the wuote box.

 

Just type your response in the Reply box at page bottom ref @person-you-are-replying-to, then click the green Reply button.

[Chrissaf]

@Crofty58

Please read TIPS 1, 2 & 3 in the link below to add more in depth detail to Rob's instruction.

 

The rest of the TIPs will also give you a good grounding in how to use this forum efficiently.

 

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[Seacommander]

I agree with Crofty58 that a resistance of 33 ohms for a short length of 5 amp fuse wire is very high. Five amp copper fuse wire is around 35/36 SWG and the resistance of this gauge copper wire is approximately 0.5 ohms per metre meaning that 66 metres would be necessary for a resistance of 33 ohms.

 

I strongly suspect that original smoke heaters are actually wound using nichrome resistance wire. An equivalent diameter nichrome wire has a resistance of about 35 ohms per meter - still a long length for a smoke unit heater. Even at 0.1 mm dia about 0.25m would be required to achieve 33 ohms but this is far more realistic than 66 metres or even 1 metre.

 

Nevertheless is seems that ordinary 5 amp fuse wire does the trick; but I would be interested to know what current is being drawn.

[Crofty58]

Well...I wired an element  up with 5 amp fuse wire today with 4 turns  ...but it didn't work as it tripped my controller...which I thought it might.

[Oyster Creek]

Great tip so I thought I'd give it a shot; bought some 5 amp fuse wire, soldered it in with 5 turns and then discovered to my surprise that the resistance across it registers zero and all it does is short out my power supply. Are you sure about the wire? I'm no expert but I wonder why fuse wire would act as a heating element; isn't a nichrome wire more likely to work?

[ColinB]

I must admit when mine broke I threw it away, the whole lot went brittle. I think you are meant to use resistance wire (I don't know if they still make it). I don't know if they used that in the past as fuse wire, but modern fuse wire has very little resistance.

[Seacommander]

Well, I did suggest nichrome back in September.

 A possible problem with nichrome wire though is establishing a stable connection. In my experience it doesn't take solder, and anyway the temperatures involved would problem melt ordinary tin/lead solder. Some form of secure mechanical connection would be needed I think. How were the coil terminations secured in the original units?

[Ruffnut Thorston]

There is a brass cap on each end. Some are bright plated brass, others are natural brass finish.

I would hazard a guess, not having looked closely, that the wire is secured by these end caps.

[ColinB]

I think there was also a bit of PCB I think. The wire as you said was connected via a collar. The whole lot fell apart on mine. Trouble is I noticed on both locos they were fitted to, there was a slight distortion of the loco body. 

[Philip-1243481]

From looking at my X.594 (broken). I think that you need to use 44AWG nichrome wire as the diameter of the coil will be about 1/8". 44AWG nichrome is around 167Ω / ft. So for 33Ω you need 2.3" -- which is about 6 turns on a 1/8" form.

46AWG Nichrome is actually a better match at around 3.8 turns.

Amazingly enough, 46AWG Nichrome wire is available in small quantities (10M) for cheap... Worth a shot to try and do the repair.

[RDS]

@Philip

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[Christopher-1219225]

Resurecting an old thread.

im trying to repair my late brothers Triang smoker I can get the resistance to create smoke but my GaugeMaster D just goes into safety mode registering a short.

What about adding a diode?

Anybody else managed to overcome the short issue on modern controllers?

[RDS]

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[Topcat2018]

@CH

I'm not sure why you think a diode will help. If you put one in series with the smoke element it will typically only provide a voltage drop around 1 to 1.2 volt at most, which is the forward voltage of a normal (non-Schottky) silicon rectifier.

If the resistance of your smoke element is in fact 33 ohms then the current it draws at 12 V should be 12V/33 ohm = 0.363 amps. Since your Gaugemaster D should be able to supply 1 amp per channel it sounds as if the resistance of your smoke element is less than 12 ohms if the controller is tripping out.

Just in case the myth about using 5 amp fuse wire is still floating around, can I put it to bed. The resistivity of fuse wire is very low because you don't want a voltage drop across a fuse, and a 5 amp fuse would effectively have zero resistance. If it had a resistance of 33 ohms then the voltage drop across it when used in a mains circuit at maximum current would be 33 ohms x 5 amps = 165 volts, which is more than half the mains supply voltage - clearly nonsense.

[37lover]

Topcat,

I know from our previous exchanges you are very experienced with electronics and presumably electrics. Whilst I agree with your comment above haven't you overestimated the resistance of a 5 amp fuse in a mains circuit. Philip in his posting in Feb 22 suggested for 6 turns you would have 2.3" of wire, SoT originally recommended 4 turns, so let's say 4 turns is 1.5". It's a very long time ago that I saw wired fuses but weren't they more like 1/2" between contacts, or even less. Bottom line is resistance would be at most a third of 33 ohms and the voltage drop "only" 55 volts -still far too much to make sense.

[P-Henny]

I'm not sure why you think a diode will help. If you put one in series with the smoke element it will typically only provide a voltage drop around 1 to 1.2 volt at most, which is the forward voltage of a normal (non-Schottky) silicon rectifier.

 

 

Are you not mixing this up with a bridge rectifier. A single Silicon diode has a forward voltage drop of 0.6 - 0.7 volts and it is the bridge that drops 1.2 volts.

I am assuming just a slight slip of memory as it happens to me too.

[Topcat2018]

@37

I wasn't overestimating the resistance of a 5 amp fuse. A cartridge fuse has a single strand of fuse wire inside it, which is obviously not 33 ohms. What I said was that for 5 amp fuse wire to work as a smoke element the resistance would have to be 33 ohms, which is clearly nonsense, (and clearly not four or 5 turns of wire as has been suggested previously).

@PH

A normal silicon diode will start to conduct at about 0.6 V (Schottky and super barrier diodes at a lower voltage), but the forward voltage increases with current because of the diode's internal resistance. As a general rule a low-current diode with a small junction area, operating at its maximum current, will have a greater forward voltage drop than a higher current diode operating at the same current.

I may be wrong in this, but I assumed that CH was thinking that putting a diode in series with the smoke element would give a voltage drop and thus limit the current through the element, and I was pointing out that the maximum voltage drop to be expected would be 1 to 1.2 V, which would have little effect. If you did try this you would want to use a small diode that could just handle the current, both for greatest forward voltage drop and taking up less space.

This strategy wouldn't work anyway. If you drop the voltage to the element obviously you also reduce the power and it very likely won't vapourise the smoke oil.

[JJ73]

I'm not sure if this helps, but I've got a Hornby Railways R.378 LNER Class D49/1 Loco 'Cheshire' with a Smoke Unit & all what was wrong - was a wire had came off inside as you can see in this video :-

- then in my next video some one called Tobeshadow help me to get smoking again :-

🙂🚂

[PeterWW]

Hi, saw this in the community and appreciate written a while ago. I have tried your advice and still can’t get any smoke, do you know if the Lionel SMOKE UNIT ELEMENT 18 OHM 3W WIREWOUND REPLACEMENT PART 691RS18OH, would work?

many thanks

 

 

[Topcat2018]

@PE

This doesn't seem to make sense. You say the Lionel part is 18 ohms and rated at 3W, but if 12V is applied to it it will be dissipating 8W (Power = Voltage squared divided by Resistance). Maybe there is an extra resistor in series when used in Lionel locos, though I can't imagine why???

It has been stated that the resistance of the Hornby smoke element is 33 ohms. If this is correct then the Hornby smoke element will dissipate only 4.36W at 12V.

ADDITIONAL

Lionel elements of 27 ohms are available, which might be more suitable, but so far I've only been able to find these available from the USA.

[What About The Bee]

Hi Top Cat

Whilst you have computed the watts, there are two other primary criteria which must be considered to determine if the unit will produce smoke.

The first is the liquid, which is mineral oil. The boiling point of generic mineral oil is between 260°C and 330°C. The actual boiling point will be a function of the precise petroleum distillate in the smoke oil. We need to raise the temperature of mineral oil in contact with the heating element to boiling point. The actual boiling point can be found empirically for any given smoke oil product.

The second criteria is the conversion of watts to temperature. For this, we need to know the mass of the object (heater element) being heated and its thermal resistivity.

Without knowledge of these criteria, the power to be dissipated is insufficient to determine if a unit smokes.

The "mass of object" is the heating element. I think this calculation must ignore the large mass of the mineral oil, considering only the small volume of oil in close proximity to the heat element. Is it just the surface film of oil on the element? This part will require some more thought.

Bee

[Topcat2018]

I wasn't commenting on whether or not the unit would produce smoke as this depends on a lot of factors other than the heating element, of which I have no knowledge. I was simply pointing out the situation from an electrical point of view - that it seemed odd that the Lionel element with a resistance of 18 ohms and rated at 3W would actually be dissipating 8W at 12V, which is almost twice what a Hornby element with a resistance of 33 ohms would dissipate, so it might not be a good idea to put it in a Hornby smoke generator.

[John Salton]

Hello, My Davy Crockett ( Triang Hornby358s was smoking realy well - Toped the smoke up - now its not smoking and doesn't seem to be heating up?.

Anyone here have any idea how I can get the smoke working again - or advise on what's wrong ?. Many Thanks, John.