# Puffing the smoke



## norman (Jan 6, 2008)

Hi:

1)

I want to pulse the constant stream of smoke of a fan driven smoke unit into chuffs or puffs of smoke. Pulsing the electric current to the fan motor has the limitation that the fan is still rotating between pulses of current.

I want to block the output flow and then unblock the output flow of the smoke generator's steady fan driven stream of smoke to create chuffs or pulses of smoke.

What electro mechanical device can I purchase to restrict and then permit the flow of smoke through a flexible tube?

2)

The low cost battery powered train locomotives have puffing smoke. How is this done?

Are these puffing smoke units available for separate purchase?

3)

I do not want to get involved with the latest electronic smoke and sound systems of Lionel and MTH.



Norman


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## Semper Vaporo (Jan 2, 2008)

I believe most have a small bellows that works off of a cam on an axle.


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## Totalwrecker (Feb 26, 2009)

One cheapo I disemboweled had a thin wall flexible bottle that was depressed for each puff, to send clear puffs through the smoke...


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## Greg Elmassian (Jan 3, 2008)

Several DCC decoders (which will also run on DC) will pulse the fan.

That's the easiest way, trying to make a mechanical shutter is very tough and probably not long lived, the bellows was tried many years earlier and has been abandoned as far as I can tell. One recent exception is a piston and valve in the USAT 0-6-0, but it really did not work well.

Greg


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## Dan Pierce (Jan 2, 2008)

My HO 0-6-0 engine (purchased in 1959) had a pulsing smoke unit and a chuff sound. This was done by adding a heated cylinder with a piston tied via a gear to the motor. A small hole allowed the piston to create a noise as well as to draw smoke back into the cylinder as well as to push it out. Still works to this day!!!


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## bdp3wsy (Mar 14, 2008)

Aristo's original Pacific had pistons that drew air in and out of the smoke box, made the stack chuff and smoke out the pistons, my Pennsy 401 has it and it still works but I changed the smoke unit to the last version


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## ddrum31 (Aug 30, 2017)

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com.au/ulk/itm/162936221564


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## Greg Elmassian (Jan 3, 2008)

Well, the OP posted 3 weeks ago, and no response.

I see all the things he asked for, but the solution is a combination of electrics, electronics and a smoke unit.

The mechanical shutter does not seem to stand up..

The piston and a valve can work, but nothing commercially available.

The fan does indeed pulse, especially if you use a BEMF-braked fan, you can get pretty darn good pulses.

So Norman, I'll give you my best answers after doing this for almost 20 years.



1)

I want to pulse the constant stream of smoke of a fan driven smoke unit into chuffs or puffs of smoke. Pulsing the electric current to the fan motor has the limitation that the fan is still rotating between pulses of current.
>>>> Using a high speed fan with a fair amount of voltage will give you a large difference between powered and not powered, i.e. you WILL get good pulses. In addition some electronics can actually "brake" the fan between pulses... fan is your best bet.

I want to block the output flow and then unblock the output flow of the smoke generator's steady fan driven stream of smoke to create chuffs or pulses of smoke.
>>> not a good idea at all. People have tried mechanical shutters, they are too big and do not last with the opening and closing, and have to be opened and closed with a solenoid. Trying a rotary shutter has sort of worked. The issue is you still need a fan too... the whole thing gets unreliable and big since you have a shutter and a fan.

What electro mechanical device can I purchase to restrict and then permit the flow of smoke through a flexible tube?
>>> I'm sure someone makes a shutter, but most likely it will be too large and costly.

2)

The low cost battery powered train locomotives have puffing smoke. How is this done?
>>>> usually some kind of piston

Are these puffing smoke units available for separate purchase?
>>> never seen them as separate parts, but heck you can buy the whole locomotive for the cost of a quality smoke system, but still you will have a mechanism only designed to last 3 Christmases

3)

I do not want to get involved with the latest electronic smoke and sound systems of Lionel and MTH.
>>> Son, you are not doing this without some electronics. If you are bound and determined to do this without electronics, modify a small model airplane engine that has valves and pump the smoke through it.

Bottom line, there's ways to do this, but the longest lasting pulse the fan, and modulate the power to the smoke unit, and that needs smart electronics.

Greg - 117


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## Pete Thornton (Jan 2, 2008)

> but the longest lasting pulse the fan, and modulate the power to the smoke unit, and that needs smart electronics.


I wonder if you could take the valve mechanism out of a live steamer and use just one valve to pulse the smoke. [You 'airplane engine' comment triggered that one.] 1/2 a Stephenson's valve gear would open and close a valve every revolution.










It's just an eccentric and a valve block. Just like a real steamer!


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## Semper Vaporo (Jan 2, 2008)

If you are going to go that far, why not make the simulated cylinders on the electric "steam engine" into the pumps and you will get 4 pulses per revolution of the wheels... just need to put some one-way valves off of the cylinders to keep the air flow in the right direction and not one cylinder feed another.

But if you go that far, why not replace the electric motor in the simulated boiler with a real boiler and go "Live Steam" whole hog!  SEMPER VAPORO!!!! 

(That is not just my user name... that is a CREED!)


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## Greg Elmassian (Jan 3, 2008)

Using valves might work, but realize the small size means a huge increase in the pressure required to get the smoke volume.

The designs of these heater type units have relative open passages inside and a pretty high speed fan usually almost an inch across.

Yeah, the valves could work, but you would be adding huge complications to the smoke generation and delivery.

So the simple answer is no, that won't work.

Greg


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## Semper Vaporo (Jan 2, 2008)

Yeah, the problem is trying to get "air" to perform like "Steam"... the "chuff" comes from the final expansion of the steam escaping from the cylinders. Moving the same "volume" of air is not the same as moving steam. You could generate plenty of smoke with many smoke units, but getting it to leave the stack with any velocity would require a large quantity of air moving fast.


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## Greg Elmassian (Jan 3, 2008)

Yeah, pressure alone is very different, and then the unique properties that steam is expanding... so, this is interesting, but not helping the OP unfortunately.

Greg


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## Pete Thornton (Jan 2, 2008)

> why not make the simulated cylinders on the electric "steam engine" into the pumps


Isn't that what the Aristo Pacific used to do?


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## Greg Elmassian (Jan 3, 2008)

Yes, and they worked for a while... never quite as good as a fan driven one, but definitely synchronized.


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## ereuter (Feb 7, 2017)

There is a device called SUPER-CHUFFER that the O scale guys use to puff smoke, and it brakes the fan between puffs and varies puff duration depending on speed. It has other features that may or may not be useful (automatic Rule 17 headlight control, for example), but it may be a good fit for this situation. 

http://henningstrains.com/JWA.html


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## Greg Elmassian (Jan 3, 2008)

Most of the DCC decoders do vary the fan pulse, and I think some do dynamic braking, which really gives "contrast"... the super-chuffer is $70 bucks as an add on, and wants AC input, but it could probably be modified. 

I think I'll figure out the dynamic braking circuit to add, that does give a nice effect, should be simple... especially since I have a few guys that work for me that can do it.

Greg


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## ereuter (Feb 7, 2017)

I'm just offering a solution that doesn't require a DCC decoder, since the OP indicated that he didn't want complicated electronics. Of course he's been conspicuously absent since the first post, so who knows. 

I've worked up a circuit for this, since I'm going to do this with my Hudson. I'll post it tomorrow. I need to polish it up.


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## Greg Elmassian (Jan 3, 2008)

I figure if it runs from AC, DC should be easy...... I did see a limitation in the current for the fan, most LS decoders budget up to 1/2 amp for fan, not 100ma.

Greg - 99


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## ereuter (Feb 7, 2017)

It's pretty safe to assume that the input just gets rectified by one of the two bridge rectifiers on the board, so it should work fine with DC or DCC as well. The microcontroller is obviously DC, and the PWM outputs for the fan and headlight are pulsed DC.

Here's a concept for automatic braking with a single input for run (high) and stop (low).










If there were a desire to modulate the fan speed, however, the transistors should be driven separately so it's not braking during every PWM cycle. In this version, the run line is grounded to run and the brake line is brought high to brake. There's not protection to keep both transistors from conducting, though, so the software has to be pretty tight.


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## Greg Elmassian (Jan 3, 2008)

I would think that first circuit could be added on to what people are using from ESU, Massoth, QSI, etc.

I'll have to gen one up and see how it works. Could be made cheaply enough.

Greg


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## ereuter (Feb 7, 2017)

Yeah, it could theoretically be attached straight to the Hall effect sensor. 

I haven’t actually tried this yet. I don’t seem to have any P-channel MOSFETS on hand, and I’m about to go on vacation. If you try it out, let me know how it goes! 

The pull-down resistor on the input is intended to brake the motor if the input is floating, e.g. during startup


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## Greg Elmassian (Jan 3, 2008)

I'm thinking the fan "output" from the decoder... on these units, whether you are in autochuff or use a sensor, the fan and heater outputs are from the decoder itself. Should be simple.

Greg


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## ereuter (Feb 7, 2017)

After I last posted, I realized that using it directly with the sensor won't work because it would burn up when the engine stops. 

Just keep in mind that with that first design, if you modulate the fan speed with PWM (e.g. while stopped or decelerating), it will try to brake the motor during the off portion of the PWM cycle. I think that's probably undesirable.


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## norman (Jan 6, 2008)

Hi guys:

The Lionel and the MTH control systems apply back EMF to the fan motor at the end of each on pulse to stop the fan motor immediately at the end of each " on pulse ".

What is a simple circuit to replicate this function in order to apply back EMF to the fan motor at the end of each pulse of voltage applied to the fan motor to produce CHUFFS of smoke by immediately freezing the rotation of the fan motor with back EMF to then use this circuit to drive any fan driven smoke unit?

Does this circuit not already commercially exist for consumers to purchase as an off the shelf package?

Norman


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## norman (Jan 6, 2008)

Hi guys:

The Lionel and the MTH control systems apply back EMF to the fan motor at the end of each on pulse to stop the fan motor immediately at the end of each " on pulse ".

What is a simple circuit to replicate this function in order to apply back EMF to the fan motor at the end of each pulse of voltage applied to the fan motor to produce CHUFFS of smoke by immediately freezing the rotation of the fan motor with back EMF to then use this circuit to drive any fan driven smoke unit?

Does this circuit not already commercially exist for consumers to purchase as an off the shelf package?

Norman


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## ereuter (Feb 7, 2017)

Norman:

The simple circuit that I posted this morning should do just what you're describing, but you need some other logic to run the fan when the engine stops so it doesn't burn up the heater.

The SUPER-CHUFFER is the only off-the-shelf device I have found dedicated to this task. You give it power (rails or battery), chuff sensor input, and it runs the fan for you. It uses BEFM braking and runs the fan at low speed when the engine stops. I can't personally vouch for it, but it gets good reviews on the O scale forum.

Eric


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## Greg Elmassian (Jan 3, 2008)

I believe the QSI will idle the fan too... I will see soon...

Greg


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## Greg Elmassian (Jan 3, 2008)

Norman, any progress on your "quest for smoke?"

Greg - 87


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