Water or oil smokers?

[Stephen White]

I've had an ultrasonic evaporator smoker in my Pz III for a while, with the Benedini controller:







Although the controller varies the blow and volume according to the revs, the smoke effect is a bit thin, particularly in cold weather.

I decided to give oil a try and build the Armortek high volume smoker with Adrian's new smoker controller, which is designed to produce blasts of smoke on acceleration:









Plusses and minuses?

Water system - clean, virtually instant smoke, no smell, simple and cheap to refill, 12 volt system relatively low power consumption but the smoke effect is a bit thin.

Oil system - a bit more messy, smoke fluid costs, takes a while to heat up, 24 volt system and significant power consumption compared with the evaporator but the smoke is more effective and not temperature dependent.

I should also say that the build quality and documentation of Adrian's smoker controller are first class and the two LEDs provide a visual check of power and function.

Each has its place but on balance, the oil system is more effective. Views?

Regards

Stephen

[Garry Coomber]

Stephen,

I have been using the same system, and you absolutly right about the volume of smoke. Unfortunately because the evaporated water is cold, it is less effective in the cold.

I tried alsorts of ideas to get the maximum smoke, but then had a brilliant idea. You can get multiple diaphram evapoartors which could give me more smoke. But first I emailed Thomas. The control module cannot cope with the multiple diaphram version but he advised me that the module was capable of running 2 single diaphram evaporators. I ordered another from Maplin's and installed it. The module does get a little warm, so I have included a fan to blow air over the module. The result, twice as much smoke, just about the right amount for my tiger. a Simple and fairly inexpensive modification.

What I would say is that there are a couple of things to be aware of. Firstly if you leave water standing in the smoke unit for any period of time, unless you use distilled water, it tends to start leaving muck in the bottom and on the diaphram. This reduces the efficency and the diaphram needs to come out and be cleaned off. Also reduce the amount of metal the smoke passes through. I used silicon model exhaust pipe to connect the smoker to the exhaust, and also tried to make it run up hill as much as possible. The smoke does condense and if you have sumps in the pipe work it can fill up and block the smoke.

As to which is best. Liquid parafin works fine, but as you say, is messy, smells and the thing I find with it is the smoke is much heavier and doesn't drift quite as well. It tends to sink unless there is a bit of wind to blow it. Certainly doesn't require as much care to plumb it in. Water is the opposite. For me, water is the most realistic, for a petrol engine anyway.

[Dennis Jones]

Garry,

Can't find evaporators on Maplin's site, do you have a part number ?

Dennis.

[Stephen White]

Garry, Hi

Thanks, very interesting. I did buy a second evaporator but hadn't got around to testing a double installation. I might have a go on the bench for my Comet or Cent. I wanted to get the Pz III up and running for Tiger Day. Agree with all your other points.

To think about too is the interest in getting a muzzle blast of smoke on firing the main armament.

All the best.

Stephen

[Garry Coomber]

We all know them as evaporators but maplin call them mini foggers. It's the evaporator and a mains power supply, I believe that part number is LA38AK. The last one I purchased was about £20. I does mean cutting the cable, don't thing it cares which way around it is wired up. Unfortunately the supply is 24Vac.

[Garry Coomber]

This is my smoke unit. I sectioned off the bottom with platicard to keep the evaporators from moving around, but there is no restriction on where the smoke goes. Therefore if one of the diaphrams needs a clean or replacing, I still get smoke out of both exhausts but probably more out of one than the other. Another tip, all the bolts are stainless, I found that even if they didn't get wet, in time mild steel rusted, more mess to help it stop working. I also put a perspex flap over the holes inside under the fan, this helps spreads the air out inside and also helps stop water splashing out into the fan.

[Fabrice Le Roux]

Hi
Water gets my vote. Clean, odourless, low power consumption, and can be used inside or out. At worst your tank may leave a few drops of water...

But you need to add warm (not hot) water from a thermos just before running. Gary covered most of the points. Plastic pipe, designing out water traps etc. I would add baffles in the water reservoir or coarse aquarium filter material to kill the tendency for the water to slop about. I also silicone glued a lump of expanded polystyrene to the spare space in the reservoir as the fogger is only filled from the top surface so less water is required and hence less need to be drained out after running. It is a good idea to maintain or reduce the bore of the pipework, there is a marked drop in flow rate if the pipe widens, and if possible use a continuous plastic hose right up to the exhaust port. The various push-fit plastic overflow pipe parts (B&Q) are convenient but I have come to the conclusion that the turbulance that sharp changes in direction creates serves to slow the flow of vapour.

For a Cent I would consider seperate fogger units for each side, plumbed into the last muffler with the shortest pipe run feasible. The JJB units that were around a few years ago worked very well with a nice diesel mode that pulsed vapour when idling. However the microprocessor board was quite prone to failure. Mark's Model Bits will make up custom units (http://marksmodelbits.com/) or can supply just the foggers at reasonable cost. I do not know if this gear will interface with the Benedini sound/fx module.

I use a large "Carry On, Nurse" scale syringe to fill and empty the reservoir, it makes a great water pistol too!

cheers, Fabrice

[Adrian Harris]

Adding a power resistor to the tank should be enough to keep it a few degrees above ambient.

Looks like I need to get hold of a water fogger to test out.

Adrian

[Garry Coomber]

A search on Maplin's website for mini fogger will find them straight away. As it comes is great for testing as you can build your system and plug the transformer and off you go. No need to spend too much initially.

Somthing I forgot to mention was that the little black bobble sticking up is the water censor. If the water drops below the tip of the black ball, it automatically stops. So when designing the unit, bare in mind the volume of water you need above the evaporator and allow for a reasonable amount of air space above the water.

The only thing I did which breaks the rule is in the final exhaust. I built the exhaust stacks from steel and they mount to the back of the tank in the same way they would on the real thing, bolted on. I don't find it causes too many problems, if anything helps because you get a slight build up of vapour in the stack. The down side is water in steel, but they are 3mm seemless steel tube and I but a drain bolt in the base plate, so I don't really see them rusting through in a hurry.

I like the idea of filling the bottom with polystyrene of something to cut down the volume of water. Once you drop below the sensor level, the rest is just surplus. I could be considering that.

[Dennis Jones]

Garry,

You mention that it works on 24 volts AC if so, does it also work on 24 volts DC, if not then not much use in the tank.

Dennis.

[Garry Coomber]

Dennis,
Yup the evaporator is definately 24Vac. All the units I have seen all use the same evaporator so I can only assume they all use a transformer and electronics to provide the required feed. Mine is driven by Thomas's water smoker module which in my case has a 12v feed to do the business with the voltage, so 24Vac is no problem.

[Fabrice Le Roux]

Hi,
There used to be 24vDC units available, but the last one I got from Maplins on an unverified recommendation was 24vAC and did NOT work . As I said in my previous post you can get DC units from MMB, because he specially imports them. Mine cost me £12 a couple of years ago, but he is probably still cheaper than Maplins...
cheers, Fabrice

[Dennis Jones]

Hi Fabrice,

Have emailed Mark at MMB as I bought one of his foggers a couple of years ago and he has replied and said he can supply at £12 each but has none in stock at present and is expecting them in 4 weeks.

Dennis.

[Adrian Harris]

> the last one I got from Maplins on an unverified recommendation was 24vAC
> and did NOT work

I've just bought one of the current Maplin "Mini Fogger" units and have dismantled it.

<< You can just imagine my parents dismay every Christmas and Birthday >>

I had hoped that I might be able to simply open it up to suss out the circuit, but it had been completely packed with potting compound the colour and consistency of fine china.

Having finally managed to chip my way through to the PCB, the only thing the 24AC hits when it reaches the board is a bridge rectifier and capacitor, so there isn't (in theory) any reason that it wouldn't work with 24DC.

As this one didn't survive the inspection , I'll see if I can find another one cheap and try playing around with it on DC and seeing if/how it behaves.

Adrian.

[Dennis Jones]

Hi Adrian,

Hopefully I will get some from MMB before I go on holiday in April. Are you going to Tiger Day ?

Dennis.