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Thursday, October 16, 2014

Liquid- Fueled Lighting, Part 2.0

This is going to be a two-article series with parts and theory in this post, and operation in the second.

In Part 1, I covered kerosene lanterns. Simple, cheap, and efficient, a kerosene lantern will provide enough light to see by, but not enough to really light up a room. To get a lot of light, you need to look at a system that releases more energy in a controlled manner. This is where pressurized-fuel lanterns (and lamps) come in handy. There are different kinds of lanterns and lamps that all run using the same basic principles burning kerosene, butane, gasoline, etc., and they are similar enough that explaining one will cover them all.

This is a Coleman gas lantern. It works by storing very volatile fuel in the base under pressure, feeds that fuel through a "generator" that converts it into a high-pressure vapor, and then  feeds the vapors into a combustion chamber made of ashes.  The smaller red ones are single-burner and the larger green ones are double-burner. I personally prefer the smaller ones for their fuel economy as well as sentimental reasons; I grew up using the red ones during campouts and night fishing. I own several and just picked up a dead one that is being stripped for parts, so I'll have plenty of pictures to go with the explanations.

Parts are becoming harder to find for the small lanterns, with the glass globe being the worst. I used to be able to get them at any hardware store and now I have to mail-order them. Camping supply stores may, or may not, have them on hand. Parts for the larger lanterns are easier to find. Here is a PDF with the parts list for the small ones.

Let's start with the fuel. Coleman lanterns use a Naphtha-based blend of hydrocarbons commonly called "white gas" or "Coleman fuel", which can be found in most camping supply stores and on the shelves of any Wal-Mart with an outdoor section. Common lighter fluid is also Naphtha-based and works just as well as white gas, and I am testing VM&P Naphtha (a paint thinner that's cheaper and easier to find) to see how well it works.

Prices have gone up in recent years; a one-gallon steel can of white gas used to be the staple size and cost less than $5.00. The last time I checked, they are now selling plastic one-quart bottles for about the same price, with one-gallon metal cans still available for about $15.00.

Being Naphtha-based, the fuel has no shelf life that I've been able to find. A 20-year-old can will be just as clear and just as usable as one bought last week, as long as it has been kept sealed. The can in the picture on the right has been sitting on a shelf for about ten years and is still full. (It also has a price tag that says $3.29.)

 Naphtha is very volatile and will evaporate faster than gasoline, so be sure to keep containers sealed and away from open flames. There are some Coleman stoves and lanterns that are designed and marketed as "dual-fuel" burners -- they will work with either standard white gas or unleaded gasoline. Using unleaded gasoline in a lantern not designed for it will work, but will gum up the internals since gasoline has additives in it that don't pass through the tiny orifices very well.

I'm going to go through the parts and functions of the lantern from the bottom up, so here's the base.

Made of welded steel, the base has an opening for adding fuel (on the right side in the picture) and a pump (on the left side in the picture) for pressurizing it. The base holds about a pint and a half of fuel (24 ounces), enough for at least eight hours of light.

Always use a funnel to add fuel. The opening is about a half-inch wide and trying to pour clear liquid from a gallon can into such a small opening is a guaranteed spill. Spilled fuel evaporates quickly, but that just leaves explosive gasses in the area, so use a funnel.

Using the pump is a bit tricky at first, so here's what you do:
  1. Turn the pump knob to the left two complete turns. This opens a valve at the base of the pump. 
  2. Place your thumb over the hole in the knob and leave it there while you're pumping. 
  3. Pressurize the fuel supply with 35-40 full, quick strokes of the pump.
  4. Then turn the pump knob back to the right until it is snug. The valve at the bottom of the pump is made of brass, so don't tighten it too much or you'll damage it.

Here's the pump assembly pulled out for cleaning/inspection. Remove the wire retainer and pull up on the pump knob and it comes right out.
The square rod in the middle of the pump chamber is the valve stem that is turned when you turn the pump knob.There is a spring on the pump shaft to keep you from slamming the pump head into the cap on every upstroke.

This is the working end of the pump. It is a leather cup held onto the shaft with a spring washer. The bevelled sides of the cup allow air past on the up stroke, and create a seal on the down stroke to force air into the base of the lantern.

Since it is made of leather, a few drops of oil will keep it flexible and help it make a tight seal. This one is still flexible, but is very dirty from being left outdoors for a long time. I'd use it in a pinch, but will probably end up replacing it.

Putting the pump back together takes a bit of care:
  1. Squeeze the leather cup with your fingers as you line it up with the pump hole to make sure it goes in without folds or cuts. 
  2. You may have to rotate the pump knob a bit to make sure the square valve shaft lines up with the squared section of the pump shaft. 
  3. Push the pump down until the retainer is touching the top of the pump and rotate the cap until the holes line up, then replace the retaining clip.

The mid-section of the lantern is mostly covered by a metal shield with the control valve sticking out of the front and the cleaning lever sticking out the back. The control valve meters the liquid fuel from the base up to the generator and the cleaning lever operates a very fine wire that will clear debris out of the tip of the generator.

The base of the air-tube and mixing chamber are attached to the mid-section, and it also serves as the base for holding the globe. There are small air holes abound the globe support as well as one or two (some models vary) larger hole for lighting the lantern with a match.

Which brings us to the top part of the lantern. The larger tube on the right in the picture is the air tube, which brings fresh air up to the mixing chamber (the curved part at the top). The smaller tube that sticks into the air tube is the generator. This is where the fuel gets heated by the lit lantern and turned into a vapor that will burn more efficiently than a liquid. The down leg of the mixing chamber ends in a round metal ring with a groove in it for attaching the "mantle".

Just as a wick in a candle or oil lamp carries the fuel to where it will burn, a mantle in a pressurized-fuel lantern/lamp serves to contain the flame and put out light due to the chemicals it has been treated with. They used to be treated with Thorium Dioxide which is a low-energy alpha emitter. The Thorium salt produces light (fluoresces) from the heat of the flame and boosts the light output beyond what the flame itself is capable of producing.

(Yes, some mantles are radioactive. They emit alpha particles, which are the lowest energy form of radioactivity that exists --they can't penetrate a sheet of paper or more than a few inches of air, let alone the glass globe of the lamp. Naturally-occurring granite emits more radiation than mantles. Don't eat them and you'll be fine. )

Mantles come in a couple of styles, usually tie-on or clip-on. The tie-on style is more versatile as it will fit more styles of lamps.

The top cap and carrying handle finish off the assembly. The carrying handle is spring steel and the ends hook into holes on the lantern frame through holes in the top cap. The cap is designed to drop down over the holes in the frame, so it's easy to tell when you have it in the right position to insert the handle ends.

A word of warning:
  • When the lantern is lit and running, the top cap will get extremely hot. 
  • If you leave the handle sticking straight up when you set the lantern down, the handle will also get hot. 
  • Make it a habit to always turn the handle down when you're not actually carrying the lantern to avoid getting burned. 
  • Keep children and fools away from lanterns that are lit or are cooling down, since the glass globe and top end will be hot enough to cause up to third-degree burns.

Since this style of lantern has been in production for almost a hundred years, with tens of millions of them made, it is likely that you may have one or may find one after TSHTF. Knowing how they operate and being able to get one to produce light is good to know, and knowledge is one prep that you'll always have with you.

The Fine Print

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