459 - Theory of Operation

[BobA]

Coleman 459 Stove - Theory of Operation

The Coleman 459-499 Stove is a unique model. It was manufactured for only a short time - from late 1977 to early 1978. It was unique because it dispensed with the "standard" stove valve, that continues to be used even on today's stoves, and replaced it with a single knob "Easy-Lite" control valve. This valve did not use the control lever (UP to light, DOWN to burn) that we are all familiar with. The fuel tank was slightly different than the 413G tank in that the outlet (which some refer to as the "bung") is slightly offset to the right in order to accommodate the new valve design.

The remainder of the stove (except the decal and the model number stamped on the front) is the same as the 413G.

It is my opinion that perhaps this stove was produced as a limited run for market test purposes, and did not catch on. Was it a failure in marketing, or a failure in design? We may never know for sure. In any case, the purpose of this article is to describe and explain the theory of operation of this stove, so that the owner of one might more fully understand just what is happening when he or she turns the knob & lights it. Keep in mind that I am not a technical illustrator. I can't draw a straight line. So, I can not provide graphics to show you what is actually happening inside the assembled valve. What I will do is provide photos and try to describe how it works - hopefully making it somewhat clear!

So as Jackie Gleason used to say - "and away we go!"

The Valve

The heart of the 459 valve is the valve stem. It is actually a stem & cam assembly. The cam is a modified cylindrical cam, which operates both horizontally and vertically. I will attempt to explain this later.




Here is the front of the cam. The groove is for an o-ring seal. When the cam is turned to the OFF position, the cam moves fully forward, pressing the o-ring against the front of the valve body. This shuts off the flow of fuel to the generator, turning the stove off. The center hole is for the needle assembly.




This is the valve body. The valve stem & cam fits into it as shown.





This is a view of the inside of the valve body. The center hole is the outlet to the generator. The cam's o-ring seals against that wall, around the hole, to shut the fuel off.



Here is the F/A (Fuel & Air) tube. The upper part (arrow) fits into the groove of the cam and acts as a stationary follower. In the 2nd photo, the F/A tube is screwed into the valve body so you can see that the follower protrudes into the area where the cam will be.






These next 3 photos show the follower riding in the groove of the cam, in different positions. Of course, this is taking place while installed in the valve body, but since we don't have x-ray vision, I can't show that!




The whole point of this is to show that, since the follower is stationary in the valve body, turning the valve stem causes the cam to move back & forth horizontally, as dictated by the cam groove.


Now we have the F/A tube with the F/A rod & spring installed.




The top of the F/A rod is another cam follower which rides in the groove vertically. The groove is cut so that its base varies in diameter as the stem is turned, which causes the F/A rod to move up & down.




If I have you thoroughly confused by now, I apologize! But - worry not! Next, I will simply show how the valve works operationally (and externally)! Note that in the following photos, the gas tip protector is removed in order that we can see the position of the needle at the different valve settings.

Here is the valve turned to the OFF position.



The F/A rod is inserted into the orifice of the F/A tube.




The needle is inserted fully into the orifice of the gas tip.


Most importantly, as I described earlier, the cam is fully forward against the front wall of the valve body, compressing the o-ring seal, which shuts off the fuel flow to the generator.


Here, the valve is turned to the LIGHT position. Inside the valve, the cam has retracted from the front wall of the valve body, allowing fuel & air to flow into the generator.


The F/A rod is again in the orifice. This blocks most of the fuel flow, allowing a small amount through, which mixes with air coming from the orifice at the top of the tube. This gives a nice lean & clean fuel/air mixture for easy lighting.




Here, you can see that the needle has been retracted and is NOT in the gas tip orifice. This allows full flow of the fuel/air mixture.



The knob is turned to the HI position.



The cam has allowed the F/A rod to retract from the orifice, opening it wide and allowing full fuel flow into the tube. This fills the tube with fuel and cuts off the air, allowing fuel only into the valve and generator.




The needle is still retracted and the gas tip is wide open. The burners run on high.



The knob h
ere is in the LOW position. This moves the cam partially forward in the valve body, but not enough to shut off the fuel flow.




The F/A orifice is still open, providing fuel only to the valve.




The cam has moved the needle partially forward into the gas tip orifice. This throttles some of the fuel flow into the burners. They run on low.



The valve can be adjusted steplessly between HI and LOW. This moves the needle in & out of the gas tip orifice, varying the fuel flow, so the flame can be adjusted to any desired intensity. I want to point out, though, that this adjustment takes place in just slightly more than 1/4 turn of the knob. So it is more of a "touchy" adjustment, than a standard valve provides.


There are some other components to this valve that were not covered in the description above. This was done to avoid any further complication and confusion. These parts are located around the valve stem, between the cam and the stem nut (this is the huge nut, just in front of the valve knob, which screws into the rear of the valve body.



Here are the parts, from left to right:

The spring, the washer, and the rear o-ring.




They are located in exactly that order, on the valve stem, as these photos show.






As you might have guessed, these parts perform the equivalent function of the valve stem packing. That is, they prevent fuel from leaking at the valve stem and nut. The o-ring seats against a machined surface inside the nut. The spring and washer provide a constant load on the o-ring to keep it firmly in contact with both the nut & the stem. When the cam & stem move back & forth as the operator turns the knob, the o-ring will stay firmly in place.

The spring also provides a secondary function. When the knob is in the OFF position, the spring provides a constant forward force on the cam, pushing it against the valve body to stop the flow of fuel. This assures that even when setting and/or wear of the forward o-ring occurs, a solid seal will be maintained, and no fuel will leak into the generator.

That completes the Theory of Operation of the 459 stove. I hope that my explanation is adequate.

Now, as Lt. Columbo would say...

Just one more thing, sir!

I do want to point out some weak points in the design of this valve. Since I am not an engineer nor a metallurgist, these are just my opinions. The first one could be a potential safety issue. The other two are premature wear issues.

1) The front (shutoff) o-ring sits in its groove in the cam. The side of the o-ring is compressed against the wall of the valve body, to effect shut off of the fuel flow. Let's imagine that the stove is stored for a period of time with the valve in the OFF position, as would be normal. I can envision a situation where the o-ring could conceivably "stick" to the valve body. In this case, the next time that the stove is used, and the knob is turned to LIGHT - the cam retracts, while the o-ring remains stuck to the valve body. In other words, the o-ring could pull right out of the groove in the cam. When the knob is turned back to OFF, the o-ring might not just slip back into the groove. It could twist and jam. If this should happen, you would not be able to shut the stove off.

2) The rear (packing) o-ring looks like it could be a high-wear point. The rotational and sliding forces of the stem through this small o-ring in normal operation would take a toll. The load of the spring compressing it would likely accelerate the wear from these forces. I know that mine arrived completely disintegrated. If it were not for the parts list showing that the front & rear o-rings had the same part number, I would not have been able to determine what kind of seal was used. That's how badly it was deteriorated.

3) The cam itself looks like it could be an extremely high wear point. The groove in the cam has some relatively quick and sharp turns, changes of direction, and detents. The metal to metal contact of these areas with the (F/A tube) follower appears to be a situation in which wear would quickly occur. It doesn't seem that Coleman fuel has a great deal of lubricity, so I would imagine that these areas might not survive for very long, under moderate or heavy use.

So, did Coleman discover some of these possible difficulties after release (a la 501), and decide to discontinue it? Or did customers simply not care for the new valve style and decided to stick with "tried & true", resulting in poor sales? I don't know. I'm hoping that, with time, more evidence will be found that answers these questions.


BobA

[Chucker]

Thank you for your work on this Bob. I'd still pick one up in the wild if I came across it.

[Rhubarb]

What a great write up! Thanks Bob!

[mikew]

Great explanation and illustrations!! Another problem it seems would be if trash got under the o-ring or if it failed while running, would not be able to shut the stove off.

[Deanofid]

I've never seen this kind of valve before, Bob. Thanks for the pics.
This is something I gripe about, to myself mostly, but sometimes here; That a well proven and long reliable system is sometimes fooled with. I can imagine, just in my guessing and supposing, that someone high up in the company had a kid graduate from engineering school. He got his kid a job and the kid wanted to prove out his new great ideas, and got the chance by daddy hiring him.
Well, the kid was a flop. This is terrible engineering. It happens a lot in all kinds of business. Some slick new idea comes along and a few hot shots bite into it. Few years later they are spitting it out and going back to the old proven method. That kind of stuff costs companies money. In Coleman's case, it cost a whole new model production and promotion when they could have just let folks be happy with the old 413.
Dollars to donuts they had a mark of about a half million units to see the cost savings in going from brass parts to some other metal, besides paying for tooling up, and they ended up going back to brass anyway.

[Gunhippie]

Excellent write-up, and fine photography!

I'll probably never see one of these in the wild, but will keep it in mind.

[brucesheehe]

Amazing work and educational effort. Thanks!

[BobA]

Thanks to all of you. I'm glad that you liked it!


Bob

[BobA]

deanofid wrote: I've never seen this kind of valve before, Bob. Thanks for the pics.
This is something I gripe about, to myself mostly, but sometimes here; That a well proven and long reliable system is sometimes fooled with. I can imagine, just in my guessing and supposing, that someone high up in the company had a kid graduate from engineering school. He got his kid a job and the kid wanted to prove out his new great ideas, and got the chance by daddy hiring him.
Well, the kid was a flop. This is terrible engineering. It happens a lot in all kinds of business. Some slick new idea comes along and a few hot shots bite into it. Few years later they are spitting it out and going back to the old proven method. That kind of stuff costs companies money. In Coleman's case, it cost a whole new model production and promotion when they could have just let folks be happy with the old 413.

I agree with you on all the above, Dean. Probably not too far off from what actually happened!

I am a bit confused, though, on the last paragraph you wrote:

Dollars to donuts they had a mark of about a half million units to see the cost savings in going from brass parts to some other metal, besides paying for tooling up, and they ended up going back to brass anyway.

I apologize for being dense here, Dean, but - the valve on this is brass, so I'm not sure what you are getting at.


Bob

[Deanofid]

You're not dense, Bob! Looking at the pictures I thought the valve stem/cam was made of some white metal, like aluminum. My mistake, obviously. Still, for all the money it takes to tool up, they would have had to sell quite a few to pay for the new design.

[BobA]

deanofid wrote: Still, for all the money it takes to tool up, they would have had to sell quite a few to pay for the new design.

Indeed - and given how uncommon these stoves apparently are, it seems that Coleman must've taken a bath on them. Ah, well. That's what sometimes happens when a company invokes one of the worst of my pet peeves - "Change for the sake of change" (or perhaps, as you said, "change for the sake of the President's nephew" ).

In any case, I tend to like the unusual (particularly the technically unusual), so I am thrilled to have found one and I had a lot of fun working on it!


Bob

[Terry_Marsh]

My congratulations also for an excellent write-up, Bob!

Would it be fair to say this stove's mechanism regulates the fuel-air mix by a flat O-ring rather than a Schrader valve or the earlier "push-rod" design?

When Coleman - Toronto switched to O-rings to regulate the fuel-air mix (in their Easi-Lite series) they used round O-rings made of Viton. They are a pale blue color. Viton withstands petroleum products and high temperatures I believe. Are the O-rings in the 459 also Viton do you know.?

Thanks,
Terry

[BobA]

Terry_Marsh wrote: My congratulations also for an excellent write-up, Bob!

Thanks, Terry!

Would it be fair to say this stove's mechanism regulates the fuel-air mix by a flat O-ring rather than a Schrader valve or the earlier "push-rod" design?

No. The o-ring only provides the ON/OFF function. The HI-LO regulation is provided by the needle in the generator's gas tip, much like with the conventional stove valve. The regulation of the fuel & air (for lighting) or fuel only (for burning) function is provided by the cam moving the F/A rod up & down, as appropriate for the given knob setting.

When Coleman - Toronto switched to O-rings to regulate the fuel-air mix (in their Easi-Lite series) they used round O-rings made of Viton. They are a pale blue color. Viton withstands petroleum products and high temperatures I believe. Are the O-rings in the 459 also Viton do you know.?

There seems to be a bit of a misunderstanding here. Unless different o-ring manufacturers use different color codes (of which I'm not aware), Viton rings are black. Blue o-rings are fluorosilicone, and are the ones used on Canadian lanterns (not sure about their stoves). In any case, the 459 uses black Viton, square-cut o-rings.


Bob

[hahoe03]

There seems to be a bit of a misunderstanding here. Unless different o-ring manufacturers use different color codes (of which I'm not aware), Viton rings are black. Blue o-rings are fluorosilicone, and are the ones used on Canadian lanterns (not sure about their stoves). In any case, the 459 uses black Viton, square-cut o-rings.


Bob




Many manufacturers can make any O-ring in any color. While some viton O-rings are black, the most common color is brown. This is of course based solely on my personal experiences in ordering replacement orings.

[BobA]

hahoe03 wrote: Many manufacturers can make any O-ring in any color.

After reading your post, Mike, I went out and looked specifically for this, and you are correct. Some manufacturers advertise this capability. I really hate it when there are no standards! Absent a laboratory test, if they all look the same, how the heck do you determine the composition of one? Unwise, in my book.

While some viton O-rings are black, the most common color is brown. This is of course based solely on my personal experiences in ordering replacement orings.

Now, that's strange. In my experience, the most common color (for Viton) is black. In fact, I have never seen a brown o-ring (other than in pictures). I will only say this - given what I've read in many posts on this forum, as well as my own experiences, there seems to be a consensus that when dealing with Coleman lanterns & stoves, at least - a black o-ring indicates Viton, and a blue o-ring indicates fluorosilicone. Would you disagree?


Bob

[hahoe03]

Unfortunately I only have a few Coleman's that use o-rings and/or Schrader valves. On my 222's I replaced the blue orings with green refrigeration grade ones. With there being no "color standards" all you can do is to assume what the OEM oring is. This is by no means saying that anyone is right or wrong, just pointing out the inconsistency.