A couple of months ago (November) I followed with great interest two threads on this forum that more than a little touched a problem I've had with a stove of mine.

Combining the information from the discussion around Peter Watchhorns analyzis of an Optimus 5S with that from the thread on Valors patent for reducing underburning I sought advice on a problem I have with a 111T.

I'm certain that the answer to my question can be found on this forum, and that the lack of response to my post is merely due to it being overlooked in a long thread...

So I try again (cut & paste from my previous post):

Some time ago I bought a "New Old Stock" Optimus 111T at the Norwegian Defence Museum, a present for my brother. Along with this I got 2 used 111Ts ("shelf warmers" for some time) for a very reasonable price. The first lacked one of the brackets fitting the tank to the box, as well as the box had had all its paint burned off. The second had a worn spindle valve, and some paper/paint/plastic "guey" melted onto the bottom of the box (which by the way has embossed logo and a nice dark green military colour, presumably original).
I've fixed the valve on the green one, and will do something with the guey.
What I haven't been able to fix is the underburning that this stove suffers from! The I'm planning to give it to a friend of mine, who still makes his camp food on gas... However, I can't present him with an underburner.
The tube above the jet does not have the 4 holes leading into the chamber under the lower cap.
I'm tempted, but do I dare...

Do I drill the 4 holes or not?

Eivind

Before taking drastic action with the burner I'd recommend changing the jet. As they get worn the burner can become more prone to underburning - I am experiencing this at present with a Svea 5 I use daily after months of flawless operation.
Just as a tip I'd always recommend lighting the burner from above after the priming flame has gone out - even with a good jet & burner using the last of the priming flame to light the burner can sometimes cause underburning.
Cheers,
Ross

Hello All,
While we have this new thread going. I have always been confused with the term underburning. Is this a problem with silent burners only?
Is a under burn when the flame burns directly at the jet (nipple) rather then up at the top of the burner?

Chuck

Also you said you are going to give this stove to your brother for camping.
A silent burner is not a good stove for camping. The slightest brease will create burning problems and largly pre-heat problems. This is with out a wind protector.
Under burn, I don't think this has ever been recterfyed 100%. I can go into this in great depth but this will not help you out. The only sergestion I can make here apart from what Ross has sergested is may be try another outer flame spreader.
Albert

Thats it Chuck. It also sounds like a jet (747) going over. If you get this shut it down ASAP. Then start again or light at the outer flame spreader. I have seen the complete burner melted because of this.
Albert

Albert,

Thanks for the quick and to the point reply. I have had this happen before and I shut down the stove and pricked out the nipple. So can we safely say that under burning is caused by a problem with the jet (nipple)?

Melting the burner makes sense since the flame is below the burner instead of between the dome and the burner head.

What about the holes on some of the inner domes. I have read that this helps with under burning.


Chuck

I will try the recommendations from Ross and yourself. Fortunately I do have a brand new jet, and I can use the outer flame spreader from the other (cindered) 111T I got along with this.
The one I gave to my brother was an unused one (NOS). Nice shiny brass, and according to reports behaving perfectly. Yet(!) another (used) one that I bought for myself is also behaving well! I haven't tried it in windy conditions, though. I guess my Primus MFS then would be preferable...
Still I can't stop thinking of the fact that all the other 111 burners have 4 holes leading into the lower chamber, combined with the article on this site about the Valor patent: http://www.spiritburner.com/patent_valor_618139.htm

I'll promise not to drill holes until I've tried all "non-destructable" suggestions first...

Regards
Eivind

While jet problems may make a silent prone to underburning, a silent can underburn without any jet problems, and I have experienced this a number of times.
Underburning is when the outer burner dome acts like a roarer burner; that is, the flame ignites at the underside of the dome like a roarer does at the underside of the burner plate/flame spreader. It can be eliminated (at least on a stove with no jet problems) by igniting the burner on the outside at the dome holes after the meths have burned out, as Ross says.

I agree that silents are not satisfactory for camping. When I first got my Hipolito 2 silent adjustable, I used it a lot inside. Then I took it to a picnic to impress my friends with my hobby. I could not get the thing to light in the slight breeze; double and triple priming were no help. I got only sooty yellow flame and liquid kero all over the place.

Well that explains why my first attempt at lighting my Primus #56 went so badly.I not only didn't use a wind screen I tryed to light it in a high wind.Can you say four foot flames? I kept thinking (she will settle down)NOT! When the flaming kero started dripping on the tank I let her have it with the garden hose.I also had about thirty pumps on her.I can laugh at myself now but it was pretty intense. Dan

Yep,
Doesn't take much for that kero to leap up and take the form of a flaming fountain. Always better when noone is looking.

Chuck

I got a great stove arrived this morning I bought on ebay - an Optimus 85 Loke. As an 'enthusiast' I've been after one of these for a long time. This storm cooker with a Trangia style windshield runs on paraffin with a silent burner. I've tried it tonight & it works like a dream & the thing quickly boiled a pan of water due to the confines of the upper windshield & I'm looking forward to trying it under more testing circumstances. Theres's a picture of Dag using one in the action gallery - any reports on how these perform in wild & windy conditions?
You can even use other pans with it as long as they fit within the windshield as there is a small X-trivet that fits on the burner - it takes my big Trangia kettle no bother. The pans it comes with nest in the upper windshield in use.

http://www.spiritburner.com/actionshots_4.htm

I don't remember seeing this on Ebay. This is also on my short list of stoves I would like to acquire. I am a sucker for stoves that include cookware as part of the package.

I thought I was the only one that had a thing about stoves w/ cooksets! It does add a bit of depth to stove collecting. By the way I just won the Auction for the Optimus 77 Cookset that was here on the trading post. Bill (the guy running the auction) said some people from UK had bid on it, was it any of you guys? I am also looking for the 1.5 liter pan for the Primus PSS cookset. Does anyone know where I can buy it?

Phoebus 625 has a silent burner, and is a great performer in the wind -- it was a popular expedition stove in the '70s. Maybe the higher volatility of gasoline (petrol) makes a difference(?) They do occasionally have the underburning problem though, and have to be shut off and relit.
....Arch

I ve used my Loke for years, and have never had trouble with it.

In windy conditions I have tried to get protected by positioning near a stone, the backpack or tent, (it's more comfortable).

The users manual had orginally a text for use on kero or gas, but the gas was wiped out. I will guess that gas may be risky, the tank may be pretty hot. The stove should not be plased on snow witout anything under, it will melt the snow, and become unstable.

I have only used kero, whitespirit (nearly kero), diesel and lamp-oil. All theese works well after preheating with mets or equal.

When pumping before use, I have never needed to pump during operation.

I have tested it with alcohol, and restrictor, it works, low output or high consuption and some soot.

The Loke makes less soot on kero than my new Nova.
I still prefere Nova and homemade windshield due to low weight, and easy preheating. The perferformance may be different but for my use the difference is of no importance. The Trangia and and adaptor is not easy enough, but the Trangia version of Nova seems better, but I do not know.

Dag S

You are not alone. Someday I'll pick up a 77 as well, along with a Sigg Traveler, an Optimus 85, the few Trangia's I don't already have, ...... These will complement my Primus 71E, Optimus 88, Sigg Tourist Kit, Optimus 81, and a couple of Trangia's.

You can succesfully use a stove with silent burner(s) in any amount of wind, from the lightest zephyr wafting o'er summer meadow to the shrieking, ice-laden,
psycho-gale blasting down from the frozen wastes if, and its only hot weather that stops me from doing it, you cook in the tent.
Of course, this has its drawbacks if you camp in something like this

in which case the heat may become overpowering & a flare-up unhealthy, likewise the dread CO. It is also inadvisable if this pair and their chums are likely to rootle about in your kitchen area.

But if you camp in one of these in places where the most serious wildlife threat to your food, barring the Beast of Bodmin Moor, is Brock the badger

the extra warmth is generally a bonus and the odd flare-up does not spell immediate and fiery doom, nor has our CO indicator ever changed colour (new one every trip!) The only downside is that the corners of the wheel-arches tend to stick in your back. Something like this tends to reduce Brock's enthusiasm for scoffing your breakfast at 3am.


Ian

Camping Gaz GlobeTrotter. Could be a classic!

Ian

I've just come in from the cold after having tried a couple of suggestions from Ross and Albert.
First I compared the inner and outer domes of the "problem 111T" with the ones from my fully working 111T. The outer "dome"/cap had the same dimensions as the one on the good 111T, but the inner dome was ca. 2mm shorter than the "good" one. I decided to try the inner dome under the hypothesis that a lesser volume between the outer and inner dome could increase the flow velocity and reduce the risk of underburning.

Before this I thoroughly primed the burner with its "original parts", pumped sufficiently and lighted it from above after the priming flame had extinguished. It burned nicely for about 2 minutes before it started underburning. (There was no wind during these experiments.)
So I swapped the inner dome for a "good" one, primed again and relit the burner. This time it took 5 min before underburning started.
I swapped the inner dome back and changed the jet to see if this might help. This time it took again about about 2 min.
I did not try the other outer dome due to lack of dimentional difference as well as because the fitting "lips" are slightly different, and so would require some bending to fit.

I can't avoid thinking there must be a mathematical reason for underburning. It must have something to do with gas flow behaviour vs. gas/air ratio (explosion/igniting point) and probably also temperature.

Another thing: why are there 3 x 3 holes leading into the inner dome from above?
Does anyone else own and (successfully use) an 111 silent with no holes in the tube leading into the lower chamber?

Frustrated regards...
Eivind