Monatauk Gnat Stove Review

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Jul 7, 2010 at 6:41 am #1626874

John S.
BPL Member

@jshann

Agree with Carlos. You still have to carry a lighter/matches. We had a jetboil piezo ignition fail this past weekend in the Pecos Wilderness.

Jul 7, 2010 at 7:52 am #1626895

Roger B
BPL Member

@rogerb
Locale: Denmark

I have never purchased a piezo ignitor stove, preferring to use a mini lightmyfire striker instead, which can also be used to start a "fire" in the old fashioned way as well.

Jul 23, 2010 at 1:24 pm #1631779

John Hurley
Member

@backpacker56
Locale: Central Texas

No one has said anything about the corrosion resistance of titanium.

Is the burner itself titanium? How does it look after it's been fired a few times? I've seen used non-titanium stoves of similar type for sale (ebay) and the burner is all rusted. May still work okay, but aesthetics are important too. Charred, rusty stoves are ugly. If this stove avoids that, it should score points.

On the other hand, some parts are aluminum, how well do these parts hold up?

Aug 17, 2010 at 1:23 pm #1638142

Stuart R
BPL Member

@scunnered
Locale: Scotland

When first lit, my Gnat burns a blue flame, but after 30 seconds it turns orange.

Anyone else experience this?

Does it matter?

Aug 17, 2010 at 1:37 pm #1638150

Bob Gross
BPL Member

@b-g-2-2
Locale: Silicon Valley

As a general rule, if the flame color is different from what you expect, then there is a problem of some sort. If the flame is supposed to be blue-hot and it is only orange-hot, then that suggests a "breathing" problem, like if the cold air intake is clogged with foreign material. It is possible that the fuel is contaminated with something, but with a butane canister stove, that would be very unlikely. It is possible that there is some foreign contamination in the top of the burner, like spilled food. The top of the burner is normally titanium or stainless, so it does not corrode even after serious heat. Those metals might change color slightly, but that is normal.

–B.G.–

Aug 17, 2010 at 1:44 pm #1638151

Stuart R
BPL Member

@scunnered
Locale: Scotland

Bob

The same canister wth a different stove is fine, so not fuel contamination.

I took the burner apart to look inside. The burner is titanium with a fine mesh (presumably stainless steel) inside. No dirt. The jet looked ok although I didn't remove it as I may want to return the stove.

The flame starts off blue as I would expect, but turns orange once the stove has heated up, about 30 sec

Aug 17, 2010 at 2:03 pm #1638156

Bob Gross
BPL Member

@b-g-2-2
Locale: Silicon Valley

On most of these stoves, the cold air intake is a pair of open holes on the sides and between the fuel port screw and the burner. Did you poke around in there? One tiny bit of leaf could really clog things this way.

–B.G.–

Aug 18, 2010 at 12:41 am #1638303

Stuart R
BPL Member

@scunnered
Locale: Scotland

Bob

This stove is brand new, fresh out the box.
There is no accumulated dirt and no obvious bits of swarf anywhere I can see.

Aug 18, 2010 at 3:59 am #1638313

Roger Caffin
BPL Member

@rcaffin
Locale: Wollemi & Kosciusko NPs, Europe

Hi Stuart

Same problem as we discussed before.
But I don't think mine does that … what happens when you turn the power up?

cheers

Aug 18, 2010 at 5:55 am #1638325

Stuart R
BPL Member

@scunnered
Locale: Scotland

Hi Roger

Similar problem as previously discussed – *some* part of the burner must be getting too hot.

The only part glowing visibly are the pot supports. However, the 'windscreen' on a Pocket Rocket also glows but doesn't result in an orange flame, so I don't think that is the problem.

So, it must be something inside the burner? I had a quick look and saw nothing obviously wrong, but I'll take another look.

The power is already quite high in the photo, turning it right up doesn't make much difference.

I didn't see any video reviews of this stove showing this problem, it must be just me :-(

Aug 18, 2010 at 9:33 am #1638395

John Donewar
BPL Member

@newton
Locale: Southeastern Texas

Stuart,

I found this in a gear review of the Gnat on Backpacker.com.

>>Two tips: 1) Don’t forget to pack your own windscreen because the burner is very susceptible to breezes, and 2) Screw the canister on tight. (I noticed a big difference in output between a lightly screwed on and a cranked on canister.)<<

How close is the aluminum control valve housing to the "rim" of your fuel cannister? Does it contact the rim of the cannister as you are attatching the stove to the cannister?

The change in the color of the flame suggests to me a change in the air fuel ratio. Is it possible your are going to a "lean" mixture of air and fuel due to the fuel cannister not being firmly attached and fully open at the self sealing cannister valve?

Compare the parts of the two stoves that connect to the cannister. Is the part of the Gnat that opens the self sealing valve on the cannister clean and able to fully open the self sealing cannister valve?

Looking at pictures of the Pocket Rocket stove I notice a seal of some sort between the stove assembly and the fuel cannister. Is it possible that the Gnat is "drafting" excess air into the fuel mixture at the cannister / stove connection?

I am very interested in this thread as I am contemplating the purchase of a Gnat/Fire Maple stove myself.

Party On,

Newton

Aug 18, 2010 at 1:53 pm #1638478

Stuart R
BPL Member

@scunnered
Locale: Scotland

John

"How close is the aluminum control valve housing to the "rim" of your fuel cannister?"

Gas starts to come out of the canister when the clearance from the control valve housing (the orange bit) to the canister rim is 0.3 – 0.4mm for two different canisters.
The stove then screws on for a further 0.3mm without excessive force.

I think the seal between canister and stove is good. In any case, a bad seal here would result in gas leaking out, not air leaking in.

I took the stove apart again and had a good look, but still didn't notice anything obviously wrong.

Ho hum

Aug 18, 2010 at 3:10 pm #1638501

John Donewar
BPL Member

@newton
Locale: Southeastern Texas

Stuart,

Are all other parts of the stove above the orange "valve bit" assembled tightly before and after the testing? Excess air in the mixture?

Can there be anything blocking the flow of gas to the jet/burner? Pressure of the fuel being delivered to the burner reduced? A part of the cannister seal?

Is there anything that can be causing a catalytic reaction of the flame where you are testing the stove? The color change?

Party On,

Newton

Aug 18, 2010 at 3:19 pm #1638506

Roger Caffin
BPL Member

@rcaffin
Locale: Wollemi & Kosciusko NPs, Europe

Hi Stuart

OK, I got mine out and fired it up. It started out with a blue flame as should be, but as the middle of the Ti pot supports bits got red hot it gradually developed the orange colour you showed.

Diagnosis:

The red-hot metal at the burner face is causing a change in the chemistry of the flame, with atomic carbon being generated too early for combustion. The carbon atoms are glowing in the flame as the hydrogen is being burnt first. I think most of the carbon does get burnt up higher up. This does not (normally) happen with other stoves when there are no red-hot bits in the flame.

So … I took the pot supports off and tried the stove again. It lasted longer before getting an orange flame, but the top of the burner face did slowly get red-hot, and then the orange glow returned.

I note that this burner has a double layer of mesh under the Ti burner face. That should stop it from getting any flash-back or internal ignition, and the inner layer is unlikely to get as hot. Field testing has not shown any problems of flash-back either.

You can 'improve' the performance (ie reduce the orange glow) by *restricting* the inwards air flow. This makes the flames just a little longer, so they don't heat the burner face as much. The heat is higher up or further away. Blocking one air inlet hole may be enough.

However, as I said, field testing has not shown any problem with this burner, so you could just ignore the problem ***in my humble opinion***.

Cheers
Roger

Aug 18, 2010 at 4:00 pm #1638520

. .
BPL Member

@biointegra
Locale: Puget Sound

Does it make a difference when there is a pot of water on it heating up? Perhaps the stove will not have a chance to develop much of the orange flame if a pot is on top and the stove is switched off after boiling. That is, perhaps field use will prove to be less enigmatic.

Aug 19, 2010 at 9:35 am #1638667

Stuart R
BPL Member

@scunnered
Locale: Scotland

Hi Roger

Thanks for taking the time to reproduce this and for your diagnosis.

"I think most of the carbon does get burnt up higher up."

Normally, formation of carbon/soot is associated with carbon monoxide which is not further oxidised, usually due to insufficient oxygen altering the reaction pathways, or flame quenching.

In the Gnat flame carbon is being formed, and the flame will be partially quenched by the cold surface of a pot.

That might be expected to lead to high CO levels. Your published measurements indicate that this is not the case, but despite this I can't help being just a little worried, as I often cook in the tent vestibule.

cheers

Sep 4, 2010 at 10:25 pm #1643109

Dennis Park
BPL Member

@dpark
Locale: San Francisco Bay Area

If there is an increase in carbon in the flame, will it create soot on the bottom of pots?

Sep 5, 2010 at 2:59 am #1643125

Roger Caffin
BPL Member

@rcaffin
Locale: Wollemi & Kosciusko NPs, Europe

> If there is an increase in carbon in the flame, will it create soot on the bottom of pots?

I don't think the amount of free carbon is all that high. the orange glow is very faint compared to, say, a candle flame. And I have not seen any soot accumulate on the underside of my pot.

Cheers

Feb 2, 2011 at 1:10 pm #1691518

Bob Gross
BPL Member

@b-g-2-2
Locale: Silicon Valley

Being a gear junkie, I was forced to purchase one.

I started a sea level test with everything at a temperature of 60 F. One 16-ounce aluminum kettle with 16 ounces of water in it. I had a full rolling boil in a hair over 3 minutes.

In the protective case, it is smaller than a Pocket Rocket. Out of the protective case, it is much smaller than a Pocket Rocket. Not bad.

–B.G.–

Apr 25, 2011 at 1:21 am #1729062

Rick M
BPL Member

@yamaguy

del

Sep 8, 2011 at 1:51 pm #1777451

Stuart R
BPL Member

@scunnered
Locale: Scotland

On my last trip, I noticed that the flame one one side of the burner was bigger than on the other side. When I got home I took it apart. On the underside of the jet there is a little 'plug' made from lots of tiny balls sintered together to act as a filter, to stop the jet getting blocked by any bits I assume. Anyway this filter plug was loose – one tap and it fell out!

Reassembled without the plug and the stove was not happy at all – the flame was lifting off the burner and had big yellow tips. Clearly the filter must restrict the gas flow and the jet must be sized to account for this.
I disassembled, replaced the filter plug, pushing it in firmly with the shank of a 4mm drill bit, and reassembled the stove. Now it's running fine – a nice blue flame evenly distributed around the burner.

So if you have any problems with the flame on a Gnat, this filter plug is something to check!

Sep 8, 2011 at 2:51 pm #1777477

Franco Darioli
Spectator

@franco
Locale: Gauche, CU.

Did it look like this ?

This one is the one in that BuLin 153g stove…
Franco

Sep 8, 2011 at 4:01 pm #1777498

Tony Beasley
BPL Member

@tbeasley
Locale: Pigeon House Mt from the Castle

Hi Stuart,

Thanks for that advice, my Gnat stove (sold as Kathmandu Backpacker stove Titanium in Australia) has problems too, when the flame is turned up the flame goes very strange, it is interesting that the filter is required to slow the gas flow down. I will have to dismantle my Gnat to check the sintered bronze filter has not come out.

I have been trying to remove the sintered bronze filter out of my Bulin BL100-B5 stove jet, it is not budging.

Hi Franco,

Thanks for the high quality photo of jet filter, I know your photographic skills are better than mine.

Tony

Sep 9, 2011 at 3:03 am #1777684

Stuart R
BPL Member

@scunnered
Locale: Scotland

Hi Franco

Similar, but not the same. It consists of lots of small brass balls packed together into a truncated cone shape which then press fits right inside the jet screw, whereas yours looks like it sits at the bottom surface of the screw.
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