Converted my Optimus 99 from white gas to alcohol!

Yes. A spectacular 7 days.
West coast trail
West Coast Trail: Hike of a lifetime

 

Following. The idea of a 99 with silent cap running on alcohol is interesting. While I see the argument that it does not become a 199, it seems to be the "poor man's equivalent" considering the going price for a 199 these days.

 

Sort of.
Like calling a VW a poor mans Porsche.

 

Just a quick update. I bought a generic silent burner from Amazon, the thread was slightly larger and was bit too tall. After some simple mods, I got it to fit properly and got clearance between the burner top and the bottom of the pot. Without needing further mods, the little Optimus 99 now runs 99% iso alcohol with the silent burner happily.

A few things I noticed with the silent burner:
1. It takes more fuel to start
2. Because the flame is more concentrated at the center of the burner, it really need a pot or something to sit on top of it to keep going (a flat bottom the spread the flame closer to the tank)
3. The entire system is now more sensitive to cold wind.

But it is now the perfect table top coffee/tea stove! Works nicely with my moka pot and mini tea pot!

 

I agree. the most ideal case would be I adopt a pressure regulator valve with pressure gauge to it, might get that on my to-do list in the future.

I actually have a degree in Mech engineering, so I'm a bit more comfortable doing things that most people may feel uncomfortable doing.

And I briefly worked in a natural gas water heater company before, so not a complete stranger to the burners.

That being said, just because I got my stove working this way, I do not encourage anyone else take my words for it. And unless you are completely sure about what you are doing and the consequences of things go wrong, never mod the safety design on anything. Playing with flammable liquid can go wrong really fast.

I'm just sharing a bit of my personal experiments and curiosity here, but don't do it if you feel unsure. Use white gas is more fun than having an alcohol explosion.

 

Just spent the past few hours doing more experiments, and as I suspected, the 0.6mm hole that worked well for the original tulip burner was too small for the silent burner.

The 0.6mm jet hole was not able to supply enough fuel to generate enough heat to keep the cycle going, unless it was in a very stable environment, meaning it was running on a low margin.

Long story short, I ended up drilling the jet to 0.7mm, guess what, it runs much happier! I did the usual test: cold wind, stop&restart, water boiling...

With the silent burner, it now works just like the noisy burner (quietly), good restart, fast boiling, easy flame adjustment, and it is now resistent to cold wind.

Since I have no plan to use the noisy burner with alcohol, this is going to be the final setup.

A few notes:

1. It still takes more fuel to start
2. It uses alcohol much faster than the original design (naturally)
3. Safety valve now back as safety valve (it no longer slowly seeps alcohol vapor)

A big note: Do not let this setup run without a pot on it, and keep an eye on the burner top, at one point it got hot enough that the carbon steel burner cap turned glowing red (as seen in the last picture) and started an alcohol catalyst reaction, meaning that it no longer provide any flame, instead, when I turn up the gas, the burner top glow brighter and when I turn down gas, it glows darker. This means that the glowing hot carbon steel burner cap consumes the alcohol vapour and sustains a reaction on its own.

Now this is actually pretty cool and can be a completely new topic of how to build an alcohol catalyst heater, but this is also very dangerous:
1. I have no idea how well this reaction is contained, looks to me its generating enough heat to keep it self going.
2. It is not a very effcient way to boil things, but it irradiates heat very well, particularly to the fuel tank, because there is no longer flame going upwards, its a piece of glowing steel, and I have no idea if it will boil the tank if I left it long enough (and I don't want to try it)
3. I don't know what kind of steel they used and I don't know if this will do damage over time, normally a properly designed cat should last a long time but this is not the case
4. Since this is not a properly designed cat system, it burns very inefficiently, I could smell a very strong smell coming from it and that won't do any good to your health. Normally a properly designed system (i.e gas catalyst heater), you should not smell gas, or at least, very minimal. I have a coleman gas heater running white gas and it burns extremely clean, if you smell raw fuel, it means fuel particles are not consumed by the catalyst material and it is not a good news.

I guess my little experiment with this Optmus 99 shall ends here, I have achieved what I wanted: a non-permanent silent burner alcohol stove that I can use in my room.

If I ever go camping, I probably will swap it back to white gas, but I think the alcohol silent burner setup will work just fine.

Maybe I will give 95% ethanol another shot, with the 0.7mm jet hole, I feel 99% iso alcohol is supplying too much fuel, so a fuel with less energy density might be just right.

 

I’ve always thought of white gas as being more ‘explosive’ than alcohol by far…

 

Oh yeah, I mean, the stove was designed to run white gas, so odds of Optimus engineers screw up is lower than me pushing it too far with alcohol loll

 

Normally when the silence cap turns red is because it under burn, meaning you have a flame between the jet and silence cap and it is not normal.
To fix the situation , stop the stove and relight it.
Also if you have a pump it will be much easier to start when it is cold.
Thank you for sharing
I thing

 

I think I have a spare jet to dry it . Good to know o .7 mm.

 

Thank you for the suggestion.

I initially thought it might be burning under the cap, so I turned off the gas then turned it back on but still no flame, only the cap keep glowing.

The reason I concluded it is catlyst reaction is, when I turn off the gas, the glow slowy dims, but when I turn on the gas again, without re-light, the cap will slowly glow brighter and eventually glow as bright as a vintage light bulb filament, and I looked under the cap, there was no flame, just the cap glowing. I tried a few times, as long as the cap is glowing, even very dim, I can turn on the gas and make it glow brighter without needing to re-light or making any visible flame, so I think it has looped into some catalytic reaction.

 

.7 mm for sure works, but I would say start from .65. The flame from .7 is bit too large in my taste, might be around .68 will be perfect for 99% iso alcohol, but I don't have .65 or .68 drill, so that would be for someone else to find out.

Or maybe, use less concentrated fuel might help. That's why I'm gonna try 95% ethnal once this tank is empty.

 

Wow, this is a really nice cap, the generic one I bought on Amazon has bit height issue, which takes some time and effort to adjust.

Do you happen to have a model number or name for this cap?

Cheers!

 

I cannot find it for now. Here in action. Lol

 

That is a beautiful cap and nice flame! Much better than the generic one I got! Now I gotta go hunting for it hhhh

 

It is a South Korean silence cap.