Ali $22.00 Silent burner head?

The silent cap runs similarly well on this Primus 96 as it does on @Blackdog's Radius 20:


On a Svea 123R, combustion began nice and efficiently, but the flame soon became yellowed, and pulsing occured:


I think I'll do some further tests.

 

Looking good, was it just the slightly bent burner bell on the No.96* causing problems?

Wonder if something similar is happening on the Svea, the orange haze is fuel/oxide related but the yellow looks to be one sided?

*Responding to Stanislaw's post of his 1949 Primus this morning reminded me that your No.96 is late 1940s, uncommon in the UK due to the import restrictions at the time, perhaps one of those smuggled in by hardcore outdoor enthusiasts at the time who preferred Swedish stoves over the British offerings,as mentioned by Bryan Miller.

 

With a 123R I’ve noticed its sensitivity to insufficient priming.

Even without the mass of that converter cap, the little ‘dimple’ of a spirit cup can in even mildly adverse conditions (breeze) and with just the regular roarer plate hold insufficient meths to give a thorough priming of the burner. The symptoms then are pulsing as you describe (blue flames to yellow intermittently) and this can continue without the primary combustion of the burner ever catching up leading to a breakdown in vapourisation completely.

The solution is additional windshielding and multiple priming charges. Certainly the mass of metal in that converter cap has to be got well up to vapourising temperature to enable it to take over in maintaing vapourisation when the priming phase ends.

John

 

I’ve seen similar behaviour with such caps on a 123r - pulsing, soot on the cap and a build up of deposits inside the jet.

If I recall correctly I tried the same thing on a 8r with similar results.


-R

 

My PT-1 has some carbon felt in the spirit cup which may have helped things.

In the name of a science (and also because I was thirsty) I tried the cap on my Radius No.42. It wouldn't fit the burner bell due to the two internal projections designed to hold the accessories unique to this stove so I borrowed a burner bell from a Primus No.71 awaiting overhaul.

It ran perfectly on a single prime with carbon felt, and boiled the tiny kettle very quickly. The cap makes the stove too tall for the No.42 enclosure although it still worked fine.




I trusted the stability enough to bring the stove into the dark stairwell for a photo at tickover:




And one at full bore:



A success!

 

My solution to the need of multiple primes is to start with a smaller flame to heat the vaporizer before full on.

 

@Blackdog, possibly. I tried to bend the bell back to round as best I could and it performed far more stably. I'm very happy with it; the silent cap has found a home in the pocket outfit tin.

I tried to get the cap as level as possible in the Svea by eye, and, @presscall, your suggestion of insufficient priming sounds very likely.

I'll give it another go soon, which needs doing anyway, as the cap is stuck pretty firmly in the 123R's burner bell at the moment

 

Erm yes I've discovered that too- it's best to poke the cap out of place with the spanner on releasing pressure, otherwise it gets wedged in there as things cool.

 

Seems like those pot supports should come up a little as like in this attached photo.
I know this burner head works great on my No71 plenty of space.

 

I've tied welders felt even fine steel wool around all my 123 stoves tube's the welders felt absorbs a lot of priming alcohol compared to the steel wool so you get a good fire time. That Priming well is useful but hard to see sometimes when your squirting alcohol into it.
Next thing you know your priming the Picnic table as well.
Never liked the 123R fussy beast.

 

You're right, but mine are rusted where they are and I've been slowly and gently trying options to free them.

 

Fine brass wire brush and some PB blaster.