Bought cheaply as a Gemini that was one of those subject to a safety recall by Optimus, identified by the serial number RG 023297 on the gas canister connector. The recall related to this device in black anodised aluminium, incorporating individual regulators for the two burners and (in the central block with the gas hose going into it) a gas pressure regulator … … which Optimus haven’t published a schematic for but Soto have for their version (in the Windmaster). The Soto works by having a 'floating' micro-spring loaded valve (the heart of the regulator) in conjuction with a jet nipple with a much larger jet orifice than in an orthodox canister gas stove. Soto jet on the left, a Primus stove jet on the right. When the vapour pressure of the gas has reduced due to evaporative cooling, made worse by cold outdoor temperature, the Soto sprung-loaded bobbin valve in the regulator opens more than when the vapour pressure is higher on a hot day. Whereas a conventional stove jet would throttle the gas flow the larger bore of the Soto jet doesn't to anywhere near the same extent and in spite of the reduced pressure of the gas the flame intensity and heat output is maintained. The Optimus Gemini surely has an equivalent device incorporated in the ‘black box’ and sure enough, each of its jets has a jet orifice larger than the 0.32mm for a conventional gassie, where the jet is the final restriction to maintain the correct air/fuel ratio and not a clever mechanism (gas regulator) ‘upstream’. The recall notice referred to a possible metal burr on some component in that ‘black box’, that had led to seal damage in a handful of examples reported to Optimus, resulting in a leakage of gas. Thankfully, no injuries were reported. My thoughts on this, and will I be using a stove subject to a recall 4-5 years ago? Well, it’s been in use for that length of time, judging by the heat blueing of pot supports and burners. I can detect no malfunction at present and I’ve rectified a regrettable omission by Optimus in not having a gas shut-off valve at the canister. Without such a valve, were a fault to arise in the black box, the hose or perhaps one of the flame regulator spindle seals resulting in a leakage which then ignites, there’s no way of shutting off the gas supply other than by unscrewing the gas canister, which takes too long to do in the vicinity of a fire and itself fuels the fire at the moment of separation of connector and canister with a spurt of gas. It happened with this reviewer at 17 minutes into the video, not a leakage from the gas regulator black box but due to him having inadvertently exposed the gas hose to a burner flame. Optimus have put that right on their Mk2 Gemini with a shut-off valve in the canister connector. If only they’d have used their Vega stove valve for the Gemini application, removing the fold-out wires that allow for inverted canister use since the Gemini cannot vapourise a liquid gas feed and a fireball would result if it were tried. The Vega’s valve is compatible with the Gemini’s hose connector and that’s what I used for my initial try-out of the stove. Not wanting to lose the use of the Vega I constructed an equivalent using off-the-shelf Chinese adaptors, these two specifically … … and one of these. From the top two I made this, silbrazed up. Coupled with the Gemini’s valve-less connector this results, not sleek like the Vega connector, but functional with thread-lock smeared on the joining threads to prevent unscrewing when in use and providing a back-up seal to the O-rings incorporated. So, to conclude, IF the black box gas regulator springs a leak that ignites before I hear it or smell it, I can stay at arm’s length to shut off the gas. Out of interest if it fails, I’d surely have a go at inspecting the black box’s internals. The Allen key sockets on these two portholes beckon … If a repair were not possible, I’d reduce the orifices of the jets using my ‘hypodermic needle insert’ method and would bypass the gas regulator altogether. Whatever the outcome, I visualise using the Gemini for the forseeable future. Those discouraging faults in the Mk1 aside, it’s really rather a fun stove to use. John
