Hello, today I decided to restore and test the Auto Optimus 8 stove. This model is known to auto start without the need of pumping after priming. Please follow all the story in this post, at the end we will discover if the Auto Optimus 8 stove can start and work WITHOUT A SINGLE PUMP STROKE. This functionality has never been tested before and so this restoration, till the end result, has been a beautiful trip for me As first thing we can enjoy the stove in its beauty after the restoration, with an action shot (of course the stove works normally). All nice, but now let’s go in detail about how this stove would auto start without pumping. As for the 1915 patent well described here by @Staffan Rönn https://classiccampstoves.com/threa...ur-burners-rising-tube-chamber-se41203.39542/ to achieve the auto start has been added into the riser an inner tube, that AFTER THE FIRST USE, will save some kerosene that, from the second use, will be easily vaporized by the priming session, allowing the start of the stove with the little pressure generated by the heat of the priming. Here the riser details with the inner tube described by the patent: After the first use of the stove some kerosene will fill this inner tube thanks to two little holes that I have indicated in the following photos: So everything pretty clear and if they sold this stove describing this functionality why then it shouldn’t work? Why this invention has been abandoned during the following years? Well, the first thing I thought before starting the restoration is that, for sure, to work, the stove must keep every little bit of pressure generated by the priming heat, so the stove must be pressure tight. Also a good cleaning of each component, especially the burner, would contribute to the low pressure vaporization. For example some carbon into the burner would decrease the heat transfer and so the vaporization. Everything must be clean. First thing to fettle is clearly the NRV. SURPRISE SURPRISE, the NRV head was worn and the tool failed to remove it, so the only option was a complete desoldering and resoldering of the pump tube. Considering this need, I decided to remove also the 3 legs because were badly soldered. Here the initial details of the restoration: Well, everything was then cleaned and prepared for soldering. All parts prepared and then the stove assembled again: Ok, we have seen the stove fully working at the beginning of the post. As described in the patent, the first use should follow the normal procedure and so I did and the stove worked great. Action shot taken and stove shut off. NOW time to test the special functionality… tight filler and air release key, added alcohol to the cup and ignited… no pump strokes obviously. Will the stove start by itself? I suggest you to live as I did the moment watching the video without skipping: Should I spoiler? Well of course it auto started!!! So my satisfaction was great! With time the flame increased constantly, so I am sure that within some minutes it would have reached a decent level by itself! All without any need of a single pump stroke! I am sure this would work even better with a kettle on the stove, that would increase the heat by reflection… in the end this invention had the goal to light the alcohol and do something else without the need of waiting the alcohol to finish and ignite the stove by pumping. Now a question: a normal stove, with air release key closed, would auto ignite as well? I never tried to be honest… I hope you enjoyed! Nicola @OMC @Radler @multi-cho @gieorgijewski @igh371 @presscall
Nice demo and excellent presentation. A clear rival to the Pyro for 'auto-start' functionality, but with an advantage in the greater size of the burner. And better on balance than the low, tank top, spirit cup versions of the Primus No.s 1 & 5, which do work to auto-start but don't pick up to such a strong burn without supplementary pumping, and which are also exceptionally vulnerable to the slightest external drafts. I guess the reason for this and other rival 'auto-lighting' stoves not lasting long in production was almost certainly production costs. In the eyes of the average customer this may have been the best in the field, but was the relatively minor saving in lighting time and effort worth the admittedly small addition cost of purchase?
@igh371 thanks for your valuable opinions. I do agree that the advantages probably didn’t justify the higher productions and end user cost… in the end the “common lighting format” was already internalized by the users. As I said I didn’t test the auto light of the low cup Primuses, I will do that for sure. Regarding the sensibility of these stoves to the outside use, I would say that these were more intended for home use… In any case has been interesting analyzing and testing this invention, thinking about all the efforts put into these innovations to improve something that was almost perfect. Nicola
Thanks for the detailed review Nicola. I’ve wondered how the auto-start functioned. Very well described and presented. I’ve regularly had ‘96’ series stoves auto-start and a ‘100’ (Petromax) with roarer plate too. The spirit cup sitting on the tank presumably warms the pocket of air above the kerosene and self-pressurises the tank to a limited extent. I must see whether the intensity of flame increases without pumping. John
@presscall thanks for your feedback! I do agree that many other stoves can auto start, especially if of a smaller mass like 96s… in this case was interesting to test the concept at the base of the patent… the steady burning on a 2 pints stove has been a good result. I will now test other 2 pints stoves to see if they work equally or not. Cheers, Nicola
Only roarer burners are at all likely to be capable of doing it. A silent burner would underburn, lit from below the caps. That’s another limiting factor, apart from the manufacturing cost, in greater adoption of the design. The popularity of silent burners, particularly for indoor use, works against a roarer-only auto-start design. Additionally, use of the auto-start outdoors where all-round windshielding would be necessary for it to work in even the slightest breeze wouldn’t be encouraging for sales.
@presscall I agree with all you’ve said. I think that these auto starting stoves were meant for domestic indoor use… many of the advertisements of stoves that I have seen from the past have, as their main commercial target, the housewives These inventions were like the magic kitchen robot that cook by itself, that we have seen advertised in the recent past So while cooking and taking care of the housework, they would have been able to start a stove and do something else. Clearly not all the stoves are intended for outdoor use, especially during the early years of 1900. Cheers, Nicola
There is some discussion and testing of the Primus low-cup auto-light system here and here, and of the Pyro system here. And, yes, it will be seen that the Primus version does work with silent burners! In fact there are more surviving silent examples than roarers, extraordinary as that may seem! (@presscall) But it is even indoor drafts that it is so very vulnerable to.
@igh371 thanks for the links, I have low cup 4 and 5, when possible I will test them. As side note, the auto start of the Optimus was completely odorless. I think that the inner tube into the riser plays a key role in the absence of odors. Additionally, on the Auto 8 the main burner riser is reached by a slower quantity of fuel in my opinion, I suppose there is a restriction at the feeding stage. When I was testing the new pump leather, with my thumb on riser without the burner, I noticed that the pressure was released way slower than usual when I removed the thumb. Usually the pressure escapes immediately on other stoves. Nicola
The Auto-Optimus system certainly does seem to be much more refined than the others. You have done us a great service with this first modern test and evaluation. The meticulous quality of your restoration and preparation really has enabled the system to be shown at its best
Well, as I understand it Optimus is meant to actually work (reasonably) without extra pumping. That's not the case with the low-mounted cup Primuses. They are only meant to auto ignite the stove so you don't need to sit and watch out the preheating flame in order to start pumping. So the self-igninting Primus models are slightly more convenient than regular stoves since they don't need any watching in that critical moment, but they still need to be pumped once they have auto-ignited if you want to have a cookable flame.
@igh371 thanks Ian! I will make a final test with a kettle on it, to see if that increases performances noticeably. Nicola
Hi, I observed the auto start function in some of my stoves and tried to analize common construction details which are responsible for this phenomenon. Can assure, that those stoves were of quite different origine ( producers ). For me the solution might be less sophisticated: burning alkohol in the bowel warms intensively the burner, but the heat is also conducted to the tank and paraffine vapours inside tank. The rest is the physics...
@Stanisław Grajewski thabks for your message. I would be curious to see a video, of the stoves you say, auto starting and progressively build an acceptable pressure. Cheers, Nicola