There are quite a few small upright heat-exchanger stoves on the market now. In general they consist of a stove unit which screws onto the top of a canister, and a special pot with a heat exchanger on the bottom. The first one was released by Jetboil, and we believe that it was made for Jetboil by Primus. It was distinguished by having a very bulky black plastic surround on the stove, which was meant to support the pot - except that the bottom parts of the support didn't connect with the canister.
The astute reader will note that the measured weights listed below add up to considerably more than the claimed weight of 365 grams. Frankly, we have no idea of how the claimed weight was reached. We are sure about the measured weights.
The Primus Eta Solo, courtesy Primus
|Specifications and Features|
|Materials||Brass, titanium, plastic, fabric, foam|
|Size||approx 105 mm dia x 160 mm tall (4.1 in x 6.3 in)|
|Weight (claimed)||365 g (12.9 oz)|
|Weight (measured)||Pot: 151 g (5.3 oz)
Stove: 164 g (5.8 oz)
Lid: 23 g (0.8 oz)
Cozy: 39 g (1.4 oz)
Supports: 37 g (1.3 oz)
Hanger: 24 g (0.8 oz)
Base: 24 g (0.8 oz)
|Boil time (claimed)||2.1 min for 0.5 L|
|Power (claimed)||2.1 kW (7150 BTU/hr)|
Well, this stove looks very similar to the Jetboil - but it also looks similar to the copies made by other brands.
Heat exchanger stoves are all a bit more fuel-efficient than the basic upright stove such as the Primus Express, but you usually pay for this small saving in fuel weight by a large increase in the weight of the stove system. Exactly why a heat exchanger stove needs such a bulky lump of stuff around the basic burner is not at all clear, although this one does have an extra feature not found on other similar models. It comes with a 'hanger system' which has two parts.
The first part is a folding bracket or clip and some attached wire: you attach the clip to the pot and then hang the stove by means of the length of wire going upwards from the clip. The design is such that the system does hang vertically. This could definitely be useful for climbers.
The second part makes sense when you think about what happens when you lift the pot up in the air. Normally, the stove would stay on the ground, but in this case the pot is actually secured to the stove by two metal clips. That makes for a quite neat integrated solution to cooking dinner on a small ledge 1000 m above the ground.
The rest of the stove and the 0.9 L pot is pretty standard. It has a built-in piezo lighter and comes with a three-legged plastic canister stand and a plastic lid with a pouring hole. In case you want to use a more conventional pot on the stove it also has three wire pot supports which can clip into the structure. The canister stand can be useful, as the stove and pot is a rather tall combination. Yes, the 0.9 L pot is very narrow and tall. There is also a cozy to wrap around the pot, and this can be used even when the stove is running.
Normally, a tall narrow pot is an inefficient design, and in this case the heat exchanger fins do a very good job of sucking the heat out of the flame and hot gases. You can put your hands around the pot while the stove is running without burning them. That's why the cozy survives, of course. With the cozy and the lid, hot water stays hot for quite some time.
The stove fits into the pot with the extra pot supports and the hanger. It makes for a fairly solid package.
Field Use and Assessment
Well, the stove certainly works well at heating water. We did not try actually cooking food in it, as the shape is just not good for stirring. But, you could always boil the water and then throw the stuff into the pot to 'dutch oven' or 'freezer bag' it. You might be advised to put the pot on the ground for this, to lower the centre of gravity.
Unfortunately, it must be recorded that we had several problems with this stove. We list them here, although they risk dominating the Spotlite. It should be noted up front that the stove heats water very well.
The first was a small problem with the pot supports: the first unit received was not made to specification. That was fixed by replacement. Perhaps the original unit was pre-production.
The second problem was that the pot always seemed to be a bit tilted on the stove, even when clipped down properly. The tilt was not large, but combined with the height it did suggest care was needed lest it be knocked over. It was not clear why this was so, but it seems that the threaded base to the stove was at an angle to the rest of the stove. Very odd, but definitely there.
The next problem was found when the water boiled, and I wanted to detach the pot from the stove. You can see a large red clip handle below the pot in the photo. There is a second clip on the other side of the stove, and these clips are what secures the stove to the pot. In principle you push both clips inwards and the pot is released. In practice that proved very hard to do. The clips have to be pushed in a fair way to let the pot go, and that is difficult to do with one hand, especially because the region where the palm of your hand would be was pretty hot. It was easy to do with two people: one person pushed a clip in with each hand, while the second person held the pot and removed it. Getting the pot off the stove single-handed without spilling the water was rather difficult - and the name and size of the pot suggest it is meant for a solo walker.
Once the water was boiling, the lid went a bit soft and bulged downwards. Getting it off was not too hard, but the lid did seem to acquire a bit of permanent distortion after the first couple of boils. In addition, it did smell a bit at first, possibly from the molding process. This eventually went away. Care was needed when the water came to the boil: the steam comes out that small hole in the lid rather strongly. Care was also needed to avoid putting too much water in the pot: boiling water could come splashing over the edges or out of the hole in the lid rather easily.
While I was trying to get the pot off the stove I found that the cozy could easily slip downwards, covering the air outlets at the bottom of the pot. If this happens while the stove is running two very nasty things could happen. The first is that the heat build-up under the stove would quickly melt the bottom edge of the cozy, and very possibly set it alight. Not good. The second, and even worse possibility, is that the blockage could suffocate the flame inside, causing it to go out. That would leave gas pouring out of the canister, but not being immediately burnt. The consequences could be less than desirable.
The enclosed underside of the stove had another unfortunate consequence, as I found when I first tried to use the piezo igniter. I fumbled the action twice, and that let a fair bit of fuel vapour build up inside the heat exchanger region under the pot. After the third click, the igniter worked - with a kaboom, and flames out the side. Fortunately, I did not get burnt. Unlike conventional stoves, the fuel does not dissipate when there is no flame. Mind you, other brands of heat exchanger stove with the same configuration present the same risk.
The stove certainly does work and could be useful for a single climber, but it has a number of little problems which would make it rather problematic for many users.
- Hanger system good for climbers
Whats Not Good:
- See Field Use text for a list of problems