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Pocket Rocket Deluxe (PRD) with Stash Pot and Comparison to GearSkeptic


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Home Forums Gear Forums Gear (General) Pocket Rocket Deluxe (PRD) with Stash Pot and Comparison to GearSkeptic

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  • #3806649
    David D
    BPL Member

    @ddf

    The Jetboil Stash system is known for its great (light, good capacity, efficient, aluminum for simmering) Hx pot and it’s stove that sputters in any wind.

    In ’23 I switched over my Pocket Rocket deluxe (PRD) stove to full time use with a Stash pot, for about 30 days ranging over water temperatures from ~ 45F to 70F and air temperatures from 35F to 90F.

    I was curious to see how it improved fuel consumption and how the combo faired in the wind.

    It’s useful to compare first against some controlled results.  I deep dove GearSkeptic’s test results of the Toaks 118mm pot with the PRD, with lid on.  He runs his tests with 50F water and up to 200F only.  All his tests are tightly calibrated and repeated then averaged.  I then extrapolated his test results to add a few more conditions: 212F, and 70F starting water temp.   In my area, water temp ~ 50F in late April and May, plus Oct, and ~ 70F in between.  Bounding  the best and worst cases gave this:

    The yellow bars denote the flame settings that achieved the best efficiency, and are represented in the graphs. Mis-setting the flame results in significant excess fuel consumption, and these were the optimum settings.

    This was a baseline for the PRD results with a flat bottom 118mm diameter pot.

    The next step was to estimate the efficiency gain with the Stash pot (122mm dia).   My semi controlled field tests (accurately measuring fuel and water consumption, estimating water temp, and guestimating wind) showed ~ 55% gain with the Stash pot.  This was pretty close to the 61% efficiency gain with no wind from BPL’s internal tests here.

    GearSkeptic also showed its safe to take boils only to 200F, vs 212F.  He justified this based on WHO recommendations here.

    Pulling this all together, here’s a comparison of fuel consumption starting from 50F and taking to 200F with the Stash pot, vs taking starting from 50F and taking to a full boil (212F) with the Toaks 118mm:

    I added “Field estimate” values which are samples from my own ’23 trips.  The g/L consumption numbers are highly accurate but the wind speeds were just a guestimate.    GearSkeptics test results show that placing the stove behind a tree to block the wind can cut down wind speed to half or even less, and this is how I use my set up in any wind.

    It’s worth pointing out that my field numbers are averages over multiple days ranging from high wind to little wind (all converted to 50F).  All year long I never exceeded these average consumption values for any of 8 trips, but I do have the benefit of heavily forested campsites each time.  Above treeline or in meadow, operation creeps up the blade of the hockey stick.

    I found this all pretty interesting, and the combo of the the Stash pot, PRD, 200F “boils” and trees for block wind worked out pretty well.   The combo was light, wind resistant, simple, sips fuel, and was reliable.

    I never had to carry more than a 4 oz cannister even on an 8 day trip.   I like that I now have some solid consumption estimates for future planning with this combo.

    I’m tempted to take the next step and Dremel cut outs in the Stash Hx bottom, to get the PRD burner head closer to the pot bottom (similar to the Firemaple Pretrel).  The value would be even better wind resistance.

     

    #3806652
    Jon Fong / Flat Cat Gear
    BPL Member

    @jonfong

    Locale: FLAT CAT GEAR

    Great Job!

    I do like looking at data!  I do need some clarification on a title/axis.  On the chart labeled GearSkeptic Cups/oz, the vertical axis is labeled the same as the left-hand chart: g/L.  Is this correct?

    I found that the original Stash performed pretty well up to about 4 mph: 10g/L.  But above 4 mph, it dropped like a rock, couldn’t reach a boil at 5 mph.  That was probably at a medium or high setting, I have found that HX pot tend to be more robust in the wind at higher burn rates.

    Measuring wind behind a tree is very difficult as the structures create vortexes.  An anemometer cannot pick up the changes.  I made a video where I attached a string to a thin metal rod, you can see how the string bounces around at the 6:30 mark (https://www.youtube.com/watch?v=_uM_DC6h1lo&t=29s).  Stoves that have a large burner to pot distances (like the Stash System) are impacted by the vortexes.  The BRS 3000t and the Fire Maple Hornet II really struggle with vortexes.  My 2 cents.

    #3806654
    David D
    BPL Member

    @ddf

    > the vertical axis is labeled the same as the left-hand chart: g/L.  Is this correct?

    Nice catch (cut/paste oversight).  That right hand graph should be cups boiled/oz.  GearSkeptic tests using 1.75 cup boils, where my field results are mostly 2 cups/boil.

    >couldn’t reach a boil at 5 mph

    Great to know the cut off point.  In high wind, the Hx eventually can’t provide enough shielding and the flame doesn’t even touch the bottom.   I only had one case (40kph winds forecasted) where a tree wasn’t going to cut it but I was able to successfully boil quickly in the vestibule.  Which suited me fine as I forgot my mid, and it was 40F with those winds so I was ready to hide in the nest.

    >the structures create vortexes

    Nice video.   I’m a long term sport motorcyclist and sometimes get to feel these vortexes directly on a grand scale: when they’re trying to tear my head off behind a poorly designed windscreen.  You make a good point because GearSkeptic’s anemometer was steady (didn’t register the turbulence) and he didn’t test a pot behind a structure.  It would interesting to see fuel consumption tests run behind obstacles to get real data.

    > Stoves that have a large burner to pot distances (like the Stash System) are impacted by the vortexes

    That’s the only real drawback to the Stash pot.  On average over days it still provides 60% more boils than a non Hx pot that sits closer.  A few minutes with a Dremel to the Stash will rectify this.  The design makes it very friendly to cutting out some material to drop the pot down.  It’s a bit hard to make out but I confirmed Dremeling 3 slots into the bottom of the Hx ring and maybe some slight  bending to the PRD support arms with pliers will make this a nice fit without having to alter the heat fins:

    #3806674
    Adrian Griffin
    BPL Member

    @desolationman

    Locale: Sacramento

    Good work. BTW, testing to a 200°F “boil” gets variation of boiling point with altitude out of the picture for our widely-scattered stove testers. Also, water boils at 200°F at 6,400 feet, so that might be closer to actual conditions on a trip.

    #3806678
    Jerry Adams
    BPL Member

    @retiredjerry

    Locale: Oregon and Washington

    or, you can use a nominal temperature change, for example 150 F

    measure the actual temp change in one run

    then scale the grams of fuel used by the ratio

    use that value to compare with other runs

    try to get all of the runs close to that 150 F increase but compensate for small deviations

    #3806689
    David D
    BPL Member

    @ddf

    > or, you can use a nominal temperature change, for example 150 F

    Water temp in test can be anything to anything, as long as it’s accurately recorded.  It can then be converted to any other temp to any other temp2 knowing specific heat of water.  That’s what I did to generate the data in my graphs, to convert GearSkeptic’s results to include 70F and 212F.

    BTW GearSkeptic dropped a new video on fuel efficiency of Hx pots.

    He observed in the limited tests that larger pot to burner distances were more efficient in zero wind but rightly cautions this is currently correlation, not causal.  He feels he can’t test this more because his shop is no longer 50F.

    I posted there trying to convince him to test the Petrel pot both with stove nested in the slots and with the pot perched on top of the arms, to see what the difference in fuel consumption is and obtain some real real comparative data with the same stove and pot combination for both tests.  It can then be easily converted to his 50F to 200F standard.  The difference in heat loss through the pot by using 70F air ambient vs 50F should be only a minor error factor since its the change in fuel use between the two use cases that’s important.

    I think I’ll hold off hacking away at the expensive Stash until this is better understood.  If a tighter pot to burner spacing harms fuel efficiency without wind, it’d be worth knowing the extent of it and the extent of the gain of the tighter spacing with wind.

    Looks like the Dremel may be a winter ’25 project.

    Another nice finding from his latest tests is that the Stash shows the same fuel efficiency at low, medium and high flames, in zero wind.  Flat bottom pots don’t (showing significant fuel efficiency drop the higher the flame setting, in no wind) and the Stash was better at this than any other Hx pot he tested.  So if the wind is dead, I can feel free to crank the PRD under the Stash and get the boil done quickly.

    The efficiency in wind for a safety factor, larger size and quicker boil times makes the Stash+PRD extra weight well worth it to me over something like the BRS+Toaks550. I also have the very light Stash stove and don’t bother ever bringing it.  In fact, I don’t think I ever lit it up.

     

     

    #3806694
    jscott
    BPL Member

    @book

    Locale: Northern California

    If you hike solo and just need to bring water to a boil…a full on titanium windscreen will not overheat the canister, ime.  And it will radically improve boil  time and fuel consumption. by ‘full on’ I mean a large wrap around screen that starts on the ground and extends to the pot, leaving an open area for oxygen to enter that’s  away from the wind.

    I can’t speak for those who cook for groups over one flame, or simmer for a long time.

    #3807783
    Don Montierth
    BPL Member

    @chumango

    Locale: East TN

    My thoughts exactly on the Gear Skeptic video re: stove/pot gap.  If he wants to make the statement that the smaller stove gap is less efficient, it would have been very easy to confirm this with the same pot and stove, but just not using the slots in the heat ring.  I think this leaves a potentially erroneous conclusion out there for all to believe, when it would be so easy to confirm.

    Also left out of the analysis is that the Stash stove is a low output stove, so using the low, medium, high fuel usage for that stove is not the same as for the other stoves.  High for the Stash is only medium for the other stoves.  S0 not a very good comparison.

    Additionally, the different pots have different numbers of fins.  The Petrel has the fewest.  Less surface area, all else being equal, means less heat recovery.

    All of these need to be part of the analysis/conclusions drawn.

    #3807785
    Jon Fong / Flat Cat Gear
    BPL Member

    @jonfong

    Locale: FLAT CAT GEAR

    Keep in mind that the purpose of GearSkeptics part 4 video was to establish a baseline understanding of Heat Exchange pots.  That knowledge is needed to understand and internalize the impact and potential advantage of HX mugs in the wind.  He clearly demonstrates that in calm conditions, there is really no weight advantage of an HX over a regular titanium pot.  In calm conditions, the only real advantage of an HX pot is speed.

    Comparing HX pots to HX pots is very difficult as all of the geometries are different.  Additionally, most are designed as a system so swapping components is almost impossible.  Again, as a baseline, this is a great start.

    In my experience, HX really shines when the wind picks up.  They inherently can be robust in the wind IF the stove/mug is configured correctly.  The MSR WindBurner is a shining example of a well-crafted system that is know to be robust in the wind.  Unfortunately, it is far too heavy (an expensive) for most needs.  Part 5 looks to be about 6 months away.  Funny, with all of his high-tech gear you would think that using a temperature controlled water bath would not be out of reach.  I am willing to wager that at the end of the day, he will; find that an HX system with some sort of windscreen will consume about half the fuel of a comparable non-HX system with a windscreen in high winds.  My 2 cents.

    #3807788
    Don Montierth
    BPL Member

    @chumango

    Locale: East TN

    Jon, I agree with what you have said.  But I think that when someone who has as large a following as the GearSkeptic goes beyond quoting results and enters the realm of extrapolations there should be a bit of due diligence to be sure the correlations he proposes are correct, especially when it would be so easy to do so in this case.  Just one more boil would suffice.  People make purchasing decisions based on what he says because of the logical, apparently scientific method used, but most won’t see how an amended test protocol (one more boil) would go a long way to support or refute the theory.

    Maybe the smaller gap is less efficient; maybe it is not, and what was observed was a happenstance resulting from the specific stove/pot combinations.  I don’t have the gear to do the test myself, which is true for most folks.  Before long I will have the Petrel and I can do a test with that pot and the PRD at the two different gaps available.  But I don’t have the audience that GS has.

    #3807790
    David D
    BPL Member

    @ddf

    I agree it was a lost opportunity.  As I tried to point out, retesting the Petrel doesn’t have to wait 6 months because test results are all easily convertible to different temperature ranges.

    On the other hand, it’s important to not lose sight that he does these for free and is generous in sharing in a clear and detailed way.  I’m glad we have him.

    He takes pains to state:

    1. Don’t assume the lesser gap height means less efficiency

    2. all his tests use an external fuel regulator and he sets the stoves to max & so doesn’t rely on a subjective decision on what high/med/low flame mean.   I agree it would be worth confirming that all stoves have enough flow to have equal gas flow at high, hopefully he’s done that?

    I look forward to your Petrel tests!  I’ve been wondering about flame quenching with Hx pots as posted here.

    >In my experience, HX really shines when the wind picks up.

    Same here, I definitely see that with the Stash on the PRD stove.

    The 1-2 min quicker boil time 3 season is inconsequential though YMMV. There are enough time pressures 9-5, I try to not import that mentality into my trips into nature

    #3807795
    Jon Fong / Flat Cat Gear
    BPL Member

    @jonfong

    Locale: FLAT CAT GEAR

    Here is my opinion. The Pocket Rocket Deluxe and the Soto WindMaster were specifically designed for close burner to pot distance. They both have a similar design concept: a huge number of jets. From what I can tell, the Pocket Rocket Deluxe has 148 jets (the Soto Windmaster is similar). My hypothesis is that a tiny jet will complete the combustion process faster, but at a low power output. That is why they need so many jets. The BRS 3000t, Fire Maple 300T and the Fire Maple Hornet II have under 10 jets. I believe they need a larger gap for complete combustion. As I said, it is only an opinion.

    Pocket Rocket Deluxe

     

    #3807798
    Art
    BPL Member

    @verysimpleoutlook-com

    Adventure Alan also did a nice comparison: https://www.adventurealan.com/best-backpacking-stove-system/

    #3807800
    David D
    BPL Member

    @ddf

    >That is why they need so many jets

    Interesting hypothesis: small jets = close spacing; big jets = large spacing.

    In my view, small jets should increase air/gas mixture flow velocity, so there may be some truth to this if the faster velocity enhances turbulence and a more complete fuel burn.  This is what happens in an auto cylinder and engine designers are at pains to increase the air/fuel turbulence inside the cylinder head in order to extract maximum horsepower with minimum emissions and minimum fuel consumption.

    For an Hx pot, the million dollar question is an overlay onto all this.  Does the heat exchanger choke out air flow, or equivalently in effect, heat the incoming air so that its less dense and the reduced amount of oxygen offered results in a lower flame temperature?

    And if doing so, does a stove specifically designed for an Hx pot require a larger pot to stove gap to let more oxygen in?  Of course the trade off is reduced wind performance.

    Here’s the PRD on left, and the Stash stove on right.  Roughly similar number and size of jets, but the PRD is designed to sit 10mm below a pot, and the Stash stove, designed specifically for an Hx pot, sits 27 mm below the pot.

    That’s a clue that an Hx ring may choke out oxygen.  With wind, oxygen is supplemented offsetting this, so an Hx pot like the Petrel designed for a smaller stove to pot gap may start showing it’s advantage again over the taller gap like the Stash system.

    #3807813
    Jon Fong / Flat Cat Gear
    BPL Member

    @jonfong

    Locale: FLAT CAT GEAR

    OK, just a reminder for those of you who do not know, Full Disclosure:  I manufacture adapter plates to couple various stoves to various HX mugs (the Cheetah line of windscreens).  In my experience, it has been best to set the burner to pot distance to the same distance as that when used with a non-HX pot.  Our first plate for the Sterno Inferno was ideal for the Fire Maple 300t: about a 0.9” burner to pot distance was matched with the HX geometry (about 0.9” from the HX shroud to the bottom of the pot).  Other HX pots had a smaller gap in the range of 0.5” and this didn’t work so well.  Spacers needed to be added to get the Burner head to pot bottom optimized.  Coupled with that, we have always left a reasonable gap between the burner and any support structure in order to allow adequate airflow.

    Now, with respect to the Stash, the stove is designed to operate with the Mug AS WELL as a regular pot.  It seems to me that they would have been much better off putting slots on the bottom of the HX shroud (like the Petrel) to position the burner much deeper into the stove.  Since they didn’t the Stash is no more wind resistant than a regular cannister topped stove with a large gap: not very good.

    A note about flames.  Keep in mind that the blue flame that you see is the interface between where the gas is burning and the unburnt gas/air mixture behind it.  While it looks like a large flame, it is only the outside surface that is burning.  With the Pocket Rocket Deluxe and the Soto WindMaster, you can see the tiny flame and that gives an indication of a complete burn (IMO).

    In general, you can tell if you are chocking out a stove as the pitch changes when you lower the pot.  Both the volume and maybe the frequency change: you will hear a difference.  That being said, if you are interested in fuel efficiency, you shouldn’t be running the stove at a high burn rate anyway.  My 2 cents.

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