Jetboil Zip Hacks … Part 2

Great job Curt!!!

I never thought of this adaptation. Hmmmm.

What did you buy @Target w/that lid?

And do you think this would work w/a Snow Pead Gigapower stove too?

Thanks,
Todd

Thanks, Todd. The lids are part of a set of custard cups at Target. I think it was 4 cups (glass) + 4 lids for something like $5 or $6. I actually wanted the cups, so it was an easy purchase for me. It was a bonus to find out the lids could be ordered individually from the website.

I have a Giga and just put it up to the base of the Jetboil pot. It's actually a great fit. The edges of the pot hit really near the middle of the stove arms, so it should be really secure and there should be little worry about it sliding off. Obviously you'd need 4 slots instead of 3 and you'd have to get the depth right, but I don't see any reason it shouldn't work.

If you do it post up pics. I'd love to see how it works out!

I appreciate you trying this for me, Curt.

It will weigh more than your Gnat, though :)

I have never been a fan of jet boils, but this could change that. What is the weight of the pot and heat exchanger?

Naked pot with exchanger – no lid or anything else – is 4.7 ounces. Not titanium light, but not bad, either. Wouldn't take more than a couple days to make up for that in fuel if you cook much.

Great job Curt. The cutting edge design feature is the heat exchanger, not the burner. The regulated stove is a great idea too but I see no reason why a enterprising cookpot company (GSI??) couldn't replicate this for general consumption paired with a range of stoves.

Very nice work, Curt. Do you think you would have any problems dremelling (a new verb?) the Ti companion pot?

@Kevin Thanks! Supposedly Olicamp is coming out with a heat exchanger pot that is not only cheap ($30??) but lighter. I can't find anything about timing, but it was at the OR Show.

@Steven Not sure. I have tried to abuse titanium like that before. It's pretty tough stuff, though. I'm sure some of the hard core DIY folks around here will know. Maybe experiment on an old ti spoon handle or something where it wouldn't be a huge consequence if it was a disaster?

Curt – I am curious abut how this might work with other stoves. Looks like it would depend on the length of the pot support arms. Could you do us a favor and measure the diameter of the bottom of the skirt of the Jetboil pot?
thanks

"Naked pot with exchanger – no lid or anything else – is 4.7 ounces"

Now that is interesting. A good deal lighter than the Primus EtaPower pot.
And it would go well with my remote canister Gnat too.
Hmm, I'll have to look out for a companion cup…
A quick look reveals they are not much less than a Zip :-(

Nice stuff Curt, I don't think I have noticed anyone try another stove with the JB cup. Should be of interest to some b/c of increased heat output over the JB burner.

That Olicamp xts pot looks very interesting (don't know if I could burn the money on a JB pot) and it is larger @ 1L.

I have been stove testing lately (winter boredom) and am finding I can duplicate the BPL test results* of the JB system with a simple Al pot, pie pan shaped to just slightly larger than the pot and foil lid for about 5.2oz/$75 total (stove, 1.25Lpot, windscreen and lid). I am still optimizing the "system" but will probably post some results soon enough. If I get my hands on one of these pots I will might pick it up just for comparision purposes.

*have yet to pull out a box fan to simulate the mild wind test but it is in the plans.

***Update, I checked and actually my 5.2oz system costs about $60 not 75….$50 for the gnat, $10 for the stanco pot and $1 for the windscreen pie pan.

@Paul – The outer edge of the base is about 3.5". Inside edge is about 3". Should fit most small stoves pretty well.

@Stuart – Yep – the price difference isn't that great, which is why I think the Zip is the best deal in the Jetboil lineup by far. Consider that it's around $70 and the two Sol setups are $120 and $150. I have seen the Companion Cup for around $35 occasionally, but it was worth it for me to get the Zip because I had no experience with a Jetboil and wanted to play with it a bit.

@James – I'm really interested in that XTS. Especially if the weight is accurate. The blurb I saw had it under 4 ounces. From the pic, it looked like it had some big heavy handles and surely the lid could be lightened. A little hacking on that could yield an interesting 3 oz heat exchanger pot. I'm not sure how that's actually possible, so I'm skeptical of the weights already. Haven't seen anything about release date or where it will be available. Have you?

Curt: Nice job. You've got me sold.

I've toyed with the idea of duping jetboil-style corrugated fins for the bottom of a pot but (1) you can already buy jetboils off the shelf and (2) the jig is maybe a little more involved than for the other styles of fins I've fabbed.

But with the simpler the way you've fitted the pot to the burner, it would be easier to do a jetboil-ish style HX on a Ti pot. My fins wouldn't be a light, but they could be better at heat exchange. And a flush skirt (instead of their formed skirt) would be easy to do at home.

If anyone doesn't have a dremel to do this hack, there are abrasive wheels that fit in an eletric drill. I'd suggest having a second person hold the drill tight to a workbench so that the position of the spinning wheel is fixed. But you could also cut those three notches with a file then smooth off the corners with sandpaper/emory cloth.

Yeah, I saw 3.7oz and the same heavy handles. I think it is possible. The 1.25L pot Al pot I have is 2.5oz.

I haven't seen anything about the release date…hadn't noticed it till you mentioned it.

After your mods, does the pot still work with the jetboil burner, in the sense of, does it still lock on?

The Olicamp pot looks identical to the Fire Maple FMC XK6, which is advertised as 221g including the lid. I think Olicamp are being a bit optimistic. You can buy them already on eBay.

A US pint is 473ml. Heating this much water from 10C to 100C requires 178.2kJ. Another 10.5kJ is required to heat a 130g Al pot by the same amount. Dividing the total by the net calorific value (LHV) of the propane/butane mix at 49.5kJ/g reveals that the absolute minimum amount of gas required is 4.1g.

But the heat transfer efficiency can never be 100% in reality. What is the efficiency of a HX pot? I don't know an absolute value, but an optimistic 90% would imply that 4.55g of gas would be required. A more likely 80% would imply 5.1g gas.
The only way to heat 1 pint to boiling using only 4.0g gas would to start with water at a temperature of at least 20C

BTW, the efficiency of a convential (non-HX) pot is 40% to 50%

@Paul – Absolutely. It works just as before with no compromises. The slots I cut end up sitting down inside the JB base, so when it's locked on there you can't really even tell it's been modified. Not that I care, though. Hard to imagine using the stock setup now :)

@Stuart – I don't doubt your numbers at all. My scale only does 1 gram increments. I boiled 4 pints and then weighed the canister after each boil. Each time the total went down either 4 or 5 grams. Could be a sketchy scale, but it's pretty accurate for my other stuff and my numbers matched up pretty close to Will's super test here at BPL. All I care is that it's more efficient than my Gnat on a regular pot. I used the same scale and protocols for those tests, so whether it's 4 or 10 – I'm confident it's less going this way than my previous setup. Plus it's just fun to tinker :)

I had been assuming Curt was bringing room temperature water to a boil. That matches up with what I would expect.

Regarding JB style HX and its effect on efficiency…I hadn't really bought into the HX as in improvement until testing bore it out. I can't imigine the fins do much to increase the temperature of the bottom of the pot, therefore they couldn't do much to increase the heatrate thru the pot.

At this point I am guessing that the improvement comes from keeping the hot gases in contact with the pot longer. The heat rate throught the pot isn't really changed just the of rate of fuel consumption required to maintain it.

On specific efficiency figures – I am finding:
-standard pot with gnat and no wind: efficiency of ~%50(up to %60 with a slow burn)
-Add enveloping pie pan to above: efficiency of ~%85.

I am still interested in a HX type pan b/c of the drop in fiddlefactor and increase in ruggedness over my current setup.

Looking at Ebay…. this one came up too. Reported weight is 180g and better suited for a Super Cat.

http://www.ebay.com/itm/0-9L-Camping-Tea-Pot-High-Efficient-Cook-set-Cookware-Outdoor-Boiling-/220854176787?_trksid=p4340.m263&_trkparms=algo%3DSIC%26its%3DI%252BC%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%26otn%3D15%26pmod%3D220854176813%26ps%3D63%26clkid%3D6186442152468343532

@Curt – with a scale which has a resolution of 1g, you have a potential error (due to rounding) of +/- 1g when you subtract an end weight from a start weight. If you boiled 4 pints then subtract the weight after 4 pints from the start weight and divide by 4. Then your error is reduced to +/- 0.25g

@James – the HX pot efficiency is due to the area of the fins allowing more heat to be extracted from the hot gasses. This heat increases the temp of the base of the pot very slightly and the heat transfered thru the pot base is increased significantly (for a fixed rate of fuel burn).

I concur with Stuart's calcs. I repeated them in the English system:

1 pound of water (plus the aluminum cup is the equivelant of 1.06 pounds of water)
50F to 212F = delta T of 162F
171 BTU needed
divided by 19,700 net BTU/pound fuel gives 0.00872 pounds
x 454g/lb = 3.96 grams butane/propane with 100% efficiency.

Kitchen pots on a kitchen stove run about 30% efficiency. Wider pots and smaller flames can give 40%. That heat exchanger might double efficiency to 60-70% but could never do 100% (some hot gases escape, there are losses off the side and top, and radiant heat leaving the bottom) so I can't see you using less than 5.5-6 grams of fuel per pint.

Maybe the scale is off on the low end. Maybe the water started out a fair bit warmer than 10C/50F. Maybe it wasn't a full pint (weighing is better than measuring volume).

It's still a GREAT mod and it's got me ready to either get that Solo Jetboil or to do jetboil-style fins on the bottom of a pot myself.

If the external surface temperature of the pot only increases "very slightly" than how could the change to heat rate thru the pot change with any significance? My back of the envelope type calculation says the temperature difference across a pot's thickness should be on the order of 1000C (my specific calc said 700C) if you increase the delta slightly the heatrate only changes slightly.

Stuart I understand the goal of adding the fins, I just meant I have struggled understanding how they could make a practical difference in this application.
I keep imagining that the stove will give the bottom of the pot all the heat it wants sans "flux ring" b/c the pot-to-water heat rate is the bottleneck – though I am only speculating. Also, it seems the crossection for the fins is too small to make much of a difference.

@James – if 1 pint of water is heated to boiling in say 3 minutes then the water is absorbing heat at a rate of 990W. If this heat is absorbed thru the base of a pot 10cm diameter and 1mm thick aluminium, then the temperature difference across that 1mm is 0.53C Yes that's right, half a degree C.

If the fins on a HX pot permit the water to be boiled in say 2 minutes, the temp difference across the tickness of the pot base is increased to 0.8C The fins themselves will get a good deal hotter, but not the pot base.

In a pot w/o fins, only the heat from the thin layer of hot gas in physical contact with the pot base is transfered to the pot. The hot gas below this conduction layer remains hot and is wasted. The fins on a HX pot are able to extract heat from all the hot gas from the stove.