Roll-up stove

[Colin Krusor]

Ben, the foil is from ebay (the same seller still advertises it, I think) and the Ti sheet is from TitaniumJoe. The foil was cut with scissors and a punch was used for the holes. The sheet was cut with a radial-arm circle cutter in a drill press and a dremel.

Derek, I have considered some of those ideas (upright rods on the outside, double wall). I think they definitely merit some exploration. At this point I feel like I'm afloat in a sea of ideas and I need to do some more tinkering to weed out the bad ones (whether any will remain after that remains to be seen).

Steve, thanks for the advice about cutting. I've been in contact with several laser cutting shops here in central CA, and a few have said that cutting Ti foil is a specialized operation and they aren't equipped for it. I'm still looking. I'm also going to order some of your 0.003" foil this evening. I played a bit with some 0.005" CP2 foil a while ago, and found that it was difficult to cleanly punch. It would tear or distort around the holes. Is your CP4 foil punchable?

[Roger Caffin]

> I sent in a provisional application for a utility patent this morning
Could be invalidated by the prior publication here, although there may be a small time window allowed – check.

> the 15-3-3-3 alloy foil becomes brittle after the beta transition, and can crack at the edges.
> I'm personally interested in trying 0.003" CP4 foil,
Indeed, the highly alloyed varieties are not so good for repeated thermal cycles plus mechanical cycles. Yes, I would try a CP foil.

> I'm afraid the thinner and softer foil might warp or bulge when red-hot.
Ah well, if it gets really bright red there could be a problem if the stuff is under load, but I doubt that a wood fire would get hot enough for it to be a problem. Only one reliable way to find out though … :-)
I thought you were using 0.005" foil? You could always go up one thou'.

Cheers

[Jim Pemrick]

The United States uses a first-to-invent system, unlike most other countries in the world. Invention in the U.S. is generally defined to comprise two steps: (1) conception of the invention and (2) reduction to practice of the invention. When an inventor conceives of an invention and diligently reduces the invention to practice (by filing a patent application, by practicing the invention, etc), the inventor's date of invention will be the date of conception. Thus, provided an inventor is diligent in actually reducing an application to practice, he or she will be the first inventor and the inventor entitled to a patent, even if another files a patent application, constructively reducing the invention to practice, before the inventor.

However, the current patent reform bill will change the US to a first-to-file system. This is a major change in the US patent system, but will make our patent system more similar to other foreign patent systems.

Bottom line – When the new patent reform bill passes, do not publish anything without filing a patent application first.

[Jim Pemrick]

Under section (b) below, as long as the inventor files within one year of the date of public disclosure, then the disclosure (i.e., web post) cannot be used as prior art.

35 U.S.C. 102 Conditions for patentability; novelty and loss of right to patent.
A person shall be entitled to a patent unless –

(a) the invention was known or used by others in this country, or patented or described in a printed publication in this or a foreign country, before the invention thereof by the applicant for patent, or

(b) the invention was patented or described in a printed publication in this or a foreign country or in public use or on sale in this country, more than one year prior to the date of the application for patent in the United States, or

(c) he has abandoned the invention, or

(d) the invention was first patented or caused to be patented, or was the subject of an inventor's certificate, by the applicant or his legal representatives or assigns in a foreign country prior to the date of the application for patent in this country on an application for patent or inventor's certificate filed more than twelve months before the filing of the application in the United States, or

(e) the invention was described in – (1) an application for patent, published under section 122(b), by another filed in the United States before the invention by the applicant for patent or (2) a patent granted on an application for patent by another filed in the United States before the invention by the applicant for patent, except that an international application filed under the treaty defined in section 351(a) shall have the effects for the purposes of this subsection of an application filed in the United States only if the international application designated the United States and was published under Article 21(2) of such treaty in the English language; or

(f) he did not himself invent the subject matter sought to be patented, or …

[Colin Krusor]

Jim, thanks again very much for this information and for your expert advice.

Roger, I found in my cursory patent-law reading exactly what Jim described. In the US, publication of the details of a "novelty" does not interfere with obtaining a patent (at least not within the first year following publication).

To be honest, sharing ideas with the MYOG community is a big part of my interest in MYOG gear. If I had to choose between protecting an idea from people like the mKettle guy and sharing it with the MYOG community, I would share it and let the mKettle guy have it. I'm glad that US patent law allows me to share and protect.

[Colin Krusor]

One of the shortcomings of the initial design, I think, is that it is sensitive to wind. I experimented this afternoon with a windscreen. It doubles as a pot stand, and replaces the tent pegs in the initial design. The windscreen increases the weight from 2.60 oz to 2.75 oz, although it could be argued that the weight increase is somewhat greater than this because the three tent stakes in the prior pot stand design were multi-use.

I also modified the bottom screen a bit to create a platform for an esbit tab or an alcohol stove. I haven't tried an alcohol stove yet, but I found that one esbit tab was not quite enough to bring the water to a boil (another half-tab was required). I put the pot directly on top of the stove (without the windscreen or tent-stake pot stand), but I think it was still a little too far from the esbit tab. I don't know if the same would be true of an alcohol stove. The tent stake pot stand, though, could be used alone, as a tripod, over an alcohol stove or esbit.

[Mike M]

that definitely appears further (pot <-> Esbit) than any of the Esbit stoves I've used

[Colin Krusor]

Yes. I think some modifications would be required to make this stove compatible with esbit or alcohol.

[Kevin Beeden]

Without a doubt; beautifully made.

I can offer some expereince with water-cutting of 0.003" Ti foil, as Steve Evans gave it a go with his setup for an attempt at my Squeezebox Stove. Neither of us was satisfied with the result, as the edges were rippled by the high pressure jet, and left fairly rough. We concluded that laser cutting was probably the way forward for thin Ti foils.

I'd thought of making a roll-up Ti woodstove body a while back; an obvious progression from jointing cylindrical windshields, Caldera Clones, etc. and a discussion of the optimal grate area relative to the number of sides for a sheet-walled burner (an infinite number of zero-width panels is best: i.e. a circular grate). But I never got around to doing anything… Congratulations on a superbly implemented design. I love the stove door…

[Tom Peterson]

I can't add anything that hasn't already been said. Brilliant workmanship.

[Kevin Beeden]

I only managed a quick look last night, but thought about it a bit on the cycle home…

It looks from the pictures as if the door is made as a continuous piece of the foil. For a maufactured item, this may be rather inefficient in terms of use of expensive Ti foil, and a two-part solution may allow you to use the foil more efficiently.

The other question that popped into my head was: can you open the door whilst the stove is running? Your photos show the door open, but I'm not sure how you avoid burnt fingers (some handy tool or tent peg, no doubt…)

Apologies to Steve for missing his post re. the Squeezebox.

Apologies also if I seemed to be dismissive with my comment about a roll-up stove being 'an obvious progression'; the problem is that when you've had an idea, it always seems obvious afterwards…

[Connie Dodson]

I have two of the smaller backpacking wood stoves that work very well: the titanium and stainless steel MK1-UL by DarenN and the stainless steel folding Woodgaz wood stove by Zelph.

"I'm glad that US patent law allows me to share and protect".

This, itself, is a primary reason U.S. moved ahead so swiftly in invention. Some people contribute, and, others may have a different idea inspired by the discussion.

"I do plan to make a few modified versions over the summer, though".

"Does everyone who expressed an interest see nothing about the first version that could be improved"?

I would say, any burn tests?

Over at bplite forum, the characteristics of the fire itself are considered. The volume of the wood stove is an imperative to function, as well as size and placement of holes, height of the fire grate, height above the flame, and such.

Then, get the specification of the metal and thickness of foil worked out.

Does your college have students in metallurgy or materials science classes or instructors teaching those subjects? The people good at that get top pay and it all seems to go to either the military or to "proprietary information". That is why during your college years is the best, if not the only time, to find these things out.

If not, just try different foils available.

Discuss results in a forum specifically of stove builders, as well, like bplite forum.

My college had a sequence of required courses in drawing, making a prototype and writing a patent. Signed, dated, bound notebooks (no pull-out pages) are a start. It is for your protection: "sign and date" every page of sketches, scribbles, and, notes.

It is the roll-up design that will likely get your patent. For patent purposes, because it involves art, as well, I suggest the design patent specify small differences like a Victorian or Art Deco motif, for example, are included. It is the hole size and placement, volume and the height and distance between involved that make it function exceptionally well.

I had fun with Myst when it came out, but steam punk? ;-) There are people who just love everything Victorian. Art Deco would be my choice.

I want one.

[Connie Dodson]

"One of the shortcomings of the initial design, I think, is that it is sensitive to wind".

Hmm.. roll-up stove and windscreen wrap.

If the windscreen is foil, only partially encircling the stove, it could be moved and placed into the wind, or, not put in place for calm weather.

[Colin Krusor]

Kevin, thanks for the observations about the water jet cutting. I'm looking for a laser cutting shop that is equipped to cut thin Ti foil, and it turns out these are not easy to find. It seems that I may have to affix the foil to a rigid substrate (plywood or heavy cardboard) for cutting, so it doesn't curl up.

I had considered designing the door to be a separate piece of foil, but I think I prefer the one-piece design. It's simpler, lighter weight, and more durable, I think, than a two-piece design with some kind of hinge. The door can be opened and closed securely when the stove is hot. The door has a bit of ceramic-fiber twine at the "latch" and can be opened when the stove is hot by a gentle tug on this twine. I'll be replacing the twine with a wire for durability. The protruding tabs from the lower ring allow the stove to be grasped (with gloved fingers) while the door is pulled closed.

Connie, thanks for the input. I have considered a large number of foil options, and I made quite a few prototypes from stainless steel foil to arrive at the current arrangement of holes, the burn chamber volume, etc. I found CP2 foil (like that sold at Ti Goat) a bit too soft, and 15-3-3-3 foil a bit on the brittle side (although maybe serviceable). I am now experimenting with CP4 foil, which I hope will be a good compromise. The arrangement of holes and the shape of the screen allows a large air throughput, which helps to keep the fire hot but also goes through the fuel pretty fast. My intention was to design a light stove that performs best with suboptimal (damp) fuel, which is a typical situation in the NW where I do most of my hiking. This design is not as well suited to areas (like the SW) where fuel might be good quality (very dry) but scarce. I'm working on a way to adjust airflow, though, to make the burn rate controllable (without introducing too much complexity). I'll consider posting this to bplite or one of the other stove-focused forums, as you suggested.

Thanks again for the feedback.

[Kevin Beeden]

It's interesting to see comments re. US patent law, and how it differs from the rest of the world. In the rest of the world, we usually refer to the US patent process as being 'first to file', in that the protection is applied at the point of application. So, if someone publishes an idea, and someone else then applies for a patent on that idea, it seems that the person who applies (files) the patent acquires the patent rights. This can lead to a situation where the actual inventor doesn't get the rights to their idea.

My understanding of this may be wrong…

In the UK (and thus rest of the world bar US, which uses the same model for patent law), a prior art search is performed. Thus, if 'prior art' is found during the patent search, the patent application (e.g. by a third party) is likely to be rejected. It does require the 'prior art' to be found; a limitation of the system. However, appeals on the basis of previously published prior art may well be used to contest a patent grant. One cheap way of preventing anyone else from patenting the idea is to apply for a patent, but allow the application to lapse; since patent searches are performed on previous patent applications and grants, it ought to be found.

The fact that publication of prior art may make a patent grant impossible is what encourages potential patentees to remain silent until an application is made (notwithstanding non-disclosure agreements). The patent application is the vital part of the process, and the drafting of this application is critical; no further 'claims' may be added to the application beyond this initial submission (revisions are often made in the light of the patent review process and prior art searches).

The original purpose of UK patents was to spread knowledge of technologies by publication of patents; the exclusive rights that accompany this publication is the 'reward' for sharing technology.

As for Connie's comments about including 'art' (e.g. Victorian, Deco etc) in the patent, this may be a misunderstanding of the use of the term 'prior art'. In the UK, certainly, stylistic art plays no part in a patent application; a patent is concerned purely with the functional aspects of technology. Stylistic art features use a different form of protection; either a Registered Design, or a Copyright. In the UK, a Registered Design would be a pretty good way of protecting this stove design.

Of course, as with all Intellectual Property, actually contesting violations of your rights (be they patent, Design, or Copyright) is an expensive business. And, as such, it may not be worth taking out any form of protection.

[Kevin Beeden]

> It's simpler, lighter weight, and more durable, I think, than a two-piece design with some kind of hinge.

All certainly true. But likely to be more expensive in material cost, which was my thinking (being an engineer, my brain can't help considering all the various efficiencies and manufacturing costs…)

As for a hinge; well, with such thin foil, I don't think you'd need a hinge (just as you don't at the moment). You'd just fasten one end to the body, rather than cutting the entire thing in one piece. It was merely a cycle-home thought, and not a major criticism.

[Colin Krusor]

Kevin, I think you're right about keeping materials cost in mind in finalizing the design. It's a good idea. I think in this case, since this stove won't require any welding, and a little bending (rod and sheet) for the pot stand is really the only fabrication operation beyond cutting out the pieces, I'll accept the extra materials cost that the one-piece design entails.

Your idea is a good one, though. I don't mean to seem dismissive of it. I'll keep it in mind in case materials costs seem to be getting out of hand.

[Eric Blumensaadt]

A very elegant and simple design.

I feel your improved windscreen is important. If it were ADJUSTABLE for pot size (within limits)and let the pot sit down in bit you'd greatly improve the stove's efficiency. This would put it above the less efficient Bushbuddy and Bushcooker "sit-on-top" pot holder design.

I just bought a Caldera Cone Sidewinder with the Inferno woodburning kit. It too rolls up and stows inside the pot I got with it. The nice thing about the Sidewinder is that Trail Designs has figured out how to make it work well with alky and ESBIT. That's your challenge.

Plus, of course, all Caldera Cones fit their pots closely and gain great efficiency. Their "custom fit" design requires you to use pots of only one diameter and height per CC stove. A close-fitting Adjustable windscreen is the advantage you'd have.

Several slots to recieve the windscreen's horizontal tabs would likely give you that diameter adjustability. Your overlapping design is EXACTLY what's needed to make the adjustability work. To support the pot just use two Ti tent stakes through holes.

Good luck!

[Kevin Beeden]

Colin, no worries about your comments; as someone mentioned earlier, it's nice that we can discuss design issues like this. And you're certainly right that you'd need to calculate both material and machining costs for any production solution.

[JD McGyver]

I work with AutoCAD for a living. Many of my clients do plasma, abrasive waterjet and laser cutting. I know exactly what is necessary. I'd be happy to program the part for cutting and adjust the part as it evolves. My only fee would be your sending me a free stove with each new revision that is made.
All I need is a tracing on paper mailed to me.
FYI I have a large format scanner that handles 40" wide x any length if any of the other folks need CAD files for projects. I'd probably be willing to work the same type deal.
Let me know if you are interested.

[Colin Krusor]

Hi JD,

I actually found a plugin that allows me to export the design from Sketchup as a .dxf file for laser cutting. The major obstacle at this point is locating a laser cutting shop that will cut thin Ti foil under argon for a reasonable rate. If I run into any difficulties with rendering the design into the .dxf format, though, I'll let you know. Thanks for the offer.

[John Nausieda]

Here are some folks using scroll saw blades, and bandsaws to cut titanium.
http://bbs.homeshopmachinist.net/archive/index.php/t-23474.html

[Colin Krusor]

The foil, the sheet, and the rods can all be pretty easily cut with hand tools. The prototypes pictured in this thread were made with stout scissors, a sheet metal punch, a drill press with a radial arm circle cutter, and a dremel tool (and a propane torch for bending the rod). For me the stove is about an eight hour project using these tools. Shaping the rings from the 0.016" Ti sheet with the dremel tool is the most time consuming part of the process.

This fabrication process is fine for making one at home for myself, but it is much too time consuming for producing 20-50 units. Producing this stove in quantity and making it available to interested people on this forum will require a laser cutter.

[leon lynes]

kevin was spot on… material investments…
but I want to add my 2 cents also for LONGEVITY…
I think I saw 2-3 cracks/tears in your photos…

I WANT ONE! heavier is better / UL I am not… yet… IT IS MY LONG TERM GOAL…
but the gadgets keep coming!

[Colin Krusor]

Hi Leon,

I do plan to revisit this project sometime soon, but I'm still in grad school and it isn't easy to find time for it.

There is only one crack/tear that I have noticed, but I agree that this problem would need to be resolved before I considered making any stoves for anyone else. A softer alloy, like CP4, might warrant consideration.

I'll post updates as soon as there is anything new to report, but I can't promise to get to it right away.

[Author]

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