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Roll-up stove
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Colin Krusor

Locale: Northwest US
Stove on 03/15/2011 13:20:21 MDT Print View

Thanks again for all of the feedback. I wasn't prepared, I guess, for so enthusiastic a response. In light of the arguments many of you have made for intellectual property protection and small-scale production, I have reconsidered my intitial position a bit.

I sent in a provisional application for a utility patent this morning (which is limited in legal fortitude in that it does not include a detailed report on prior patents, but establishes a first claim to a described "novelty"), and this entitles me to one year of protection in which to complete and submit the more rigorous full patent application (with all of the substantial associated fees). The provisional patent application is essentially like buying an option. It creates a paper trail and guarantees that I have first dibs on obtaining a full patent for one year.

Also, I found a Sketchup plugin that will allow me to export .skp files as .dxf CAD files, which would be required for laser-cutting. I've contacted several laser-cutting shops here in the Central Valley and in the Bay Area (CA), and I'll try to compute per-unit materials costs (including cutting) some time this week.

However, I'm not promising anything. I'd rather not take any money beforehand, and, at this point, I'm not committing to any delivery date or update schedule. My principal obligation is graduate school, and this project will have to take a backseat to that. I appreciate all of the interest in this stove, and I'll do my best to find a way to produce a batch that I can distribute to the readers of this forum, but it may be a slow-moving project.

Also, I'd like to mention some of the shortcomings of this design before anyone vows to obtain one. I'm really pleased with how it turned out, on the whole, but I just want everyone to be familiar with the imperfections.

Assembly isn't confusing or complicated, but it is a little tedious, especially the first few times one tries it. Once you're accustomed to it, it's not difficult. It can be slow going with cold fingers, though. It's like setting up a tiny model of a tent.

Also, as I mentioned in an earlier post, the 15-3-3-3 alloy foil becomes brittle after the beta transition, and can crack at the edges. The pictured prototype has a small crack. This isn't likely to affect the function, but you might find it unsightly, and it creates a new sharp edge. There may not be a way to remedy this.

Lastly, the screen is a store-bought stainless steel screen, in a circular stainless steel frame. The frame is just pressed onto the edges of the wire, and, over time, some of the wires will inevitably slip out, I think. So, keep in mind that the screen might need occasional replacement.

As long as the limitations are clear, I'm interested in hearing design feedback. Does everyone who expressed an interest see nothing about the first version that could be improved? Any ideas about the aforementioned shortcomings? I'm personally interested in trying 0.003" CP4 foil, but I won't be using it on versions that I might hypothetically distribute, because I'm afraid the thinner and softer foil might warp or bulge when red-hot. I plan to replace the ceramic-fiber twine on the door with a wire, for durability, and I plan to shorten the "crook" part of the tent stakes and enlarge the triangle in the pot stand (to make the stakes more functional as stakes). Any other ideas? What would you like to see if you were to receive one, hypothetically?

Derek, I think the top ring could have fewer tabs, and the upper part of the foil could have fewer slots. The main three might be enough. I doubt that it will be possible, with a good fit, to insert the top ring during assembly with the bottom ring already "locked in", even with a reduced number of tabs/slots. This would require a looser fit, which, for stability, I'd rather avoid. It has to be assembled bottom-ring first with the body tabs in the slots, then the screen, then the top ring, then cinching up, then the pot stand.

Edited by ckrusor on 03/16/2011 12:16:45 MDT.

Henk Smees
(theflyingdutchman) - MLife

Locale: Spanish Mountains
This ain't fair on 03/15/2011 14:32:59 MDT Print View

Hi Colin,

This ain’t fair. It’s only a few weeks ago that I received (from Steve Evans) a few feet of his 0.003” ti sheet. I THOUGHT I had some good ideas about turning this into an UL multi-fuel stove and was only waiting for a few packages of JB-Weld (can’t buy this here in Spain and they’re in the mail) to start working on same and now you’re “throwing soot in the food” (the old Dutch saying “roet in het eten gooien” means you’re spoiling the fun) with this absolutely stunning design of a roll-up wood stove. Now I HAVE to go back to the design-table and start all over again. I HATE you – just kidding :).

I’m really impressed with your stove and can only say that I fully agree with what all the others have said before. I’d be one of your prospective buyers if it wouldn’t be for the fact that I already bought the ti-sheet, so now I have to turn this into SOMETHING (even tough it won’t -not even remotely- be as nice as yours). Whatever comes out, I’ll have to live with it.

Edited by theflyingdutchman on 03/15/2011 14:35:53 MDT.

John Nausieda
(Meander) - MLife

Locale: PNW
roll up stove on 03/15/2011 15:02:26 MDT Print View

Good move on the patent. I'm wondering one thing right off the top of my head: What is the largest pot relatively full of water that the stove can handle without tipping over? Width? Must that pot be without a handle unless it is a removable handle since the stove is more or less symmetric? Another issue. Many people at BPL us pop-can alcohol stoves. Is there anyway one would fit down in the stoves bottom for alternate use? And I notice all of those air-holes punched all the way through. I'm wondering if some could be left mostly punched though as on some Anti-gravity gear windscreens so you can close some up in the face of a strong wind. Many Asian stores sell stainless steel sink traps . Most are very cheap and could be recycled at the end of their service life.

Colin Krusor

Locale: Northwest US
Stove on 03/15/2011 16:16:12 MDT Print View


I'm not familiar with the Anti-gravity gear windscreens. They have metal tabs that can be bent toward or away from a hole to allow more or less air to pass through? I think flex fatigue would eventually cause flexible tabs to break off with titanium.

One of the objectives I had in mind when I made this stove was improved reliability with damp fuel. I found that the air holes help it to burn hotter and more vigorously, which aids in keeping it going when the fuel you're adding is damp. This also requires more tending and feeding of the fire, and it makes the design somewhat sensitive to wind. This approach is the opposite of a Caldera Cone, which burns more slowly and has excellent performance in wind but can sputter out if the fuel is damp because air throughput is small.

I don't know how this stove would fare with heavy pots. The footprint is a 4.5" diameter circle, so it should be pretty stable, but I haven't tested it with anything more than a full Firelite 900.

I haven't tried an alcohol stove inside yet, but esbit tabs work well. In fact, the screen at the bottom already has a bump in the middle, and I was thinking about giving this bump a flat top to accommodate esbit tabs or alcohol stoves.

John Nausieda
(Meander) - MLife

Locale: PNW
Roll-up stove on 03/15/2011 16:35:49 MDT Print View

Absent bendable tabs for windscreen holes I would then just use aluminum foil over the holes in the case of severe winds or constant winds from one side etc. The pot size is something I consider to be very important . In my case I'm usually traveling with my wife and daughter so that pot size is about right for us. For larger groups some might want to see a scaled up stove but it's also possible that you would just bring two stoves. The Esbit option seems ideal to me for back up , but the alcohol option would really help in those situations where wood fires are technically prohibited.

Jim Pemrick
(Troy64) - F
Provisional Patent on 03/15/2011 17:38:29 MDT Print View

A US patent gives you the right to exclude others from making, using or selling your invention (in the US) for a period of 20 years from the date of filing. Of course, you can license your patent to others for a fee.

A provisional patent application only locks in your date of invention and gives you priority over later filed inventions that may be similar. In itself, it does not give you the right to stop others from making, using or selling your invention, only an issued US patent can do that.

You must file a regular utility (non-provisional) patent application within one year from the date of filing the provisional application. It typically takes the USPTO (US Patent & Trademark Office) about 2-3 years to send you out a first office action. So you are looking at 3-4 years until the application issues into a patent if it is found novel.

The wording of a patent application is critical and many pro se inventors (inventors that write and prosecute their own applications) end up with patents that have very limited if no commercial value.

If you are serious, I would recommend hiring a professional (e.g., a registered patent attorney or patent agent) at some point. If anyone offers to market your invention for a fee, run away as fast as you can. If you see ads on TV or in magazines, do not use them.

Please PM me if you have any additional questions regarding the patent application process.

Colin Krusor

Locale: Northwest US
Stove on 03/15/2011 19:00:18 MDT Print View

Thanks for the information and advice, Jim.

Ben Egan

Locale: The Grid, Brooklyn
cool stove on 03/16/2011 14:10:46 MDT Print View

That's a great stove. And a great idea.

I was wondering where you got the titanium? The titanium foil as well as the center pieces.

And how it was cut? The holes and the center pieces.



Derek Goffin

Locale: North of England
Roll-up stove on 03/16/2011 14:31:52 MDT Print View

Hi Colin,
If you change the top pot triangle so you can use straight pegs and drop it over the heads so they cannot move apart and it can only lift off not slide sideways, and put the pegs not inside but outside the foil body through the 6 main outer tabs it would trap the foil. Then the cinching tabs would not be needed or at least would not be so important. Your door would have to go over the pegs somehow.
A preheated secondary air supply with a second half height outer foil cylinder in lighter foil should be possible to add for some sectors of the market, also I suppose an insulated foil base to stop scorching for the ultimate LNT.

Steven Evans
(Steve_Evans) - MLife

Locale: Canada
Re: Roll-up stove on 03/16/2011 19:31:17 MDT Print View

That looks great! Very cool and good for you for thinking outside of the box. I really think there is some potential for something like that.

Laser cutting is the way to go for the thin titanium. I have cut my 0.003" ti foil with the waterjet but it doesn't leave a very nice finish. I wouldn't say it is "bad" but just not clean.

Here a picture of the squeezebox I cut for Kevin a while back. He may have some better pictures but you can see the rippling.

WJ Ti Foil

And just to get the mind churning, if you used the 0.003" stuff, you could weld it into a permanent cylinder and it would still roll up tight. Sort of like a version of the Titanium Flexible Windscreen available on my website. Just thinking out loud.

Colin Krusor

Locale: Northwest US
Stove on 03/16/2011 23:16:40 MDT Print View

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
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Stove on 03/17/2011 03:05:46 MDT Print View

> 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'.


Edited by rcaffin on 03/17/2011 03:06:49 MDT.

Jim Pemrick
(Troy64) - F
First to Invent in US on 03/17/2011 04:55:26 MDT Print View

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
(Troy64) - F
102 on 03/17/2011 05:02:00 MDT Print View

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

Locale: Northwest US
Patent on 03/17/2011 10:59:36 MDT Print View

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

Locale: Northwest US
Developments on 03/17/2011 19:53:57 MDT Print View

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.



Edited by ckrusor on 03/17/2011 19:55:26 MDT.

Mike M
(mtwarden) - MLife

Locale: Montana
esbit on 03/17/2011 20:54:06 MDT Print View

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

Colin Krusor

Locale: Northwest US
esbit/alcohol on 03/17/2011 22:24:20 MDT Print View

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

Kevin Beeden
(captain_paranoia) - F

Locale: UK
a thing of beauty on 03/23/2011 12:57:13 MDT Print View

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...

Edited by captain_paranoia on 03/28/2011 05:49:29 MDT.

J Thomas Peterson
(tpeterson1959) - MLife

Locale: Southwest
Wow on 03/23/2011 15:46:53 MDT Print View

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