You open the box and inside are lots of aluminum parts that remind you of an Erector set. Somewhat expensive, not because of all the parts (many are identical), but because of the special welding tool that was included. It can either spot-weld or, using the same principle, roll along a seam and weld that.
You connect and weld miniature girders until you have the framework for a scale model dirigible, perhaps 3 meters long. Big! When the frame is done, you carefully unroll and attach an outer layer of aluminum foil. The seam-welder is really handy here! You must be sure to seal every edge of the foil completely.
When finally ready, you call the manufacturer, and they send out someone to test your seals, and to fill the dirigible with lifting gas. The neat thing about an aluminum skin is that if it is sealed enough to hold a slight amount of air pressure above the normal barometric value, then it is also going to be able to hold in hydrogen. Your dirigible should float for a nice long time. Note also that the total quantity of hydrogen here is a safely small amount. Leaking hydrogen never hangs around -- it always rises swiftly to high in the atmosphere.-- Vernon, Mar 06 2005 Insdustrial spot and seam welders http://www.weldingnet.com/wt-catalog.pdfAbout 1/2 the way through, see the disk-electrode seam welding. [Ling], this .PDF is loaded with info, such as an ad for a silver-based goo to keep the welder-contacts from sticking to the workpiece. [Vernon, Mar 07 2005, last modified Jun 28 2005] "Fluxless Aluminum Brazing Rod" http://www.aluminumrepair.com/order.htmHey, it's fluxless now. [half, Mar 07 2005] Lawn chair Larry http://www.markbarr...m/lawnchairman.htmlHe's got more nerve than I do..... [normzone, Mar 08 2005] Aluminium solder http://www.tinmante...razing_.html#solder [Ling, Mar 08 2005] (?) Parts for aluminum/seam welding http://www.boschrex...inverters/index.jspThe original link I found is no longer there. In seeking an alternative I rand across this page. [Vernon, Jun 28 2005] I'll get my goggles.-- 2 fries shy of a happy meal, Mar 06 2005 Larry the Lawnchair Man.-- DesertFox, Mar 06 2005 "hey, it's not working, okay, let's have a look... Turn it on Jerry! AAAAAARRRRRRRGGGGGGHGHH!!"-- froglet, Mar 06 2005 Welding aluminum? That must be one special mother of a welding tool, care to elaborate?-- zeno, Mar 06 2005 (See "TIG welding")
Be careful not to confuse the hydrogen and argon tanks included in the kit.
(I'd imagine that you might be able to seam weld aluminum foil. Would likely take some very precisely controlled equipment. I've heard of people being able to weld aluminum cans with a TIG. Not me.)-- half, Mar 06 2005 "...perhaps 3 meters long..." "the total quantity of hydrogen here is a safely small amount"
which?-- Basepair, Mar 07 2005 Model zeppelins exist. Is the metal aspect the 'hook' for this idea? I don't get what's new about this.-- waugsqueke, Mar 07 2005 Using a metal skin that is leakproof is the idea here. If it works on a small scale, it could perhaps work on a large scale....
Regarding welding, I had in mind a specific spot-welding type of device, which is very gentle compared to arc-type welders. For spot welds, two big electrodes are placed, with the power OFF, against the two pieces of metal you want to weld. First the prongs physically press the two pieces of metal together, and then, with the power ON, electric current causes localized welding at that "spot" only. Oxygen is basically excluded from this process.
Now perhaps I am mistaken, but I THINK they can also use this trick to do continuous welding of seams, by replacing the contact-prongs with two conductive rollers. If not, then consider such a welder as also part of this Idea.-- Vernon, Mar 07 2005 Won't the "continuous" weld actually just be a series of tiny spot welds, allowing leakage? I remember back in the 70s reading an article by a guy who'd built a model Zeppelin that was about 4m long, IIRC, using beech and doped tissue. Filled with helium, he just about managed to lift four small model aero engines, fuel and some R/C gear.-- AbsintheWithoutLeave, Mar 07 2005 I'm not so sure about the seam-spot welder. The current is very high, and the melt must be controlled so that only the inside faces of the joint actually melt (otherwise you'll have a hole). Why not use adhesive? For example silicon sealant?-- Ling, Mar 07 2005 Seam welding works as Vernon describes. Regarding the similarity to spot welding: I have worked with a higher end spot welder which had a seam welder option. Seam welding can easily result in an "air tight" vessel. The joining of two stamped halves to form an automobile fuel tank is one common application. Of course those have external flanges to permit the closed shell to be created.
Seam welding of aluminum foil, though, is way outside of my personal experience. It would likely require a piece of equipment more expensive than a typical seam welder. I know that ultrasonic welders are used to join plastics. Maybe there's some help to be found there. Aluminum has properties which render it challenging to weld.
Also, I believe there are fluxes and brazing rods which supposedly permit the joining of aluminum with a flame heat source such as an oxy-acetylene torch. It's technically not "welding". I've never done it, but doubt it would work on the aluminum foil shell. (I have some of the flux/rod that came with my torch, but I've never tried it.)
Given that a seam welder works by applying pressure from both sides of the joint, the final weld in a dirigible might be tough to make.
I'm with Ling. Adhesives would likely work on the proposed scale. ("Silicon" sealant, Ling? Will that work to repair the leak after I've let the smoke out of an IC?)-- half, Mar 07 2005 I do some mean aluminum foil seam folding that keeps the turkey well steamed in the oven.-- FarmerJohn, Mar 07 2005 And it's supposed to actually float? Has anyone done the math here on how much hydrogen it would take to float a rather heavy metal frame? I think the dirigible would be quite out of proportion.-- RayfordSteele, Mar 08 2005 See link. Aluminium solder (aero solder). I stand corrected on the resistance seam welding on tin plated steel. However, I think half has a point with 'the final weld might be difficult to make', and aluminium foil is *much* thinner. If anyone can do it, I would be impressed.-- Ling, Mar 08 2005 Forget aluminium for this| The new plastics would be much lighter, particularly for framing| Not as rigid, and flexibility in balloons is a must| And use simple a glue for sealing| Think of colours, printing, different shapes and themes| Metal balloons, SO 20th century.. :-)
Remember that volume triples while wieght merely doubles, (inverse cube rule or sumthin) so the larger your balloon, the more lift. Buckminster Fuller, surely the Patron Saint of half bakers everywhere, proposed a Geodesic Sphere about 2 miles in diameter. The WEIGHT would be enormous, but the VOLUME was such that simple sunlight would raise the air temperature inside by a couple degrees, enough to LIFT IT OFF THE GROUND and float through the atmosphere, carrying a population of a couple hundred freely around the world.. *sigh*-- TadPoleVaulter, Mar 08 2005 [Ling], could be. Perhaps a slightly thicker than standard foil?
[TadPoleVaulter], plastics were deliberately ignored because hydrogen leaks right through them like a sieve (helium, too).-- Vernon, Mar 10 2005 I designed, constructed and operated the largest model of the Hindenburg in the world. Any questions? Want to see the link?-- mensmaximus, Mar 10 2005 Is mylar plastic? Those mylar helium balloons seem to last forever. Are they aluminized mylar?
Maybe electroplated plastic is less gas permeable?
[mens] is your model bigger than the original?-- bristolz, Mar 10 2005 Mylar is plastic and used two ply with polyethylene to package weiners for example. The aluminum coated mylar keeps gases out, the the poly is melted to seal it. The model 'was' four inches short of 45 ft long. It was designed to fit in a tractor trailer with an inch or two to spare. I'll read the link to consider putting it here. The NLHS guestbook notes for 2004 site, is not responding where I describe it in detail.-- mensmaximus, Mar 10 2005 What's a dirgible?!-- ignorantimmigrant, Mar 11 2005 //What's a dirgible?!//No such thing. A dirigible is like a blimp or airship, as reading the idea would have shown, I would have thought.-- angel, Mar 11 2005 Oooooo! Someone's out to get me!-- ignorantimmigrant, Mar 11 2005 [+] what's an igonrant?-- pashute, Mar 29 2011 //What's a dirgible?!//
It's a navigable lighter-than-air craft about which sad songs are sung. Which applies to many of them.-- MaxwellBuchanan, Mar 30 2011 hydrogen, oxy-fuel welding, metal bits... I see nothing that could possibly go wrong. (+)-- Voice, Apr 01 2011 [Voice], the main text says that the hydrogen is to be added AFTER the dirigible is constructed.-- Vernon, Apr 02 2011 Okay, here we go:
Yes, that is how continuous-seam welding works, and yes, it would create an airtight seal. The equipment is very expensive, as is the medium-gauge aluminum sheet you're describing.
Hydrogen= BAD!
Helium= GOOD!
It takes about 55 cubic feet of helium to lift one pound of dead weight, only slightly less hydrogen. A 3-meter-long aluminum-skinned rigid airship constructed heavily enough to support its own weight would be too heavy to fly. Use mylar to create the bouancy chambers (at least three if you want to properly trim the thing). Mylar can be purchased in large sheets and adhered to itself using a simple heat-sealer. Use aluminum rod to create the rigid frame. Weld it using a TIG welder- don't mess around with brazing or MAPP-gas welding, it'll just come apart on you. Connect your chambers using a gang regulator for on-the- go trim adjustments. Finally, if you must power it, use a two-stroke radial Rotax engine. Loud and dirty as hell, but the best PTWR you'll find in a small engine.
Happy flying.
Signed, the guy whose wife said no.-- Alterother, Apr 04 2011 random, halfbakery