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* Posts by Holtsmark

31 posts • joined 7 Jul 2008

Drone-assisted Swiss construct virtual 3D castle

Holtsmark
Go

Re: have a look at insight3d

Or try Point Cloud Library : http://pointclouds.org/

Have played around with it myself, and was suitably impressed.

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LOHAN in FIGHT to DEATH with brace of cantankerous canards

Holtsmark

Re: Interior

A playmobil reconstruction will have to be sufficient.

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Holtsmark

Re: Threadlocker

Looking at the way the canards are fixed to the fuselage, I am a bit worried about how the forces from the canards are introduced into the aircraft structure. At the very least, a lifting force will introduce severely increased friction loads on the surfaces that work as glide bearings.

If you were to introduce a shaft that could transfer bending moments (but not torque) from the right canard to the left canard, then the bearings would only have to deal with the lift generated by the canards, and not the bending loads (Assuming both canards are moved in the same direction). If the canards are used as ailerons, then the bending loads would be reduced by a factor close to 10 (using the width of the fuselage rather than the width of one glide bearing sleeve to offload the canard..

oh.. and IAAAE :P

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Picture special: LOHAN makes fire in the sky at 15,000m

Holtsmark

Re: Addition for the Truss

Lester should consider replacing the Playmonaut with a Kerball.

http://www.shapeways.com/model/1010779/bill-kerman-on-iva.html?li=shop-results&materialId=26

LOHAN style space exploration could come directly the Kerbal universe (Notice that Bill Kerman already has the correct facial expression).

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Holtsmark

Re: Might be unduly pessimistic, but...

In which case you can assume that you picked the wrong tape.

I spend much time looking for spec-sheets going down to at least -45°C, and these can be found with some effort (we do not fly as high).

-77°C means that one has to start looking into tapes for the process industry. Kapton tape with a silicone glue might work.

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Holtsmark
Boffin

Yep, you tested it in a way that conforms to the glorious ideals of your former career.

However; I have seen enough pictures of you guys wearing pipes and white frocks to demand a proper boffin- type testing. A limit load test well as a peel test at the appropriate temperatures should provide the required info. ..or just find and read the technical specifications for the tape....

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Holtsmark
Boffin

Have you checked the properties of the aforementioned tape at the temperatures experienced at altitude?

Both glue and structural part may behave quite differently than on ground level.

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NASA quandary: Should Curiosity channel Fast and Furious for Martian dune-buggy jump?

Holtsmark
Boffin

Re: Question...

..Because rubber will behave very strangely in space / on Mars (Not to speak of the problems with de-pressurizing and re-pressurizing them).

You get degassing, temperature effects etc.

The moon rover wheels were not made of rubber. They were made of metal wire and plate:

http://www.collectspace.com/ubb/Forum39/HTML/000193.html

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Sweet work, fellas: Boffins build high-density battery powered by sugar

Holtsmark
Boffin

Re: Energy density

Thank you..

I looked at the article, but did not see the table.

596 Ah kg−1 at 0.5V yields 298 Wh/kg, which fits to 15% maltodextrin (24 e) found in "Supplementary Table S3 Comparison of energy densities of batteries and EFCs". If I read the table correctly, then this means that the 298 Wh/kg relates to the fuel mixture, not to the complete system.

For comparison

Li. Ion: 180 Wh/kg is a reasonable value for a cell with good power and lifetime values. I know of alternative chemistries that have achieved 300 Wh/kg in lab conditions.

Although I would be happy to see a good and lightweight fuel cell that can use this fuel, I fear that the 298 Wh/kg will be slashed substantially for any application that is not "low power over extreme intervals". Even for such an application, 298 Wh/kg is not "one order of magnitude higher than that of lithium-ion batteries". However, it is also not one order of magnitude less, which means that this is a technology to keep an eye on.

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Holtsmark
Boffin

Energy density

Energy density is measured in Wh/kg.

Proclaiming an energy-storage density of 596 Ah kg−1 is meaningless, because the voltage is missing.

I could claim that our drive battery has an energy density of 10000 Ah/kg simply by lowering the output voltage sufficiently (using a DC/DC converter).

Also, seeing that this is a fuel-cell, not a battery: What does the mass data relate to?

Mass of fuel cell alone? -Then they should compare to other fuel cells, not to Li-Ion.

Mass of fuel cell and fuel? -Then it is easy to fake good results by combining an oversize large fuel tank with a minuscule fuel cell. .. Which, when taken to the extreme, equates to the energy density of the fuel alone.

-Which is also quite misleading. We fly some 500 km on 5 kg of hydrogen. Sounds nice?

Wait until we have added the weight of the fuel cells, the peripheral systems and the pressure vessels.

El Reg is not at fault here though. Whoever wrote that press release either was being willfully misleading or ignorant of the matter at hand.

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Boffins invent LUMINOUS PIGS again, glow-in-dark bacon sarnies presumably imminent

Holtsmark
Happy

I have previously had artwork published, but I never expected to see my "flying pig" joke picture published in the noteworthy el Reg!

The picture used in the link uses a 3d model that I in my former life generated for open source (slow)MMO found at www.worldforge.org combined with a pair of wings. I hacked up that picture in order to convince another contributor that it definitely was the right time for her to release some more artwork.

Some years ago I noticed that someone had contributed the picture to wikipedia http://en.wikipedia.org/wiki/File:Flying_pig_hell_freezing.jpg , pretending to be the creator. Have never bothered to rectify, but think it is funny to be the creator of the most used "flying pig" image available in the interwebs (says something about the quality of the net doesn't it?).

some more piggyness:

http://purple.worldforge.org/~munin/logo/wf_media.jpg

http://purple.worldforge.org/~munin/models/pig/pig05.jpg

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ULTIMATE ELECTRIC driving machine? Yes, it’s the BMW i3 e-car

Holtsmark
Thumb Up

Re: That's some battery

We have a product with an automotive size battery pack. early units have been in customer hands for eight years now, and we see no degradation.. so yes it is possible.

Note that the 8 years are with regards to natural aging of the cells (which is mainly dependent on charge state (higher is worse) and storage temperature (higher is worse). Each charge cycle also has an effect on battery life, but if you buy good cells, then you can get more than 4500 SAE cycles (80% discharge - recharge). I am convinced that we will all be driving electric cars in a not so far off future. The advantages are simply to many, and the technology is progressing steadily.

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Mini-Me, stop humping the 'L-A-S-E-R': New 3D tech can make a Mini-You

Holtsmark
Go

Re: Lots of dots

Here is a link which describes a working open source tool-chain very well:

http://wedidstuff.heavyimage.com/

The core program is visual sfm:

http://www.visual-experiments.com/demos/sfmtoolkit/

I tested it using reduced resolution (as suggested in the article) and the results came out surprisingly well.

Following the article, the whole tool-chain is surprisingly simple to follow. Add a 3d-printer at the end, and you can set up your own business.

However, Note that the software requires a non-transparent surface with texture in order to work well.

A uniform white box tends to end up with only the edges being detected, and with gaps in the sides.

Have fun!

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IRON MAN MUSK: Elon reveals Tony Stark-style 3D design smarts

Holtsmark
Boffin

Re: I call bullshit @Holtsmark

Nope, it is not fear.

I have spent the last 4 weeks fixing under-defined models where the "engineer" created parts with "wide sweeps of his hand". I would LOVE tools that would speed up my work-flow more while yielding well defined models. Such tools would not lay off engineers, but rather result in the same amount of engineers (there is never enough of us) produce more refined designs.

However, having world + dog bow before Mr Musk and his new way of using BOTH HANDS to view an object where a single hand plus an input device, or just head + Track-IR could do better (Leaving one or two hands to actually work the model), then thats when I CALL BULLSHIT.

And yes.. It is only proof of concept. However, the proof should show a little more novelty before it becomes a newsworthy "breakthrough". There is enough cool engineering out there that does not get coverage.

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Holtsmark
FAIL

I call bullshit

Spending my day designing Aerospace parts in CAD, I can not come over the impression that this is pure management porno.

Engineering is parameter driven. All important thicknesses, angles, lengths are set by entering numbers on a keyboard (or using filtered output from computer analysis). You do NOT gesture a wall thickness of 2.467885423456mm, instead you enter 2.5 mm on your keyboard

.

All that I can see in the video is some manager impressing other managers by using hand gestures to move around an ALREADY ENGINEERED part.

This is NOT progress

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An autopilot the size of a postage stamp

Holtsmark
Black Helicopters

Re: "clearly Top Gear"

I did read the bit about "open source" and "low cost". However, the post I replied to described this in "leading edge" terms, and I therefore noted that leading edge was already quite a bit further.

That this comes at a price is quite clear, but the users seem quite happy with what they get for the money.

If proxydynamics has been all over the place for a while, then I have not noticed.

All in all, it is nice to see development moving ahead. Now I am only waiting for an available certified sense and avoid system, and interesting things can start to happen.

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Holtsmark
Black Helicopters

"clearly Top Gear"

Sorry,

impressive as this is, "Top Gear" is already for sale.

These guys http://www.proxdynamics.com/products/pd_100_prs/ have obviously already achieved a much higher degree of integration and miniaturization, they just prefer to keep a somewhat lower profile than your usual academic research group. Only problem: you can not buy it unless you have government backing :(

Black helicopter because the gray helicopter icon is missing.

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LOHAN plugs into some hot LiPo treatment

Holtsmark

Re: LiPo at altitude

"LiPo capacity drops nearly exponentially with temperature.

I suspect it needs to keep itself warm as much as it needs to keep warm the motor. That will add some more weight and logistics around insulation."

First: Use low temperature capable cells.

Second: Insulate them well (keep them inside truss payload compartment

Third: Do something like this: http://lange-aviation.com/htm/english/products/antares_20e/img_battery_module_xl.html

The red stuff is the battery heating wrapped around 3 individual cells.

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Holtsmark
Coat

LiPo at altitude

Dear Sirs,

may I respectfully suggest that you load-test LiPo in REHAB?

LiPo usually is kept together using the coffee-pack principle, meaning that the active ingredients are inside an air-tight bag at (close to) vacuum. The outside air pressure then presses the cathode, the conductive polymer and the anode together, do that beautiful chemistry may occur. Remove said air pressure, and chances are that the spark will be missing, with the sad result that LOHAN will fail to see an ejection while suspended under her massive orbs. Should LiPo fail in REHAB, then you may want to consider using potted Li-Ion. The hard enclosure means that energy/weight is somewhat reduced (chemistry can be the same), but these batteries can work successfully in space (check specs for individual cell types).

Also note that you will get more energy out of the pack if some energy is used to keep the pack itself at temperature.

..mine is the one with a 12.5 kWh / 289V space grade Li-Ion pack in the pocket...

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Vulture 1 sprouts wings and a tail

Holtsmark
Pint

Levers

I build these things for a living, and although I do not doubt that the wings will reduce the rate of decent somewhat ("fly"), I am sure that weight could easily have been reduced substantially, and performance increased. I will spare you the long and tedious analysis.

The additional strengthening of the fuselage will indeed undergo tension, so unless the but-end glue joints have been strengthened locally, the tubes will probably do little.

To all who discuss levers: The bending force created by the aerodynamic lift is simply carried over into the other wing (assuming continuous wing spar. All the fuselage sees is an upwards force, no bending force.

Anyway: Good luck on Saturday. Bring enough alcoholic beverages to either celebrate or forget .

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PARIS unveils impressive box

Holtsmark
Thumb Down

Oxygen?

Not enough oxygen available at critical altitude.

Chemical or electical solutions may be better. If you go electrical: LiPo batteries may have problems due to lack of external atmospheric pressure to keep the (vacuum-) pack together and working. Go LiIon with a cylindrical metal shell if you can. Make sure that the battery heats itself as well.

Not impressed with weight of box. Better get someone to sponsor you with low density Rohacell foam. Extremely good insulator as well. Glue it with epoxy or polyurethane and skip the duct tape. .

Y.I.A.A.A.E.

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Linux game-time refined with latest Wine

Holtsmark
Grenade

Blender

Nope,

Blender 3d is a clear winner in this field

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Holtsmark
Linux

Chasing the wrong program

Sadly, the moment FreeCAD approaches AutoCAD capabilities, the developers will discover that most engineering (Not Architecture) is performed in parametric modellers like SolidEdge, SolidWorks or (Ugh!) Pro-Engineer. (Or CATIA, if big wealthy Aerospace or Automotive companies are involved)

I never touched AutoCad again after I started working with these. In my experience, ONLY architects still work in AutoCAD. ..And I do design stuff that is slightly more complex than a custom tray...

The penguin? ..because I actually have a fully parametric solid model of him laying around somewhere on my HD.

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Nazi-doodlebug-powered father of all paintball guns patented

Holtsmark
Headmaster

Doodlebug? -Beetlebug!

This is not a pulse jet engine.

Pulse jet engines, like the WW2 Argus engine uses reflected shock waves both to inhale fresh air and to create sufficient compression of the fuel-air before ignition.

This invention does not appear to use shock waves, and appears, technically to be closer to a quite normal two stroke engine. Sadly this does not make for a just as good headline, since Mr. Page cannot insert NAZI into it without looking ridiculous.

"Nazi-WV-beetle-powered father of all paintball guns patented" really does not have the same ring to it does it?

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'Optionally manned' spy plane to fly this summer

Holtsmark
Pint

Diesels

The reason why the DA42 is so popular in the UAV scene is that it is powered by two diesel engines with very high fuel economy. There are reports of DA42 UAVs with 40h endurance. This is impressive for a system using a conventional (infernal combustion) propulsion system, allowing for persistence at the target.

The beer? Well if it is a "Sink the Bismarc", then it can probably be used to fuel the DA42...

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India's Reva to pitch 'invisible' e-car reserve battery

Holtsmark

A bug or a feature?

Some cheaper Li based batteries get a SUBSTANTIALLY lower lifespan (factor 10 or worse) if they are regularly discharged below 50%. It may very well be that what we see here is the properties of a bad battery being sold as a "feature". Not something you want to give your customers regular access to.

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Electric plane takes to the skies

Holtsmark
Coat

@Al Taylor

All aircraft are built to an order.

Any manufacturer that builds aircraft in the hope that it will be sold has serious problems.

The article says "the world’s first commercially available electric aircraft.". The Antares 20E fulfilled this description 6 years ago. Whether the aircraft mentioned in the article will be built in the numbers of the Antares still remains to be seen. There is a vast gap between a flying prototype and a press release and a series production aircraft.

Mine's the one with a 11 kWh battery in the pocket.

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Holtsmark
FAIL

Please perform your research before publishing

The first electric aircraft to be commercially available was the Antares 20E.

First flight was in the summer of 2003.

See http://lange-aviation.com/htm/english/products/antares_20e/antares_20E.html for further details.

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Obama weighs into Shuttle-v-Soyuz ISS brouhaha

Holtsmark
Coat

The alternative route

Or go the alternative route:

Skip the troublesome Ares solution and reuse the proven shuttle components:

http://www.directlauncher.com/

This is at least what a number of NASA Ares engineers believe in and work on in their spare time.

Cheaper, Faster, Lower technical risk.

Downside:

No mammoth launcher like the Saturn V

Mine is the one with a slide ruler in the pocket

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First Merc hybrid first to use laptop battery tech

Holtsmark

Wrong description

"Laptop battery tech" is simply a completely wrong description. Without further research I would guess that the cells used will be similar to these: http://saftbatteries.com/Produit_Large_VLM_cell_range_301_62/Default.aspx

These are high performance industrial cells which cannot be compared to the (China made) cells which can be found in laptops, electronical gadgets, or model aviation.

Which is why real aviation goes in a similar direction:

http://lange-aviation.com/htm/english/products/antares_20e/battery_system.html

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Prius hybrid to get rooftop solar panel

Holtsmark
Black Helicopters

The real value of Prius

In my eyes, the real value of the Toyota Prius is that it got the alternative drivetrain out of the concept cars and into the mass market. Suddenly all the car manufacturers had to come up with a similar or (,and here is the good part,) better product.

In my eyes, the biggest problem with most hybrid cars available right now, is that one cannot drive the first 100 km or so (to work thus) on batteries only. However, doing so would require the utilization of some really good batteries (like these http://lange-aviation.com/htm/english/products/antares_20e/battery_system.html ), and they again require a slightly more serious investment than most people are ready to make.

The good news is that prices are falling, and that the technology is moving forward.

Personally I hope that my next car can have a primarily electric drivetrain.

....A helicopter because anything is simpler than a vehicle consisting of 10.000 parts doing their best to shake apart.

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