Of course, designs will be published into public domain, after I get to the point of having something, that produces feasible result after milling Maybe you or someone will be able to make valuable design improvements?

Can I have mine made from Reynolds 531 pls?

if You can get a "brick" of it for milling, why not? Or scavenge some 1960's Jaguar, parts of it were made from it.

Sorry if this has been mentioned before but I couldn't stop my urge for posting after having read the first four pages.

In principle I'd be interested in the slim back cover version, but I have a suggestion for it:
As we all know the stock back cover is not flat because the camera is protruding about two millimeters. Long time ago I've been thinking that if one would have made the back cover flat a full-sized SD card might fit between standard battery and back cover. And with a very flat adapter it might be possible to connect an SD card sitting there to the microSD port.
If one can afford the bigger format full-sized SD cards only have advantages over microSD cards. They are cheaper, faster, have more storage capacity and hit the market earlier.
Of course as an all-thumber I'd still need someone else to build this tiny adapter for me. But I'd be optimistic to find someone if there were some drafts available.

It may be hard to fit everything on standard slim cover. It seems rather like idea for big cover, but, of course, I'll check possibilities.

/Estel

How about 4140? It'd be just as heavy, and probably as nice.
But, well, it'll be a brick either way.


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As far as anodizing goes, you can go two ways:
First, backyard anodizing - Easy to do with a 12V battery charger, plastic bowl, sulfuric acid, and a pan of Rit clothing dye for coloring the part. Works great, provided the part is clean and not corroded before it goes into the sulfuric acid.

Second, oxidizing/"cooking" the part - I've found, through extensive testing, that you can make your 60- and 70- series aluminums turn a light brown to almost black by simply dumping the part in a boiling pan of water for a couple of hours. With this method, the hotter the better - A pressure cooker would probably be the way to go, or use a pan, lid and weight.
It looks cool, is incredibly simple to do, and is worth a shot.

@Estel, How about a Auto-Expanding-Design..

1) it will stay inside normally when there is one Extra battery "Aligned Normally(0˚ with main battery)"(Total 2 Batteries)


2) it will slide out(both sides) a to accommodate Two Extra batteries "Aligned Perpendicularly(90˚ with main battery)"(Total 3 Batteries)

3) And will get back inside when you want to use one extra battery like in #1

4) This Arrangement will also hold the main Battery in place when No Extra Battery is used in Big cover i.e "(Total 1 Batteriy Only)


something like this:





Transparent Render showing Design of Auto-Expanders



Transparent Render showing How Auto-Expanders Accommodate 1 extra Battery in Normal mode(total 1 Batteries)



Transparent Render showing How Auto-Expanders Accommodate 2 Extra Batteries(total 3 Batteries)



Auto-Expander Inside when Normal (1 Extra Battery total 2)



Auto-Expander Out when Extreme-Mode (2 Extra Battery total 3)



Almost flat & Sleek along the Body when Not Used



By IMMI.SHK at 2012-05-09


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P.s. - @Estel, @dr_frost_dk
IMHO to make it possible.. we will be requiring a detachable extra battery circuit.. for comfortable using it in 1-Extra Battery Mode & 2-Extra Battery Mode or even No-Extra Battery Mode
the circuit can be shifted aside camera region leaving just "3 + 3" i.e. 6 Contact pins in Auto-Expanding-Bracket


GODbless

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NOTE - THESE ARE NOT ESTEL'S DESIGN...
IF SOME(I HOPE NOT ALL) OF YOU GUY'S "DONT LIKE IT/FIND IT UGLY/WEIRD/FAT/TANK"... THEN THE CREDIT GOES TO ME

THEY ARE JUST TO EXPLAIN THE CONCEPT "THATS IT"

M SURE ESTEL'S ORIGINAL DESIGN R GOING TO BE MUCH BETTER AND SLEEK

CHEERS

That could work, and give the phone some nice extra gripping surface when being held.

However, wouldn't that introduce quite a bit of additional parts (holders + springs/clips to lock batteries in place) that wouldn't be as rugged as a simple back cover with a thick kickstand?

BTW, Estel, adding a bit of space to the plain cover for mods (touchstone, full SD cards?) sounds like a good idea. You can use some small protruding things about the thickness of 1 and a half SD card to make additional space and still hold the battery in place.

Side note, if we could ever find a way of interfacing other displays with N900 display controller, we could probably make a 4" or more N900 out of the current board.

The keyboard can probably be done like the Game Gripper - have plastic keys protruding to press the keys on the board, or make a separate board for the keyboard, with FN keys, etc. hooked up to (I2C? internal USB hub for extensions such as gyroscope etc?)

This thing is gona be huge

I would definitely take a full body replacement. I wouldn't want anything larger than the standard size battery case though, because size is an issue to me personally.