[Arm-netbook] 15.6in laptop progress

[Luke Kenneth Casson Leighton]

is there no end to the detail that's needed??

okaay so i started on the screen edge, which (surprise) turned out to
need to be thicker than anticipated. increasing the thickness by 2mm
had a knock-on effect because, naturally, the base end depth has to be
increased to match.

then i began work on the friction hinge for the screen lid, so that it
will remain upright. you'd think it would be easy to create an
interlock between two pieces 8mm in diameter that looks aesthetic and
is strong enough, but nooo i can tell you it damn well isn't :)

now i am onto one of the final pieces of the puzzle: creating a lid
lock. this needs to be spring-loaded (ball-point biro pen spring, cut
into 1/4s 7mm long) and i am kinda amazed at how much detail is needed
in such a small space. the clasp is 10mm x 9mm x 8mm but requires a
5mm diameter hole in the centre (for the spring)... we'll have to see
how it works out.

l.

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[Simon Kenyon]

Post by Luke Kenneth Casson Leighton
is there no end to the detail that's needed??
okaay so i started on the screen edge, which (surprise) turned out to
need to be thicker than anticipated. increasing the thickness by 2mm
had a knock-on effect because, naturally, the base end depth has to be
increased to match.
then i began work on the friction hinge for the screen lid, so that it
will remain upright. you'd think it would be easy to create an
interlock between two pieces 8mm in diameter that looks aesthetic and
is strong enough, but nooo i can tell you it damn well isn't :)
now i am onto one of the final pieces of the puzzle: creating a lid
lock. this needs to be spring-loaded (ball-point biro pen spring, cut
into 1/4s 7mm long) and i am kinda amazed at how much detail is needed
in such a small space. the clasp is 10mm x 9mm x 8mm but requires a
5mm diameter hole in the centre (for the spring)... we'll have to see
how it works out.
l.
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most laptops these days have dispensed with a lid lock.
imho this is a good idea.
so i respectfully suggest that you dispense with it.

[Luke Kenneth Casson Leighton]

Post by Simon Kenyon
most laptops these days have dispensed with a lid lock.
imho this is a good idea.
so i respectfully suggest that you dispense with it.

yeah i thought about how to achieve a lockless lid, and with the
available materials i concluded that it would not be practical right
now: notably, it would require custom-machined metal parts or to
source parts and to redesign the laptop casework based around those
parts.

(a) sourcing parts takes time (b) custom-machining metal parts costs
money (c) chances are high that sourced existing parts would not fit
the unusual design (d) even using high-strength magnets there is no
available space to fit the magnets into the lid without weakening the
plastic lid surround to the point of impracticality.

so, logically, with all other options eliminated for various reasons,
a lid lock is the sole remaining option.

's'the way it goes, simon.

l.

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[Christopher Havel]

@Luke -- how about having hinges with a little bit of a spring-click
mechanism? That way you wouldn't have to put anything in the lid itself.
I've seen hinges like that (for doors tho) at the hardware store.

[Luke Kenneth Casson Leighton]

On Thu, Jul 23, 2015 at 8:32 PM, Christopher Havel

Post by Christopher Havel
@Luke -- how about having hinges with a little bit of a spring-click
mechanism?

that's where the machined metal would be needed. the screen weighs
450g, and its depth is around 21cm. 1/2 way point is 10cm, so we're
looking at .45*10/10 = .45 Nm of torque.... on an 8mm diameter hinge,
which means average .45/.02 = 22N of force exerted.

Post by Christopher Havel
That way you wouldn't have to put anything in the lid itself.
I've seen hinges like that (for doors tho) at the hardware store.

where would one obtain custom-made 8mm diameter spring-click hinges
without requiring paying machining fees or to place an order with a
MOQ beyond realistic levels?

over the past 4 years we've been down this road before several times,
and i've decided i'm not going to waste time and effort on it.

so i've decided i'm taking the path of least resistance, knowing that
once that path has been successful any changes may be accommodated
*afterwards*, when there is finance available from steady sustainable
income.

l.

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[Christopher Havel]

Oh well, it was just an idea... apparently not a good one, though.

[Luke Kenneth Casson Leighton]

On Thu, Jul 23, 2015 at 8:46 PM, Christopher Havel

Post by Christopher Havel
Oh well, it was just an idea... apparently not a good one, though.

it's a good one.... *if* there's a budget for - and time to source - the part.

l.

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[Christopher Havel]

Ah. In that case...

Small rectangular notch in one side of each hinge barrel (I think barrel's
the term... the part that goes around the pin). Little teeny ball bearing
(like 2-3mm dia, you know, the sort of stuff you find in a BB gun) with a
stiff spring behind it (either a coil spring, or a leaf spring with a long
lip and a dimple to hold the BB). One on each side ought to do it. You can
even have the notch on the same side for both hinges, if there's room... if
not, I say notch both sides of the hinge so it'll work in either direction.

Again, just a thought. File it somewhere if ya can't use it now... never
know when it'll come in handy ;)

[Luke Kenneth Casson Leighton]

On Thu, Jul 23, 2015 at 8:58 PM, Christopher Havel

Post by Christopher Havel
Ah. In that case...
Small rectangular notch in one side of each hinge barrel (I think barrel's
the term... the part that goes around the pin). Little teeny ball bearing
(like 2-3mm dia, you know, the sort of stuff you find in a BB gun) with a
stiff spring behind it (either a coil spring, or a leaf spring with a long
lip and a dimple to hold the BB). One on each side ought to do it. You can
even have the notch on the same side for both hinges, if there's room... if
not, I say notch both sides of the hinge so it'll work in either direction.

yeahhh you remember i said there's an 8mm barrel to work with?
that's the outer dimensions. printing a part to fit in there needs to
be a maximum of a 37mm radius, and there's a 20mm diameter bolt down
the middle as well.

but the accuracy of the printer is, when creating parts, esp. complex
ones, limited to about 1.5mm *if that*.

so there's no way i would be able to fit even a 1.5mm diameter ball
bearing inside... and still have it be strong enough. the only way
i'm confident about what i've created with the friction hinge that
i've designed is that it's reasonably chunky. when i made things too
thin (1.5mm or below) they just... broke off.

no, what i considered reasonable would be to have a D-shaped ring
which you push-fit onto one end of the friction hinge, then house a
simple flat spring that bends against the D.

when the spring hits the flat of the D, that's when it helps keep the
lid closed.

when it's bent, it helps act as a friction hinge.

.... but even just sourcing steel flat springs and D-shaped rings i
just... i can't be having with it. i've had enough. really. i want
this done, and i want it out the door, no delays dealing with
suppliers or with creating experimental prototype mechanical
custom-made custom-machined parts.

i have a 3d printer, i have some 2mm threaded bar, i have some M2 8mm
screws, and i have a spring from a biro. once product is sold, *then*
we can get fancy.

l.

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[Philip Hands]

Post by Luke Kenneth Casson Leighton
is there no end to the detail that's needed??
okaay so i started on the screen edge, which (surprise) turned out to
need to be thicker than anticipated. increasing the thickness by 2mm
had a knock-on effect because, naturally, the base end depth has to be
increased to match.
then i began work on the friction hinge for the screen lid, so that it
will remain upright. you'd think it would be easy to create an

Nope ;-)

Post by Luke Kenneth Casson Leighton
interlock between two pieces 8mm in diameter that looks aesthetic and
is strong enough, but nooo i can tell you it damn well isn't :)
now i am onto one of the final pieces of the puzzle: creating a lid
lock. this needs to be spring-loaded (ball-point biro pen spring, cut
into 1/4s 7mm long) and i am kinda amazed at how much detail is needed
in such a small space. the clasp is 10mm x 9mm x 8mm but requires a
5mm diameter hole in the centre (for the spring)... we'll have to see
how it works out.

You could just not bother with a lock.

I have a Lenovo Thinkpad X230, and it has no lock on the lid.

There is a slight impression that the lid snaps shut when almost closed,
but it's not clear if that's really the case.

You could alternatively do some sort of rotating thing on the corners,
like the OLPC's wifi arials.

Cheers, Phil.

[Luke Kenneth Casson Leighton]

Post by Philip Hands

Post by Luke Kenneth Casson Leighton
then i began work on the friction hinge for the screen lid, so that it
will remain upright. you'd think it would be easy to create an

Nope ;-)

you'd be right!

Post by Philip Hands
You could just not bother with a lock.

yehhh the friction hinge isn't accurate enough, there's a few degrees
of play and that means the lid will be flapping by about... at least 1
maybe even 2cm once wear sets in.

Post by Philip Hands
I have a Lenovo Thinkpad X230, and it has no lock on the lid.
There is a slight impression that the lid snaps shut when almost closed,
but it's not clear if that's really the case.
You could alternatively do some sort of rotating thing on the corners,
like the OLPC's wifi arials.

ah! of course! nice idea... i don't hold out much hope (the screen
edge plastic is only 2.5mm thick as it is) - i'll try to drop it into
my tiny subconscious and see what happens over the next couple of
days.

l.

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[Hans-Christian Jehg]

Post by Luke Kenneth Casson Leighton

Post by Philip Hands

Post by Luke Kenneth Casson Leighton
then i began work on the friction hinge for the screen lid, so that

it

Post by Philip Hands

Post by Luke Kenneth Casson Leighton
will remain upright. you'd think it would be easy to create an

Nope ;-)

you'd be right!

Post by Philip Hands
You could just not bother with a lock.

yehhh the friction hinge isn't accurate enough, there's a few degrees
of play and that means the lid will be flapping by about... at least 1
maybe even 2cm once wear sets in.

Post by Philip Hands
I have a Lenovo Thinkpad X230, and it has no lock on the lid.
There is a slight impression that the lid snaps shut when almost

closed,

Post by Philip Hands
but it's not clear if that's really the case.
You could alternatively do some sort of rotating thing on the

corners,

Post by Philip Hands
like the OLPC's wifi arials.

Magnet(s) to hold the lid closed?

Post by Luke Kenneth Casson Leighton
ah! of course! nice idea... i don't hold out much hope (the screen
edge plastic is only 2.5mm thick as it is) - i'll try to drop it into
my tiny subconscious and see what happens over the next couple of
days.
l.

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[Luke Kenneth Casson Leighton]

Post by Hans-Christian Jehg
Magnet(s) to hold the lid closed?

the edge of the lid is 2.5mm thick, so that's out. the front of the
lid.... maybe. that's a curved piece that's about.... 8mm wide. oh
wait.... i was going to cover it in a (very thin) metal sheet, to hold
the screen into its plastic surround... hmm... i should imagine poking
a hole in it to let magnetic attraction through shouuuld be ok....

... yeah i'll find some on amazon, hans :)

l.

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[Luke Kenneth Casson Leighton]

On Sat, Jul 25, 2015 at 2:56 AM, Luke Kenneth Casson Leighton

Post by Luke Kenneth Casson Leighton

Post by Hans-Christian Jehg
Magnet(s) to hold the lid closed?

the edge of the lid is 2.5mm thick, so that's out. the front of the
lid.... maybe. that's a curved piece that's about.... 8mm wide. oh
wait.... i was going to cover it in a (very thin) metal sheet, to hold
the screen into its plastic surround... hmm... i should imagine poking
a hole in it to let magnetic attraction through shouuuld be ok....

yep, making a clasp is too complex: magnets it is. and i guess if
the screen bezel is made from steel it would be magnetic.

l.

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