The "modest" construction quality of modern, mid-line DSLR's

[RichA]

Plastic internals goes a way toward explaining some of the problems we
see today.

http://forums.dpreview.com/forums/post/50984129

[David Hare-Scott]

OK I'll bite. What problems are you referring to and how are they related
to plastic components, specifically the mirror box which was the point of
the article?

David

[Robert Coe]

On Fri, 8 Mar 2013 15:31:39 +1100, "David Hare-Scott" <sec...@nospam.com>
wrote:

The only problem exposed in the article was that if you hit the lens of a 7D
or a 5D3 hard enough, you can rip it off. The observation that the metal skin
plays no structural role in keeping that from happening seems beside the
point. Metal skins flex under load, so attaching the lens mount to the plastic
mirror box looks sensible to me. I own two 7D's, and I've never had any
problems with the strength of the camera, even when using a very heavy lens.

Bob

[Bowser]

On Fri, 8 Mar 2013 15:31:39 +1100, "David Hare-Scott"
<sec...@nospam.com> wrote:

don't waste your time. I asked Rich about plastic, and it's
suitability as a body material, and he was unable to cite a single
example of where plastic was the cause of any issues whatsoever. He's
paranoid,plain and simple. He did offer a comment, where he stated
"I've read about some." Or something like that.

[RichA]

Weakness, focus problems (very likely due to plastic's inherent
incapability to be machined as accurately as metal, it's tendency to
change shape/size radically with temperature changes. Dirt. Plastic
under use, or any action wears faster than metal leading to fine dust
issues. Take a plastic-mount lens. Mount and demount it 10 times on
a camera body. Run your finger over the plastic mounting surface. See
the black residue?

[RichA]

If you can't understand that plastic is inferior to metal for most
engineering applications where precision is required, then why would
anyone bother giving you time, place, date, failure info?

[David Hare-Scott]

Thanks. I can see that there is case in principle for the problems you
list, at least with low strength and low rigidity polymers. Can you point
me to any study that shows that in normal use plastic camera components
actually suffer from these problems significantly more than metal ones?

David

[nospam]

In article
<70bb4a89-5753-4646...@k8g2000yqb.googlegroups.com>,

RichA <rande...@gmail.com> wrote:

> > OK I'll bite.  What problems are you referring to and how are they related
> > to plastic components, specifically the mirror box which was the point of
> > the article?
>

> Weakness,

some plastics can be quite strong.

> focus problems (very likely due to plastic's inherent
> incapability to be machined as accurately as metal,

complete nonsense.

> it's tendency to
> change shape/size radically with temperature changes.

only if you heat the camera enough so that it melts.

normal people don't do that.

> Dirt.

metal gets dirty, plus dirt is more obvious on metal than on plastic.

> Plastic
> under use, or any action wears faster than metal leading to fine dust
> issues.

no.

> Take a plastic-mount lens. Mount and demount it 10 times on
> a camera body. Run your finger over the plastic mounting surface. See
> the black residue?

nope. there's no residue whatsoever.

[RichA]

How many metal card or battery doors do you know that have broken off?

[RichA]

On Mar 11, 11:56 pm, nospam <nos...@nospam.invalid> wrote:
> In article
> <70bb4a89-5753-4646-b470-3ad7a36c4...@k8g2000yqb.googlegroups.com>,

You responses indicate you know little about high precision electro-
optics and plastic mounting components. Next time you see an optical
bench set-up with plastic mounting hardware, call someone, you're in
an alternate universe.

[Savageduck]

On 2013-03-11 23:48:22 -0700, RichA <rande...@gmail.com> said:

> On Mar 11, 11:52�pm, "David Hare-Scott" <sec...@nospam.com> wrote:
>> RichA wrote:
>>> On Mar 7, 11:31 pm, "David Hare-Scott" <sec...@nospam.com> wrote:
>>>> RichA wrote:
>>>>> Plastic internals goes a way toward explaining some of the problems
>>>>> we see today.
>>
>>>>> http://forums.dpreview.com/forums/post/50984129
>>
>>>> OK I'll bite. What problems are you referring to and how are they
>>>> related to plastic components, specifically the mirror box which was
>>>> the point of the article?
>>
>>>> David
>>
>>> Weakness, focus problems (very likely due to plastic's inherent
>>> incapability to be machined as accurately as metal, it's tendency to

>>> change shape/size radically with temperature changes. �Dirt. �Plast

> ic
>>> under use, or any action wears faster than metal leading to fine dust
>>> issues. �Take a plastic-mount lens. �Mount and demount it 10 times
> on
>>> a camera body. �Run your finger over the plastic mounting surface. Se
> e
>>> the black residue?
>>
>> Thanks. �I can see that there is case in principle for the problems you
>> list, at least with low strength and low rigidity polymers. �Can you po
> int
>> me to any study that shows that in normal use plastic camera components
>> actually suffer from these problems significantly more than metal ones?
>>
>> David
>
> How many metal card or battery doors do you know that have broken off?

None of the plastic card or battery doors on any of the digital cameras
I own have failed or been broken; CP-775, CP-5700, D70, Fujifilm E-900,
D300, G-11, & D300S.
So what is your point?


--
Regards,

Savageduck

[nospam]

In article
<cfc80d34-9b44-4c42...@m12g2000yqp.googlegroups.com>,

RichA <rande...@gmail.com> wrote:

> How many metal card or battery doors do you know that have broken off?

give me a camera with a metal card or battery door and i'll show you
just how easy it is to break it off.

[nospam]

In article
<d2d8d1cd-c1bc-4fb8...@k4g2000yqn.googlegroups.com>,

RichA <rande...@gmail.com> wrote:

> You responses indicate you know little about high precision electro-
> optics and plastic mounting components. Next time you see an optical
> bench set-up with plastic mounting hardware, call someone, you're in
> an alternate universe.

this isn't about an optical bench. it's about cameras.

plastic lens mounts work perfectly fine and they are strong enough for
most people. they might not be suited for a pro who changes lenses
multiple times a day or otherwise abuses a camera, but that isn't the
target market. most people rarely change lenses, if they do at all, so
any extra strength from metal is not needed.

as for precision, there are *no* focusing issues with plastic mount
lenses or camera bodies. that's one of the most ludicrous things i've
heard in a while.

other plastic parts work well too. ever try to break an old bell system
telephone? those were plastic and near impossible to break.

[David Hare-Scott]

I was hoping for something a bit more systematic and relevant to the points
you raised above about machining accuracy, thermal properties and dirt from
wear.

D

[Chris Malcolm]

RichA <rande...@gmail.com> wrote:
> Plastic internals goes a way toward explaining some of the problems we
> see today.

Speak for yourself. I've personally felt a lot better since I had some
plastic internals fitted.

--
Chris Malcolm

[Robert Coe]

I thought even lenses with plastic barrels had metal mounts. Can you cite some
counterexamples that we might have ever seen?

Bob

[nospam]

In article <19v4k8hlosp8uhjc2...@4ax.com>, Robert Coe

<b...@1776.COM> wrote:

> : > OK I'll bite.  What problems are you referring to and how are they related
> : > to plastic components, specifically the mirror box which was the point of
> : > the article?
> :

> : Weakness, focus problems (very likely due to plastic's inherent
> : incapability to be machined as accurately as metal, it's tendency to
> : change shape/size radically with temperature changes. Dirt. Plastic
> : under use, or any action wears faster than metal leading to fine dust
> : issues. Take a plastic-mount lens. Mount and demount it 10 times on
> : a camera body. Run your finger over the plastic mounting surface. See
> : the black residue?
>
> I thought even lenses with plastic barrels had metal mounts.

not necessarily. some might, some might not.

> Can you cite some
> counterexamples that we might have ever seen?

budget kit lenses tend to have plastic mounts. it's not a big deal.

however, his claim there is residue from the plastic is flat out
bullshit.

[Wolfgang Weisselberg]

RichA <rande...@gmail.com> wrote:

> Weakness, focus problems (very likely due to plastic's inherent
> incapability to be machined as accurately as metal,

Please provide proof

> it's tendency to
> change shape/size radically with temperature changes.

Quite unlike metal, which *never* expands or contracts.

Please look up the de Havilland DH 106 Comet 1.
Fun when the planes disintegrate in the air after 20k hours
due to *metal* fatigue.

> Take a plastic-mount lens. Mount and demount it 10 times on
> a camera body. Run your finger over the plastic mounting surface. See
> the black residue?

Now, your job is to weight the residue and calculate how many
hundred-thousands mounting and unmounting operations it takes
to rub off 1/100th of a mm from the mount on your camera.

(In fact: I see no residue.)

(In fact: you have never tested that, since you wouldn't
touch a camera or lens that contains any plastics. You're
just spreading FUD.)

-Wolfgang

[Robert Coe]

On Tue, 12 Mar 2013 03:42:19 -0500, nospam <nos...@nospam.invalid> wrote:
: In article

As it happens, I've broken a couple of them by accidentally dropping them on
the floor. You may have picked a poor example to make your point. And I
wouldn't have supposed that you're even old enough to remember those phones
very well.

Bob

[Savageduck]

On 2013-03-15 18:27:15 -0700, Wolfgang Weisselberg

<ozcv...@sneakemail.com> said:

> RichA <rande...@gmail.com> wrote:
>
>> Weakness, focus problems (very likely due to plastic's inherent
>> incapability to be machined as accurately as metal,
>
> Please provide proof
>
>> it's tendency to
>> change shape/size radically with temperature changes.
>
> Quite unlike metal, which *never* expands or contracts.
>
> Please look up the de Havilland DH 106 Comet 1.
> Fun when the planes disintegrate in the air after 20k hours
> due to *metal* fatigue.

The big problem with the "Comet" was the rectangular windows or ports
with square corners and a poor understanding of the effect metal
fatigue and pressurizing cycles. The corner cuts in the aluminum
provided a crack starting point, when the metal fatigue due a
relatively low number of pressurization-depressurization cycles caused
the failures and high altitude blowouts in those corners.
Note the oval shape, or soft rounded corners of today's airliner
windows. All due to the tragedy of the 1950's Comet crashes.



--
Regards,

Savageduck

[Savageduck]

Most of the old phone handsets were bakelite and unbelievably brittle.

--
Regards,

Savageduck

[nospam]

In article <drk7k85f7blt3bbb7...@4ax.com>, Robert Coe

<b...@1776.COM> wrote:

> : > You responses indicate you know little about high precision electro-
> : > optics and plastic mounting components. Next time you see an optical
> : > bench set-up with plastic mounting hardware, call someone, you're in
> : > an alternate universe.
> :
> : this isn't about an optical bench. it's about cameras.
> :
> : plastic lens mounts work perfectly fine and they are strong enough for
> : most people. they might not be suited for a pro who changes lenses
> : multiple times a day or otherwise abuses a camera, but that isn't the
> : target market. most people rarely change lenses, if they do at all, so
> : any extra strength from metal is not needed.
> :
> : as for precision, there are *no* focusing issues with plastic mount
> : lenses or camera bodies. that's one of the most ludicrous things i've
> : heard in a while.
> :
> : other plastic parts work well too. ever try to break an old bell system
> : telephone? those were plastic and near impossible to break.
>
> As it happens, I've broken a couple of them by accidentally dropping them on
> the floor.

dropped what? lenses or phones?

> You may have picked a poor example to make your point. And I
> wouldn't have supposed that you're even old enough to remember those phones
> very well.

you'd be wrong.

i've both dropped and intentionally tried to break some of those old
phones. they're quite rugged.

[nospam]

In article <2013031519295253635-savageduck1@REMOVESPAMmecom>,

Savageduck <savageduck1@{REMOVESPAM}me.com> wrote:

> Most of the old phone handsets were bakelite and unbelievably brittle.

not the ones i had. they were quite hard to break. i tried. :)

[Savageduck]

...and what vintage were those, pray tell?

--
Regards,

Savageduck

[Robert Coe]

On Fri, 15 Mar 2013 22:41:51 -0400, nospam <nos...@nospam.invalid> wrote:
: In article <drk7k85f7blt3bbb7...@4ax.com>, Robert Coe

: <b...@1776.COM> wrote:
:
: > : > You responses indicate you know little about high precision electro-
: > : > optics and plastic mounting components. Next time you see an optical
: > : > bench set-up with plastic mounting hardware, call someone, you're in
: > : > an alternate universe.
: > :
: > : this isn't about an optical bench. it's about cameras.
: > :
: > : plastic lens mounts work perfectly fine and they are strong enough for
: > : most people. they might not be suited for a pro who changes lenses
: > : multiple times a day or otherwise abuses a camera, but that isn't the
: > : target market. most people rarely change lenses, if they do at all, so
: > : any extra strength from metal is not needed.
: > :
: > : as for precision, there are *no* focusing issues with plastic mount
: > : lenses or camera bodies. that's one of the most ludicrous things i've
: > : heard in a while.
: > :
: > : other plastic parts work well too. ever try to break an old bell system
: > : telephone? those were plastic and near impossible to break.
: >
: > As it happens, I've broken a couple of them by accidentally dropping them
: > on the floor.
:
: dropped what? lenses or phones?

Phones. The most recent one was onto a wood floor from a distance of less than
three feet.

I've dropped a camera only once in my life, and that was because the fastener
on a neck strap gave way. Unlike many people who I'd think would know better,
I *never* use a camera unless it's on a tripod or I'm wearing the neck strap.

Bob

[nospam]

In article <2013031519501266298-savageduck1@REMOVESPAMmecom>,

Savageduck <savageduck1@{REMOVESPAM}me.com> wrote:

> >> Most of the old phone handsets were bakelite and unbelievably brittle.
> >
> > not the ones i had. they were quite hard to break. i tried. :)
>
> ...and what vintage were those, pray tell?

mostly rotary model 500, but there were some touchtone ones too.

i still use a touchtone trimline phone, and it's hit the floor many,
many times in its life.

they don't make 'em like they used to.

[nospam]

In article <m7n7k8h2bhg3jee37...@4ax.com>, Robert Coe

<b...@1776.COM> wrote:

> : > : other plastic parts work well too. ever try to break an old bell system
> : > : telephone? those were plastic and near impossible to break.
> : >
> : > As it happens, I've broken a couple of them by accidentally dropping them
> : > on the floor.
> :
> : dropped what? lenses or phones?
>
> Phones. The most recent one was onto a wood floor from a distance of less than
> three feet.

what kind? i've had old bell system phones fall from a table many, many
times without any ill effect. when i was a kid, i tried harder.

> I've dropped a camera only once in my life, and that was because the fastener
> on a neck strap gave way. Unlike many people who I'd think would know better,
> I *never* use a camera unless it's on a tripod or I'm wearing the neck strap.

i use a hand strap. i don't like neck straps because the camera bounces
around too much.

[Robert Coe]

On Sat, 16 Mar 2013 02:27:15 +0100, Wolfgang Weisselberg
<ozcv...@sneakemail.com> wrote:

: RichA <rande...@gmail.com> wrote:
:
: > Weakness, focus problems (very likely due to plastic's inherent
: > incapability to be machined as accurately as metal,
:
: Please provide proof
:
: > it's tendency to
: > change shape/size radically with temperature changes.
:
: Quite unlike metal, which *never* expands or contracts.
:
: Please look up the de Havilland DH 106 Comet 1.
: Fun when the planes disintegrate in the air after 20k hours
: due to *metal* fatigue.

Likewise the Lockheed Electra. So much vibration was transmitted into the body
of the plane that at least one airline provided soft cushions for the
passengers' feet. IIRC, they still used them, even after they were required to
reduce the plane's maximum speed by about 100 knots. But after the speed
reduction the planes at least stopped falling apart in the air.

The new plastic planes are quite an improvement. They only got grounded when
their batteries started catching on fire. :^)

Bob

[Robert Coe]

On Sat, 16 Mar 2013 12:42:16 -0400, Robert Coe <b...@1776.COM> wrote:
: On Sat, 16 Mar 2013 02:27:15 +0100, Wolfgang Weisselberg

: <ozcv...@sneakemail.com> wrote:
: : RichA <rande...@gmail.com> wrote:
: :
: : > Weakness, focus problems (very likely due to plastic's inherent
: : > incapability to be machined as accurately as metal,
: :
: : Please provide proof
: :
: : > it's tendency to
: : > change shape/size radically with temperature changes.
: :
: : Quite unlike metal, which *never* expands or contracts.
: :
: : Please look up the de Havilland DH 106 Comet 1.
: : Fun when the planes disintegrate in the air after 20k hours
: : due to *metal* fatigue.
:
: Likewise the Lockheed Electra. So much vibration was transmitted into
: the body of the plane that at least one airline provided soft cushions
: for the passengers' feet. IIRC, they still used them, even after they
: were required to reduce the plane's maximum speed by about 100 knots.
: But after the speed reduction the planes at least stopped falling apart
: in the air.

By that I meant I think they continued to use the cushions. They certainly
continued to use the planes. I flew on an Electra several times after they
limited the speed.

Bob

[Wolfgang Weisselberg]

Robert Coe <b...@1776.COM> wrote:

> The new plastic planes are quite an improvement. They only got grounded when
> their batteries started catching on fire. :^)

Ah, yes, there is a guy (in usenet) who's got strong allergic
reations to LiIon, it's all "eneloop eneloop über alles" and
"round cells good, 'proprietary' battery forms evil, they're
expensive and can't be replaced" (never mind you can get them
from tons of China makers for about every camera that ever
existed for much less than a handful dollars). Except for
mobile phones, because "they always draw power", y'see?

The same guy's also saying that compact cameras can't properly
use a focal length > 100 or 120mm (35mm equiv) due to airy
disk size and so on.

RichA isn't the only guy with chronic mad cow disease and
strange, unexplainable technology allergies.

-Wolfgang

[Trevor]

"Robert Coe" <b...@1776.COM> wrote in message
news:m7n7k8h2bhg3jee37...@4ax.com...

> I've dropped a camera only once in my life, and that was because the
> fastener
> on a neck strap gave way. Unlike many people who I'd think would know
> better,
> I *never* use a camera unless it's on a tripod or I'm wearing the neck
> strap.

And yet unlike you I never use a neckstrap while shooting, and have never
dropped a camera in over 40 years of serious photography. Fortunately we can
all make our own choices.

Trevor.

[Robert Coe]

On Mon, 18 Mar 2013 13:00:21 +1100, "Trevor" <tre...@home.net> wrote:
:
: "Robert Coe" <b...@1776.COM> wrote in message

From now on, I'll regard you as "Lucky Trevor". ;^)

It's like not wearing a seat belt. You can't be sure it's a bad idea until
it's too late to change your mind. But at least it's not illegal to do without
a neck strap.

Bob

[John Turco]

I prefer wrist straps, personally.

John

[Trevor]

"John Turco" <jt...@concentric.net> wrote in message
news:kib74t$olu$1...@dont-email.me...

> On 3/19/2013 11:13 AM, Robert Coe wrote:
>> On Mon, 18 Mar 2013 13:00:21 +1100, "Trevor" <tre...@home.net> wrote:
>> : "Robert Coe" <b...@1776.COM> wrote in message
>> : news:m7n7k8h2bhg3jee37...@4ax.com...
>> : > I've dropped a camera only once in my life, and that was because the
>> : > fastener on a neck strap gave way. Unlike many people who I'd think
>> : > would know better, I *never* use a camera unless it's on a tripod or
>> : > I'm wearing the neck strap.
>> :
>> : And yet unlike you I never use a neckstrap while shooting, and have
>> never
>> : dropped a camera in over 40 years of serious photography. Fortunately
>> we
>> : can all make our own choices.
>> :
>>

>> From now on, I'll regard you as "Lucky Trevor". ;^)
>>
>> It's like not wearing a seat belt. You can't be sure it's a bad idea
>> until
>> it's too late to change your mind. But at least it's not illegal to do
>> without
>> a neck strap.

Right, your life is not at stake.

> I prefer wrist straps, personally.

Don't like them either because they all slow me down. Being careful has
worked well enough for me, but obviously everyone has their own preference.
Life is good when we still get to make our own choices which don't affect
others! :-)

Trevor.

[Chris Malcolm]

Ny last two camera breaks were with the camera on a tripod, and could
have been prevented if it had been on the tripod AND I was also
wearing the neck strap.

1) Put camera up on tripod to photograph model boat in park. Boat
owner suggests he move it to better display one of the features he
takes a special pride in. I bend down to give him a hand. Large
American backpacker wearing large rucksack appears from nowhere, leans
over us both to inspect the boat, turns quickly away knocking me in
the head with his backpack and knocking the camera on tripod over.

2) Waiting for sunrise on top of a hill on a calm chilly morning,
camera on tripod. I'm warming myself with a cup of coffee while
waiting. A sudden *very* fierce squall of wind comes from nowhere and
blows over the tripod.

Of course I'd not only have to have been wearing the strap, I'd have
to have been standing up so that the distance from my neck to ground
exceeded the length of the strap...

--
Chris Malcolm

[Robert Coe]

On 20 Mar 2013 19:24:30 GMT, Chris Malcolm <c...@holyrood.ed.ac.uk> wrote:

Neck strap advocate though I am, I have to suspect that the combination could
easily do more harm than good. All you have to do is momentarily forget that
you're tethered to the tripod and step away suddenly, and ERK!!. Even worse if
you're doing a seascape at the water's edge as the tide comes in ... ;^)

Bob

[DanP]

On Tuesday, March 12, 2013 3:18:04 AM UTC, RichA wrote:

> If you can't understand that plastic is inferior to metal for most
> engineering applications where precision is required, then why would
> anyone bother giving you time, place, date, failure info?

That is the theory, but ..

Can you tell the difference between a picture taken with a plastic body camera and a metal body one? Same sensor, same lens, different material for body.

I am an engineer and I can tell you for rigidity there is no need to have the whole camera body made of metal, a metal chassis to mount the sensor and lens on is enough and you can fill the rest with plastic.


DanP

[David J. Littleboy]

"DanP" wrote in message
news:b4717432-ec05-4f17...@googlegroups.com...

>
>On Tuesday, March 12, 2013 3:18:04 AM UTC, RichA wrote:
>
>> If you can't understand that plastic is inferior to metal for most
>> engineering applications where precision is required, then why would
>> anyone bother giving you time, place, date, failure info?
>
>That is the theory, but ..

It's not even a theory. It's just stupid and wrong. All dSLRs are a metal
frame covered with a plastic body. This is simply good mechanical design.
The plastic protects the guts of the camera better than metal possible
could. Like wood, many plastics have a higher strength to weight ratio than
steel. And can be designed to absorb, instead of transmit, mechanical shock.

>I am an engineer and I can tell you for rigidity there is no need to have
>the whole camera body made of metal, a metal chassis to mount the sensor
>and lens on is enough and you can fill the rest with plastic.

Exactly.

--
David J. Littleboy
TA for 3.091 at MIT, spring term 1981, now hiding out in
Tokyo, Japan

[Wolfgang Weisselberg]

DanP <dan....@gmail.com> wrote:
> On Tuesday, March 12, 2013 3:18:04 AM UTC, RichA wrote:

>> If you can't understand that plastic is inferior to metal for most
>> engineering applications where precision is required,

Tell us, RichA, where's the problem if the camera skin is
1/10th mm thicker or thinner or wider or taller from one body
to the next?

>> then why would
>> anyone bother giving you time, place, date, failure info?

> Can you tell the difference between a picture taken with a
> plastic body camera and a metal body one? Same sensor, same lens,
> different material for body.

Sure! The one that's very shaky is the plastic body one:
whenever RichA touches such a body, he gets extreme allergic
reactions. St Vitus' dance, Parkinson's disease, delirium
tremens, the whole nine yards!

-Wolfgang

[J. Clarke]

In article <2k79k8l7b7oc72983...@4ax.com>, b...@1776.COM
says...

>
> On Sat, 16 Mar 2013 02:27:15 +0100, Wolfgang Weisselberg
> <ozcv...@sneakemail.com> wrote:
> : RichA <rande...@gmail.com> wrote:
> :
> : > Weakness, focus problems (very likely due to plastic's inherent
> : > incapability to be machined as accurately as metal,
> :
> : Please provide proof
> :
> : > it's tendency to
> : > change shape/size radically with temperature changes.
> :
> : Quite unlike metal, which *never* expands or contracts.
> :
> : Please look up the de Havilland DH 106 Comet 1.
> : Fun when the planes disintegrate in the air after 20k hours
> : due to *metal* fatigue.
>
> Likewise the Lockheed Electra. So much vibration was transmitted into the body
> of the plane that at least one airline provided soft cushions for the
> passengers' feet. IIRC, they still used them, even after they were required to
> reduce the plane's maximum speed by about 100 knots. But after the speed
> reduction the planes at least stopped falling apart in the air.

The speed reduction was temporary until the cause of the problem could
be determined. It was determined, it was fixed, and the Electra
airframe continued in production for another 50 years. The vibration
problem was also fixed--the two were not related.

[PeterN]

I believe that Lockheed was well aware of the risk, some safety
engineers had warned management, but the warnings were ignored in the
interest of timely delivery.


--
PeterN

[J. Clarke]

In article <518a62ec$0$10784$8f2e...@news.shared-secrets.com>,
peter.n...@verizon.net says...

You can believe anything you want to. I was an engineer at Hamilton
Standard and I worked on that propeller. These events happened before
my time but I had access to everything that was known about that
propeller and there was a lot in the files about figuring out the
vibration modes in support of Lockheed's effort to resolve the problem.
The people who worked the problem were still there and this is one of
the projects that they liked to talk about--from an engineering
viewpoint it was "interesting".

You know what a resonance is? Where you keep feeding energy into
something at the same frequency at which it vibrates when struck? Well
this was the problem. It wasn't that Lockheed was careless--they had
designed to cope with every vibration frequency that the engine and
propeller were known to produce--this wasn't horribly difficult as the
propeller and engine turned at a constant speed. The trouble is that
the propeller in this case started vibrating in a way that had not been
anticipated (by anybody, not just Lockheed) that was hitting a resonant
frequency of the engine mount.

This is not something that a "safety engineer" could predict. This is
not something that the propeller manufacturer could predict. This is
not something that, in 1959, the entire scientific community working
together could have predicted because the computing power to predict it
simply did not exist in the world. It had to be determined by extensive
testing, which was a significant engineering project in itself, and by
analysis of the wreckage, which showed unexpected damage to the bearings
on the blade shanks. Hamilton ultimately did figure it out and at that
point, knowing the nature of the problem, Lockheed was able to work up a
reliable fix.

Note that the whirl mode vibration that was breaking the airplane was
different from the vibration that causing the comfort problems and the
two fixes were unrelated--the comfort problem was fixed by changing the
angle of incidence of the nacelles, the structural problem required very
extensive modifications to the engine mount and the outer wing
structure.

[Wolfgang Weisselberg]

PeterN <peter.n...@verizon.net> wrote:
> On 5/7/2013 11:07 PM, J. Clarke wrote:
>> In article <2k79k8l7b7oc72983...@4ax.com>, b...@1776.COM

>>> Likewise the Lockheed Electra. So much vibration was transmitted into the body
>>> of the plane that at least one airline provided soft cushions for the
>>> passengers' feet. IIRC, they still used them, even after they were required to
>>> reduce the plane's maximum speed by about 100 knots. But after the speed
>>> reduction the planes at least stopped falling apart in the air.

>> The speed reduction was temporary until the cause of the problem could
>> be determined. It was determined, it was fixed, and the Electra
>> airframe continued in production for another 50 years. The vibration
>> problem was also fixed--the two were not related.

> I believe that Lockheed was well aware of the risk, some safety
> engineers had warned management, but the warnings were ignored in the
> interest of timely delivery.

Sounds like Challenger ...

... history repeats, it seems, for those who won't learn
from it.

-Wolfgang

[PeterN]

All I can and will say, is that my belief is not based upon mere
speculation. Andthere are times when memos disappear from files.

> Note that the whirl mode vibration that was breaking the airplane was
> different from the vibration that causing the comfort problems and the
> two fixes were unrelated--the comfort problem was fixed by changing the
> angle of incidence of the nacelles, the structural problem required very
> extensive modifications to the engine mount and the outer wing
> structure.
>

True.



--
PeterN

[J. Clarke]

In article <518b2e44$0$10801$8f2e...@news.shared-secrets.com>,
peter.n...@verizon.net says...

OK, now you're going off into tinfoil hat territory.

[Alan Browne]

On 2013.05.08 21:12 , J. Clarke wrote:

> Note that the whirl mode vibration that was breaking the airplane was
> different from the vibration that causing the comfort problems and the
> two fixes were unrelated--the comfort problem was fixed by changing the
> angle of incidence of the nacelles, the structural problem required very
> extensive modifications to the engine mount and the outer wing
> structure.

I recall flying the Grumman Tiger. The 180 hp Lycoming version of the
aircraft (AA-5B) tach had a yellow-band of about 100 RPM in the normal
operating (green band) range - you could not operate the airplane in
that RPM band. (Fixed pitch prop). During the check ride you operated
it there for about 10 or 20 seconds in order to recognize the vibration.

Nice little airplane. Fast - IIRC we could get a nice round 130 kts at
65% / 8000 ASL. Do not drink coffee before flight. (5 hour legs were
not unusual - flying eastbound, climb to just below oxygen required and
catch a good 25 - 30 kt. tailwind at 11,500 - lower throttle setting for
about 120 kts TAS. - that's economy cruise! Westbound, cruise at 70%
for 135 TAS - keep it lower and out of the higher alt. headwinds - 4
hour legs).

--
"A Canadian is someone who knows how to have sex in a canoe."
-Pierre Berton