On 08/04/2022 06:52, Roland Perry wrote:
> In message <ufudncfZTKrk09L_nZ2dnUU7-dvNnZ2d@brightview.co.uk>, at
> 21:50:00 on Thu, 7 Apr 2022, Arthur Figgis <afiggis@example.invalid>
> remarked:
>> On 07/04/2022 17:27, Tweed wrote:
>>
>>> I wonder if this is down to loss of knowledge as older engineers are
>>> replaced by younger ones who uncritically believe everything their CAD
>>> package tells them.
>>
>> Has there ever been an engineering problem which someone hasn't blamed
>> on young engineers not being as good in ye olden days?
>
> Children have always been bad:
>
> The children now love luxury; they have bad manners, contempt
> for authority; they show disrespect for elders and love chatter
> in place of exercise. Children are now tyrants, not the servants
> of their households. They no longer rise when elders enter the
> room. They contradict their parents, chatter before company,
> gobble up dainties at the table, cross their legs, and tyrannize
> their teachers. Socrates 400BC.

;-)

On Thu, 7 Apr 2022 16:08:28 -0000 (UTC), Muttley@dastardlyhq.com
wrote:

>On Thu, 7 Apr 2022 15:58:40 -0000 (UTC)
>Tweed <usenet.tweed@gmail.com> wrote:
>>Recliner <recliner.usenet@gmail.com> wrote:
>>> Tweed <usenet.tweed@gmail.com> wrote:
>>>>
>>https://www.orr.gov.uk/sites/default/files/2022-04/2022-04-07-orr-final-report-
>>on-hitachi-rolling-stock-cracking.pdf
>>>>
>>>> This is well worth a read if you have the time. It has been amazingly
>>>> polite in my opinion. I’ve drawn my own conclusions from it, but I’ll
>>>> develop these in the discussion that hopefully follows.
>>>>
>>>
>>> No real surprises: we already knew the problems were connected to the wrong
>>> material choice, poor welding and lack of heat treatment. What it adds is
>>> that the stress and fatigue analysis at the design stage was incorrect,
>>> too.
>>>
>>>
>>
>>To add to the above, I picked out the use of track data intended only for
>>use in checking passenger comfort was ok, as an input for calculating the
>>loads on the bogies. Also the data obtained on the initial first train test
>>runs didn’t match up with test data obtained after the cracks were found.
>>The loads were greater in the latter.
>>
>>Looks to me like an attempt to make the trains lighter (thus the use of
>>class 7000 aluminium alloy which is stronger so you can use less of it, but
>>is very prone to fatigue cracking), rushing to prove they can make trains
>>faster than anyone else (inadequate testing and poor quality welding that
>>was not checked properly) and to cap it all they blame a lack of rail
>>standards about fatigue cracking.
>>
>>They are supposed to be an engineering company and should take such things
>>into account, standards or no standards. Probably also in the desire to
>>show how efficient they are they removed all the margins. The report did
>>note this had not been a problem before in other trains.
>>
>>The only good thing is it seems Hitachi are entirely on the hook for the
>>costs to fix.
>
>Seems to becoming more of a problem these days. Seems all the CAF Brum trams
>have cracks too:
>
>https://www.itv.com/news/central/2022-03-20/west-midlands-metro-tram-services-su
>spended-until-further-notice
>
>You can understand it on a 125mph train but on a tram that probably rarely
>exceeds 40mph thats got to be a pretty lousy design and/or build quality.

And brand new CAF Oaris trains in Sweden....

https://www.railjournal.com/fleet/crack-causes-flytoget-to-withdraw-brand-new-caf-fleet-from-traffic/

On 8/4/22 02:27, Tweed wrote:
aused by use.
>
> I wonder if this is down to loss of knowledge as older engineers are
> replaced by younger ones who uncritically believe everything their CAD
> package tells them.
>
The engineering school I work for is trying to address that issue of
'belief in the CAD model'. However the primarily CAD subject that has
the twist that a mechanical workshop builds and tests your final design
has gotten negative student reviews as they considered it unfair to have
so much final mark depending on the actual physical model working!. (And
a significant number didn't!)
Students where challenging low final marks given on the basis that their
device jammed or otherwise ran badly, but where the CAD model 'worked
perfectly'.
Too many missed the point of the exercise 'don't place blind faith in
the CAD model'.

The trouble with our academic system is that the teachers get assessed
for promotion prospects on the basis of the student reviews of their
courses. So the teachers of the CAD to physical model subject were being
disadvantaged in their own careers by pushing this unpopular 'has to
work in the real world' aspect of the subject.

While there are good mechanical engineers in every graduating class who
understand there is a real world out there, there are also a pile who
think it's all a big computer simulation and if there is mismatch
between the simulation and reality, reality is wrong.

And back in the design office of the large company, the production
process accountants are going to pick the model that's cheapest to make,
not the one from the 1 graduate engineer in that years co-hort who
understand the real world isn't a CAD simulation and who added a little
bit extra 'margin' to account for it. (Or called for a physical model to
be built and tested to confirm the parameters)

It doesn't help that CAD modelling has gotten really good and can be
trusted a lot of the time. It the skill of knowing when not to trust it
we seem to have lost.