The problem of moisture absorbtion is often nonlinear, which is why just baking the deteriorated units would not result in another five years of service. What probably happened is that after a bit of exposure the more moisture resistant portion deteriorated and the more porous material was exposed, at which point the process went much faster. So baking and re-coating could have been a solution, but the cost would probably be similar to installing a new antenna. Sometimes repairs are completely possible but not economical to do. Given what I know about high labor costs on railroads, I would presume that was the case here.
Yes, it was good detective work, although great detective work would have been to stop and think for a while and come with a suspect at the beginning.
If the parts absorbed moisture, why wouldn't baking them drive the moisture out and give you another 5 years of operation? Obviously the design was faulty, but cycling the devices periodically through a drying operation could potentially save having to replace them unless they were very inexpensive and the cost of handling exceeded the replacement cost.
PTFE (DuPont "Teflon") is hydrophobic (water repelling). PET (material of the aforementioned housing) is hygroscopic (water absorbing). I know long term testing is sometimes sacrificed in order to get product to market. In this case the product worked for 5 years before failure. I would imagine, realistically, that when the problem was discovered, the solution would be to change the material to something better suited for long term outdoor use.
Sometimes the more expensive material is the cheaper (or should I say, more economical) and better choice in the long run.
I think it would have been a combination of incomplete specification & manufacturing (Moulding process & cleanness). The materials used were those specified by the original European design. The manufacture of this product was taken over by another company shortly after so there was no further trend analysis data to see if the problem continued to other batch lots.
Andrew Morris designed a circuit that could detect a stroke victim's groan and convert the sound into a signal so caregivers would know when help was needed.
New disc magnet motors fit into the design trend of stepping up to closed loop performance while maintaining the cost advantage of stepper motor technology.
At the Design News webinar on June 27, learn all about aluminum extrusion: designing the right shape so it costs the least, is simplest to manufacture, and best fits the application's structural requirements.
On April 21, NASA launched a novel project, putting into orbit three satellites that employ an off-the-shelf commercial smartphone as the control system.
From Dell / Intel® New Paradigms in Design Work Scott Hamilton, vertical market strategist for Dell Precision workstations, 5/2/2013 5
Early in my career, I worked as a draftsman and remember the days of drawing on vellum with numbered pencils and Mylar with plastic lead. This was a fun experience in the sense that I ...
I've been using workstations for more than 10 years and love finding ways to get more performance from my system. With demanding professional applications that require more power each ...
A lasting memory from my first job as an engineer in an auto assembly plant is standing on hard concrete at six in the morning, vending-machine coffee clutched in hand, listening to ...
For industrial control applications, or even a simple assembly line, that machine can go almost 24/7 without a break. But what happens when the task is a little more complex? That’s where the “smart” machine would come in. The smart machine is one that has some simple (or complex in some cases) processing capability to be able to adapt to changing conditions. Such machines are suited for a host of applications, including automotive, aerospace, defense, medical, computers and electronics, telecommunications, consumer goods, and so on. This radio show will show what’s possible with smart machines, and what tradeoffs need to be made to implement such a solution.
To save this item to your list of favorite Design News content so you can find it later in your Profile page, click the "Save It" button next to the item.
If you found this interesting or useful, please use the links to the services below to share it with other readers. You will need a free account with each service to share an item via that service.
Tweet This
0 
