[ARC5] An Interesting Failure Mode

[Richard Knoppow]

     Why would the cooling fan not be required?  The heat is still being 
generated. The fan or blower is running faster because the density of 
the air becomes less as altitude is increased so the load on the blower 
becomes less. Its efficiency as a cooling devise would also become less. 
Some sort of vibration isolation seems to be a reasonable solution or a 
speed regulated fan or both.
     This story fits in the catagory of opera singers being able to 
shatter a wine glass. Who was it, Memorex that featured a glass shattering.
On 12/13/2016 5:55 AM, Bill Cromwell wrote:
> Hi,
>
> I would be interested in that information, too. I would think at
> altitude a cooling fan would not be needed. I would switch it off above
> 10,000 feet. It could be done automatically or be part of the
> operational checklist. So what did "they" do?
>
> Think how awful their problems would be if they had named the system
> after accordion or banjo!
>
> 73,
>
> Bill  KU8H
>
>
> On 12/12/2016 10:02 PM, J Mcvey via ARC5 wrote:
>> so...what did they do to fix it?
>> Change  the fan
>> change the fan blade
>> reduce the fan voltage
>> install a baffle
>> shield the tube?
>> Scrap the whole system and design a new one?
>>
>>
>> On Monday, December 12, 2016 8:14 PM, Jay Coward via ARC5
>> <arc5 at mailman.qth.net> wrote:
>>
>>
>> That's what happens when you name a system after a musical instrument...
>> Jay KE6PPF
>> -----Original Message-----
>> From: Robert Eleazer <releazer at earthlink.net>
>> To: arc5 <arc5 at mailman.qth.net>
>> Sent: Mon, Dec 12, 2016 3:09 pm
>> Subject: [ARC5] An Interesting Failure Mode
>>
>> I was just reading about the use of the Oboe navigation system by the
>> RAF in WWII.  They proved the system out in Wellington bombers and
>> then switched to using Mosquito bombers, where they kept having
>> failures, a tube would seem to explode.
>> The problem turned out to be due to the higher altitude used by the
>> Mosquito, 20,000 ft rather than the 10,000 ft of the Wellington
>> flights.  At the higher altitude a cooling fan, which used a Hoover
>> vacuum cleaner motor, would turn faster due to the thinner air.  The
>> higher RPM would reach resonance with a certain tube in the Oboe
>> equipment, which would shatter.
>> Wayne
>> WB5WSV
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL