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From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-2376120@logan.com>
Subject: Re: [FlyRotary] Re: Hose clamp myth busters
Date: Mon, 8 Oct 2007 19:20:45 -0400
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Good point, George.

I certainly am guilty of over engineering things.  That is the major reason 
my aircraft empty weight was originally 1170 lbs which is about 120 lbs 
heavier than the average RV-6A.  My motto was (is?) if in doubt, make it 
stout!!  So an oz here and an oz there and soon it added up to 120 lbs more 
than I would have liked.

Fortunately 44 lbs of that was due to two batteries which I initially though 
absolute essential but after 6 years of flying and hauling around that extra 
22 lbs and never using it except to help start on a cold morning, I now fly 
with one 14 lb battery.  But, it took six years of experience before I could 
give up that extra battery.  Now, If I could get one of Bill Dube's new 3.5 
lbs batteries for less than my annual income (joke! Bill), I would put 
another battery back in.

But, as has been mentioned and inferred, if you don't feel comfortable with 
a certain approach then you will find some justification for using a 
different approach.  Like fuse vs circuit breaker - both certainly do the 
job they were intended to do, but I just can not bring myself to using a 
fuse for a flight critical system.  I do use them for secondary systems. 
Don't want to start that war again, but just using it as an example.

Ed
----- Original Message ----- 
From: "George Lendich" <lendich@optusnet.com.au>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Monday, October 08, 2007 6:26 PM
Subject: [FlyRotary] Re: Hose clamp myth busters


>>> Time and time again, experienced people place themselves in situations 
>>> where another second or two of engine power, is the difference between 
>>> an interesting story, and a heart wrenching tragedy. Last fall two 
>>> pilots, in a  borrowed Bonanza, hit the edge of a ditch off the end of a 
>>> long runway. No  engine power left to manage. Another 12 inches of 
>>> altitude. Another second  of power and they could have been explaining 
>>> this story to the FAA or plane  owner, or others at the next meeting. 
>>> They lived for weeks with terrible  injuries, and both died leaving 
>>> behind astounding medical bills and shattered  families. Spring clamps 
>>> are acceptable on vacuum hoses to power some back up  gages.
>> I love the depth of information and experience you bring to this list, 
>> Lynn;  but, unless you can point to a spring clamp being the cause of the 
>> mentioned accident, I'd say that it is completely irrelevant to this 
>> discussion.  Mechanical failures happen, and often they could be delayed 
>> or avoided altogether if one part was just slightly stronger.  But 
>> there's a long row to hoe to move from that statement to spring clamps 
>> only being acceptable for backup vacuum gauges.
>>
>> We don't have solid data, so we fall back to what feels good, but there 
>> is some unintended hypocrisy going on here.  If the spring clamps aren't 
>> up to the job, why would they be acceptable on back-up gauges?  Those 
>> gauges are going to be the primary gauges after the primaries fail, and 
>> if the clamp failed it will kill ALL of them anyway.  Why does it feel 
>> acceptable to use the clamps on the backups, but not the primaries?  And 
>> why are the spring clamps found all over the cooling system of some of 
>> the most reliable passenger vehicles ever mass produced?  I doubt Toyota, 
>> Honda, Ford, Dodge, or BMW use the feel good metric when specifying their 
>> clamps.
>>
>> I'm not really ranting about hose clamps as much as the feel good 
>> mentality . . . the dismissal of a solution without a quantification of 
>> what it's supposed to do.  I'm using little velcro straps to contain my 
>> wire bundles.  These things are amazing for a tube frame airplane. 
>> They're cheap, convenient, quick to install or move, allow some play in 
>> the wire while holding it securely and provide for non-abrasive 
>> separation from the structural tubes.  "But it's just velcro," a friend 
>> complained. So I strapped a wire to a shelving support tube, and let him 
>> hang from it. He gave up when the wire was cutting into his hands instead 
>> of coming loose.
>>
>> The aviation industry is rife with over-engineering because someone 
>> needed an extra ten feet to make the runway.  It's my belief that it does 
>> nothing but drive the price up.  I say 'belief' because I have no actual 
>> data to back up the belief.  Until there's some data showing how spring 
>> clamps will fail in a typical cooling system, I'm going to have to reject 
>> that notion.  There's just way to much evidence showing that they do 
>> work...reliably...for years on end.
>>
>> That being said, I'll actually use worm clamps.  There's less worry about 
>> having the exact right size for every hose, simplifying my inventory 
>> management.
>
> Ernest,
> I agree with your statement we tend to overengineer everything, I believe 
> through ignorance and I don't think that's too critical of myself and 
> others, but before we challenge those more experienced, I think some 
> experimentation should be involved.
> It's your idea, so what about testing these spring clams to pressure (and 
> over) and over extended time to see what the outcomes really are!?
> George ( down under)
>
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