Received-SPF: softfail
 receiver=logan.com; client-ip=64.102.122.149; envelope-from=echristley@nc.rr.com
Message-ID: <470A7214.1020403@nc.rr.com>
Date: Mon, 08 Oct 2007 14:08:20 -0400
From: Ernest Christley <echristley@nc.rr.com>
Reply-To: echristley@nc.rr.com
User-Agent: Thunderbird 1.5.0.13 (X11/20070824)
MIME-Version: 1.0
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Hose clamp myth busters
References: <list-2375350@logan.com>
In-Reply-To: <list-2375350@logan.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

Lehanover@aol.com wrote:
> 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.