Message-ID: <DE22104C1ABED211992E0090273053E204F4DB@cdim-pts-mail.ports-va.marine.cdicorp.com>
From: "Rumburg, William" <wrumburg@cdicorp.com>
To: 'Marvin Kaye' <marvkaye@olsusa.com>, lancair.list@olsusa.com
Subject: RE: gas springs
Date: Thu, 25 Mar 1999 12:59:02 -0500
Mime-Version: 1.0

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>  The good part is neither me or all my fat friends
> (@275+lbs)could collapse this thing with a bar through one end ! I would
> venture to say its at least twice as strong when compared to a new one
> from
> the factory.... It extends the gear quite smartly.
> 
	Lloyd and others -

	   There have been several postings the last few days regarding the
use of stronger and stronger gas struts to force extension of the nose gear
in free fall. I have to speak up and say that this is not a good approach
(no pun intended) to ensuring a successful nose gear free fall. If no
unintended friction is present in the nose gear mount or overcenter link
mechanism, the force of the design strut (100 lbs.) is sufficient to extend
the nose gear at 100+ mph. 
	   This topic was written up extensively in a LNN issue about two
years ago (I don't have the issue at hand). A builder reported that he'd
found a slight amount of friction in the mount, which prevented the nose
gear from falling to vertical (with the plane on a jackstand and the drag
link detached from the gear). 
	   If you don't have a successful nose gear extension on your
jackstand, disconnect the overcenter link and verify that the gear strut
freely falls to vertical when swung by hand. It takes surprisingly little
friction to prevent the gas strut from forcing it to the locked-down
position.  The builder who wrote into the LNN found that it was simply a
matter of spreading the gear mounting attach plates. I used a combination of
regular and thin AN960C washers on each end of the sleeve over the front
mounting bolt to spread the attach plates and achieve frictionless
operation. A little (Castrol Syntec) grease here might help as well.
	   It could also be caused by a builder misalignment of the
overcenter link, in which case you may be able to machine the sharp
overcenter link edges slightly to alleviate it. Since the nosegear
overcenter link carries only axial forces, I have long been an advocate of
Lancair's designing the nose gear overcenter link to incorporate a rod end
bearing to attach the gear (SAME AS THE MAIN GEAR), thus allowing for some
builder misalignment of the nose gear overcenter link.
	   The problem could, of course, be a weak (less than 80-100 lb.)
force gas strut. I wouldn't simply add force as the solution. As a
complication, the additional force must be overcome by the gear retract
hydraulic pump, which raises the required pressure.
	  
	        Bill Rumburg
	        N403WR  (Sonic bOOm)