Paul,

 

Interesting...... On the 300 series aircraft it is important to set actuator mechanical stops.. That is, on the down side (extension), the actuator piston should come to rest against the fore piece of the actuator (the piece the rod passes through).  This eliminates busting parts (i.e. over center link attach block-to-spar bond) from a hard landing with hard donuts and/or a side load that may bend the actuator push rod leading to a future gear failure.

 

On the up side (retraction), there is a metallic spacer (stop) that comes to rest against the actuator fore piece rather than have the gear slam against some sort of internal wheel stop - plus the inner door sequence valve cannot take any abuse. 

 

In our case, the bolt that attaches the leg to the over center link passes through the gear leg and a welded boss.  In the Legacy case, the leg tabs are attached to the over center link.  In either case, the gear is held up by hydraulic pressure (no physical lock) and during turbulence or maneuvers, that legacy tab is taking a beating..........  Of course, the Legacy Va must be higher than that of a 300 series aircraft and the gear is heavier, thus more beating taken by the tabs.

 

Scott Krueger

 

Interesting pictures Charles.   We have a Legacy on jacks with those links back to Lancair for fixing and it has been more than a month with continuing delays so I'm not sending mine in until I know I can get them back in short order. I doubt the 2 day turnaround is accurate on Lancair's part based on our recent experience.

On the removed parts, there was no crack but the powder coating was missing at the critical area and corrosion was apparent at that exact same spot.   Other than missing the crack, it looked just like your link.  It appeared to have been stressed at that area.  I would suggest anyone with unusual powder coating or marks in that area pay careful attention although no crack may not be evident.  It may indicate a stress problem.  And, we already know the other end of the hydraulic actuator has had failures so both welds need to be examined especially if making adjustments to the pressures or linkages.  My links do not have powder coating but the usual Florida surface corrosion is typically all I see in that area.

I note that another group here at Spruce with the SX-300 aircraft use an accumulator to absorb the pressure spikes on the gear pump.  On my Legacy I might want to include that or perhaps use the snubbers from McMaster Carr that absorb the shock as the gear is pulled into the well.   Otherwise, as I understand it, you have a full pressure hydraulic pump running at 1200 psi limits (or thereabouts) that slams the gear into the well, hits the high pressure cut out and shuts off.  It may recycle is the pressure drops and the inner gear door also comes into play but the spikes would be inherent in the design without a snubber or accumulator.  Comments would be appreciated on anyone who has gone the accumulator route--I believe the snubber has been discussed in past threads already.

Paul
Legacy RG
Spruce Creek


On 2012-04-03, at 10:21 AM, Charles Brown wrote:

> Short story:  My 2006 Legacy kit with 2008 overcenter links has the flawed parts and needs fixing.


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