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Chapter #15, Landing gear covers 

ESTIMATED COST OF ASSEMBLY:  About $40
MODIFICATIONS:  The plans don't give you any useful information on how to cover the holes in the main gear wells.  I found that it took me enough time to figure this out that it warranted a chapter on information to show people my solution.  I pretty much reinvented how my gear covers worked and how the brake lines were run.  I didn't like the routing of the brake lines as shown on the plans.  It stuffed a flexible section of the brake line into a small wet gear well, where as far as I could tell it would not really have enough room to properly rotate with the tube.  To rectify this I moved the flexing/rotating lines into the hull section 110 to 129 where they would have plenty of room to do their thing, and I could easily inspect them..  I then routed the brake lines through the gear tube and out the ends using aluminum lines.
    I solved my cover dilemma by forging a system that I will only become confident with if it works in flight.  I would love to know how Spence and Andy solved the issue.  The geometry of the covers movement is pretty complex and I saw no "simple elegant" answer.  My solution is pretty basic but I cannot call it "pretty"


Various failed attempts!

NOTES ON PLANS:  The plans only show a basic idea for a cover.  This is illustrated in one of the loose change notices.  The sketch shows a plate that rotates with the gear leg and is held on by a few screws.  It shows the side of the hull as perpendicular to the tube.  This however is not how the hull section actually IS.  This is a serious gap in the plans as far as I an concerned.  I am sure Spence worked out a solution and perhaps documented it somehow.  But I was not able to chase down any documentation.  The issue with constructing these plates is that as they rotate with the gear legs they are subject to the changing angle that is formed by the relationship of the side of the hull and the bottom of the spring gear leg.  This angle gets smaller as the gear leg goes down because the side of the hull is angled at this point and not perpendicular to the gear tube.  This angle acts like a pair of scissors and the gear leg pinches the gear cover as the legs go down.  This is aggravated by the fact that the hull side is angled upwards at this station.  The net effect is that the gear legs and hull side want to crush what ever plate is covering the hole.  I have seen several recent Aircars that appear to have solved this by simply not putting any kind of cover over the hole.  I may end up doing the same if my covers don't work out in flight as well as they do in static tests on the ground.
NOTES ON ASSEMBLY:  Maybe I was just being dense but I really struggled with these.  The movement of the cover in relation to the gear leg is fairly complex with no easy hinge point or center of rotation as the leg rotates.  I tried several different approaches including making some plates out of Acrylic so I could see what was going on inside.  The "eureka" came when I decided to just hot glue the cover to the gear leg while in the down position and remove it intact from the hull.  This allowed me to view the operation from the "inside out".  The solution turned out to be adding a "kicker" block to the inside surface of the plate that helps kick the plate around during those last few degrees of rotation where it had been previously binding between the gear leg and side of the hull.
THINGS I WOULD DO DIFFERENTLY NEXT TIME:  Call Dale Anderson and see if he remembers how he and Spence solved the puzzle

    These first shots show my routing of the brake lines through the tube and out the leg attach fitting.  There are small aluminum plates that will cover the ends of the tube once the spring gear legs are bolted in.   The right center shot shows the brake line as it is attached inside of the hull, the funny looking fittings are live swivels (two different types).  In the forth shot you can see the neoprene rubber ring that will hopefully help seal out (and not in!)  the water.

These next shots show the cover.  The nylon pucks act as a bearing surface for the plate.  Also visible is the "kicker block" that helps push the plate around during that last 10 degrees of rotation where it was binding.  The plate is held on using springs that are attached to the bolts on the outer ring of the Gear Tube. The springs hold the plate against the hull.  They are attached to the cover plate by screws that have been modified to have a "hook"  (sorry no picture yet).  I attach the springs using a custom made tool that pulls the spring into position and deposits the loop of the spring onto the screw.  The nylon "flap" that appears to cover the hole helps push the plate downward.

Next Up: Landing Gear Mechanisms


 
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