Merely holding the lever back doesn't necessarily work, as the
'undercentre' forces, once they take over, will just bend the gear
retraction lever.
This can be exacerbated by slackness in the bolt holes that secure the
lever to the retraction arms, despite the bolts being tight.
Duncan McF.
----- Original Message -----
From: clevelee@earthlink.net
To: europa-list@matronics.com
Sent: Sunday, February 25, 2007 7:46 PM
Subject: Re: Europa-List: Undercarriage Overcentre Locking
Graeme,
I'm building A198 - now moved with me to Market Harborough, and I've
been studying/worrying about the overcenter (OC) position and have come
to the same conclusion about the marginal amount of factory designed
overcenter provided. I believe this might be a compromise - as too far
overcenter and you fight the shock cord tension to raise the gear.
While the machining of the gear components is quite precise, I believe
the stops are part of a weldment - which is considerably less so.
Overcenter toggle clamps used for holding products being machined or
assembled in industry have adjustments that control the degree of
tension against the arm that puts pressure against the OC condition.
There is an adjustable nut to control this - Locking pliers the same
way. Hit them hard or vibrate these devices and they will open if the
adjustment isn't such that the lock is firm. The gear lock in the
cockpit does not put pressure into the joint, so while it helps, it's
really a 'late' way to save the day. It does not modify the geometry of
the parts by forcing increased pressure into the components.
When there is no weight on the wheel, pressure into the OC condition
is held in the static state by the shock cord. I would submit that the
degree of tension on the shock cord has a significant bearing on the
integrity of the system. And the criteria for shock cord tightness, is
only the degree of 'effective assistance to raise the wheel' .
I am considering going further OC on my ship, however, that will
require repositioning the gear handle half the four bolt holes, or less,
so will likely require pinning. It also means that 'popping' it out of
the OC locked position will be more difficult when trying to raise the
gear. Of course a better solution is to put pressure into the system.
This could possibly be done inside the cockpit with an OC clamp on the
gear lever - with the slot modified to allow it to be pulled rearward..
The clamps I referred to above come in a J-hook pull style, which could
keep rearward pressure on the Gear lever in the aft condition. Giving
correct meaning in the Mono to 'Gear down and Locked'.
Cleve Lee
A198 Mono XS Jabiru 3300
Wings closed, top on, sanding...sanding...sanding...
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