The measured compliance of the block is 350 (+/-20) lbs/mm. The free block
dimension is 3" (76.2mm) and we compress to a bearing spacing of 5", which is
a plate spacing of 71.8 mm. The block goes down 5 mm more than this due to
the packing piece, i.e. to 66. 8 mm. a total compression of 9.4 mm.
This needs 3300 lbs. and due the 4/1 arm ratio, a main wheel load of 822
lb. to overcome the compression, an auw of 960 lb. after allowance is made
of the tailwheel proportion. So one would not expect the block to compress
until the aircraft is significantly loaded, ( or bounced ). This would
appear to defeat my intention for using this for static load measurement.
Imagine my surprise to find that on climbing into the pilot's seat (+196lb)
the plate distance decreased a further 2.3 mm. This is within 5% of the
figure to be expected if the pre-compression were absent, so the system
appears to be in the linear range already. (The wings were not present so the
empty weight was only 600lb , 500lb on the main wheel).
Can it be that the block creeps and relaxes ?- It looks weird enough stuff to
do just that. (It would help exonerate all of us bouncers (:-)) )
If all with completed undercarriages would measure their plate spacings
preferably with and without loads, it would help clarify the situation. It's
easy to get a vernier gauge up there.
Graham C. G-EMIN
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