Hi Mal,

I've worked around aircraft off and on since the early seventy's
and one of the wheel/rim configurations that seems common is
a two piece arrangement.  That is, the wheel/rim is made up of
two halves which sandwich together through the centre hole of
the tyre.  You'll likely find an O-ring between the two halves,
as part of making it pressure-tight, and around six to eight
through bolts clamping the halves together.  Good luck!

73, J.B., VE3EAR - VE3WZL
Solar and wind powered
Lowfer " EAR"  188.830
EN93dr

http://www.hurontel.on.ca/~weazle