Derek
On the full size ship, the ramp is operated by two hydraulic rams. In practice, the rams lower the ramp until the chains stop it. The ramp is then grounded on the slipway, when further extension of the rams lowers the flap. My objective was to reproduce this action. The original model just raised and lowered the ramp and didn't operate the flap.
As I was unable to find any working 1/48th scale hydraulic rams, they are simulated using a servo, some cable and a clevis. Like the full size, the model 'ram' is anchored to the hull at one end, and to the flap at the other. The tubes are merely to guide the cable and look like the rams.
It took quite a bit of experimentation to find the right servo - a high torque, metal geared one with a sturdy arm, the right clevis - a metal one, and the right cable - plastic coated steel.
As I said, there is a full build log on another forum - a Google search will doubtless find it
Barrie