Have you considered using mini hydraulic cylinders for approx. 1/14 scale Tamiya dump truck trailers or the mini hydraulic pumps and cylinders for approx. 1/10 - 1/14 scale model excavators sold on Ebay usually? They have many different lengths to choose from and some are up to 3 stage just do a Google search or Ebay search. IIRC the mini pumps are approx. $100.00 US. Here's an example: LESU 110MM Hydraulic Cylinder Tank ESC Pump for 1/14 DIY TAMIYA Truck RC Dumper https://www.ebay.com/itm/284438994629?_ ... %3A2047675