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Increased control of airlift hovercraft system

Supplier: Custom Fluidpower
02 December, 2014

A hovercraft manufacturer approached Custom Fluidpower to improve an existing hydraulic drive system which was not running correctly in a controlled manner.

The manufacturer wished to use as much as possible of the existing components in order to reduce costs and were operating on a tight deadline.

The purpose of the hydraulic drive system is to transmit power from two diesel engines running a hydraulic pump set each, into one lift fan and two radiator cooling fans in an efficient and controllable manner.

The system components included a single lift fan motor to handle variable power and speed ranges up to 50kW at 1600 rpm; the two radiator fans with shaft power requirements from 40 bar at the motor with fan rpm of 1279 to 180 bar with 4250 rpm; the pump sets consisting of a main pump delivering fluid to the lift fan motor plus a small pump delivering fluid to the radiator fan motors, each supported by a diesel engine; and proportional flow controls.

The diesel engine speed of the hovercraft is variable between 700 rpm and 3800 rpm with a cruising speed range between 2500 rpm.

Custom Fluidpower audited the current system set up and concluded that the original selection of components by another supplier had not been correct as they were being over-sped in some cases. This meant that the hovercraft was not controllable with fine control as expected by the customer and operator.

In order to improve the system the lift fan needed to achieve good variable speed control by the hovercraft operator turning a variable potentiometer at the control position with fine and smooth adjustment. This was resolved by using a Custom manifold with Sun Hydraulics cartridge technology and the use of an iControl system.

The results achieved by using the manifold was adequate to enable the customer to keep costs down whilst achieving effective operation and allowed them to sell the hovercraft to their customer.

Further to this, Custom Fluidpower has made recommendations for the design and construction of the manufacturer’s next hovercraft including the use of Parker PVplus pumps with a bent axis piston pump on the back. Custom Fluidpower believes the PVplus should have an electronic control driven by the iControl package.

The bent axis pumps should be controlled by a manifold to determine the speed at the cooler motors and to boost the suction of the PVplus pumps. Custom Fluidpower has recommended Parker Voac piston motors for both the cooler fan motors and lift fan to handle the speed and bearing loads and pressures.

Ultimately Custom Fluidpower recommended that the final system must appear to the hovercraft operator as linear and stable with no oscillations. The electronic system needs to have direct control on the main pump, that is, no separate flow-control valves. The radiator fans will have basic speed control proportional to temperature sensed in the bottom of the radiator tank. The sensing and control signal will be electronic via the iControl system.

Custom Fluidpower looks forward to working with the hovercraft manufacturer on their next build project in order to help them achieve the fine control that they require.