McAllister Crab Dolly

The McAllister Dolly was developed in the USA for precise tracking shots when filming with heavy studio cameras. It was modelled on World War II bomb loaders, which fitted 750-pound rockets to aircraft.

So that they can be operated silently, dollys are not fitted with motors. They are operated manually by a dolly or crane grip* as required in consultation with the DP, a job requiring sensitivity and precision.

This dolly has three lockable steering modes that can be selected by a thumb control on the push bar:

• four locked sets of wheels for straight tracking shots
• two steered and two locked sets of wheels for tracking around corners
• all four wheels steered synchronously for ‘crab-like’ parallel tracking shots

Because of this third steering option, these dollies are also called crab dollies. The eight pneumatic tyres allow for smooth movement on flat surfaces.

Another feature is their noiseless, hydraulically operated camera boom that can be moved up and down. Since no electric motors can be used for acoustic reasons during shoots, a hydraulic accumulator is used for upward tracking shots. During filming breaks, hydraulic oil is pumped up to around 90 atm and pressurized using a gas-filled container. This way, about eight upward tracking shots can be carried out before the pressure has to be renewed.

*In addition to the construction and securing of camera tripods, the camera grip is responsible for laying the rails for the camera dolly, operating it and the safe construction and operation of the camera cranes, among other things.