W.L. Auty

This scratch built model was based mainly on photographs and full size drawings given in the 22 RB instruction book for the full size machine. The tracks each have 44 track links hinged with 1/16 ins. pins. Each side is driven by a Pittman 12 volt motor, through a 20:1 worm gear and a 2.5:1 chain drive to the tracks. The cab rotates on six ball bearings running in a modified 4 in dia V-pulley and is driven by a geared Buhler motor, mounted in the cab using a worm and wheel reduction.

The boom lifting and lowering gear is controlled by a 12 volt motor through a large ratio worm and wheel and then the eight part cable reduction as on the full size machine. Two winches are fitted so the machine can work as a grab or dragline, only one of which is required for operation as a crane. Both winches are driven by geared Buhler 12 volt motors with spur gear reduction. Both winch drums have approximately 18 ft. of 9 strand 12 lb. breaking strain fishing line twisted together 3 x 3 on a home made rope twisting machine.

The cab is constructed from 18 swg sheet aluminum. The paint was car spray applied using an air-brush. 

The boom is constructed from 1/4 in. brass angle and plate, riveted and soft soldered. The diagonal struts were reduced from .25 to .2 in. making them more true to scale. The total length of brass angle used to make the boom comes to 35 ft and the total number of ball bearings in the model reached a total of 50.

The control of the model is by remote cable as the operator never needs to be too far away. The six electric motors are split into three groups of two, track drives, boom lifting and cab rotation. Two winches.

The two speed controllers and reversing relays, can be connected to each of the above with a three position switch. The light current circuits are kept in the control box, motor circuits and batteries are all in the crane itself, no heavy currents flow in the control cable which helps to reduce voltage drops. The batteries are mounted in the rear of the cab as counter weight, while the dummy counter weight serves to hide the speed controllers and switching relays. Speed controllers and relays are built on small plug-in printed circuits which makes it easy to replace blown transistors etc.

Photographed at a National Model Engineering and Modelling Exhibition back in its Harrogate days.



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