Keith Redding of Lucas Varity responded to our request for stories regarding the cross fertilisation of technical ideas with this interesting tale.
Keith Redding writes, `It was many years ago when mechanical gear boxes for aircraft controls were at the cutting edge of technology.
`I was designing a gear box for the speed control of an American development project where the input knob had to drive a synchro to provide output for the flight computer to reference. The gear ratio was around 250:1 and it was usual practice to provide stops at the end of the geartrain to ensure the synchro rotated only a limited angle. Because of the high gear ratio the wind up of the gears was appreciable and only provided a woolly stop at the input knob.
`At the time my children were young and into the Magic Roundabout. They had a toy with all the characters doing something, plus a music box operating from a clockwork drive. This saved the day for the American aeroplane project. The winding knob had a series of moulded plates with a drive peg that allowed 3300 degrees of rotation each. By putting a number of these together, any amount of rotation could be achieved with a positive stop at the input knob.
`What an elegant solution for the flight control unit. I then incorporated this in the gearbox design to give a positive setting stop and the plane flew successfully.’
Brad Pederson also contacted us. While at University, he used existing technology to solve a gripping problem on a robot actuator.
`The robot had to move a variety of light bulbs and other fragile objects and was required to use just enough gripping force to prevent the bulb slipping from the gripper. The force was required to change dynamically due to acceleration loads caused by the robot’s motion path. Using only a force sensor was not practical since the part orientation and other factors caused too many variables. The solution I came up with was to use a small array of trackballs surrounded by a tacky gripper surface. This gave feedback if the part was slipping or not and allowed the proper action to be taken.
`Today there would be better solutions. But this was done in the early 1980s when computing and sensor capabilities were limited.’
If you have any experiences you would like to share, please e-mail them to Jon Excell at firstname.lastname@example.org