Making Working Parts on a Model
The 7 ft asphalt plant model in the shop right now will have all working parts. Anything that moves in a real asphalt plant will be replicated on the model as well. It won’t actually function as in turning tar & stones into asphalt, but it will be nearly capable of doing so in miniature.
The client wants to demonstrate how the machine operates or how it is controlled. Doors and chutes that are moved primarily by hydraulic cylinders in a real asphalt plant will be demonstrated with 12 volt electric linear actuators on the model. Those parts in a real asphalt plant that move with gear motors – like augers and buckets – will have miniature gear motors on the model.
Our model makers create drawings in AutoCAD of the doors and chutes, in an open position and closed. That way the “throw” can be calculated, which is the amount of swing needed to open them fully. Then it needs to be determined what length actuators will best represent that throw. The working model parts need to be built and the actuators installed on them and tested for accuracy. An important factor to consider is whether or not the actuators can show on the finished model design, or need to be imbedded or disguised. In this particular industrial model, the actuators will be part of the visual presentation.
The gear motors are chosen for the model based on the scale speed necessary to make the parts turn. How much torque is needed? – what sort of load does the gear have to move? This will determine how powerful the motor needs to be. Generally if the part needs to move fast, less torque is required and if the part turns slower, more torque is called for. This particular model has a 218:1 gear ratio as the miniature motor needs to move quite a bit of mechanics.
Finally you have to tie together the different voltage strengths of the various actuators and gear motors into a controller that sits in the base of the model. This programmable code (located in a circuit board) will be the power source, or “the brain” of the working model parts. It will control when power is needed and where in the model to send it.