Watt Governor in Action

grabcad

Original project made with Autodesk Inventor 2014 as a Dynamic Simulation and the clip is made with Inventor Studio. Besides the gravity force, the action is due to a imposed joint torque of 300 N mm applied to the Main Shaft (see picture „Joint Torque.jpg”).The Watt Governor was invented in 1788 by James Watt in order to stabilize the speed of a steam engine by a controlled valve for steam using the centrifugal force. Here is presented the same mechanism, but the purpose is to stabilize the rotational speed of the mechanism itself, by introducing sabots directly on the main shaft.As you can see by watching the Video, the frictional contact between the Sabots and the Drum (µ = 0.2) governs the rotational speed of the Main Shaft. Remarkable is that the speed grows up to a limit and it stands still at that speed all the rest of the time. The level of speed depends of the friction coefficient (µ). All the action is closed in 5 seconds, but the clip has a total of 30 seconds. You can extend the action to the clip by multiplying of 1 to 6 seconds.Considering the action seconds, the Main Shaft begins to rotate at the second 0.5 and the joint torque raises from zero to 300 N mm from the second 0.5 to second 0.8. After this, the joint torque is stationary to the value of 300 N mm. If you look to the included picture „Output Grapher - with sabots contact.jpg” you can see how the speed is raising as well.When the Main Shaft is rotating the brass spheres are moved to the outside due to the centrifugal force. This make the sabots to get contact with the drum. Since this contact is accomplished with the mentioned friction (µ = 0.2), then the rotational speed is reduced. This acts as a reaction to the centrifugal force. The rotation speed is calculated by using the radius of 90.51 mm in the picture „Radius with sabots contact.jpg”.Now, if we want to see what happens if the sabots are free, without any contact, we can suppress the 2D Contact joints for all the three sabots, as you can see in the picture „Suppressing 2D Contact joints.jpg”. As a result, the mentioned radius is increased to 113.37 mm (see the picture „Radius without sabots contact.jpg”), and the speed graphic changes as in the picture „Output Grapher - without sabots contact.jpg”. Look carefully to all the pictures for a better understanding of the whole dynamics. A simple comparison between the Output Grapher pictures should reveal to you the truth that the Watt Governor stabilises the rotational speed when a friction non-zero is applied at the contact between Sabots and Drum.If you use Inventor, you have to download all the files in a single directory, then open the .iam file with Inventor 2014, 2015..., enter Environments/Dynamic Simulation and click on Play button. Instead of 5000 images you can apply 500 images if you have to wait too much for the simulation. I choose a large number of images to have a greater resolution of the living clip.Maybe two balls are enough, but I like my governor - with three balls.Enjoy!