Small Thrusters v2.0 – CAD Model

We recently finished the final CAD model for the small thrusters we're using in our submersible. Four of these thrusters, two vertical and two horizontal, helps our submersible attain 4 of our submersibles 5 degrees of freedom.

The design of the small thrusters was focused around designs that were both easy to build and easy to install. We decided to work off of last years design, keeping the same idea, but tweaking it to fit in the new form factor of the sub. Each thruster assembly has only 5 total parts (excluding the motor and prop) making it an easy part to build and assemble. An image of the finished thruster is below:

Thruster Assembly

This design consists of four main parts: the thruster grill, motor mount, PVC mount, and the PVC piping. In the image above the PVC is transparent, the grills are black and both the motor and PVC mounts are green. The thruster is assembled by sliding the PVC mount into the three slots cut in the PVC pipe and then epoxying it place. The motor and motor mount are then able to slide freely into the six slots cut on the opposite side of the PVC pipe. This side is not epoxied and allows us to easily remove the motor by removing three bolts on either side of the thruster and sliding out the PVC pipe, PCV mount, and motor mount all together.

The bolts we are using are 16mm long, 4M bolts that are threaded into tapped Delrin plastic (green). These bolts mostly have to deal with torque and therefore are suitable for the size and power of motor and prop combination we're using. This is also nice because it means the thruster is mounted directly to the aluminum body and the PVC acts only to direct the flow of water. Three of the parts are pictured below:

Thruster Mount

PVC Mount

PVC Pipe

Finally we created the grill for our thrusters. The main purpose of these pieces are to keep any large pieces of material from interfering with the performance of our thrusters. They do, however, also help with the aesthetics of the sub. By using these pieces to slide into the holes cut in the aluminum body we are able to keep a relatively smooth form factor which is important in reducing the drag of the sub. There are also three bolts on either side in order to mount the thruster firmly in the sub.

Grill

Both the vertical and horizontal thrusters will be mounted close together and as far from the center of the sub as possible. This gives us finer control over the submersible due to mechanical advantage. An image of the two thrusters mounted in the aluminum body is below:

Mounted Thrusters