Ballasting Configurations - LoCO-AUV/loco_config GitHub Wiki
The page below contains information on currently used ballasting configurations for LoCO. Please make sure that you test any ballasting configuration on your own robot before using it, as small changes
Materials
- Under-board ballast blocks: lengths of stainless steel bar stock, cut into 0.5 x 1.5 x 2 inch blocks, with velcro attached to the back.
- Cheek ballast blocks: lengths of stainless steel bar stock, cut into 0.5 x 1.5 x 2 inch blocks, with velcro attached to one thin edge, so that they can be stood on their edge.
- 4oz stainless steel stick-on weights. Purchased from Amazon, wheel weights.
Note on 3D Printed Materials
Over time, 3D printed external structures may take on water, changing the ballasting/trim by increasing the weight of the robot in certain locations. This may be due to microfractures in the plastic, or simply water seeping through. We are currently considering creating new 3D printed structures which flood the majority of their volume by design, in order to alleviate this problem. The primary offenders are the rear thruster T-Mount, and the backbone (if using).
Creating Your Own
When creating a ballasting configuration, two things are important: achieving neutral or very slightly positive buoyancy and trimming the robot so that it is properly balanced. In order to determine the amount of ballast needed, one can calculate the volume of the LoCO robot, weigh it, and do buoyancy calculations to determine the amount of additional weight needed to achieve a chosen buoyancy value. In order to decide on the trim, we recommend sealing the robot, making it water-ready, then adding the ballast to the exterior of the robot with duct tape or some such removable adhesive, finding a decent balance, then applying the ballasting inside the robot, making it water-ready and testing again. You may very well find that starting from our configuration and simply shifting things slightly is sufficient, in which case we'd recommend putting all the ballast on, testing the robot, then shifting things internally afterwards based on your observations.