I'd like to build an exploratory robot that can fit within confined spaces1.
As the robot moves along the inside of a 4" pipe, it's likely to encounter some obstacles that need to be removed. Typically, that will be tree roots up to 1/2" thick. There could also be globs of tissue paper caught by the roots.
The majority of the pipe is made from clay, but a small portion of the pipe is cast iron. The portion that has the obstacles is clay and was laid in the early 1960's.
The pipe to be traversed will likely have fluid (assume water) within it to varying degrees from partially full to completely full. I'm initially planning on tethering the robot with coaxial cable and possibly an additional line like a steel cable. The propulsion mechanism is still being defined, but I expect that the robot will have some ability to fix itself in place while clearing out an obstacle.
The typical way of removing roots and other obstacles is through using a drain cleaning system. The cutting head is usually a pronged piece of metal that can burrow through the obstacle. The problem with this approach is that the pipe is damaged as part of the cleaning process and some amount of roots are left behind.
Another commercial approach that completely clears the line utilizes a spinning wire brush. The downside of this approach is that pipe wall is severely damaged as part of the cleaning.
I would like to devise a cutting mechanism that doesn't significantly damage the pipe but also removes the majority of the obstacles encountered.
What type of cutting, shearing, grinding, etc... mechanism should I consider in order to clear out the path in front of the robot as it explores the line?
1 It's a rather boring application, actually. I want to see how badly the roots are creeping into the sewer line from my house. Ideally, I'd like to clear out the roots too without damaging the clay pipe.