For my senior design in aerospace engineering at NC State, we are building a reduced-gravity simulator to test rovers on. I have kept the idea of building a CNC machine in the back of my mind for a while for when I get out of college and can get a shop set up and have often lurked on these and other CNC forums. So when I saw that this thing would pretty much be a 2 axis CNC machine without the milling, I knew I should come here for solid information.
The design consists of one axis suspended above a “sandbox” test area, a carriage containing a servo slides along the top of the rails and is attached to the rover below by cable. The servo motor maintains a constant torque on the chord attached to the rover in order to simulate reduced gravitational pull using the equation: τ=r(mfg)sinθ.
Where r is the radius of the servo reel, m is the mass of the test body, f is the fraction of earth’s gravity being simulated, and g is earth’s gravitational acceleration.
The carriage has to be powered and move along with the rover below. The carriage must travel 5ft and be able to travel at least 6 in/sec, I would like it to be more like 10 or 12 in. The carriage will carry a servo with a maximum weight of 50 lbs, as well as suspend a 40-50 lb weight below.
We have some spare parts from previous projects including two 5.5 ft long 80/20 Series 10 pieces, and six 1.5 ft pieces. There are also two 4in x 3.5in x 5ft aluminum I-beams.
We currently have about $500 budgeted for this part of the build. That can go up if necessary, but I hope not for just one axis. I was thinking we could use the 80/20 as rails, mounted on top of the I-beams for rigid support. I'm not sure whether to try to go with a ball screw or rack and pinion (leaning toward the latter). I also don't know where to get wheels that would work with the 80/20 as they seem to be obsessed with their teflon bearings.
Ignoring the vertical supports, can anyone help us figure out a configuration including motors and controllers that would work within our budget? We can have parts machined, but prefer something that can bolt together. Any help would be appreciated and links to parts would be amazing.