This is a train car for wooden track train sets with pegs on top for connecting Lego-style bricks. This allows you to make your own custom train cars. It is a derivative of http://www.thingiverse.com/thing:11671 by sconine, with steel axles and magnet couplers. For the couplers, it uses acorn nuts on the ends with magnets behind them for coupling to other cars. The wheels and body were made with OpenSCAD, so they can be modified as needed to fit different hardware or to get a good fit with the pegs. There is also an assembly fixture which was made in Alibre Design, as I had trouble doing it with OpenSCAD. The fixture helps with gluing the wheels onto the axles and getting them straight. It is especially handy if you are going to use cyanoacrylate which sets quickly. NOTE: The STL files are nominal size. I had to scale the body up by 1.5% to account for shrinkage and get the pegs to align. You will need to print (1) body and (4) wheels for each car.For each car you will also need: (2) #6-32 steel acorn nuts (2) 8mm x 3mm rare earth magents (2) 1/8" steel rods cut to 27mm length. epoxy or CY glue.You may also want to print the assembly fixture to help get the wheels straight.Put a magnet onto the back of each acorn nut. Make sure the acorn nuts will stick to each other. If not, turn one magnet around. Dry fit the magnets and acorn nuts into each end of the body to make sure they go in straight. Then, glue them in. Drill the two axle holes out to 9/64" so the axles will turn freely in them. Drill the holes in the wheels out to 1/8". Put the axles through the body and glue the wheels on with the hubs facing inwards. The 27mm axles should be flush with the outer faces of the wheels. The inside spacing between the wheels should be 23mm. If you are using the fixture, you can set the body and wheels in place first, and then push the axles through everything, gluing the tips.