I know how to make one!
Use mini black holes or singularites to distort gravity!
Ok, I've just made a time machine.
Here is a blueprint.
The picture is small but I'll name each part of it.
1. Magnetic housing units for dual microsignularities.
2. Electron injection manifold to alter mass and gravity of microsingularities.
3. Cooling and x-ray venting system
4. Gravity sensors (VGL system)
5. Main clocks (4 cesium units)
6. Main computer units (3)
This is the time machine itself. It needs to be attached to a large 4 wheel drive for safety.