Page 8 Modeling a Mountain Bike: The Seat

To construct the saddle, deselect all and use ‘Surface/Loft’. The figure below shows in what order the first half of the curves should be lofted, and when you continue selecting the curves on the upper half of the image, the order is mirrored.

To make the screws under the saddle, select the curve shown below.

When done, go ‘Surface/Revolve’, and while using the Object Snap ‘End’, make the cursor snap the right end of the curve and hit LMB, hold Shift and drag to the left and hit LMB to finish the revolve process.

Select the curve shown below, and go ‘Solid/Pipe’. Rhinoceros asks for the Starting and End radius, type in 0.15 in the command line and hit Enter for the starting radius, then just hit Enter again as Rhinoceros remembers the value. If you want the End radius to be different from the Starting radius, type in another number.

Now you have a good idea of what direction the screw should point to. Go ‘Transform/Rotate’ and when Rhinoceros asks for ‘Center of rotation’, hit LMB at point 1 as shown in the figure below.

At ‘Angle or first reference point’, set the pointer at point 2. Then rotate the screw up so the rotation line lines up with the pipe you created in the previous step. Repeat this step in the Front viewport so the screw lines up with the pipe from that view as well. Then move the screw so it looks like it is attached to the pipe as shown below. (You need to move it in the Front viewport as well.)

Use the Object Snap ‘Mid’, and when the screw is selected in the Top viewport, mirror it to the other side as shown below.

Select the curves shown below (there are two curves in the middle, so make sure both curves are selected). Then loft these together with the ‘Closed’ option.

Loft the curves selected below with the order middle-top-bottom curve. NOTE: To set the order of the loft, you must start the loft command with everything deselected.

Hit Enter when Rhinoceros asks for the direction of the curves. Use the options shown below.

Make the screw under the saddle with a revolve. As usual, use Object Snap ‘End’.

Select the curves shown below, and do a ‘Sweep 2 Rails’. Use the default options.

As you can see, only half of the rail is swept, because the sweep starts from middle, where the profile curve is positioned. Select the surface and mirror it in the Top viewport as shown below. NOTE: Object Snap ‘Near’ would be appropriate to use here.

Finally, go ‘Surface/Edit Tools/Merge’ and select both surfaces to merge them into one.