Redesigning Driver Wheels to shorten print time

The main driver wheel design was revisited with the aim to hollow portions and reduce the printing time as was recently done with the axels.   The main driver wheel requires 1.076 cubic inches of material and would require about 20 minutes to print with a solid design.

After examining several ways to hollow portions of the wheel, a redesign aimed at a hollow configuration was started.  This seems to be a possible way to proceed.

The hollowed portions completed so far do reduce the volume of material, but required a very large amount of time to generate the new design.  The design at the left shows the central hub and wheel less the spokes.  The hollowed portions have reduced the amount of material but did not reduce it by half as the sections need to support the rim and shaft for the drive rods.  The spokes also will need internal bracing to permit self supported printing of ABS material.

An alternate cutaway view at right shows how the rings of internal brace material look.  The material is deposited from the right towards the left as the part would be oriented in the machine with the right side down.  The material is deposited in thin layers from the right and internal supports must be provided to support overhanging sections on the left side of the drawing above.   The overhangs when initially deposited by the machine would otherwise collapse and fail to accurately model the outer walls of the wheel.

It appears now that the better approach will be to simply build the part solid as shown in the first drawing.  That way full support is provided for all overhangs except portions of the spokes.  To deal with those, the machines build software will be set up to provide suitable PLA supports that will subsequently be removed to complete the wheel models.  Their will be three slightly different wheel designs, front / back, intermediate and main with differences in details between  those on the engineer's side of the locomotive from those on the fireman's side.  Overall eight plus cubic inches of ABS material and perhaps 10% of that volume of PLA material will be needed.  Assuming about nine cubic inches in all, it will take 2.7 hrs of print time to build those parts.   It has taken about that much time to attempt to hollow the main driver wheel design, so in the interest of time the existing finished solid designs will be used and design work continued on the rear 1/3rd of the chassis.