Gears, Gears, Gears -- Make Anything Move - a 3D Printed Gear Drive Train for Spring Powered Phonograph Motor

In a separate instructable, I recently restored an antique phonograph motor that was missing a drive gear. I enjoyed making the missing gear so much that I decided to create as much of the gear drive train as possible as a learning project.

All of the gears in this instructable are involute gears with the exception of the worm gear on the governor shaft. The involute gears are manipulated by the 3D application to produce the various gears in this instructable.

The gears are very strong, and printed using Carbon Fiber PETG (Atomic). The Governor portion is partially recreated but in reality, lacks the strength needed by the gear train

Attached are the images, Sketchup, and 3D STL files.

Parts Not Printed:

• Because of its weight and the spring strips, the governor was not printed.
• Locating a linear spring these days is difficult so I did not replicate the spring canisters (easily fabricated in 3D).
• If you have such a project the original springs and canisters can be attached to the large gear. The original governor and worm gear can also be integrated.

The 2D images illustrate the project from several views.

The STL files can be used to view each part of the project in 3D and to 3D print each part.

3D Printer (PRUSA used in this Instructable)

3D Filament (Carbon Fiber PETG used for the gears)

3D Modeling Software (SketchUp)

Involute Gear Plug-In (http://kansascitykitcompany.com/explorations-and-speculation/sketchup-gears-plugin) (or applicable Plug-In for your drawing software).

All of the drive train is included in the SketchUp file. Each part is grouped so it can be copied and pasted into a new file.

Gear Terminology: https://www.theengineerspost.com/gear-terminology/

Wiki Involute Gear: https://en.wikipedia.org/wiki/Involute_gear

All of the gears have a pressure angle of 20-degree and a except the Taper Gears have a 2.5mm tooth pitch.

The crank gear assembly consists of 3 gears, 2x45-degree crank gears, and a standard involute wind gear that winds the spring drive. The taper gears are identical, TaperGears2.stl contains a tapered gear and the winding gear (printed grouped together). The concentric upset in the winding gear is for a spacer washer to keep the gears elevated, the spacer washer is printed separately.

• Winding gear parameters: 34 teeth; OD 32.2mm; pitch Diameter 30mm; height 6.4mm; center hole 6mm
• The concentric inset in the bottom of the gear is 19mm in diameter and 4.2mm deep.
• The Spacer washer is 18.8mm in diameter, 6mm canter hole, and is 6mm thick.

The 45-degree taper/right-angle gear design is the most difficult. These gears are the only 2 gears with a 3mm Pitch.

• Initial Taper gear parameters: 22 teeth; OD 26.8mm; pitch Diameter 23.8mm; height 6mm; center hole 6mm.
• Ungroup/explode the involute gear so there are no grouped parts.
• Select the top portions of the gear and scale these inward 6mm to create a 45-degree angle (see images).
• Combine one angle gear with the winding gear, and use a second for the crank.

The spring gears are very simple involute gears connecting to a single 3/4" (18mm) shaft. Two spring gears make up the motor. The holes near the outer diameter secure the spring casing to the gear.

Spring gear parameters: 132 teeth; OD 128mm; pitch Diameter 126mm; height 4.6mm; center hole 18mm.

These gears make up the final drive to the shaft. The small gear is driven by the large spring gear and the large gear drives the shaft gear. Using a common 1/8" steel shaft and concentric Spindle Spacer as an axis. Both gears are printed from a single STL file. The Spindle spacers in a second print.

• Small drive gear parameters: 14 teeth; OD 13.1mm; pitch Diameter 11.1mm; height 10mm; center hole 3.2mm.
• Large drive gear parameters: 96 teeth; OD 63.5mm; pitch Diameter 62mm; height 8mm; center hole 3.2mm.

The Spindle Shaft can be printed in 3D, adjusting the orientation for the best adherence to the bed. The Spindle Drive gear is printed separately.

• Spindle Drive gear parameters: 16 teeth; OD 11mm; pitch Diameter 6.5mm; height 7.5mm; center hole 6mm.

The second most difficult gear design is the Worm Drive gear. Like the taper gear, the involute teeth must be angled to mate with the worm gear. The "threads" on the worm are 10 degrees so the top of the worm drive gear needs to be rotated 10 degrees counter-clockwise from the bottom. As with the taper gear, select the top plane of the worm drive gear and use the "rotate" tool of the CAD program to rotate the top 10 degrees ccw to the bottom.

Printing the worm gear, governor springs, weights, and shaft does not provide the necessary strength but I did create the worm gear and a plastic shaft for this model without the governor pieces. I used a Ruby Script plugin (whorl) designed for "threads". Parameters below for the Whorl variables for a 7 rotation worm gear.

• Worm Drive gear parameters: 24 teeth; OD 26mm; pitch Diameter 23.6mm; height 8.5mm; center hole 11.5mm.
• Worm Gear using Whorl thread plugin: End & StartRadius 2.5mm; Pitch 2.8; Tapered ROTS 0; Fixed ROTS 7; Sectors per 24; Tooth Height 2mm; Tooth Length 0.62mm; Edge Height 0.7mm.