Hand Crank Air Raid Siren

DISCLAIMER: I don't personally own a printer and can't print this out to test so it might jam up bc of the insane overdrive ratio and lack of actual bearings

So its basically just an air raid siren powered by a hand crank. It uses a series of 3 planetary gearboxes to produce a 1:52 overdrive ratio.

The whole assembly consists of 35 parts that are fit together with snap fit mechanisms. Attached below is a 3mf file with every single part in it, but there are also stl files of each unique part with how many copies are required in the name.

recommended print settings:

• add supports only on 18T sun gear (hex output) and siren rotor

• 40% gyroid infill and 6 wall loops for all of the gearbox parts (planet gears, sun, gears, ring gears, and carrier pieces)

• 15% 3D honeycomb infill and 2 wall loops on the rest

• outer->inner wall order

Onshape link for the model here

assembly instructions:

1. Assemble the gears and the carrier for the bottom gearbox. I recommend first inserting the planet gears onto the snap hooks and then inserting the sun gear and then other carrier piece after that. The carrier pieces used is the pair that is slightly larger than the rest, and the gears used are the 24T sun gear and the 15T planet gears. Make sure the shims on all of the gears are on the same side as the carrier piece with the hex shaft. 

   

2. Insert gears and carrier assembly into the bottom ring gear piece (the one with the floor). Insert 3 of the straight snap hooks into the ring gear.

   

3. Assemble the gears and carrier for the middle gearbox the same way the previous one was assembled. Either pair of the remaining carrier pieces can be used, and the gears that should be used are the 18T sun gear with the hex bore and 3 of the 18T planet gears. Attach the middle ring gear (the one without the chamfers near the hook slots) using the snap hooks from step 2. Then insert the gear/carrier assembly into the middle ring gear, making sure to press fit the hex shaft of the carrier into the hex bore of the ring gear of the bottom gearbox. Then insert the straight snap hooks on the top side of the middle ring gear as with the bottom ring gear before.

   

4. Now assemble the gears and carrier for the top gearbox. Use the remaining carrier pieces, the 18T sun gear with the hex output, and the remaining 18T planetary gears. Make sure the hex shaft of the sun gear goes through the carrier piece with the snap hooks, and that the shims of the planet gears face the carrier piece with the hex output. Insert the extra shim onto the sun gears hex output when done.

   

5. Insert the top ring gear piece onto the snap hooks from step 3. The orientation is important here; make sure the side with the chamfers faces away from the other gearboxes. Then insert the gear/carrier assembly from step 4 into the ring gear.

   

6. On the main stator piece of the siren, insert the 3 L shaped snap hooks from the side. Make sure the shorter end is the side that are inserted.

   

7. attach the main stator piece with the snap hooks into the slots on the ring gear.

   

8. Press fit the siren rotor onto the hex shaft of the sun gear, and then snap on the top stator piece onto the main stator piece.

   

9. Finally press fit the crank onto the hex shaft from the bottom gearbox