Help with Assembly

tarek_mustafa

Hallo,

With the help of many of you I managed now to finish the design of the Music Box! 

The last piece is to make it spin with all parts using mates. That is something I have no experience with at all so if anyone like to help me with this please leave your email and I will send you an invite to edit.

Thank you!

philip_thomas

Pthomas =(at) =onshape.com

lougallo

@tarek_mustafa We want to avoid people posting their emails in the forums since that can be picked up and spammed.  Better yet, ask them to message you via the message feature here in the forums.  If they click on your name you can send a message to a user here:



You can add me as well if you like.

philip_thomas

Ok - i assembled the music box and got it working
The hard part of course was the worm drive and its worth re-iterating here how to build it.
I am not a 'gear guy' so if i get some of the terminology wrong, please just bear with me.

Problem - we want with one revolution of the driving handle to rotate the driven gear by exactly one tooth.

There are some not-so obvious steps to doing this.

1) Decide what the 'pitch circle' is. This is the diameter of the driven gear at which the velocity of the gear teeth exactly matches the velocity of the worm drive. In this case i used 7.5 mm (diam).

2) Calculate the circumference of the driven gear at this diameter (pi*d) = 23.5619449mm

3) Divide the circumference by the number of teeth (22) = 1.0709974mm This is the PITCH OF THE HELIX

4) Create the two mates that define the motion of the two moving parts (both revolutes)

5) Create a gear mate between the two revolutes. The gear ratio is the number of teeth on the driven gear (22) divided by the number of 'teeth' that advance on the worm gear in one revolution (1). If the gears run in opposite directions, edit the mate and reverse the chirality. If the gear ratio is inverted, just enter the reciprocal of the ratio.

6) How to make the teeth mesh in the initial state? First 'reset' both revolutes (RMB on the mate and select 'reset'). Next edit any of the four mate connectors that make up these two mates and select 'move' and 'rotate about Z' - enter an angular offset that perfectly meshes the teeth.

DONE!

Also - here is a video that shows some of these steps
https://www.onshape.com/videos/whats-new-gear-mates

philip_thomas

Pthomas =(at) =onshape.com

dave_c

Very nice!

lougallo

@tarek_mustafa We want to avoid people posting their emails in the forums since that can be picked up and spammed.  Better yet, ask them to message you via the message feature here in the forums.  If they click on your name you can send a message to a user here:



You can add me as well if you like.

philip_thomas

Ok - i assembled the music box and got it working
The hard part of course was the worm drive and its worth re-iterating here how to build it.
I am not a 'gear guy' so if i get some of the terminology wrong, please just bear with me.

Problem - we want with one revolution of the driving handle to rotate the driven gear by exactly one tooth.

There are some not-so obvious steps to doing this.

1) Decide what the 'pitch circle' is. This is the diameter of the driven gear at which the velocity of the gear teeth exactly matches the velocity of the worm drive. In this case i used 7.5 mm (diam).

2) Calculate the circumference of the driven gear at this diameter (pi*d) = 23.5619449mm

3) Divide the circumference by the number of teeth (22) = 1.0709974mm This is the PITCH OF THE HELIX

4) Create the two mates that define the motion of the two moving parts (both revolutes)

5) Create a gear mate between the two revolutes. The gear ratio is the number of teeth on the driven gear (22) divided by the number of 'teeth' that advance on the worm gear in one revolution (1). If the gears run in opposite directions, edit the mate and reverse the chirality. If the gear ratio is inverted, just enter the reciprocal of the ratio.

6) How to make the teeth mesh in the initial state? First 'reset' both revolutes (RMB on the mate and select 'reset'). Next edit any of the four mate connectors that make up these two mates and select 'move' and 'rotate about Z' - enter an angular offset that perfectly meshes the teeth.

DONE!

Also - here is a video that shows some of these steps
https://www.onshape.com/videos/whats-new-gear-mates

tarek_mustafa

Awesome! Thank you!

andrew_troup

Nice summary, @philip_thomas. As a 'gear guy' (with a special soft spot for wormgearboxes) I can report that you nailed the concepts, and the terminology you adapted was no barrier. For instance, the "pitch" you calculated in 3) is referred to in the trade as "circular pitch", so you got that pitch-perfect.

"Chirality" will be familiar to topologists and surfacing geeks and those who study molecular structures (among others - including, more sadly, thalidomide victims!) but to the rest of us, (including humble gear geeks) think "handedness" ...