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I have a cog wheel and I want to make the spokes a bit longer than they are. I can select the tip of one and drag it out a bit, but how do I precisely measure how much I've moved something so that I can then move all the other tips the same distance?

I can't have uneven cog spokes.

enter image description here

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    $\begingroup$ Can you use array modifier for the cogs? that will be the best option for symmetrical objects $\endgroup$ – Denis May 19 '15 at 23:17
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For symmetrical shapes the best method is to use array modifier.

Delete all the faces leaving only one cog then change to object mode and add an empty in the origin of the gear and rotate the empty 45 degrees.

enter image description here

Then add array modifier on the gear object, set count to 8, disable Relative Offset. Then enable Object Offset and select empty from the selection box and enable Merge and First and Last.

enter image description here

This way you can control the gear shape by modifying only on cog.

enter image description here

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    $\begingroup$ I have created an addon to do that a lot faster,you can use it in this condition. github.com/emaema/procedural-dupli-spin read the documentation if you dont know how to use it. $\endgroup$ – Omar Emara May 20 '15 at 5:57
  • $\begingroup$ Does the 'merge' ensure that vertices are merged when they touch so that the resulting mesh isn't a bunch of overlapping but disconnected edges? $\endgroup$ – leigero May 20 '15 at 11:20
  • $\begingroup$ @leigero Yes it will merge the vertices that are within the specified distance from eachother $\endgroup$ – Denis May 20 '15 at 13:26
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Blender can move more than one face at once by various means.

  • You can extrude more than one face at time. Be in Face Select mode. Depicted in the image below (vertex, edge, face enabled). Select your faces. Use shift + click. Then E to extrude. Return Key. Selection is still there. Alt + S to move face on normals (See menu Mesh/Transfrom/Shrink Fatten).

enter image description here

  • If you want to casually work, you can place a cylinder around the cog as a circular guide.

  • The same circular guide can be used as target for shrink wrap modifier. You must create a vertex group for the faces on the teeth of the cog. Shrink Wrap can be applied:

enter image description here

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  • $\begingroup$ Wonderful keystroke editing by another author. $\endgroup$ – atomicbezierslinger May 19 '15 at 23:54
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You can precisely define the value of any element's movement. After pressing G, S or R and selecting the desired transformation axis (press x,y or z) you may input the number from the numerical keyboard. As pictured below I selected the edge of the spoke, pressed G, then Y and then 0.2 enter image description here

Select all the spoke's edges and press Shift+S-->Snap-->Cursor to Selected. It will place the cursor in the center. Set the pivot point type to a 3D Cursor. Press S and input the desired transformation value. You may also enable the Snap Tool (click the magnet icon, and change the snapping type to Increment). It will allow you to increase the spoke's lenght very precisely while scaling (hold Shift while scaling and you'll be able to change the lenght's value in smaller increments). enter image description here

Now change the pivot point type to Individual Origins. enter image description here

Press S and input the desired value to make all the spokes scale the same way. enter image description here

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