Answers.Body: <blockquote>
    <p>How can I get 2 opposing gear's axles to be perfectly parallel? Are there any good workarounds?</p>
  </blockquote>
  
  <p>You could use an <strong>idler gear</strong>. It will even out the offset. </p>
  
  <p>Yet, at the same time, it (or any odd number of idler gears) will cause both axles to spin in one direction. </p>
  
  <p><a href="https://i.sstatic.net/KBdb8.jpg" rel="noreferrer"><img src="https://i.sstatic.net/KBdb8.jpg" alt="enter image description here"></a></p>
  
  <p>On the other hand, two (or any even number of) idler gears will not affect the asynchrony of the axles, but will bring back the offset. </p>
  
  <p>Then again, <strong>placing a single idler gear crosswise</strong> will compensate the offset without changing the desired clockwise/ counterclockwise movement. </p>
  
  <p><a href="https://i.sstatic.net/coBJ3.jpg" rel="noreferrer"><img src="https://i.sstatic.net/coBJ3.jpg" alt="enter image description here"></a></p>
  
  <p>Besides, here's two 8 tooth idler gears in line. Both axles seem to be perfectly in parallel to each other. </p>
  
  <p><a href="https://i.sstatic.net/I4y1s.jpg" rel="noreferrer"><img src="https://i.sstatic.net/I4y1s.jpg" alt="enter image description here"></a></p>
  
  <p>Unfortunately, that's actually because of the large amount of play involved. So this solution just benefits from the wiggle and does not run too reliably. </p>
  
  <p>Edit:</p>
  
  <blockquote>
    <p>Are there any older or special gears that are useful here? </p>
  </blockquote>
  
  <p>At least theoretically. </p>
  
  <p><a href="https://i.sstatic.net/FdiHq.jpg" rel="noreferrer"><img src="https://i.sstatic.net/FdiHq.jpg" alt="enter image description here"></a></p>
  
  <p>Having an uneven number of teeth, these nowadays obsolete gears from the early 70s would work as well.</p>
  
  <p>As you can tell from the overlapping grey gears, the axles are quite parallel (minus some backlash). </p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-04-04T14:44:13.640Z
Answers.Text: Thanks for sharing. Your second solution is by far the best I've seen - low backlash, adjustable spacing between the outputs, and easy for input.
Answers.UserDisplayName: MindS1
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-04-03T21:31:13.623Z
Answers.LastActivityDate: 2019-04-05T11:44:09.917Z
Answers.LastEditDate: 2019-04-05T11:44:09.917Z
Answers.UserDisplayName: Uli
Answers.Body: <p>If you use a crown gear or bevel gear to connect your gears twice perpendicularly, they are exactly opposing each other, turn in opposite directions, and are parallel (if the respective axle is aligned to the coordinate system of the construction). Like with all gear-to-gear connections, you have a little wiggle room that may exceed half a tooth.</p>
  
  <p><a href="https://i.sstatic.net/0S2i8.png" rel="noreferrer"><img src="https://i.sstatic.net/0S2i8.png" alt="illustration of construction"></a></p>
  
  <p>If you want the opposing gears next to each other, you can use further gears attached to these (coming with yet more wiggle room).</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-12-22T08:04:38.587Z
Answers.LastActivityDate: 2018-12-22T08:04:38.587Z
Answers.UserDisplayName: Wrzlprmft
Answers.Body: <p>You could use a belt system to get a perfect, parallel rotation. The chain links used in <a href="https://youtu.be/997LGqEFkyU?t=37" rel="nofollow noreferrer">this video</a> are <a href="https://www.bricklink.com/v2/catalog/catalogitem.page?P=3711#T=C" rel="nofollow noreferrer">#3711</a> and the gears appear to be the same as the ones shown in your example.</p>
  
  <p><a href="https://youtu.be/997LGqEFkyU?t=37" rel="nofollow noreferrer"><img src="https://i.sstatic.net/v9x8p.png" alt="enter image description here"></a></p>
  
  <p>There doesn't seem to be an easy way to get the gears to turn in opposite directions without the use of gears (without that half tooth lag).</p>
  
  <p>Two high friction, Technic rubber wheels, placed directly against each other will rotate almost perfectly. Although they might de-synchronise after many revolutions. </p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-12-22T10:46:55.883Z
Answers.LastActivityDate: 2018-12-22T10:46:55.883Z
Answers.UserDisplayName: Ambo100
Answers.Body: <p>What about a clutch gear ? It can help with its center axis that can slip. </p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-04-04T19:15:05.530Z
Answers.LastActivityDate: 2019-04-04T19:15:05.530Z
Answers.UserDisplayName: Ivato
Body: <p>Due to the way all the modern LEGO gears are perfectly quarter-turn symmetrical, there doesn't appear to be any way to assembly 2 opposing gears such that I get a 2 perfectly parallel axles.</p>
  
  <p>This image illustrates the problem:</p>
  
  <p><a href="https://i.sstatic.net/UoME9.jpg" rel="noreferrer"><img src="https://i.sstatic.net/UoME9.jpg" alt="enter image description here"></a></p>
  
  <p>When one gear it perfectly centered, the other gear is rotated half a tooth.</p>
  
  <p>How can I get 2 opposing gear's axles to be perfectly parallel? Are there any older or special gears that are useful here? Otherwise, are there any good workarounds?</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2018-12-22T07:05:48.310Z
Comments.Text: Do you have any restrictions on the maximum distance of the gears or similar?
Comments.UserDisplayName: Wrzlprmft
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2018-12-22T07:06:53.007Z
Comments.Text: @Wrzlprmft No necessarily, just that they turn in opposite directions.
Comments.UserDisplayName: Alexander O'Mara
Tags: <technic><building><gears>
Title: How can I assemble 2 opposing gears so that the axle rotations are perfectly parallel?
UserDisplayName: Alexander O'Mara
ThreadText: # How can I assemble 2 opposing gears so that the axle rotations are perfectly parallel?
  
  (Asked by: username_0 on 2018-12-22)
  
  Due to the way all the modern LEGO gears are perfectly quarter-turn symmetrical, there doesn't appear to be any way to assembly 2 opposing gears such that I get a 2 perfectly parallel axles.
  
  This image illustrates the problem:
  
  [![enter image description here](https://i.sstatic.net/UoME9.jpg)](https://i.sstatic.net/UoME9.jpg)
  
  When one gear it perfectly centered, the other gear is rotated half a tooth.
  
  How can I get 2 opposing gear's axles to be perfectly parallel? Are there any older or special gears that are useful here? Otherwise, are there any good workarounds?
  
  **Tags:** technic, building, gears
  
  > **Comments:**
  > **username_1**: Do you have any restrictions on the maximum distance of the gears or similar?  
  > **username_0**: @username_1 No necessarily, just that they turn in opposite directions.  
  
  ---
  
  ## 4 answers
  
  ### Answer by username_2 on 2019-04-03. Score: 9 | Accepted answer
  
  > How can I get 2 opposing gear's axles to be perfectly parallel? Are there any good workarounds?
  
  You could use an **idler gear**. It will even out the offset.
  
  Yet, at the same time, it (or any odd number of idler gears) will cause both axles to spin in one direction.
  
  [![enter image description here](https://i.sstatic.net/KBdb8.jpg)](https://i.sstatic.net/KBdb8.jpg)
  
  On the other hand, two (or any even number of) idler gears will not affect the asynchrony of the axles, but will bring back the offset.
  
  Then again, **placing a single idler gear crosswise** will compensate the offset without changing the desired clockwise/ counterclockwise movement.
  
  [![enter image description here](https://i.sstatic.net/coBJ3.jpg)](https://i.sstatic.net/coBJ3.jpg)
  
  Besides, here's two 8 tooth idler gears in line. Both axles seem to be perfectly in parallel to each other.
  
  [![enter image description here](https://i.sstatic.net/I4y1s.jpg)](https://i.sstatic.net/I4y1s.jpg)
  
  Unfortunately, that's actually because of the large amount of play involved. So this solution just benefits from the wiggle and does not run too reliably.
  
  Edit:
  
  > Are there any older or special gears that are useful here?
  
  At least theoretically.
  
  [![enter image description here](https://i.sstatic.net/FdiHq.jpg)](https://i.sstatic.net/FdiHq.jpg)
  
  Having an uneven number of teeth, these nowadays obsolete gears from the early 70s would work as well.
  
  As you can tell from the overlapping grey gears, the axles are quite parallel (minus some backlash).
  
  > **Comments:**
  > **username_3**: Thanks for sharing. Your second solution is by far the best I've seen - low backlash, adjustable spacing between the outputs, and easy for input.  
  
  ---
  
  ### Answer by username_1 on 2018-12-22. Score: 7
  
  If you use a crown gear or bevel gear to connect your gears twice perpendicularly, they are exactly opposing each other, turn in opposite directions, and are parallel (if the respective axle is aligned to the coordinate system of the construction). Like with all gear-to-gear connections, you have a little wiggle room that may exceed half a tooth.
  
  [![illustration of construction](https://i.sstatic.net/0S2i8.png)](https://i.sstatic.net/0S2i8.png)
  
  If you want the opposing gears next to each other, you can use further gears attached to these (coming with yet more wiggle room).
  
  
  ---
  
  ### Answer by username_4 on 2018-12-22. Score: 4
  
  You could use a belt system to get a perfect, parallel rotation. The chain links used in [this video](https://youtu.be/997LGqEFkyU?t=37) are [#3711](https://www.bricklink.com/v2/catalog/catalogitem.page?P=3711#T=C) and the gears appear to be the same as the ones shown in your example.
  
  [![enter image description here](https://i.sstatic.net/v9x8p.png)](https://youtu.be/997LGqEFkyU?t=37)
  
  There doesn't seem to be an easy way to get the gears to turn in opposite directions without the use of gears (without that half tooth lag).
  
  Two high friction, Technic rubber wheels, placed directly against each other will rotate almost perfectly. Although they might de-synchronise after many revolutions.
  
  
  ---
  
  ### Answer by username_5 on 2019-04-04. Score: 1
  
  What about a clutch gear ? It can help with its center axis that can slip.
  
  
  ---
  
  