Answers.Body: <p>The piece you show must have steering axle 92906.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-10-23T06:05:35.377Z
Answers.Text: Please be more specific. This is not in the inventory of any of the variants.
Answers.UserDisplayName: mike
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-10-23T07:21:40.140Z
Answers.Text: You suggest to replace the universal joint 3L (61903) with the steering CV joint (32494)? That corresponds to the steering axle 92906. It already has the steering CV joint (32494) on the wheel side and seems to have issues due to that when the car rises, the wheels seem to go intermittently, jerky.
Answers.UserDisplayName: mike
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-10-23T05:37:10.793Z
Answers.LastActivityDate: 2017-10-23T13:35:09.087Z
Answers.LastEditDate: 2017-10-23T13:35:09.087Z
Answers.UserDisplayName: JBoeuf
Body: <p>I have built the following MOC, with details <a href="http://www.moc-pages.com/moc.php/340947" rel="nofollow noreferrer">here</a> and <a href="https://rebrickable.com/mocs/MOC-0308/unroller/8297-4x4-offroader-rc/" rel="nofollow noreferrer">here</a>.</p>
  
  <p>It is pretty complete, although I would have tried some servo motor for steering.</p>
  
  <p>But after I've finished it, I've got into trouble:</p>
  
  <ol>
  <li>Wheels on one side of the car seem to work sporadically. Could this be related to the steering joint and Cardan joint below?</li>
  </ol>
  
  <p><a href="https://i.sstatic.net/6Wcq4.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/6Wcq4.png" alt="Steering joint"></a>
  <a href="https://i.sstatic.net/3pL4B.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/3pL4B.png" alt="cardan joint"></a></p>
  
  <p>Or the differentials?</p>
  
  <p><a href="https://i.sstatic.net/MrrWk.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/MrrWk.jpg" alt="differential"></a> (image taken from <a href="https://bricks.stackexchange.com/questions/3065/is-it-possible-to-create-a-differential-if-i-dont-have-it-as-a-ready-to-use-ele">Is it possible to create a differential if I don&#39;t have it as a ready to use element?</a>)</p>
  
  <ol start="2">
  <li>It's too weak.</li>
  </ol>
  
  <p>A wool carpet of 2cm thick is an insurmountable problem for the car to climb on it and go, especially for the last wheel or pair of wheels that have to pass the carpet's border (and difference in level), regardless which ones have to do it (back or front).</p>
  
  <p>Are there too many differentials? Too many tooth gears? Too much elastic parts to deal with the torque? I can't find parts blocked.</p>
  
  <p>The driving ring 2L, 
  <a href="https://i.sstatic.net/uXgD0.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/uXgD0.png" alt="driving ring 2L"></a>,
  at the page 28 of <a href="https://rebrickable.com/external/view/?action=BI&amp;url=https%3A//docs.google.com/open%3Fid%3D0B6p_C0b8jM_ySTJXS1V3WFNPaG8&amp;designer_id=4313&amp;set_num=MOC-0308" rel="nofollow noreferrer">the building instructions</a>, should act as differential to switch between 2 x 4 and 4 x 4.</p>
  
  <p>Could it be a defective motor? Is one XL motor too weak? Would be more powerful with two motors (in the back)? Which kind?</p>
  
  <p>Batteries are OK for 9398, so it's not them.</p>
  
  <p>Did anybody tried this MOC?</p>
  
  <p>Sorry to have too much questions, it seems I need more experience with LEGO Technic.</p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>I have changed it consistently, adding a gear down for each wheel (horizontally) and that made it 4L longer.</p>
  
  <p>Also, moved the steering motor in front and the up/down and winch motor in the middle (switched their places), using a servo for steering.</p>
  
  <p>As result, it is a bit more powerful, it climbs the carpet now, but I need to work more on the steering because it is not that smooth when it comes back in the default position. 9398 is better at going back to the default steering position. Also, 9398 is more powerful as it gears down 3 times instead of one.</p>
  
  <p>Overall, the new design feels better, yet too lazy.</p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-10-22T22:31:48.040Z
Comments.Text: This is a beautiful MOC. From a glance at the pdf instructions I get the impression that the front M-motor operates the winch, the middle one is for steering, and the XL motor in the back does the driving. Is that correct? The clutches are not connected with the driving, right? I have a 9398 crawler with two L-motors and a servo, it crawles over almost anything.
Comments.UserDisplayName: Metalbeard
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-10-23T04:30:20.070Z
Comments.Text: A beautiful MOC indeed. You are correct regarding the motors. I would have used a servo for steering, though. I don't really understand what should do the clutch at page 28 in the instructions. I see no difference when the position of the driving ring is moved. 9398 has several tooth gears pairs to increase the power (over speed). 8297 does not. Also, 9398 has 2 driving motors, one for each pair of wheels.
Comments.UserDisplayName: mike
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-10-24T09:09:57.833Z
Comments.Text: I would guess that one motor, even an XL, has more difficulties to distribute the power to 4 wheels than two motors as in the 9398 crawler. I switched the gears in my 9398 (the first gears at the motors) to make it faster, and it works fine. To conclude: I'd say you built the moc correctly and the parts and motor are also fine, but the one-motor setup is the reason. Instead of powering the winch, I would try to power the front wheels. And use a servo for the steering as you suggested. Again, nice MOC and excellent pdf instructions.
Comments.UserDisplayName: Metalbeard
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-10-24T11:09:22.563Z
Comments.Text: Indeed, the MOC is wonderful, but I have no clue from the author if it really works better than my implementation. I think too, two motors are needed, but it loses the central differential. Would [this](https://www.eurobricks.com/forum/index.php?/forums/topic/71769-combining-two-pf-m-motors/) be a solution?
Comments.UserDisplayName: mike
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-10-24T12:04:38.887Z
Comments.Text: I doubt that more power solves the issue. You would still have one powered axle distributing force over three differentials to four wheels. This gives too many degrees of freedom to the system. As the comments in your link say, it could work for a racing car but not for all terrain purpose.
Comments.UserDisplayName: Metalbeard
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-10-24T12:52:21.737Z
Comments.Text: Probably, but it does not even pass a tiny obstacle that some regular racing car does already. Of course, as I have some spare parts, I will test and see. This is the fun, actually.
Comments.UserDisplayName: mike
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-10-24T12:54:08.877Z
Comments.Text: Anyway, does LEGO has too weak motors for its applications? I think this MOC naturally comes and proves this. I wonder if a buggy motor would do better. Too bad it is no more produced.
Comments.UserDisplayName: mike
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-10-25T18:31:26.857Z
Comments.Text: Replaced the direction motor by a servo. This is better, still weak compared to servo on 9398, probably due to the gears and transmission used.
Comments.UserDisplayName: mike
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-10-26T06:08:10.627Z
Comments.Text: Interesting. Are you going to improve the MOC even more? I would like to hear about the results.
Comments.UserDisplayName: Metalbeard
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-10-26T08:05:37.237Z
Comments.Text: Hi, I have the impression some think it is my MOC, but it is not, I'm just a hobbyist having fun with it. AS it did not perform well, I try to make it better.
Comments.UserDisplayName: mike
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-10-26T08:13:27.510Z
Comments.Text: I know, but your improvements are valuable information.
Comments.UserDisplayName: Metalbeard
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-10-26T08:40:09.327Z
Comments.Text: Actually, I'm thinking to put the steering servo in front and the winch/raiser motor in the middle, but I am not sure it is enough place below to the central differential.
Comments.UserDisplayName: mike
Tags: <power-functions><moc>
Title: How to power up MOC-0308, based on Technic 8297 Off-Roader?
UserDisplayName: mike
ThreadText: # How to power up MOC-0308, based on Technic 8297 Off-Roader?
  
  (Asked by: username_0 on 2017-10-22)
  
  I have built the following MOC, with details [here](http://www.moc-pages.com/moc.php/340947) and [here](https://rebrickable.com/mocs/MOC-0308/unroller/8297-4x4-offroader-rc/).
  
  It is pretty complete, although I would have tried some servo motor for steering.
  
  But after I've finished it, I've got into trouble:
  
  1. Wheels on one side of the car seem to work sporadically. Could this be related to the steering joint and Cardan joint below?
  
  [![Steering joint](https://i.sstatic.net/6Wcq4.png)](https://i.sstatic.net/6Wcq4.png)
  [![cardan joint](https://i.sstatic.net/3pL4B.png)](https://i.sstatic.net/3pL4B.png)
  
  Or the differentials?
  
  [![differential](https://i.sstatic.net/MrrWk.jpg)](https://i.sstatic.net/MrrWk.jpg) (image taken from [Is it possible to create a differential if I don't have it as a ready to use element?](https://bricks.stackexchange.com/questions/3065/is-it-possible-to-create-a-differential-if-i-dont-have-it-as-a-ready-to-use-ele))
  
  2. It's too weak.
  
  A wool carpet of 2cm thick is an insurmountable problem for the car to climb on it and go, especially for the last wheel or pair of wheels that have to pass the carpet's border (and difference in level), regardless which ones have to do it (back or front).
  
  Are there too many differentials? Too many tooth gears? Too much elastic parts to deal with the torque? I can't find parts blocked.
  
  The driving ring 2L,
  [![driving ring 2L](https://i.sstatic.net/uXgD0.png)](https://i.sstatic.net/uXgD0.png),
  at the page 28 of [the building instructions](https://rebrickable.com/external/view/?action=BI&url=https%3A//docs.google.com/open%3Fid%3D0B6p_C0b8jM_ySTJXS1V3WFNPaG8&designer_id=4313&set_num=MOC-0308), should act as differential to switch between 2 x 4 and 4 x 4.
  
  Could it be a defective motor? Is one XL motor too weak? Would be more powerful with two motors (in the back)? Which kind?
  
  Batteries are OK for 9398, so it's not them.
  
  Did anybody tried this MOC?
  
  Sorry to have too much questions, it seems I need more experience with LEGO Technic.
  
  **UPDATE**
  
  I have changed it consistently, adding a gear down for each wheel (horizontally) and that made it 4L longer.
  
  Also, moved the steering motor in front and the up/down and winch motor in the middle (switched their places), using a servo for steering.
  
  As result, it is a bit more powerful, it climbs the carpet now, but I need to work more on the steering because it is not that smooth when it comes back in the default position. 9398 is better at going back to the default steering position. Also, 9398 is more powerful as it gears down 3 times instead of one.
  
  Overall, the new design feels better, yet too lazy.
  
  **Tags:** power-functions, moc
  > **Comments:**
  > **username_1**: This is a beautiful MOC. From a glance at the pdf instructions I get the impression that the front M-motor operates the winch, the middle one is for steering, and the XL motor in the back does the driving. Is that correct? The clutches are not connected with the driving, right? I have a 9398 crawler with two L-motors and a servo, it crawles over almost anything.  
  > **username_0**: A beautiful MOC indeed. You are correct regarding the motors. I would have used a servo for steering, though. I don't really understand what should do the clutch at page 28 in the instructions. I see no difference when the position of the driving ring is moved. 9398 has several tooth gears pairs to increase the power (over speed). 8297 does not. Also, 9398 has 2 driving motors, one for each pair of wheels.  
  > **username_1**: I would guess that one motor, even an XL, has more difficulties to distribute the power to 4 wheels than two motors as in the 9398 crawler. I switched the gears in my 9398 (the first gears at the motors) to make it faster, and it works fine. To conclude: I'd say you built the moc correctly and the parts and motor are also fine, but the one-motor setup is the reason. Instead of powering the winch, I would try to power the front wheels. And use a servo for the steering as you suggested. Again, nice MOC and excellent pdf instructions.  
  > **username_0**: Indeed, the MOC is wonderful, but I have no clue from the author if it really works better than my implementation. I think too, two motors are needed, but it loses the central differential. Would [this](https://www.eurobricks.com/forum/index.php?/forums/topic/71769-combining-two-pf-m-motors/) be a solution?  
  > **username_1**: I doubt that more power solves the issue. You would still have one powered axle distributing force over three differentials to four wheels. This gives too many degrees of freedom to the system. As the comments in your link say, it could work for a racing car but not for all terrain purpose.  
  > **username_0**: Probably, but it does not even pass a tiny obstacle that some regular racing car does already. Of course, as I have some spare parts, I will test and see. This is the fun, actually.  
  > **username_0**: Anyway, does LEGO has too weak motors for its applications? I think this MOC naturally comes and proves this. I wonder if a buggy motor would do better. Too bad it is no more produced.  
  > **username_0**: Replaced the direction motor by a servo. This is better, still weak compared to servo on 9398, probably due to the gears and transmission used.  
  > **username_1**: Interesting. Are you going to improve the MOC even more? I would like to hear about the results.  
  > **username_0**: Hi, I have the impression some think it is my MOC, but it is not, I'm just a hobbyist having fun with it. AS it did not perform well, I try to make it better.  
  > **username_1**: I know, but your improvements are valuable information.  
  > **username_0**: Actually, I'm thinking to put the steering servo in front and the winch/raiser motor in the middle, but I am not sure it is enough place below to the central differential.  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_2 on 2017-10-23. Score: -2
  
  The piece you show must have steering axle 92906.
  
  > **Comments:**
  > **username_0**: Please be more specific. This is not in the inventory of any of the variants.  
  > **username_0**: You suggest to replace the universal joint 3L (61903) with the steering CV joint (32494)? That corresponds to the steering axle 92906. It already has the steering CV joint (32494) on the wheel side and seems to have issues due to that when the car rises, the wheels seem to go intermittently, jerky.  
  
  ---
  
  