Answers.Body: <p>This modification won't change the rate of reduction.</p>
  
  <p>You can calculate the ratio of the angular velocities of two adjacent gearwheels as</p>
  
  <p>i12 = w2/w1 = n1/n2</p>
  
  <p>where w is the angular velocity and n is the number of teeth of the gears. Hence the original reduction reads as:</p>
  
  <p>i12*i23*i34*i45*i56 = 12/20 * 16/16 * 20/28 * 12/20 * 12/20 = 27/175 = 0.1543</p>
  
  <p>while the modified is:</p>
  
  <p>i12*i23*i34*i45 = 12/20 * 12/20 * 20/28 * 12/20 = 27/175 = 0.1543</p>
  
  <p>What you did is you simply removed the 16/16 and replaced the 12/20 gears, which results in the same reduction because the order of the multiplication is arbitrary.</p>
  
  <p>To the second question:</p>
  
  <p>You can change the 12-20 gears to 16-24 ones to fit the increased distance. In this case, the new reduction is</p>
  
  <p>i12*i23*i34*i45 = 16/24 * 12/20 * 20/28 * 12/20 = 6/35 = 0.1714</p>
  
  <p>Note that the new gears may intersect parts not shown in the figures.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-06-19T10:56:11.920Z
Answers.LastActivityDate: 2018-06-23T07:40:20.580Z
Answers.LastEditDate: 2018-06-23T07:40:20.580Z
Answers.UserDisplayName: BalazsToth
Answers.Body: <p>If the only change is replacing the two 16-tooth gears with a 12-tooth gear and a 20-tooth gear, then you will <strong>reduce speed</strong> by a factor 12/20 and <strong>increase torque</strong> by the same factor.</p>
  
  <p>If you want to increase the distance between gears by 1/2 stud, then you can experiment with using bigger gears and offsetting the motor sideways so the gears don't touch vertically. This may induce some play in the gears.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-06-22T05:44:31.533Z
Answers.Text: I would drop the portal axles, so the performance will be kept. The reason is for implementing this on other model with less axle height (42069). Well, I did it partially, but using a horizontal transmission and keeping a similar design, with only 2 reductions instead of 3 (as this model has). It performs acceptable - a little faster than 9398, but powerful enough to run over decent obstacles for its tracks. I couldn't find a combination of gears for that 0.5 stud displacement, though. The gears are usually too tight to work safely together.
Answers.UserDisplayName: mike
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-06-20T07:49:12.220Z
Answers.LastActivityDate: 2018-06-20T07:49:12.220Z
Answers.UserDisplayName: ShutterFreak
Body: <p>I am studying implementation of 9398 crawler reduction.
  Here is the stripped part, in order to see the gears and their relation - the image is made with the excellent tool which is LDCad.</p>
  
  <p><a href="https://i.sstatic.net/tqTc8.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/tqTc8.png" alt="enter image description here"></a></p>
  
  <p>My idea is to use this Lego design for other model and I need to know how would I calculate the effect of changing it a bit.
  My intention is to replace the two 16 teeth gears 94925:</p>
  
  <p><a href="https://i.sstatic.net/CPoY1.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/CPoY1.png" alt="enter image description here"></a> </p>
  
  <p>with a pair of 12 and 20 teeth (32270 and 32269):</p>
  
  <p><a href="https://i.sstatic.net/tg7tP.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/tg7tP.png" alt="enter image description here"></a><a href="https://i.sstatic.net/Kxzbd.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Kxzbd.png" alt="enter image description here"></a></p>
  
  <p>and to remove the last reduction pairs, the ones in portal axle:</p>
  
  <p><a href="https://i.sstatic.net/p3Hhx.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/p3Hhx.png" alt="enter image description here"></a></p>
  
  <p>so it would be as follows:</p>
  
  <p><a href="https://i.sstatic.net/fIMuL.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/fIMuL.png" alt="enter image description here"></a></p>
  
  <p>Would this become faster/less powerful or slower/more powerful?
  My aim would be to keep it pretty close to how it performs now.</p>
  
  <p>Also, is there a way to combine gears in order to add a distance of half of a stud between the motor axle and the next or the second one? In the image below, I have moved the parts and created a gap between the gears, in order to point what I intend to move, but the contact must be assured by some gears, obviously by replacing the existing ones. Would be there possible?</p>
  
  <p><a href="https://i.sstatic.net/emSPZ.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/emSPZ.png" alt="enter image description here"></a></p>
  
Tags: <gears>
Title: 9398 reduction change
UserDisplayName: mike
ThreadText: # 9398 reduction change
  
  (Asked by: username_0 on 2018-06-09)
  
  I am studying implementation of 9398 crawler reduction.
  Here is the stripped part, in order to see the gears and their relation - the image is made with the excellent tool which is LDCad.
  
  [![enter image description here](https://i.sstatic.net/tqTc8.png)](https://i.sstatic.net/tqTc8.png)
  
  My idea is to use this Lego design for other model and I need to know how would I calculate the effect of changing it a bit.
  My intention is to replace the two 16 teeth gears 94925:
  
  [![enter image description here](https://i.sstatic.net/CPoY1.png)](https://i.sstatic.net/CPoY1.png)
  
  with a pair of 12 and 20 teeth (32270 and 32269):
  
  [![enter image description here](https://i.sstatic.net/tg7tP.png)](https://i.sstatic.net/tg7tP.png)[![enter image description here](https://i.sstatic.net/Kxzbd.png)](https://i.sstatic.net/Kxzbd.png)
  
  and to remove the last reduction pairs, the ones in portal axle:
  
  [![enter image description here](https://i.sstatic.net/p3Hhx.png)](https://i.sstatic.net/p3Hhx.png)
  
  so it would be as follows:
  
  [![enter image description here](https://i.sstatic.net/fIMuL.png)](https://i.sstatic.net/fIMuL.png)
  
  Would this become faster/less powerful or slower/more powerful?
  My aim would be to keep it pretty close to how it performs now.
  
  Also, is there a way to combine gears in order to add a distance of half of a stud between the motor axle and the next or the second one? In the image below, I have moved the parts and created a gap between the gears, in order to point what I intend to move, but the contact must be assured by some gears, obviously by replacing the existing ones. Would be there possible?
  
  [![enter image description here](https://i.sstatic.net/emSPZ.png)](https://i.sstatic.net/emSPZ.png)
  
  **Tags:** gears
  
  ---
  
  ## 2 answers
  
  ### Answer by username_1 on 2018-06-19. Score: 1 | Accepted answer
  
  This modification won't change the rate of reduction.
  
  You can calculate the ratio of the angular velocities of two adjacent gearwheels as
  
  i12 = w2/w1 = n1/n2
  
  where w is the angular velocity and n is the number of teeth of the gears. Hence the original reduction reads as:
  
  i12\*i23\*i34\*i45\*i56 = 12/20 \* 16/16 \* 20/28 \* 12/20 \* 12/20 = 27/175 = 0.1543
  
  while the modified is:
  
  i12\*i23\*i34\*i45 = 12/20 \* 12/20 \* 20/28 \* 12/20 = 27/175 = 0.1543
  
  What you did is you simply removed the 16/16 and replaced the 12/20 gears, which results in the same reduction because the order of the multiplication is arbitrary.
  
  To the second question:
  
  You can change the 12-20 gears to 16-24 ones to fit the increased distance. In this case, the new reduction is
  
  i12\*i23\*i34\*i45 = 16/24 \* 12/20 \* 20/28 \* 12/20 = 6/35 = 0.1714
  
  Note that the new gears may intersect parts not shown in the figures.
  
  
  ---
  
  ### Answer by username_2 on 2018-06-20. Score: 1
  
  If the only change is replacing the two 16-tooth gears with a 12-tooth gear and a 20-tooth gear, then you will **reduce speed** by a factor 12/20 and **increase torque** by the same factor.
  
  If you want to increase the distance between gears by 1/2 stud, then you can experiment with using bigger gears and offsetting the motor sideways so the gears don't touch vertically. This may induce some play in the gears.
  
  > **Comments:**
  > **username_0**: I would drop the portal axles, so the performance will be kept. The reason is for implementing this on other model with less axle height (42069). Well, I did it partially, but using a horizontal transmission and keeping a similar design, with only 2 reductions instead of 3 (as this model has). It performs acceptable - a little faster than 9398, but powerful enough to run over decent obstacles for its tracks. I couldn't find a combination of gears for that 0.5 stud displacement, though. The gears are usually too tight to work safely together.  
  
  ---
  
  