more detail on rocker bogie wiring (#530)

* differential pivot instructions / pics

* major restructuring of rb wiring instructions, more pics

* major restructuring of rb wiring directions, more pics

* update ref to control arm assembly image

Author: knickels

mechanical/README.md

@@ -19,6 +19,7 @@ If you haven't already, now is a good time to attach the PCBs to the bottom body
 
 ![exploded view](images/exploded_mechanical.png)
 Inserting the left rocker-bogie in the body. Note that the 45 angle bracket in blue should already be attached to the rocker-bogie and the wheels should not be attached yet. A 32mm ID round spacer that should be installed below is also not seen on this image.
+**I didn't have space on the outside of the body, just one spacer in the center**
 
 ### Inserting the rocker-bogies in the body
 
@@ -31,9 +32,17 @@ Secure the body axis to the body using another 32mm ID spacer and flat 2-hole br
 
 ### Attaching the differential pivot to the rocker-bogies
 
-Attach the differential legs to the rocker-bogie 45 degree brackets using M4 screws.
+Attach the differential pivot legs to the rocker-bogie 45 degree brackets using M4x8 screws.  It may be easier to unmount the blocks, attach them to the bracket, then attach the pivot legs to them as shown in the sequence below.  A curved pair of needle-nose pliers or a hemostat is helpful to secure the M4x8mm screw while placing the block on the top, as it's hard to reach.  The button head screw that attatches to the inside leg is a bit tight.
+
+|![](images/dp_reaching_block_screws.jpg)| ![](images/dp_blocks_installed.jpg)|
+| ----------------------------------------------- | ---------------------------------------------------------- |
+| Holding the blocks in place | Blocks Installed |
+
+
+|![](images/dp_tightening_back.jpg)| ![](images/dp_assy_done.jpg)|
+| ----------------------------------------------- | ---------------------------------------------------------- |
+| Tightening the back leg | Differential Pivot Installed.
 
-> TODO: requires image
 
 ### Attaching the middle drive motors
 

mechanical/images/dp_assy_done.jpg

@@ -26,7 +26,7 @@ You will be creating two almost identical assemblies. Below instructions are for
 
 ### Creating the rocker-bogie joint
 
-First, gather the parts you'll need for the joint.
+First, gather the parts you'll need for the joint that connects the rocker to the bogie.
 
 | Joint Parts |
 | ---------------------------------------------- | 
@@ -42,48 +42,81 @@ Wait with the yellow and orange (ball bearing) parts. The bearing should first b
 
 > **Tip**: Use the OnShape model and navigate to the tab 'rocker-bogie' in the bottom to isolate this assembly. Then right click on various parts to temporarily hide them so you can see how the assembly works in 3D.
 
-### Attach the joint bearings to the servo arms
+### Attach the control arms to the joint bearings
 
-Connect the hub (yellow) with the inserted bearing to the servo arm using 8x socket or button M4 screws of length 12mm (or 10mm). Use washers so that the screw doesn't bury itself in the plastic servo arm and to make sure the screw doesn't extend (much) on the insides of the hubs. When done, the bearing should not be able to fall out. Put these 2 assemblies aside for now. We'll connect each finished joint to the rockers in the following step.
+Referencing the orange and yellow parts in the image below, connect the hub (yellow) with the inserted bearing to the control arm using 8x socket or button M4 screws of length 12mm (or 10mm). Use washers so that the screw doesn't bury itself in the plastic control arm and to make sure the screw doesn't extend (much) on the insides of the hubs. When done, the bearing should not be able to fall out. Put these two assemblies aside for now. We'll connect each finished joint to the rockers in the following step.
 
 ![exploded view of the rocker-bogie joint](images/exploded_view.png)
 
-### Attach the extruded shafts
+### Create the bogie
 
 Attach a 3 hole x 5 hole plate `1116-0024-0040` to each of two length 96mm aluminum extrusions `1118-0024-0096` with 10mm button head screws as shown below.  Pay attention to direction of the slits for the cabling. You'll want the slit to face the short side of the plate.
 
 Now attach the plate to a 3-hole flat beam, and to the bogie joint, with 10mm socket head screws.  You'll want the slits to face the top of the rover (the bogie arm) so you can route the cabling going to the front servo and motor inside of the channel.
 
-| Plate on rocker shaft| Assembled joints |
+| Plate on bogie shaft| Assembled bogie |
 | ---------------------------------------------- | ---------------------------------------------- | 
-| <img src="images/rocker_w_plate.jpg" height=400/>  | <img src="images/joints_assembled.jpg" height=400/>  |
+| <img src="images/bogie_w_plate.jpg" height=400/>  | <img src="images/joints_assembled.jpg" height=400/>  |
 
-So at the end, you should have all of the slits in the rocker assembly pointing up, and the slits in the bogie shaft pointing into the center of the rover.
+#### Attach the front servo bracket and middle wheel bracket
 
-### Attach the front servo
+Attach bracket `1111-0003-0001` to the top of the extruded shaft you just attached to the joint using three or four M4 screws.
 
-First attach bracket `1111-0003-0001` to the extruded shaft you just attached to the joint using three or four M4x10 button head screws, routing the wiring for the front servo and front motor from the servo motor through the hole and into the extruded shaft. Then assemble the servo block to the servo motor per [the manufacturers drawings](https://www.gobilda.com/servoblock-standard-size-25-tooth-spline-hub-shaft/). Insert the set screw that came with the servo inside the hollow shaft that fits onto the spline profile on the servo output, but don't tighten it yet as we'll have to readjust later when calibrating the corner motors. This screw prevents the corner assembly from falling off the rocker-bogie while driving. Finally, attach the servo motor and block to the front rocker-bogie bracket. The image below shows the resulting assembly.
+Attach U channel `1120-0002-0072` to the bottom of the other extruded shaft you just attached to the joint using three or four M4 screws.
 
-| ![bracket and bogie joint](images/front_servo_to_rb.png) |
-| --- |
-|![wiring closeup](images/wiring_detail.png) |
+#### Route wiring through bogie
 
-### Connect the servo arms and shaft to the joint
+Install `2911-0014-0001` grommets at the top and bottom of the extruded aluminum goRail (inside the U channel on the bottom, and inside the servo bracket on the top), to protect your wires as they go around corners.
 
-Make sure the slit in the bogie extruded shaft `1118-0024-0096` (same as the other two shafts you already connected to the bogie joint) faces the inside of the rover (you can also point the slit upwards or downwards if you prefer).  Route the wiring going to the front servo and motor through it and route the wiring for the middle drive wheel motor through it before you attach the screws. It helps to temporarily keep the wiring in place with some tape as you attach the shaft to the bogie joint.
+Run the servo wiring, including a 54cm extension, down from the front servo, which should be near the front servo bracket, down toward the joint.  
 
-> **NOTE**: the OnShape model may represent the orientation of the slits incorrectly. In order to make the model nimble, the same rocker-bogie assembly is used on both sides of the rover which has the side-effect that the two assemblies aren't mirrorred like they are supposed to be. Always stop to think about what you're building to avoid having to take things apart later.
+Run the 54cm encoder wires for the front corner motor from the front servo bracket toward the joint.
+
+Run the middle motor power wiring from the U channel up toward the joint.
+
+Run the middle motor encoder wires from the joint down to the U channel (or as shown in the picture, around it if you choose to notch your shafts), and encase in the protective sleeve.  
+
+It should look like the last picture below, except that your servo block and servo won't be installed at this point.
 
-Take one of the servo arms with bearing and hub you made in an earlier step amd attach the steel bracket, two hurricane nuts, and 4x socket screws like in the image. Repeat for the other servo arm. If the screws don't slide freely through the holes in the black servo arm, drill the holes out to make sure the hurricane nuts rotate and lock in place in the rail.
+|![bogie parts step 1](images/bogie_parts_step1.jpg) 
+| --------- | 
+| Bogie wiring installed.  |
+
+#### Attach the front servo and servo block
+
+Attach bracket `1111-0003-0001` to the extruded shaft you just attached to the joint using three or four M4 screws.
+
+Then assemble the servo block to the servo motor. Insert the set screw that came with the servo inside the hollow shaft that fits onto the spline profile on the servo output, but don't tighten it yet as we'll have to readjust later when calibrating the corner motors. This screw prevents the corner assembly from falling off the rocker-bogie while driving. Finally, attach the servo motor and block to the front rocker-bogie bracket. The image below shows the resulting assembly.
+
+| ![bracket and bogie joint](images/front_servo_to_rb.png) |
+| --- |
+| Bracket and Bogie Joint |
 
-![picture of the servo arm assembly](images/servo_arm_assembly.jpg)
+### Connect the control arms and rocker to the joint
 
-Place one servo arm assembly over one side of the rocker-bogie joint such that the hurricane nuts fit all the way in the channel. Tighten such that you can still slide the servo arm relative to the channel. Flip the assembly over and repeat on the other side, making sure the setup is symmetric. Now tighten the screws all the way.
+Take one of the control arms with bearing and hub you made in an earlier step and attach the steel bracket, two hurricane nuts, and 4x socket screws like in the image. 
 
 > **NOTE**: Consider using an extra screw and hurricane nut in the middle to strengthen the joint further
 
 ![attaching the shaft from the rocker to the bogie joint](images/rocker_extr_to_bogie_joint.png)
 
+Repeat for the other control arm. If the screws don't slide freely through the holes in the black control arm, drill the holes out to make sure the hurricane nuts rotate and lock in place in the rail.
+
+![picture of the control arm assembly](images/control_arm_assembly.jpg)
+
+Connect the short part of the rocker (shaft `1110-0024-00096`) to the control arm on one side such that the hurricane nuts fit all the way in the channel.  Tighten such that you can still slide the control arm relative to the channel.  Make sure the slit faces the underside/back of the rover (you can also point the slit upwards or downwards if you prefer). 
+
+Route the wiring coming from the front, middle, and rear motors and servos through the slit (see left image below). It helps to temporarily keep the wiring in place with some tape as you attach the shaft to the bogie joint.
+
+Flip the assembly over and repeat on the other side, making sure the setup is symmetric. Now tighten the screws all the way.
+
+| ![wiring for bogie joint](images/wiring_bogiejoint.jpg) | ![wiring for bogie joint](images/wiring_bogiejoint_done.jpg) |
+| --- | --- |
+| Running wiring through short shaft of rocker | Joint installed. | 
+
+
+> **NOTE**: the OnShape model may represent the orientation of the slits incorrectly. In order to make the model nimble, the same rocker-bogie assembly is used on both sides of the rover which has the side-effect that the two assemblies aren't mirrorred like they are supposed to be. Always stop to think about what you're building to avoid having to take things apart later.
+
 ### Assemble the back servo
 
 Attach the 1-channel U bracket to the long extruded shaft `11118-0024-0288` using 3 or 4 M4 socket screws of length 10mm. Assemble another servo block as you did before. Insert this into the 1-channel bracket and attach using 6 button M4 screws of length 10mm (6mm or 8mm also works).
@@ -98,7 +131,7 @@ Flip the assembly over and attach the two brackets like in the picture below, us
 
 | ![assembly with wiring](images/cabling-rocker-bogie.jpg) |
 | --- |
-| Wiring snugly fits inside the extruded aluminum channels. Only use this image as an idea of how the wiring should be routed, other parts of this image may not reflect the current state of the rocker-bogie at this stage in the process. |
+| Wiring snugly fits inside the extruded aluminum channels, even with little or no sheathing. Only use this image as an idea of how the wiring should be routed, other parts of this image may not reflect the current state of the rocker-bogie at this stage in the process. |
 
 Secure the channel to the rocker-bogie using 5 hurricane nuts (2 at the bottom) and socket screws, making sure the channel end sits flush to the other channels and the wiring isn't squeezed inbetween.
 
@@ -107,4 +140,6 @@ Secure the channel to the rocker-bogie using 5 hurricane nuts (2 at the bottom)
 
 Repeat these steps for the other rocker-bogie, making sure it mirrors the first assembly. Once you're done, you're ready with these very important subassemblies!
 
+![complete assembly](images/rocker_bogie_assembled.jpg)
+
 > **Help improve documentation!** Please make an issue on Github when you spot something that's off or can be improved. Pull requests are even better! If you have a question, post in the #troubleshooting channel in our Slack group.