dmalawey/SCTL_Feedback.md

## SCTL_Feedback.md

      
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              SCTL_Feedback.md
            
          
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PART_0 Query Topics 10.20


Platform for payload

Is there a kind of Payload rack design in place?

YES see Brey's Platform design


Buying Extra Hardware

Where can we order more fasteners?

Part numbers have been updated on our BOM for all M6 screws & extrusions
Latest Bill of Materials is posted here


PART_1 Hardware Assembly 2021.10.21


Wheel brackets

They feel too tight
It's hard to place the fasteners, they must be slid into position blindly


Caster Wheels

Unclear how many screws
Unclear position of screws
Unclear if it needs 1 washer per screw?


Wheel pulley:

It's easily broken if inserted in the wrong side
Note: Vijay has USA wheels + Asia pulleys combo (check tightness)
It was easy to plug in the correct side but too late
Not clear which side of wheel has "deep dish"
User may hesitate before gluing permanently
Remind users to glue the pulley

(doesn’t matter if the finger breaks)


Not clear if fingers are structurally integral

If it breaks, that's OK but user does not know this


Encoders:

Were not sent with header pins included
Header pin spec should be communicated if users buy their own
CAD model does not show the magnet
Instructions don't explain placement of magnet, poles, etc.

There is a video but no guarantee user will discover it


Motor Pulley:

Not clear how the pulley goes on the motor shaft.

Need to refer to video with magnet & encoders & pulley together


If pulley is inserted backwards, it will be broken


Motor spacer:

It's included but not necessary
Need to verify motor shaft length (by parts variants) to include or not
Need to provide instruction about it


Wheel Assembly

There is binding/friction when he tightens the M8 screw
We need to check root cause of this binding


Comparison

Turtlebot assembly, 1 year back by same user (software eng)
Kids can also assemble successfully
Had more subassemblies pre-built in the kit
fairly easy overall


Pros/cons of self-build for all pieces of SCUTTLE:

Confident in knowledge of the system after having built the unit


PART_2 Initial Setup Electronics 10.24


Test of Electronics

Seeking an automated test to verify all devices connected properly


PDF Manual disbursement

Kit should give access to manual right away, perhaps a postcard in the box with hyperlink


HDMI connection

experienced user prefers to connect to monitor for setup
HDMI or MICRO-HDMI would be needed.


Minor Software Errors

We could make corrections in the github directly
Need to show the process for user to "git pull" updates for their existing image


PART_3 Test Encoders & Gamepad 2021.10.25


Encoders Spacing

Customer unaware of spec (too close/too far)?
Variants of (motor, motor spacer, wheel pulley, and encoder bracket) can stack up tolerances.  Must document variations & share.


Encoders test

User trying out /dev/i2c to discover encoders - is it a valid method?
Enable i2C bus if not enabled (this is in manual, but can we put somewhere else?)


Encoders Error

right wheel & left wheel directionality: need troubleshooting resource
TRY:

see Beagle version of wiring guide for details about i2c bus
verify soldering is bridged, per wiring guide
verify encoder cables are unique and connected per wiring guide


ACTION: We need to update Pi wiring guide with matching details.


PART_4 Personalizing Electronics for the user (11.05)


Accessing the HDMI ports:

HDMI ports are hard to reach on Pi
If the user slides Pi bracket over for access, it pulls the cord from the

suggested CM: Include slightly longer dupont cables.


PART_5 Troubleshooting the motor driving with BEAGLE (2021.11.12)


When running L1_motors.py, I see both wheels turning forward but the right wheel does not move backward. It moves forward that means the power connections are ok.


The below condition is possible for motor driver for a given wheel:


Positive terminal
Negative terminal
Goal
result


3.3v
NC
DRIVING FWD
SUCCESS


0v
NC
DRIVING REVERSE
FAILED


Another Common Failure Mode is:

Ground signal wire is disconnected (this agrees with diagram)  AND 18awg ground (source voltage) does NOT come from battery.

In this case, there is no common ground between the motor driver and Beagle, therefore the 3.3v signals have no reference.


PART_6 Re-assembly of SCUTTLE and Adjusting Chassis (2022.02)


Corner Blocks loosen over time

Engineering notes: A torque spec should be issued, with instructions on how to achieve such torque without an instrument.
Barriers: Torque for aluminum corner brackets should be probably 10x higher than the wheel brackets.  So, two different torques for one kind of screw could be a pitfall.  The lock washer will be considered, or alternately making hex-shaped heads on corner brackets (to allow allen wrench) and keep phillips heads on the wheel brackets (disallow high torque, which will crush the plastic).


Caster wheels float if chassis is non-level

In theory this will not affect tracking.  It can affect tracking if: a) the robot has no payload and the movements are slow, b) the rear wheel also has a chance to float.
SCUTTLE team should make a video to describe this issue in depth


Wish to check flatness of frame before final assembly.

drop-in nuts will be replaced by slide-in nuts for the wheel bracket to help alignment
next version of wheel brackets will have fewer nuts
a version of the rod brackets are available with twist-in option (but the strength is lower)


Height of the wheel brackets is flush with frame, impacting ease of assembly

team needs clarification from customer.  (can we have a photo for this issue?)


Camera bracket is weak

let's see what was the failure mode and try to enhance strength.
video instructions MIGHT help, so user doesnt stress the bracket the wrong way.  We could issue this with QR code attached to the parts.
really we will have trouble if customer does not have easy access to 3D printer.  The very least we could do is offer lists of links to reputable, affordable printing companies in each country.