Fixes & Changes

First item on the agenda post event 2 was to fix all areas of damage. The notable areas for repair included:
  • Axe damage to arm & self-righter brackets (superficial)
  • Axe damage to main bulkheads (superficial)
  • Axe damage to electronics covers (superficial)
  • General wear & tear of lower front scoops (superficial)
  • General damage to fixed front forks - Spare set of forks to be made

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Robot teardown revealed no internal damage. I have included the image below is I think it is a good representation of the up to date condition & layout of main chassis as seen in previous posts.

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Relay & link outer protection
As with many other components on FeatherDozer, I wanted to add additional protection to the relays (and link on the right side) without compromising the look of the robot. These panels are easily removeable with just 2 bolts per side and do not interfere with either the lifting mechanism or the ability to install/ remove the link. Below is the CAD and installation of the protective panels.
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New drive speed controllers
After using a basic recalibration of the Hobbyking F80 speed controllers for 2 events, I decided I wanted more adjustability of settings with a high emphasis to low speed control. In an ideal world, I would be moving into motors and escs with direct feedback from the motor via a position sensor to have better low speed control (e.g. VESCs), however, I do not (as usual) have the space in this design but I wanted to try an alternative.
The speed controllers I have been testing are 80 amp BLHeli_s ESCs designed for high performance drones. From what I have seen, this type of controller is common within bettleweights but not with featherweights. As the setup can be changed without modification via an Arduino, I can now make setup changes quickly as well as play with numerous settings with lower risks. These speed controllers are not prefect as current limiting functionality is not available . However I thought I would give them a go and early testing of gyro assisted drive setup was relatively unsuccessful. To try to help these speed controllers survive, I have added a larger heatsink and more shock damping (fire resistant foam).
Early load testing (pushing me along with my office chair) have been positive and I now have better control at low speed with may help some of the lack of control I was having. The F80 speed controllers will become spares in case of issues in real combat with the new ESCs.
Below is a comparison of the old ESC on the right and the new one with is much smaller and lighter.
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New Lifter motor
As the final event of 2020 was cancelled due to lockdown, I have had some additional time to change the motor in the lifting mechanism as the arm operation is a bit slower than I wanted. The original motor is a standard 18V 775 brushed motor that came with the gearbox from Gimson robotics. As the robot is currently running on 4s lipos, the full capability of this motor is not being utilised. Therefore the new motor is a Vex 775 pro as it is a 12V version of the same motor size. I am hoping that the full speed and torque range can be used with the lower voltage motor. Alternatively I am also considering a brushless setup alternative for the future but it will require a motor of a high KV rating to increase the speed of the mechanism.

For now, this bring us up to date (early 2021) as we are all experiencing the joys of national lockdown. When the next event happens I will be ready and the meantime, I will continue drive testing and practice.

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