Time to Modify - Mk1.5

Despite a lot of successes from the first event, a number of changes were required. Apart from the obvious driving practice, I needed to focus on two of the issues:
  1. Unable to lift opponents without become unstable (lifting the rear wheels)
  2. Unable to self-right

Unfortunately the main reason for these limitations was the fact that a lot of the mass of the robot is in the lifting mechanism. So when the weapon operates, the centre of gravity changes significantly. However, as the robot baseline is a good, solid platform, only minor changes were required.

Lifting Issue Fix
The simplest way that I found to amend the limitation to Mk1, was to extend that front of the chassis with fixed forks. These forks are an extension of the front inner impact panel/ bulkhead brackets. When the robot is sitting on the floor, the fixed forks are lifted to reduce front contact patches (only the scoop is in contact). When the arm is lifted, the fixed forks stabilise the front to help prevent the rear from lifting. As the forks have to be very long to be effective and clear the scoop, lower bracing was added to the fork assembly. This is shown in the CAD images below.
Mk1.5 CAD 1.PNG Mk1.5 CAD 2 (No Scoop).PNG
Fixed forks mocked up in the robot.
IMG_20200816_145913.jpg IMG_20200816_145918.jpg
Cut-outs were made to the inner impact panel to accommodate the forks. The image below and to the right shows the final assembly (without the front scoop).
IMG_20200818_214944.jpg /IMG_20200822_143253.jpg

Self-Righting Issue Fix
A complete redesign was required from Mk1.0 as it was clear that the design was very flimsy and didn't work well. This task however proved to be a very difficult and lengthy process. I think I went through 5 different design concepts ranging from a completely separate arm linkage running from the weapon actuator, to a fixed anti tipping beam. But in the end the only design that came close to the aims of functionality and not look as if I had lost my mind , was to revisit the MK1.0 concept with better geometry. After 10 prototypes of various geometries, the design is shown below. The design is much sturdier as the main polycarbonate sections are now part of the main weapon arm assembly. The self-righter inner bracing is now much more optimised to stop flex when upside-down.
When testing, results were promising but once the robot self-rights in the arena I will deem this design as successful.
Mk1.5 CAD 3.PNG PXL_20200924_191944424.jpg

As additional items were added, some additional weight reduction was required elsewhere. Most notable areas of weight reduction were:
  • Front scoop mount (made from hardox) was replaced with an aluminium alternative of the same thickness.
  • Main arm inner aluminium mounts reduced in length to use less fasteners.
  • Cutouts in the self righting arm without compromising functionality.


Final assembly went smoothly ready for my second event on 26/09/20 (Robodojo again) which I will go through in the next post. For now, here are some images of the final assembly (FeatherDozer Mk1.5).

PXL_20200924_151323389.jpg PXL_20200924_151336540.jpg PXL_20200924_192009391.jpg