My general design philosophy for RS2 is similar to RS1:
- small: less of a target for the opponent
- tight: the smaller the package, the less weight used on structure and armor
- tough: components must not fail in combat, period
RS1 was designed as a two wheel bot with a rudder (the rear two wheels). The wheels were offset, moving the pivot point closer to the front of the bot. This proved to be difficult to steer. RS2 will utilize a standard 4 wheel based skid steering system, with the wheels as close to square as the design can allow.
The size of RS2 will be reduced, namely, the height. Providing a smaller target will thwart some of the opponents weapons, and reduce weight in structure, possibly allowing the use of tougher materials.
All of the wheels will be moved inside the structure. This will reduce the chance of wheels being attacked from the side. RS1 intended to protect the front wheels, but this had to be eliminated due to excessive weight.
One of my first decisions was to ditch the 24v Dewalt motors in favor of the 18v version. This was done for a number of reasons. First, reliability. As hard as I tried to mount these in my design, I couldn’t get them secured reliably, resulting in the gearboxes spinning, and self destructing. Second, I found the torque that I originally sought wasn’t gaining the results I desired. Third, the 18v are smaller, but when run at 24v (which I’m limited to by using the Victor 883 speed controllers), they are as powerful as the 24v version.
Since making this decision, a few things have changed. First, I realized that with the motor and wheel combination that I would be using, my top speed was approximately 16mph. This is slower than I was hoping for. I found that Dewalt had come out with a new version of the 18v combo that provides 2000rpm in it’s highest gear. This would take me near 20mph when powered at 21.6v. The downside is that the new combo is as hard to mount as the original 24v combo. I’ll be devoting extra attention to this mounting, as it is now apparent how important it can be.
Another decision was to ditch the home made battery packs based on Dewalt XR+ battery packs (2.4ah cells). Because the design will change substantially, the old packs will not fit, and their is newer technology available, so it’s time for a change. I will instead use BattlePacks, based on the new 3.6ah cells. This will provide a battle tested package, with far more efficient cells.
I will continue to use the Victor 883 speed controllers. They are smaller than other alternatives, and have proved reliable, except for the durability of the fan mounts. The new design will reinforce the fans so they do not break off due to shear.
Structurally, I will stick with my choice of steel angle iron as the attack weapon, but will change it from Cold Roll Steel to Stainless Steel. At 3/16″ thickness, I don’t believe any lightweights can significantly damage it (Ziggo and YU812 would be the ultimate tests of this). I will switch from 3/8″ aluminum to 3/8″ Stainless Steel for the main structural members. They are thick enough to be stiff, and allow tapping for mounting of the armor. The armor will be .06 Stainless Steel. I will have all of it cut with a waterjet to save my tools, and make them much more precise than I was able to achieve in the past..
The spindles, and their connection to the sprockets, have haunted RS1. RS2 will hopefully solve this. I’ll be using spindles machined by Team Delta. They have done strength tests that show them to have a 120% safety margin before failure. Mounting the sprockets will be done through a keyway and set screws.
The connection between the structural members and the angle iron must be improved. I will be welding the structural members to the angle, which will provide superior strength. I will also weld the bottom armor to the structural members and the angle, providing a very stiff frame. The top armor will then be screwed on with alloy screws, tapped into the structural members.