TrotBot climbing 1/3-scale stairs with a lower center of gravity

Recently I’ve been working on getting TrotBot to climb 1/3-scale stairs. The first video below shows TrotBot climbing stairs  at the standard 32 degree angle of life-size stairs, both with and without wheelie bars.  The second video shows TrotBot attempting steeper 38 degree angle stairs without wheelie bars, and required a bit of expert driving to avoid flipping backwards!

​In this process, I found that TrotBot’s center of gravity needed to be lowered to prevent it from flipping backwards, so I lowered the battery box.  

In general, vehicles handle better with a lower center of gravity, so I should have mounted the battery box lower in my original instructions.  

​Instructions to modify TrotBot to lower its battery box: ​

These instructions require the vertically oriented 7 hole beams that mount the battery box to the frame be replaced by 11 hole beams. Using 11 hole beams allows the battery box to be mounted a half dozen holes lower than it would be otherwise.

Start by removing the battery box and vertical 7 hole beams from the TrotBot frame, and get four 11 hole beams to replace the 7 hole beams.   NOTE:  it's easier to pull the two sides of TrotBot apart incrementally while rotating each metal support rod between pulls so that the LEGO beams can slide along the rods.

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The following photo shows the attachment of two 11 hole beams to the battery box along with the 9 hole beams that attaches to them to the metal support rods to form the hypotenuse of the frame triangle. The 9 hole beams that are used as the hypotenuse will remain on the metal support rods and are only in the pictures to provide context.

Attach the 11 and 9 hole beams together to form the basis for the frame triangle. The 9 hole beams must be mounted on the 5th hole from the top of the 11 hole beam. 

Mount these parts onto the battery box. Notice that the 9 hole beams are mounted on the outside of the 11 hole beams, that they are facing away ​from the battery box. 

Repeat this process for the other side of the battery box.

Next mount this structure back into the TrotBot frame.   

And that's it, TrotBot with a lowered center of gravity - time to work on TrotBot's next climbing challenge: