Here is a new rear protection bumper
      design we just came up with for our indoor traversing robot that
      may be just what your looking for in an inexpensive and very
      effective bumper design for small robots. The design started
      to gel when we had to add an extension to the back of the bot
      to accept the rear drop off sensor array, and an elegant bumper
      design had to cover the extension plus some of the side areas.
      We have many hours of "field" testing on this design,
      and it has held up very well in gentle as well as ramming impact
      situations.

 

      
 Rear view of robot,
      just below the power switch you can see an extension plate of
      lexan that will carry the additional sensors for ground detection
      and drop off sensing. The bumper consists of two .032 inch thick
      brass strips about a foot long purchased from the hardware store.
      The inner hoop is connected on both ends with machine screws
      into the base of the robot. It loops around gently, and connects
      on both ends to hold it taught. It is connected in the middle
      with lacing cord to the lexan extension, however the end screws
      alone were adequate for support and tension. 

      
Mounted on four nylon standoffs,
      two each side right on the first brass band is a second band,
      about an inch shorter. It is mounted with nylon screws for electrical
      isolation and is a constant distance of about 1/4 inch from the
      inner band. The idea is when force is applied to any part of
      the band, it deflects inward, touching the inner band and making
      an electrical contact, thus alerting the robot that it has backed
      into something and to stop backing up.

      
Now here's the neat trick
      - see the next image!


 
 When you
      press on any part of the band (except right next to the nylon
      spacers of course) the band deflects inward, and the other parts
      of the band expand OUTWARD like pushing jello around. This gives
      it the proper spring tension on any surface of impact.

 
 Now here
      is a side impact, note that the opposite side bulges outward
      in a springy, and will then return to the neutral position ready
      for the next impact. Even ramming into hard walls will not dent
      the brass, and it is sensitive to the light touches as well for
      our 10 pound robot.

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