Posted by Wade Vagle
Like how we appreciate Nike's when running on concrete, large-scale walkers benefit from shock-absorbing feet. By increasing the spring's travel, shock-absorbing feet may also be able to smooth the gaits of high-stepping walkers like TrotBot and Strider. And of course this would create new problems to be solved!
First, here's the Mondo Spider's feet in action, which provide some shock absorption, and they also slide on the smooth concrete, which helps with turning and with smoothing Klann's speed:
It walks amazingly fluidly considering how Klann's foot-path comes to a stop at each end, and the springs probably smooth the transition between feet somewhat:
Watching the video raises some questions, like:
Implementing Klann's linkage without shock-absorbing feet that slide results in a more halting gait, as can be seen in this version of the Walking Beast:
Next, here are some shock-absorbing feet ideas from Mechanical Walker pioneer, Professor Joseph Shigley:
Feet with such springs extend the feet toward the ground. So, in addition to absorbing shocks, the springs also increase the percentage of ground contact of each leg per crank rotation.
Taken to an extreme, feet with very long springs could theoretically increase an 8-legged Strider's ground-contact to the point that it always had one foot on the ground at each corner of robot, and do so without causing the robot's height to drop when the feet touching the ground switch. This is because both of the feet will be near the ground at the foot transition, meaning two springs will be pushing the robot up, reducing how far the robot falls at foot transitions.
However, a few of the (probably numerous) issues of long-spring feet are:
Maybe the smoothest solution for larger scale Striders would be to add shock-absorbing pads to the bottom of Strider's feet with toes, like the toes simulated below? Pads with a smooth, hard surface to facilitate sliding while turning like the Mondo Spider's feet? Note: the more refined dimensions of this non-LEGO version of Strider's linkage can be found here.
Strider's linkage variation 7 may also be smoothed by shock-absorbing foot pads, since the bump in it's gait occurs at the foot transition, and this should be easier to test since variation 7 can be built in LEGO.
Foam insulation for pipes or doors may be an easy way to add damped, shock-absorbing pads to feet. Pipe insulation is one possibility, which can be purchased at hardware stores (thx for the idea, Oracid!), and further down is a test of a jumping robot using foam weather stripping for doors.
On a related note, our LEGO walkers' gaits are somewhat smoothed by the flexing of the metal support rods, although such shock-absorption isn't consistent since it varies depending on how far the legs are from the inner frame. You can see this in action in the following video, where the outer frames bounce more than the center frame:
Welcome to DIYWalkers! I'm Ben Vagle, and I've been building mechanical walkers since I was 11 years old, both big and small. I started this blog to share what I've learned, and to collaborate with you. Let's see if we can take walkers to the next level!