[Gregg Eshelman] reproduces plastic parts for antique car restorations for a living; likewise, he’s very good at it. Greg always chimes in with helpful hints whenever we post about resin casting. Shown above is a lens for a car turn signal. Manufactured in 1941, having [Gregg] cast a few copies is an easy option for replacing the rare part.
[Gregg] uses a similar method to us, but it is easy to see that he has done it more and his process has been refined by lots of experience. We really liked how he avoids using expensive foam core by wrapping cardboard in packing tape, or using the kind that has a plastic coating on it; the kind most retail packaging is made out of. He also has better techniques for keying the part to be manufactured, and prepping difficult geometry between different mold halves. It also never would have occurred to us to use Dremel cutting disks to cut the sprues and air vents in the silicone, a surprisingly tricky material to cut precisely with a knife.
It’s always nice when a professional takes time to write about their processes for the hobbyist trying to emulate it. We hope [Gregg] writes more tutorials, and continues to contribute in the comment section. If you have your own fabrication techniques to share we’d love to hear about it on the tips line.
Walking, jumping, rolling, flying, swimming – robotic locomotion is limited only by the imagination of the inventor. [Roger Rabbit] apparently has a pretty vivid imagination, because he’s building robots that move like worms.
Version 1 of [Roger]’s robot is only semi-vermiform and is more of tube climber. It has a pair of 3D-printed pantographs that expand and contract with servos and move along the robot’s axis on a stepper-driven lead screw. An Arduino reads sensors and coordinates the expansion of the pantographs to grip the internal diameter of a pipe and push the worm-bot along. It’s a slow but effective way to get around in the limited confines of a pipe.
The next iteration, dubbed [Wolly], is much more worm-like and not restricted to pipe-running. It has four expandable triangular frames connected to each other with rack-and-pinion backbones. The first frame contracts, the racks push it forward, it expands, the next contracts, and soon it’s doing the worm across the floor. Still slow, but pretty neat to watch, and you can see how it can be steered. It might even be able to roll around its long axis, and it’d make a decent tube climber as well.
This creepy autonomous worm-bot seems very similar to [Wolly], but aside from that we haven’t covered too many robots like these. There’s a lot of thought and effort in these worm-bots, and we’re keen to see where [Roger] takes this unique robot body plan.
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