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Strandbeast motion problem
yip_cm
Member Posts: 26 ✭
in Simulation
May I know, what's wrong with the joint?
https://cad.onshape.com/documents/cd23915d1a1ec75124bc8f2f/w/612cec551d2bfea6b477b8e8/e/9891485f435bfebec602bd34
0
Comments
The distance of holes in Part 9, or the the length in parts 4 or 5 is a bit off, creating an ambiguous situation that cannot be solved. The grey triangle (Part 2) kind of over-rotates. The same would happen in the real world.
In my version, I shortened Part 5 by 1 cm and that makes it work.
Thanks for your comments, I made the full assembly as below:
https://cad.onshape.com/documents/357763fc8d1bfb1f3b57bcf6/w/74dd8fb30f6178705e8e7e51/e/f34f085a3940a4dea3b0a67f
But I found that it has another problem now, the middle rod cannot be rotate horizontally, I tried to mate it in parallel with the supporting rod but it cannot work. Could you please help? Thanks. : )
That is not a problem specifically with Onshape, it is a design flaw. The frame, the two arms and the middle rod form a parallelogram. When rotaing, there is a mathematically ambiguous position when the arms and the rod are in parallel position: Then, the direction of rotation can 'flip' and still be mathematically valid.
You need to synchronize the rotation of the drive shafts. In the CAD model, the "Gear Relation" would do the job, but you'd still shoot yourself in the foot in real life, if you don't add that synchronisation in some sort of hardware.
If it is going to be all rods, no belts, then it might look somewhat like this:
Also, you might want to make subassemblies. That'd make it much easier to handle.
These Strandbeesten all sem to suffer from Lemming Syndrome. They run more or less downwind until they hit an obstacle or reach the the waterline, get cornered there and finally go extinct. I'd like to see one change it's behavioural principles, maybe creep upwind again and try another direction.