Let's Make Robots!

Gilligan's "Delta Head" #fail

It's pretty simple, I have learned 3 things already in building a delta "pick and place" robot arm...

1) There seems to be a lot of math involved in making these guys move properly. I didn't know that going into this project. Hmm..

2) Every joint must deflect quite a bit, both ways, and in BOTH THE X AND Y directions. More than 45 degrees each way seems to be a minimum.

3) What Gareth is to polymorph, I am to brass tubing. Yes, after cutting (24) perfect spacers in a row, I am now the Tubing God. --Modest too!

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OK, I second rik's request to learn what your new tubing cutting technique is. I've seen (and used) the one you previously posted (http://letsmakerobots.com/node/4494).

Also, is your decision to make Gilligan's Delta Head a 'steampunk' look mean you might come out for the International Steampunk City in Waltham, MA on May 6-8th? ; j

I'm hoping to have complete by then my Venux fly trap, and a solenoid driven calliope. Also, last night I learned how to make a balloon ray gun. I can see myself handing those out to passing children and sufficiently goofy adults.

I'll bite: How did you cut those spacers then, Mr Coppercutter?

You are very correct. I need longer threaded rod for the bottom linkages (to widen them and make the main rods parallel). The problem is the only place I can get 4-40 threaded rod is almost an hour's drive. The craft store (that is close) didn't have any. At any rate, you are correct, it is making my problem worse but I can sorta "do the math" on how far it would go without the trapazoid problem and it still wouldn't be enough.

I am going to wait to do any rebuilding until I can fix those lower joints, but I fear when I do, it is not going to get much better. Those model airplane ball joints were simply not designed to move that far. --Or at least not the ones I have... ...the are Dubro's --should be the "standard". I guess not.


I know what you mean. I have some hanging around which I bought just for a delta robot but they don`t really have enough side to side wiggle to be properly effective. 2 "clevis" hinges screwed end to end for each joint would give good movement but then the axis of pivot would be offset and might screw with the mathematics involved.

Your joints are binding because on each servos link the bottom 2 ball joints are much closer to each other than the top 2 joints making your arms form a trapezoid. That way the top and bottom joints are "opposing" each other. Try making the bottom horizontal bars the same width as the top and you should see a lot more movement.