by erdinger, published
M about 1:20
And yes: there is sand at the teeth of the bucket out of my kids sandbox ;-)
I hope the pictures are descibing the project best. On pic SAM_4173 the lower part of the body is shown with holes for batteries. It was redesigned that a big pb battery fits now. The two servos in the arm have about 120 Ncm, the big one in the body about 260 Ncm.
In the tracks and for turnig there are the the cheapest servos ever in there for about 2,5ÃÂ¢Ã¢ÂÂÃÂ¬.
The servos in the tracks are hacked so that the pwm signal still works but they do it continously. Just search the web for "pwm servo hack"!
In the turnshaft i soldered the + and - of the servos togeter to reduce lines from 6 to 4.
The tooth gears are bought:
Maybe you can also print them, I can't.
The tracks are in fact a derivate from thingiverse.com/thing:36305
Thank you LoialOtter!
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the center shaft is ground... 4 stacks would be too high. An hydraulic system would be cool, but expensive, yea. So I only used servos.
There will be pics and videos! i'll have to learn how to upload them on here. i printed the track tighteners and power wheel stabilizers before i saw the cutouts, so i'll make the cutouts with a dremel too. i kind of thought there might be washers in the slip rings but i couldn't tell for sure. good idea! did you also use the center shaft for the ground conductor? or is there four washers stacked up?
so far i have the arm built up (need to make new linkages, with tighter tolerances) and am controlling it with arduino joystick shield.
i used #0-80 x 1 1/8" screws for track pins, from mcmastercarr.com (you have to ask for them, about $20 for 100 screws)
I added some more pics to get you a clue of the construction of the slip ring... it is assembled with 3x washerSpacer.stl and 3x washer (Hornbach for Germany / Home Depot for USA). From the inside the wires are connected to the washers from the outside there are the sliding metal wires. I placed some tape between the different level of washer and washerSpacer. It is going full circle as often as you want (in theory... somewhere I have a shortcut in there I haven't found jet... too much different things).
I use 13mm (outer diameter) bearings. the cone is that it self centers when screwing.
I think that the middle wheels of the tracks do not really need bearings... I have them but the tracks are just sliding in most cases without movement of the wheels.
One other point I found out was that on the trackTightener.stl and pwrWhlSabi.stl you need a cutout for the screws I forgot to design. So I used my Dremel after printing... please find it in the picture with the blue arrows.
I expect a video or at least some pictures when you finished it!
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