....mechanical arms....

W

wolf0

New Member
I to all!
i'm an italian cosplayer...and I need your advice!
i'm trying to build a mechanical arm:
http://pa1.narvii.com/5827/ebb0dfca8e6ff14c64840045bdb9d16a237735f7_hq.gif
i need the movement goes from completely close from totally opened.
here's the problem:i'm thinking about using linear electric piston (that she very strong) but they can'take open completely (see excavator)....then I see stepper motor.....with them I can close the arm.....but stepper motor are not strong ad linear piston ....i've to lift about 3 kg....
any idea?
thank!
 
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I always thought this style of joint was a good one. You can use it as a wrist type joint or an elbow with the load spread over two motors. Battery drills are cheap and have a wide range or gear box but might not be small enough for this configuration but might work well for the load you mention

5591001470242723347.png
 
it'seems very interesting!have you created it?how much kg this type of configuration can lift?
I need something that is not too much big....i've to put it in a structur with an area of 20cmx20cm...for the battery pack,i've not seen anything yet.....
 
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Ciao Wolf0

what about Metal Gear Servos? They're supposed to be really powerful.
Looking forward to your project!
 
I would just say some high torque servos in each joint. They're fairly cheep and move just the way you want. Can't wait to see the finished product. I love Yellow Jacket.
 
I to all!
thanks guys,now we have started with yellowjacket helmet making some structural tests with servo.....I will post here the wip!
 
Hey wolfO,

Maybe use a combination of mechanical advantages, like cables for the heavy lifting, then gear motors and servos for the lighter stuff?

.
 
The science of these types of things is beyond me, but what I DO know, is using the right gear reduction or selecting a proper gear box can make a very weak motor capable of lifting much more than it could if hooked up straight to the duty task. Might want to keep that stepper motor in mind as you can source them pretty cheap and easily, and maybe someone could explain how to gear them up to take that much weight...

Edit: I gave this idea, as servos have a limited range if I'm not mistaken? Where as stepper motors have an infinite spin. Once you figure out your gearing you would just need to program how many rotations you would need from the stepper to get you to full open or full closed.
 
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SimplyTim said:
The science of these types of things is beyond me, but what I DO know, is using the right gear reduction or selecting a proper gear box can make a very weak motor capable of lifting much more than it could if hooked up straight to the duty task. Might want to keep that stepper motor in mind as you can source them pretty cheap and easily, and maybe someone could explain how to gear them up to take that much weight...

Edit: I gave this idea, as servos have a limited range if I'm not mistaken? Where as stepper motors have an infinite spin. Once you figure out your gearing you would just need to program how many rotations you would need from the stepper to get you to full open or full closed.
Click to expand...

Limit switches help to tell when your at max and min extension too.


Sent from my iPhone using Tapatalk
 
Wimismith said:
Limit switches help to tell when your at max and min extension too.


Sent from my iPhone using Tapatalk
Click to expand...

Oh! Good deal! I remember seeing that in a set up a while back for something unrelated. Sorry. Know I'm not the OP, but this kind of stuff has been an interest for a while so I'm soaking up what I can while this thread is active.
 
If you are using gear motors with no feedback control like servos, then a DPST switch in line with the power supply,
can be used to limit upper and lower limits.
You just need a diode on both switches to get you off the switch when current is reversed and the motor turns in the opposite direction.
 
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