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Robot Arm Designs

Anyone interested in creating a team to brain storm ideas and designs for robot arms for large or small robots. Perhaps collectively we could come up with a universal design that many of us could use. We each could provide input, drawings and/or services.



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i am using higher torque servo (my design) for my arms on my omnibot 2000 project inside the arms will have aluminium,it best stuff to use for robots,easy to machine and add boards or servos and to remove them,and soon setting up a special MIG WELDER to weld aluminium,needs a high output MIG welder,plus a special mig welder feeder gun made for aluminium with gas input,and argon gas for shielding gas,also on order is a metal lathe and mill machine
work out my design to lift over 50 lbs ,more like the bionic arm in 6 million dollar man movie
project is called 6 million dollar omnibot
lot of times i make my own servo's its pretty easy all you need is the futaba s3003 servo and remove the board and pot and motor ,and add your own motor and gear box and add the pot for feedback,now on the h-bridge on s3003 board it rated at 1 amp,so 2 in parallel gives you 2 amps or remove it and add your own h-bridge
for gear box kinda easy to work it out,just need specs on motor you are using,speed and torque and torgue you want out ,then gear ratio is kinda easy
if like example you need a 4 to 1 ratio, and want to use the smallest pinion gear for the motor like 9 teeth output gear would be 36 teeth,reason for a small pinion gear is that the output gear is small to fit inside your design or get a little harder like in servo are made with a few gear ratio's, now with a 4-1 ratio speed will be 4 times less and torque 4 times more
rgordon and soon will modify robot hand with aluminum and two servos like this:

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:) :) :)
i have a hand like that as a template for my aluminium hand design,one main reason a lathe and mill machine is very needed
plastic hands makes a great template
Thanks to you all for keeping this thread alive. Just wish I had more time to work on my bots. Seems as though there are always so many things that need to be done after I get home from work. And even when I find a little time, I'm just to tired to get motivated. Guess I should feel blessed that I have a good job. Life has a funny way of putting a damper on your dreams. Just makes it seem hopeless sometimes. *tired*

Watching you guys develop your robots gives me and others lots of inspiration. Your designs are outstanding!

Those look like a great find on servos. Very good looking arm.

Do the gear motors behave and control/maintain position as well as as servo does when you set it up this way? Would love to see videos and pictures.

That robot is coming along nicely. Can't wait to see him in action. More videos:)
rgordon they are made the same as servo's,if you take apart a servo you will see a gear box,dc motor and control board and feedback pot,so you are making the same design,but with higher torque motors
feedback is very important the pot must be on the last gear
the best servo board easy to modify and there is a schematic on it is FUTUBA S3003 plus very cheap from CHINA on ebay about $4 each or less
Did you know this one from Festo, it's pneumatic, but very impressive.
I thinkl it could be made of servo driven steel ropes too.


Yeah I have seen that one and I really like it. I have thought about trying something like this using miniature linear actuators and the steel cables used on lawn mowers (the ones that position the choke or throttle).
I think Spiderman used to fight that guy all of the time. It's good to see DocOc got an honest job.

Now I have seen your avatar....your maximillian always have added a pair of festo arms....I've not seen this before. :D

I think four steel cables for the Arm, driven bei two servos should make up/down/left/right, but I think you need the same again for the wrist and one servo for the Hand.
So we need at least five Servos for one arm, but it seems to be an interesting experiment.

EDIT: I read the complete thread now, I think strong RC-Servos are really expensive.
In my opinion the better way is to use a servo elektronik and a strong motor with (planet)gearbox and pot.
I looked for "servoelektronik" on google and found a two channel servo elektronik that can handle motors with 10A.
You can get the electronic for 6V, 12V or 24V, but it seems that is fixed and have to be ordered with the needed voltage.
It's a german site, but I think there would be others in the web:

5. Servocontroller

Here is another electronic, called "Thor15 Servo" that can handle up to 12V/18A.

Thor15 Servo

Here's a diy schematic for a one channel servo electronic for 24V/15A with MosFet's:

ServoController 24V/15A

I'm Printing up the InMoov robot since I got my 3d printer working again. Stay away from solidoodle. It has been nothing but trouble for me since it arrived, and suport is bad at best. Also, if it breaks the first week, like mine did, they don't have any obligation to fix it.

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United Kingdom
Here is an AIMEC:EZ1 arm with 5 DOF just before the wiring loom has been added. We had to develop our own shoulder servo which has a massive 200 kg.cm torque.

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I am sure looking forward to the changes. Thank you Tony - EZ1 robot maker and D J Sures, EZ robot creator.
Steve S
Sheesh ! A guy goes away for a few days to build a robot and finds dozens of new posts! gotta love it..anyways, here are a few pics of my robots's arm and hand..( for @Sfoy! ) who wants something more "human like"..Thanks to ALL for really geat posts! I am using home made custom gears for three reasons... they're cheap(wood), customized to fit my robot arms and they fit into my Steampunk theme! Of course by adding gears one can increase torque.
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recycled bike cable go back to the forarm servo platform

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rivots can be used for more then just rivoting metal together

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the right arm layout with 4 degrees of movement...servos not installed yet. All servos are "gear" assisted for esthetics and torque..the wooden hand took about 2 days to complete. Its nice to have the "hand model" in sight:) the left arm will have a claw pulled together by a single servo. All supplies on "hand":) therefor zero cost (@rgordon)..but...time is a huge factor
irobot58, Your work is extremely impressive. I have always liked the look and movement of a cable type tension hand. I wish there was an easy way to apply enough torque to operate and modify a toy tension hand for my Captain Ann Droid. Looking forward to your progress. Keep up the great work. Steve S
Thomas I'd love to know how that goes...

irobot wow that arm is pretty impressive.
irobot58, cool arm and kinda creepy. I love it! Now, just don't try to do what Howard did on Big Bang Theory and end up in the Emergency Room! *eek*
Oh I love the Big Bang Theory....
I saw that Episode of Big Bang and LMAO! The total arm will be heavy but plan on either a DC motor for the shoulder and or bungees for tendon assist.
This thread is very informative about servos and math torque but I think a very direct way of knowing what kinda servo with how much torque , can be done by simply measuring the actual torque with a spring guage! They're easy to build using a spring ( and if you dont have a reference scale for calibration you can always take it to the supermarket and use their scale|) or bungee cord! Cheap fishing scales are usable as well and most of us probably have those in the garage behind the net! ..... Add in all the known payload..ie A can of Moosehead Beer(micro brewery) or the glass of wine for the Ladies.! Its the old ..which came first, the chicken or the egg(egg actually) ...build the arm or buy the servo first:)