Hi,
I am a bit confused in deciding the best robotic arm for my university project where I request kind guidance. I happened to see this robotic arm “http://nodna.de/Franconia-Robotix-6DOF-Aluminium-Arm-ready-to-run” which uses 7990TH servos and has a very high speed with reasonable torque.
Up-till now, I have shortlisted M100RAK with 7:1 gear ratio using HS785 servos however, 7:1 would significantly turn down the speed. Is it possible to use 7950/7990 servos in place of HS-785 servos to achieve higher speeds? Would this modification require 7950 continuous rotation gearboxes, 7950 360degree gearboxes or 7950 standard rotation gearboxes? Only the continuous rotation gearboxes come without potentiometers which may allow the shaft to pass through them during assembling the joints of RAK. Does, that mean continuous 7950 gearboxes are the only choice to be used in RAK or could 360 degree ones be also utilized by removing their potentiometers? What would be the disadvantage of using continuous 7950 gearboxes in place of HS785 gearboxes which come with built-in potentiometers? I just want to get a RAK using 7950/7990 servos. So, Is there a possibility to replace the 785 gearboxes with 7950 or 7990 gearboxes?
My apologies for too many questions. Please advise and help me in deciding the best solution. An early response would be highly appreciated.
Thanks.
Thanks for the clarification. This concludes that I should use only 785 servo gearboxes for the RAK. One more thing I request your kind guidance is about adding an elbow rotation joint in the RAK. Would it be possible using an additional tube gearbox attached to the elbow joint in vertical position so as to enable the rotation of the whole elbow? I want to achieve elbow rotation as shown in the following pictures. Any work around? Can you provide the required assembly to achieve this? Please advise. Thanks.
The M100RAK uses the SPG785 power gearboxes which are made specifically for the 785HB servo, based on its dimensions. As such, no other servo can be substituted. If there is a small chance that the 7950 has exactly the same dimensions as the 785HB, it’s pure luck; you would need to check the overall dimensions, hole dimensions, location of the horn, horn spline etc.
The solid shafts can be replaced with hollow ones (purchased separately) - it does not have anything to do with the servo.The 785HB can do continuous rotation, but not with position feedback. The arm can be reconfigured in many ways, but the servos and the SPG785 system is not really modifiable.
Once again, the power gearbox is made specifically for the 785HB servo - nothing else. We have not tested it with any other servos and likelier than not, no other servos will fit into the power gearbox (perhaps the 755MG is the closest, but would be useless with the arm). If you really want to see if a 7950 would work, the only way would be to test the two together.
We’ve been looking into exactly that and have yet to have a (production) solution. The Lynxmotion pattern is different than the ServoCity pattern and as such they are not compatible with one another. ServoCity will be releasing a new series based on the SPG785 power gearboxes and it is out hope that they will create a product which will satisfy this need - it is one of the last pieces required before the arm can “replace” a normal human arm.
If you are prepared to do some customization, consider the load bearing block, and perhaps mount it using the Vertical servo support to mount it to the arm. You would need to create an intermediate plate.
