First off is the delivery that made this all possible, I had ordered quite a few parts some of which would be surplus to requirements because the pieces are sold in packs of two, not a great problem as spares are always welcome and I'll be using another set of Servo Erector Set (SES) parts when I build the second arm to compliment this one.
Al had two primary building phases, the first used the parts shown in the picture below. I seen discovered that even when the servo's were running at their maximum 6V they were woefully under powered. The second building phase involved purchasing several new parts and a much more powerful shoulder servo.
HS-422 HS-645MG
Speed 0.16sec 0.2sec
Torque 4.1Kg.cm 9.6Kg.cm
Turns out blogger dons't have any spreadsheet style ways of displaying information...
The first phase of construction took me a good few hours, instructions are available on the Lynxmotion website for certain models and building techniques but none for the type of arm i was building. I had to reverse engineer a image that i was basing mine on.
One serious problem I ran into without instructions was the order of construction, I made the mistake of starting with the gripper when I now know I would of been better off building from the ground up, a second problem I faced was ordering the wrong servo mounting brackets, there are few types of each bracket available and I didn't realize the importance of the correct one at the time of ordering.
About a week later after I had received the second wave of parts I began the second phase of construction. The upgraded shoulder servo is a HS-805B+, This boasts a impressive 24.7Kg of torque at 6v as well as a equally impressive speed of 0.14sec per 60 degrees of motion. With greater power comes a much bigger servo as you can see below.
The new servo brackets are equally impressive compared to their normal sized counterparts. They are all made from high quality anodized aluminium. The brackets have a brushed finish, weather this is intentional or not I don't know but it adds to the appearance quite nicely.
There are still a number of problems that I must deal with before I can declare the arm fully finished, The most pressing matter is the oscillation created by the larger servo bracket. When the arm is held out it picks up a slight bobbing motion because of the small amount of flex in the servo bracket, The servo tries to correct the small moment which only results in the arm bobbing a little more. There is a special dampener available which applies a small amount of friction the the servo bracket to remove the oscillation. Annoyingly the supplier in the Uk seems to forever be out of stock of this part and ill be dammed if I'm paying £20 for delivery from america for a £5 piece!! I have been forced to start searching for something to make it from which is not as easy as it sounds, the material must be wear resistant, 2mm thick and have a tacky surface.
Other problems are easier but will require a little thinking to achieve a tidy elegant appearance. The cables need to be sheathed and tied down so they do not become caught in the brackets.
 |
| As proud as ever |
Last but not least Is Al in action following a simple pre-programmed pick and drop, I was trying to make the movements as smooth and quick as possible, I have made a few more adjustments since recording this and I'm somewhat happy, I'm sure I can make further improvements though.
Its getting later here and i apologies for any mistakes I have made, I've checked it over but I'll have another look in the morning to be certain.
No comments:
Post a Comment