Weight of the arm system
Thought about the weight, and I was not sure that the weight of the complete arm system is ok, or not… (too heavy or not?)
Yesterday evening I drew the bucket 3D drawing, and calculated the theoretical weight. Bucket weight is more or less 1,2kg. If I count all weight, like the cylinders, pipes, (and oil), sleeves, bolts, tripping and bucket link… the total weight of the arm is more than 8,5kg.
If the arm is too heavy, the machine will not able to lift up heavier weights. The hydraulic system have to lift up the arm and the weight (weight in the bucket), so if the arm is heavier, machine can lift up just lighter weights with same pressure. If the arm is lighter, machine can lift up heavier weights with same pressure.
By the way If the arm is “too light” machine can’t digging as big force with as a heavy arm. The arm weight helps during digging. I think this last is more important than the lifting capacity.
Tentatively I tried to reduce the weight. I rebuilt the 3D models, in the new version I used some windows in the thicker sheet metal components. (As you can see on the exploded drawing, there are some thicker plates in the Boom and Stick) I reduced the weight of these, but the new weight not more lighter, just 0,3kg lighter then before… 🙂 To reduce the thickness of the plates is a good way (4mm to 2mm), but the thinner plate is not enough strong, I think.
I don’t know, how can the machine works with this arm, but the relations between the size and weight not too bad. The full length of the arm (with bucket) is ~900mm, and the weigh is 8,5kg. The bucket width is 140mm. Digging with this “big” bucket I have to use big force, so maybe the arm weigh will help during the digging and it will works well.
Arm system with the partly finished bucket:
