Firky2010

Search this site

LEGO Facts

  • LEGO is an abbreviation of the two Danish words "leg godt", meaning "play well"
  • During the moulding process, the plastic is heated to 232°C until its consistency is that of dough
  • In 2003 LEGO  changed the minifigure's yellow facial colouring to a more authentic skin colour
  • In 2006 the LEGO  website had an average of 8,137,062 individual visitors a month
  • If you built a column of about 40,000,000,000 LEGO bricks, it would reach the moon

Hits

Free Hit Counters

845days since
Project Launch

Upper Arm

My first thoughts on the upper arm was to use Lego linear actuators and connect them to the end of the forearm and to the bottom of the upper arm near the shoulder. When the linear actuators contracted the forearm would lift and when the linear actuators expanded the forearm would lower. In theory this idea works but it does not give me the amount of movement I was looking for.  It only really gave me about 100 degrees of movement when at a minimum I was looking for around 160-170 degrees. The picture below shows four linear actuators geared together to expand and contract at the same time using only one motor. This setup changes length by 10cm or 10 lego units.


This youtube video shows the above design in action, using only one LEGO M motor. This is a fast movement but you don't get a great deal of strength. This design is definitely going to need some improvement. 

This video below shows a rough design of the upper arm, showing how much movement I have using a linear actuators. This set up uses three linear actuators - two for the main movement and a third to change the angle of the first two to give a greater overall movement. However, this was just a mock up and I'm not satisfied by this design, so I'm going to revert back to gearing using lego turn tables.


After a few different gear set ups I came up with this design using worm gears and 8 tooth gears. The worm gears help to hold the position, and the 8 tooth gears help gear down, reducing the effort needed to lift and lower the Arm. This design is very big and bulky but very strong and reliable.


However, this is not the design I'm really looking for but the gearing is very good, so I plan to put this gearing inside of the forearm to reduce the size of the upper Arm. So, to reduce the size of the upper Arm. The upper Arm does not have any gearing whatsoever - it is just a link between the forearm and the shoulder. Here are a few screen shots of my Design. 





In the video below you can see the elbow being tested the gearing is strong enough to lift its own wight