Pneumatics

Say hello to George (v1 – 2.1)

Posted on by burf2000
After Bob, I decided to adapt the KISS approach (Keep it simple stupid)!  My objective for the Great Western Lego Show 2011 was to make a Robot that worked, and worked well!  It had to move and be able to turn on anti-slip carpet, easy to control and be strong enough to take knocks / drive in to tables without breaking.
George is a fully functional 5 foot 7″ robot. Controlled via a PlayStation 2 controller, he can move about, rotate his upper body, move his arms / shoulders and grab items. His head also rotates, moves up and down and if you get too close, his eyes will roll.
More pictures can be found here:

Communications
This time around I decided to scrap having multiple NXT’s and went with the brilliant Mindsensors wireless Playstation 2 controller sensor pack. This allows you to control your NXT via a Playstation 2 controller which has a huge number of buttons / controls on it.  Then I linked the NXT to a hiTechnic IR link so that the NXT could send commands to power functions infrared receivers (all 4 channels). This setup gave me a large number of possible functions (11 different motor channels). I used RobotC to program the NXT as I find it an amazing programming language.

Weight
This robot had a large upright body beam. However it did not rise up and down so it did not require any counter balance weight. Also, it was not plated and only carried 1 NXT. This probably cut down a 3rd of the total weight of the robot, even though it was bigger than Bob (5 ft 7” tall).

Drive
The main base of the robot was smaller than the one on the previous robot which would naturally make it move a little easier, especially being lighter. Also the 4 XL motor driving it were geared down via a 8 to 24 tooth gearing. First time around, this just snapped the gears in half. The way to get around this was to use 2 sets of 8 to 24 tooth gears in parallel on the same axle per motor. Also, as a backup, in case the robot did not work on the show carpet, I could swap the 24 tooth gears for 40 tooth gears very easily which would give it even more driving power but at a cost to speed.

On the day
George was a huge success with the members of the public. Most people did not realise it moved and so jumped quite a bit when they realised it did. This was very funny except for the odd small child that got rather scared. People even started taking pictures next to it and a few people felt compelled to try to hug it or shake George’s robotic hand.

Issues
Issues were a minimum really.  After transporting George in more pieces than I hoped, I had to do a small tweak to the neck as the gears were slipping. Sadly I only had red technic with me for another one of my models and so it looked a little odd if you saw George from behind.

The main body bearing, as shown below just did not work on the day (well 2 days).  I am not sure why it worked at home and then stopped but I could only get it to turn 1 way.  Also the footballs kept falling out! I have since swapped them out and made a better version using wheels.

The only other issue which, to be fair, I already knew about, were that the large linear actuators (x3) in each shoulder joint made horrible noises (the built in clutches) and sometimes got jammed. Lego have made improvements to these actuators, but I have not got the newer version yet. I did try using pneumatics for the shoulder but that gives you little control.

The Future
I have already started work on 2 more large robots for next year (while also keeping George).  The first will be called Wheeler and is a giant wheeled robot. The start of it can be seen below.

The second robot will be based on Bob (T1) but avoiding all of the downfalls of it. I am looking forward to seeing people’s faces when there are 3 giant robots running around.

 

It started with BOB (T1 v1)

Posted on by burf2000
One of the robots that really fascinated me that I thought I could build was a T1 from Terminator 3.  It was a tracked robot with twin mini-guns (another thing I wanted to build).  So I went about building a rather large Lego version for the 2010 Great Western Lego Show which is our club’s (Brickish) largest event.
My first giant robot based on T1
More pictures can be found here:
Bob Flickr Stream
Bob suffered from a few major issues.

Weight
Due to its weight (well over 20KG) it could only turn on low friction floors.  The base of it was nearly a meter square running double tracks each side powered by 4 XL motors (directly linked to sprockets). Going forward was very quick but turning just did not work well. I only actually found this out on the day of the show where I discovered the floor was anti-slip carpet.

Communications.
The robot had very clever communications in my opinion. It used 4 NXT’s (2 slave, 2 master)  which communicated via bluetooth. One set of NXT’s had an accelerometer which when moved, would move one of the robots arms so that it would mimic the users moments. The other set of NXT’s also had an accelerometer to control the other arm however it also had a mode button so that you could control the robot’s other functions (moving, body rotation and lift, head movement) via the same accelerometer but in different modes. Each master NXT also had a fire button to fire the Zamor launchers on each arm.
The problem was that the bluetooth communication just was not stable enough and also suffered from lag and loss of data. You would put it in arm movement mode and it would instead move the tracks. There there would be a large amount of lag which meant the robot was always a few seconds behind. In practice, this caused the robot to drive itself in to a table 30 minutes after the show opened causing a partial rebuild in front of many people!  Quite embarrassing.

The robot also had a large main body beam (around 4ft long) that had to be counter balanced via many boat/train weights which caused even more weight issues. This main beam actually snapped a few technic beams while it was being built. The main beam could rise up via 5 pneumatic rams. However it required over 30psi to start it off (see below). This caused other issues.

I also completely covered Bob in black plate, which had a habit of falling off and also added more weight.

The Lego Pneumatic Beam Engine

Posted on by burf2000

A great love of mine, is to build Lego pneumatic engines. If you check YouTube you’ll see that tons of other people also enjoy building them. It’s like building a real engine but running it off of compressed air. When I was little I used to go to Steam Rallies and Steam has always interested me.

So after playing around I managed to build a working pneumatic beam engine.

 

This is one of my favourite mocs, I can watch it for ages. It can be a bit temperamental, though.

 

Random Pneumatic Creations

Posted on by burf2000

As mentioned in my Beam Engine post I have always been interested in Lego Pneumatics. Over the years I have made some creations which I thought I would share with you.

One of the first things I tried to make was a motorized pneumatic switch using an old style 9v motor. It uses the spring from the Lego Technic hockey players to re-center the value.

I also had a go at making my own pneumatic single piston engine however, I went a bit further and build a Lego compressor to power it. This was great fun!

After the beam engine (post found here) I had a go at making a pneumatic train that works like a real steam train. This requires a lot more pressure than the single piston engine above however does not require a flywheel.