Chassis testing

Here is my test bed. Pushing the button makes it move forward, then another push for a full power turn and then a final pust for a full power turn.

I wanted to have geared wheels. I wanted to use all the tires and I wanted to use all the motors for driving. So I wanted to test the best configuration.

I built the geared wheels and loved them. But they are slow. Power or speed! Agility based or Strength based. I figured there are no small fast Sumo wrestlers so I decided to keep the low gearing.

This meant I needed to test out the best wheelbase for turning and power.

I built a configurable test bed that allowed me to make long and wide or short and skinny or any combination and I tested various groupings. The best one was wide and short so now I am ready to start construciting my chassis.
Long and skinny. This didn't turn very well at all.
Medium configuration was a bit better. Wide and medium length.

Wide as possible with a short wheel base. This turned the best and will be the configuration I will be using.

Testing various configurations was a great idead and I am pleased I didn't start building the first thing that I designed.

Body shape and wheels

Aim: To build a stable robot with a low center of gravity.
I attached the motors to the side of the robot brains. This gives a very low center of gravity and a wide wheel base. Looks awesome. I thought about widening it further and putting two wheels on each motor but then I'd have no wheels for the third driving motor.For the third motor I thought that if it was geared down it could be the extra grunt I need to push out the opponent. I played around with dual geared wheels and found this arrangement worked really well.

The hard part was putting the three motors together so that the read wheel could swivel because I felt that the friction of dragging the rear wheels would slow down the turning. Here is a picture of them put together but the robot is really long which must not help with the turning circle. I will leave it like this for now and do some programming but I am not happy with the length of this design and will have to revisit it soon.

Last Years Robot

So I found my box of lego and my old robot was still constructed. It has a few features that I want to repeat this year so I took a few photos.
Here is the robot I used last year. It has the flap at the front and three motor driving. The rear motor is activated when the touch sensor picks up the fact that the front has been pushed in.

The flap or scoop at the front is there for the opponent to drive onto. Thus taking away their traction.Here are the three motors. The rear one swivels to allow the robot to turn.
Last year my robot building and design worked really well. I didn't win the competition because my program was not fast enough. However I'm sure I can still improve on this design.

First Post

Well I am teaching the robot sumo unit again and have decided to produce a teacher entry into the sumo competition. My students have asked that I blog and discuss my robot the same as them so that we are all on a level playing field so here is my blog.

I have just done the paperwork for this assignment. It took about 35 minutes so asking my students to do it in two periods is not too arduous a task.
Here is the way I am thinking at the moment. I am planning on a wedge shaped robot that is low to the ground. I would like to get all three motors driving forward but not sure how the robot will steer if this is the case. I'm looking forward to dusting off the old NXT kitset and starting to build. From memory building using these posts and beams was quite a different mindset and I have been building using blocks with the kids heaps lately.