We continue from part 3 where we finished part of the 'rear'. Power is transfered from a motor to the wheels but having about 16 gear wheels makes it more than complex for this LEGO Mindstorms EV3 Competition robot.
- 01 Mar 2015
The robot is constructed with a 'front', 'back' and a frame in between. In this video lesson we are working on the 'back' (also called 'rear' part when it comes to vehicles). Power is transfered by a differential to both wheels and more then sixteen gear wheels are used. It is interesting because the gears are placed on a triangle. However, due to the large number of gears there are many gaps, friction and loss of power which makes the whole transfer inefficient .
The Gear System
Continuing from BigDaddy Competition Robot (Part 3 - Front to Rear) we transfer power from a motor to a Mindstorms differential which then rotates a system of gears which finally transfers the power to the wheels.
We construct, experiment and post. You give us feedback and based on the feedback we make modifications on the robot. So, build it with us on the way, try to take up a specific challenge with it and leave us a comment below on what has and what hasn't worked for you in this robot.
Yes, we have watched the Marvel 'Kick Ass'. And yes, this robot will be big and angry.
Other episodes from the series:
Attaching motors is the task for this robot. Why? - actually transfering power from the motors to the wheels is challenging for every robot. Use the task in your classroom, for your team or at home to engage students in learning.
There are 3 task from an normal, medium, hard complexities giving 1, 2, 3 points respectively
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In the previous episode we finished with constructing part of the rear part of our new competition construction and we added the differential gear. In this video we are going to transfer power from the differential gear to the wheels. I've again chosen to use the large wheels And I've already constructed one of the wheels and now I'll walk you through adding the other wheel and transfering power from the differential gear to the wheel.
Again, the construction is rather complex. It involves one, two, three, four, five, six, seven gear wheels. And not even including the differential gear. Let's try to transfer some power from the differential gear to the wheel. Imagine that the motor is attached right here. So, I'm turning the motor and we can see that the wheel is turning. And the ratio between the driving and the driven wheel is approximately 1 to 4 or 5. Now, let's try to attach the other wheel. I would like to attach the wheel to the frame, on the lower part of the frame. But it's kind of difficult to transfer power from the gear wheel to the wheel because the distance between the wheel and the gear wheel is 8 Lego units. The frame has 7 - one, two, three, four, five, six, seven. And there's one more Lego unit, since the axle is attached one unit above the frame. It's difficult. For that reason we've come up with a solution that involves transferring power in a triangle. So, we are going in this direction and then return to the axle. I had several options for this video. One of the first options was to just take a notebook and start explaining the different theorems for applying geometry. But I'll skip this and I'll show it in one of the next videos. In this video I will just show you an example and you'll have a link to a specific video about the geometry of the Lego parts below this video. Now, let's begin the construction step by step. First, I have this kind of a complex construction that is a triangle. So, I have it in one direction and I have an angle here for the other parts. How do we add this? First, it's rather complex - again.
One part here and the other one here.
OK. Then we need to add some extension to the frame.
OK. We have the gear wheel which transfers power from the differential gear to another small gear wheel. Right here, below the construction. Then we add this angled beam.
Let's try this.
These are parts that are very difficult to access; very difficult to attach.
So, you might be wondering why we are doing this. Because that was a nice, interesting experiment that we did. And we proved it wrong. In the end, it turned out to be very fragile.
What do we have now? We have the gear wheel transferring power from the differential gear to a small gear wheel. Then to another black gear wheel and then to this grey gear wheel. As a last step, we need to introduce three more gear wheels. The first one goes right here.
Then the small one.
And as a result we have the wheel.
Voilà! We have the wheel connected to the differential gear. And we have the other wheel connected to the differential gear. And we can transfer power from the differential gear to the wheels. It's kind of difficult. We need to have some very powerful motor for this. Let's again count the number of gears. We have one, two, three, four, five, six, seven gears from the differential gear to the wheels. And because of the many gaps in the construction, because of the difficult construction that involves transferring power from the differential gear to the wheels in a triangle, as you can't do this in a straight line, it turns out the construction is not very appropriate for our new competition robot. It's very easy to start the robot; it's kind of difficult to stop it. We have the power but once the robot is turning it will be very difficult to stop it. So, one thing that you should always consider is to put down your ideas and try to implement them in the new, more appropriate way; in a more beautiful way. And this is something I would like to do in the next video - try to remove this construction and replace it with something that is much more beautiful.