5572's Simple Preperation Chassis

[Rosbots]

I apologize in advance if this post in any way does not seem formatted correctly. I am usually not the one to construct threads and posts. This post is intended to share what building practice we have accomplished in the past couple of months. Since our rookie year last year, we have striven to achieve more than we did last year, and since last year we weren't organized until January, these past couple of months have been a huge success for us.

https://drive.google.com/open?id=0Bx...UVVRDY3SUFmbFE

https://drive.google.com/open?id=0Bx...WNQSUhwcVE4ZFk

The pictures above show our practice with a long chassis. Since we used a wide chassis our rookie year, we wanted to make sure that we had enough practice with all sorts of chassis designs.


https://drive.google.com/open?id=0Bx...WFOMy1kS3VLLTQ

https://drive.google.com/open?id=0Bx...0cwc2hNOF9ha28

The pictures above show our very simple attempt at the H chassis. Since most of our pre-season effort was put into practicing on the long chassis, we did not get as much practice in on this one.

[jijiglobe]

The picture's aren't publicly available. I tried clicking on them and I need to request access.

[cad321]

It appears that your links above are private.

[Rosbots]

Originally Posted by jijiglobe

The picture's aren't publicly available. I tried clicking on them and I need to request access.

I apologize to everyone for that, I forgot to set the files to public on Google Drive before making the Thread. Hopefully it should be fixed now.

[Ari423]

What was your motivation for making the H chassis have two Colsons and two omnis? It would make the CoR be between the Colsons all the way in the front of the robot. While this would take away almost all the scrub forces in turning, I imagine it would also make it harder (less intuitive) to drive. Am I wrong?

[Rosbots]

Originally Posted by Ari423

What was your motivation for making the H chassis have two Colsons and two omnis? It would make the CoR be between the Colsons all the way in the front of the robot. While this would take away almost all the scrub forces in turning, I imagine it would also make it harder (less intuitive) to drive. Am I wrong?

I believe that would only be the case if the chassis were a 2 wheel drive, with the two motors on the Colsons, with the omni's moving freely. By using a 4 wheel drive, with motors on the Colsons and Omnis, the same force(or similar enough, not quite the same due to the different wheels) is being applied by all 4 corners of the chassis, and therefore the CoR should be somewhat near the center. I'm not entirely sure in my reasoning, so I may be wrong.

[EricH]

Originally Posted by Rosbots

I believe that would only be the case if the chassis were a 2 wheel drive, with the two motors on the Colsons, with the omni's moving freely. By using a 4 wheel drive, with motors on the Colsons and Omnis, the same force(or similar enough, not quite the same due to the different wheels) is being applied by all 4 corners of the chassis, and therefore the CoR should be somewhat near the center. I'm not entirely sure in my reasoning, so I may be wrong.

The same force is being applied front-to-back, or near enough.

However, that cannot be said for the side-to-side forces, which tend to resist turning. The end with two omnis will slide sideways far more easily, forcing the CoR towards the Colson end.

I've seen this effect used on many a robot. If you can harness it to pivot around the point YOU want it to, it can be a very useful tool. If you can't, it can cause some trouble.

[Rosbots]

Originally Posted by EricH

The same force is being applied front-to-back, or near enough.

However, that cannot be said for the side-to-side forces, which tend to resist turning. The end with two omnis will slide sideways far more easily, forcing the CoR towards the Colson end.

I've seen this effect used on many a robot. If you can harness it to pivot around the point YOU want it to, it can be a very useful tool. If you can't, it can cause some trouble.

I think I see what you're saying. We'll keep an eye on it and see if we can tweak with it, but if it ends up being too much trouble, we may just end up replacing the Omni wheels. I assume that would be a good and safe alternative?

[Monochron]

Originally Posted by Rosbots

I think I see what you're saying. We'll keep an eye on it and see if we can tweak with it, but if it ends up being too much trouble, we may just end up replacing the Omni wheels. I assume that would be a good and safe alternative?

If you indeed meant H-Drive (in which a 5th omni-wheel is added perpendicular to the others in the center of the frame, then replacing your two omnis with Colsons will render that center wheel useless. Judging by your other comments though I don't think you intend to build an H-Drive, maybe it was just a typo?

[Rosbots]

Originally Posted by Monochron

If you indeed meant H-Drive (in which a 5th omni-wheel is added perpendicular to the others in the center of the frame, then replacing your two omnis with Colsons will render that center wheel useless. Judging by your other comments though I don't think you intend to build an H-Drive, maybe it was just a typo?

We do intend on building a H drive, but replacing the two Colsens with Omni wheels (I was getting wheels mixed up yesterday, my bad.), and adding a 5th Omni wheel that is perpendicular to the other 4.

[mastachyra]

We will be using Talons and Victors this year for the first time. I like the terminals you use between them and the motors. Where did you find those?

[jijiglobe]

Originally Posted by Ari423

What was your motivation for making the H chassis have two Colsons and two omnis? It would make the CoR be between the Colsons all the way in the front of the robot. While this would take away almost all the scrub forces in turning, I imagine it would also make it harder (less intuitive) to drive. Am I wrong?

Originally Posted by EricH

I've seen this effect used on many a robot. If you can harness it to pivot around the point YOU want it to, it can be a very useful tool. If you can't, it can cause some trouble.

This was very useful for many teams (mine included) in 2015. If you didn't want to pull totes into your chassis, or at least not all the way in, you could use traction wheels on the front and omnis on the back so that your center of rotation was as close as possible to the center of gravity of the stack.

That being said, as a driver who is used to center drop or something similar, it is quite jarring to get used to at first.