Tribot swerve

[Gdeaver]

With the 2014 perimeter change from a fixed dimension to a perimeter specification a tribot is no long such a disadvantage. So we made a tribot swerve. Last meeting the mechanical students put the robot together and last night the programmers got code on the robot. Its crab only now. Need to work on the chassis rotation part. Here's a video.
https://www.youtube.com/watch?v=Cs8KWuuUWJY

So what do you think? What are the advantages and disadvantages of tribots? Are we foolish? Anyway I proud of the effort the students put into this. They really worked together well and accomplished this fast.

[Aren Siekmeier]

Originally Posted by Gdeaver

With the 2014 perimeter change from a fixed dimension to a perimeter specification a tribot is no long such a disadvantage. So we made a tribot swerve. Last meeting the mechanical students put the robot together and last night the programmers got code on the robot. Its crab only now. Need to work on the chassis rotation part. Here's a video.
https://www.youtube.com/watch?v=Cs8KWuuUWJY

So what do you think? What are the advantages and disadvantages of tribots? Are we foolish? Anyway I proud of the effort the students put into this. They really worked together well and accomplished this fast.

In my opinion all teams with a swerve history should be seriously considering this. 16 did it with success for a long time even before the new frame perimeter rules since 2013, and now I feel like there's even less reason to go with 4 wheels. The flexibility in number of wheels and wheel placement inherent to swerve means you're not limited to an approximately rectangular drive base (this can be stretched a la 971). I think one could find a lot of benefits to navigating the field using a frame more closely approximating a circle. Or you can go for a triangle to maximize stability. 3 is also a factor of 6, which happens to be the number of CIMs available for the last two years... (no such luck with 4 drive modules).

I've been entertaining lots of different possibilities for a drive and frame setup like this, considering the possible advantages. 2175 is in no position to go swerve, but different frame perimeter tweaks could still be possible with a WCD.

[g_sawchuk]

Well, based on the video, the tribot on swerve allows some very advanced maneuvering that could easily get around defense any day. However, defense wise I feel that a tribot would be a push over. Also, it does minimize the amount of space for a shooter, intake, etc. I could see this totally being awesome for a team like 1717 in the 2012 game, Rebound Rumble. With a 3 sided intake and an on top, rotatable shooter I think it would have been even better then it already was (which in my opinion is saying something). This year with a large game piece I could see it being slightly impractical, but in other seasons with smaller game pieces it could work. Teams would also need to focus on weight because an unbalanced weight on a tribot would definitely doom it when hit right. However, super cool video and thanks for sharing!

[Blackphantom91]

https://www.youtube.com/watch?v=vHe4MU3x3As I think there is always advantages to different types of drive trains each year. It's just a matter of getting it to work. Your swerve iteration is coming along very well though.

[pntbll1313]

When a 3 wheel drive robot locks up in a pushing match isn't a large amount of the force on the single back wheel? In which case it could have significantly less pushing power than a 4 wheel swerve driven with the same number of CIMs per wheel. (I realize swerve robots generally don't need to get into pushing matches, just curious as to how it would work)

[Lil' Lavery]

Originally Posted by GrifBot

Well, based on the video, the tribot on swerve allows some very advanced maneuvering that could easily get around defense any day.

In what way is that different from a four-wheel swerve?

Originally Posted by GrifBot

However, defense wise I feel that a tribot would be a push over.

Why?

[g_sawchuk]

Originally Posted by Lil' Lavery

In what way is that different from a four-wheel swerve?


Why?

Well, depending on how you're angled, it would be ideal to have one wheel closer to the front for steering/direction instead of two, with the back two acting as speed and stability. With one wheel upfront you should be able to turn smoother/faster.
Well, having a 3 sided bot would expose more area for a defensive bot/offensive bot to hit the bot in the corner to knock a shot off target as a triangle is essentially based off of 3 corners, not 4 corners with "flat space" in between that would do very little when hit. In short, the tribot is more exposed when it comes to being hit effectively.

[Andrew Schreiber]

Originally Posted by GrifBot

Well, depending on how you're angled, it would be ideal to have one wheel closer to the front for steering/direction instead of two, with the back two acting as speed and stability. With one wheel upfront you should be able to turn smoother/faster.
Well, having a 3 sided bot would expose more area for a defensive bot/offensive bot to hit the bot in the corner to knock a shot off target as a triangle is essentially based off of 3 corners, not 4 corners with "flat space" in between that would do very little when hit. In short, the tribot is more exposed when it comes to being hit effectively.

Who said number of sides was dependent on number of wheels?

[g_sawchuk]

Originally Posted by Andrew Schreiber

Who said number of sides was dependent on number of wheels?

True. I was just basing it off of the fact that this one had 3.

[frasnow]

Neat design.

Just be careful your shape doesn't fit into one of the game elements like when Rosie stuffed Thrust into the goal in 2010.

[BBray_T1296]

Originally Posted by frasnow

Neat design.

Just be careful your shape doesn't fit into one of the game elements like when Rosie stuffed Thrust into the goal in 2010.

I know this is off topic, but look in the thread in the quote, watch the video first, then proceed to read the comments of the thread talk about how aggressive and uncalled-for the defense was, then fast forward to this year. Kinda funny I must say

[JohnSchneider]

Just remember. More 3 wheel swerve robots have won worlds than mechanum.

[g_sawchuk]

Originally Posted by JohnSchneider

Just remember. More 3 wheel swerve robots have won worlds than mechanum.

Because that means a lot.

[asid61]

Originally Posted by JohnSchneider

Just remember. More 3 wheel swerve robots have won worlds than mechanum.

IMO, a well-designed swerve drive will beat a well-designed mecanum drive. However, mecanum wheels have only been widely available for a few years in the FIRST community, so you have to give them some time.

[Ben Martin]

Offhand, I can think of a few considerations:
- Looks like the side length would be ~37 in. for an equilateral triangle. This could make passing through a 36" door difficult if the bumpers are on (we have a hard time doing this with 28" robots with bumpers as is)
- You have ~23% less total volume available to you with the triangle configuration than the square configuration (with maxed out dimensions and an equilateral triangle).
These two items would dissuade me from pushing it in most cases, but in a game where space constraints are not an issue and you need wide pickups, I could see this configuration being useful.