Big Minibots

[dodar]

Since teams have been posting pics and vids of their robots and minibots something I have been noticing as been getting to me. Why is it that alot of teams are building these huge and complex minibots? I mean teams are building minibots that look like they are maxing out the size limits near 12"x12"x12". Why build a big one over a small one? Pros? Cons?

[Jack Jones]

IDK - Because they can?

[JesseK]

Why bother to even start this conversation?

It's pretty apparent from your remarks that you already understand that others' design processes greatly differ from your team's design process.

[dodar]

Such negative posts. The reason I started the thread was to see if anyone with a huge minibot would post as to why they made theirs so big compared to a really small one

[ATannahill]

Jack and Jesse,

There are many advantages to having this kind of thread.

The original poster was asking why the decision was made for the large minibot. Do they feel that the additional weight is counteracted by something? If so what is it?

Please don't post in a thred to belittle the person asking a legitimate question.

[BKitzrow]

In fairness to Jack and Jesse, the original post was worded in a way that seemed to insinuate that a larger minibot is a terrible idea that no team should have used. As a mentor of a team that has built a larger minibot, I will say that it mostly came down to us finding a design that worked for us. Could our design be more compact? Probably, but after several design iterations that failed miserably, we are happy to have a functioning minibot regardless of its size.

[BrendanB]

A 4 inch minibot has more distance to travel to the top than a 12 inch minbot. Ours is at the max of 12 inches and can travel up much faster than some a fraction of its size and that is before lightening and speed holing!

But we are definitely not faster than 118,148,217,and 1114!

[notmattlythgoe]

Originally Posted by BrendanB

A 4 inch minibot has more distance to travel to the top than a 12 inch minbot. Ours is at the max of 12 inches and can travel up much faster than some a fraction of its size and that is before lightening and speed holing!

But we are definitely not faster than 118,148,217,and 1114!

That all depends on how close to the deployment line you deploy either of them.

[BrendanB]

Originally Posted by notmattlythgoe

That all depends on how close to the deployment line you deploy either of them.

That is true, but again it depends on where they deploy from and I have seen several deploying near the bottom.

[MrForbes]

We didn't figure out how to make a small minibot.

I expect many other teams have the same reason.

[notmattlythgoe]

Originally Posted by squirrel

We didn't figure out how to make a small minibot.

I expect many other teams have the same reason.

Just put it in the dryer for a few extra cycles. That should shrink it down nice and small.

[czeke]

Our team just sort of figured that it would be easier to try to push 5/6 pounds up the pole, instead of 12-15 pounds. We want to maximize the traction, using 2 wheels, and minimize the drag. We aren't using magnets to hold ourselves, close to the pole, because of drag. We using 2 semicircular pieces of PVC, that are connected, like a hinge and open, before deployment, and snap together, after deployment. The magnets will hold the open ends together.

[sanddrag]

Originally Posted by dodar

Why is it that alot of teams are building these huge and complex minibots? I mean teams are building minibots that look like they are maxing out the size limits near 12"x12"x12". Why build a big one over a small one?

Potential reasons:

1. Because they don't have someone who understands Physics leading the design.
2. Because they don't read Chief Delphi
3. Because they are ignorant of the world around them.
4. Because they lack the resources, or design experience to build something custom

I don't mean this post to be harsh. I lot of teams have put a lot of work into some very successful larger minibots. But as a matter of engineering and physics principals, a small and light one is the only correct way to do it, if the goal is to get to the top the fastest.

[Richard Wallace]

As a famous engineer likes to say, design is an iterative process. I've visited the pits of a few teams* that began by building larger, heavier minibots, and evolved their designs toward smaller, lighter minibots. The physics is the same, but the numbers (weight, friction, wheel diameter, gear ratio) are different. Lighter = faster, after you get the design optimized.

*One of those teams has a leader who is also a physicist, and a teacher. I am certain she did not do the design for them, but I am also certain she did not allow them to believe their first design was good enough. The advantage of understanding the physics behind an engineering problem lies in knowing how to predict the theoretical best-case result -- after you have that knowledge, iterate until your actual result is so close that further effort is better spent on something else.

[Mike Betts]

Originally Posted by sanddrag

Potential reasons:

1. Because they don't have someone who understands Physics leading the design.
2. Because they don't read Chief Delphi
3. Because they are ignorant of the world around them.

I don't mean this post to be harsh. I lot of teams have put a lot of work into some very successful larger minibots. But as a matter of engineering and physics principals, a small and light one is the only correct way to do it, if the goal is to get to the top the fastest.

I normally respect your opinion but let's look at engineering and physics for a minute...

How many of those "small and light" minibots are using limit switches rated for AC only? Answer: All of them.

From an engineering perspective, this is reckless and stupid. AC current switches through zero 120 times a second and the arc created when one tries to open a circuit is extinguished.

This does not happen for a DC current. It is much harder to switch... The arc tries to bridge the gap resulting in contact pitting and/or welding. This arcing becomes even larger when switching inductive loads (like DC motors).

To pick an example, the Honeywell microswitch in the KOP is rated for 11 amps AC only. An electrical engineer would never use it for DC currents except at milliamp (logic signal) levels. And in the extreme cases where expected lifetime is measured in thousands of cycles, never at all...

Now, you can specify DC rated microswitches but they ain't so micro...

So... We have teams who use NXT controllers and NXT touch sensors and they end up with large, non-competitive but better engineered minibots. And then we have poorly engineered but competitive minibots whose mentors have turned a blind eye to good engineering and are just hoping that they get though the season without failures setting in.

The correct way is not necessarily the competitive way...

Just who is ignorant of physics or of the world around them?

Regards,

Mike