Effective Drive Base

[Akash Rastogi]

Originally Posted by Ram Raman

Would four wheel drive be effective, would it be able to make it over the bumps, how would the turning be?

The kit bot rolls over the bump with ease because of the large wheels, it does not bottom out on the top of the bump. However, turning with 4wd is a pain. The robot "jumps" as it counters the friction while turning with skid steer.

[=Martin=Taylor=]

Originally Posted by Akash Rastogi

The kit bot rolls over the bump with ease because of the large wheels, it does not bottom out on the top of the bump. However, turning with 4wd is a pain. The robot "jumps" as it counters the friction while turning with skid steer.

Actually, the kitbot does not roll over the bump with "ease". The tough-boxes bottom out on the top of the bump, and unless you are moving with speed you will get stuck there.

I’ve confirmed this both in CAD and testing.

Of course you can mount the T-boxes on top of the frame, and solve this problem.

Interesting design feature AM...

[Akash Rastogi]

Originally Posted by =Martin=Taylor=

Of course you can mount the T-boxes on top of the frame, and solve this problem.

That's how we have them set up. I figured teams would have figured that out when trying out the kit base. Also, the kit base's "slick wheels" help a bit with turning the 4wd.

We are most likely going with 8 with the front sets raised slightly, I think it will be a common design among experienced teams.

[Al Skierkiewicz]

Originally Posted by =Martin=Taylor=

Actually, the kitbot does not roll over the bump with "ease". The tough-boxes bottom out on the top of the bump, and unless you are moving with speed you will get stuck there.

I’ve confirmed this both in CAD and testing.

Of course you can mount the T-boxes on top of the frame, and solve this problem.

Interesting design feature AM...

Try mounting the transmissions on top of the chassis.

[Sean Raia]

Could 4 wheel crab steering make it over the bump?
Our team is looking into either that or standard 4 wheel skid steering.

[Taylor]

I would love to see a version of 2004-71 style swerve.

[Collin Fultz]

Originally Posted by Taylor

I would love to see a version of 2004-71 style swerve.

Is this possible with the BUMPER ZONE rules as they are? Would articulating your wheels change your BUMPER height?

[Chris is me]

Originally Posted by Collin Fultz

Is this possible with the BUMPER ZONE rules as they are? Would articulating your wheels change your BUMPER height?

This is the reason I ruled it out as a possible design. Bumpers ruin everything.

[Al Skierkiewicz]

We need to remember that the bumper zone is elevated this year, 10-16 inches above the floor when on a flat surface and may not be articulated.
8.2 DEFINITIONS
BUMPERS – Bumper assemblies designed to attach to the exterior of the ROBOT within the BUMPER ZONE, and constructed as specified in Rule <R07>. BUMPERS are excluded from the weight and volume calculations specified in Rule <R10>.

BUMPER ZONE – the volume contained between two virtual horizontal planes, ten inches above the floor and sixteen inches above the floor.

<R07>
A. BUMPERS must provide complete protection of the entire FRAME PERIMETER of the ROBOT (i.e. BUMPERS must wrap entirely around the ROBOT). The BUMPERS must be located entirely within the BUMPER ZONE when the ROBOT is standing normally on a flat floor, and must remain there (i.e. the BUMPERS must not be articulated or designed to move outside of the BUMPER ZONE).

If one uses 6 inch wheels, then the drive assembly would need to be a good distance behind the frame perimeter for any bumper to interfere with climbing. (The top of the bump is 12 inches high but also 12 inches set back from the base) This does not appear to rule out any type of drive system that would take into account the shape and height of the bump. As to whether a crab drive would succeed on the bump over a different drive system is up to the team to prototype and then make a decision. As is discussed in several other places, high center of gravity seems to be the more important issue if choosing to climb the bump. Considering all of the factors summed together, it appears to be a considerable challenge to design a robot that both climbs over the bump or drives through the tunnel.

[CHapstack]

My team has been doing some testing to see which drivetrain handles the bump best when driving over it at an angle (we assume that we won't be able to hit the bump perfectly straight every time). We have prototyped a few ideas, including 8WD with raised end wheels. Has anyone else considered how their drivetrain will work when driving over the bump at an angle (or if their robot gets hit when driving over the bump)?

[Brandon Holley]

Originally Posted by Al Skierkiewicz

<R07>
A. BUMPERS must provide complete protection of the entire FRAME PERIMETER of the ROBOT (i.e. BUMPERS must wrap entirely around the ROBOT). The BUMPERS must be located entirely within the BUMPER ZONE when the ROBOT is standing normally on a flat floor, and must remain there (i.e. the BUMPERS must not be articulated or designed to move outside of the BUMPER ZONE).

If one uses 6 inch wheels, then the drive assembly would need to be a good distance behind the frame perimeter for any bumper to interfere with climbing. (The top of the bump is 12 inches high but also 12 inches set back from the base) This does not appear to rule out any type of drive system that would take into account the shape and height of the bump. As to whether a crab drive would succeed on the bump over a different drive system is up to the team to prototype and then make a decision. As is discussed in several other places, high center of gravity seems to be the more important issue if choosing to climb the bump. Considering all of the factors summed together, it appears to be a considerable challenge to design a robot that both climbs over the bump or drives through the tunnel.

Heres my problem with the rule...when your robot negotiates the bumps, or hangs from the bar, your bumpers will no longer be in the bumper zone. Thus aren't you violating R07?

[Tom Line]

Originally Posted by Akash Rastogi

The kit bot rolls over the bump with ease because of the large wheels, it does not bottom out on the top of the bump. However, turning with 4wd is a pain. The robot "jumps" as it counters the friction while turning with skid steer.

Try actually adding some mechanisms to that kitbot frame. The COG is so high that it gets scary pretty quickly. We've done a lot of testing the last couple days, and 6 wheel bots long, 4 wheel bots wide, and even 6 wheel bots wide are all pretty darn scary on that bump - the smallest twitch makes them flip over. We're moving on to more exotic drive systems =). You absolutely CAN NOT decide on a drive train without at least building a small trial-bump to play with and see how your bot is going to react.

[MrForbes]

Originally Posted by Tom Line

6 wheel bots long, 4 wheel bots wide, and even 6 wheel bots wide are all pretty darn scary on that bump

We didn't test any of those, our first prototype is 8wd. I sure hope it works! We had to figure out what wheels to use on it, then order them, so we won't have it going for a couple more days

[MrForbes]

We put some old 6" rover and Bayer kit wheels on the 8wd chassis, and rolled it over the bump (human powered, not motor powered)....looks pretty good so far. Nothing too scary.

Hopefully we'll get the drivetrain and electronics going and drive it over by Friday.

[M80]

I think that treads provide too high a probability of falling off the bot on turns. I think the grip wheels that came with the kit are the best option