Brakes

[Ben Piecuch]

We, Team 228 have a brake on the front of our bot. It was pretty much a requirement as we're using 4wd with AM Omni's on the front. It's a fairly straight forward design, which uses a pneumatic to push a pad down onto the carpet.

If I remember correctly, it's a 4" throw, 1.5" diameter running at a full 60psi. The pad is about 1.5" x 4" long, with Roughtop belting over the entire patch. Because of the sideloads we anticipated, the friction pad is mounted to two extra shafts running in parallel to the pneumatic shaft, which will take most of the impact loading. These shafts are fed through two mounting plates and slide on bronze bushings.

The entire assembly weights in at about 4 lbs, but we had extra weight which we wanted to put low on the robot anyways. Most of the weight comes from the shafts, which are all 1/2" steel, about a foot long a piece. If we were weight critical, we would have used a much shorter throw pneumatic. This would have greatly cut down on the side loading, and allowed us to use aluminum shafts instead, or even just the pneumatic itself.

Unfortunately, we don't have any pictures. And, since it was pretty much built on-the-fly, we don't have any sketches of it either. It worked well enough to keep us positioned, unfortunately we had more trouble with our ball delivery system.

BEN

[Joe_Widen]

Our brakes dont use any motors or pneumatics and weigh 0 pounds.

Take a guess

[Bharat Nain]

Originally Posted by Joe_Widen

Our brakes dont use any motors or pneumatics and weigh 0 pounds.

Take a guess

Putting the victors on brakes or the driver him/herself?

[Joe_Widen]

Nope, good guess though.

Hint, its built in to the drive.

[Matt Krass]

Originally Posted by Joe_Widen

Nope, good guess though.

Hint, its built in to the drive.

Is it like our software brake?
The code monitors the encoders and whenever the joysticks fall within a deadband, it goes to hell and high water, and current limits to maintain those specific counts, so if we get pushed, it fights as hard as it can.

Mark McLeod can illuminate more on the subject.

[Fred Sayre]

Originally Posted by Joe_Widen

Our brakes dont use any motors or pneumatics and weigh 0 pounds.

Take a guess

Sounds like a worm drive to me

[Joe_Widen]

You are most definately correct. They work very nicely, well once we switched from 5:1 to 10:1. The only way to get us to move is by hitting us really hard.

[ahecht]

Originally Posted by Joe_Widen

You are most definately correct. They work very nicely, well once we switched from 5:1 to 10:1. The only way to get us to move is by hitting us really hard.

The only problem with that is that you are going to lose 30%-40% of your power due to the massive inefficiency of the worm and worm gear (and a more efficient worm gear would be backdrivable).

[ScoutingNerd175]

Well, it's nice to know that some people do actually have breaks. I believe we had one last year, although I knew a lot less about the robot last year (I don't think I could have answered my own scouting sheet!) but we don't have them this year because of weight. (we came in a bit over when we first weighed in).

But people give me the weirdest looks when I ask them if they have breaks while pit scouting. So thanks for proving that it's not that odd of a question!

[PEKMAN]

Team 293 is using brakes based off of 25's design:
A servo sticks a pin into a milled out gear in the gearbox.

For the ammount that they weigh, the benefit is huge. If the brakes are on, the wheels don't turn.

The only problem is that before we got the settings just right, we snapped several servo horns.

[amos229]

All i can say is surface area and 60 tread.

[UlTiMaTeP]

179 Does . They use a piston with waffle tread on the bottom

[Jay TenBrink]

We have used dynamic braking for the past 3 years. There is a potentiometer mounted on each of the two final drive output shafts of our 4 wheel drive skid steer. When another robot pushes against ours the wheels begin to turn. When this movement is detected, the controller applies power to those wheels in the opposite direction to oppose the movement. The more needed, the more is applied. This gives us enough braking to lock the wheels. If another robot has the power and traction to move us with our wheels skidding, then they will win the pushing match.

In 2002 we had pneumatically applied brakes that worked great. There were two flat pads about the size of a playing card covered with rubber belting. The back of the robot and the movable goal we were latched on to was lifted off the carpet when these were applied. Nobody was able to move us that year.

Jay

[UlTiMaTeP]

Now with the presence of, off the shelf 2 and 3 speed tranny's and 4 and 6 cim's on a drive train, it is pretty hard to not be pushed around.

[Aren_Hill]

on thurday in atlanta we (1625) put grippy tires on the back and a "foot" that rotated down in the front lifting up our omniwheels making us practically unpushable but a few team found this out and moved us by ramming Our major weakness before nationals was getting pushed while shooting and made our accuracy terrible so when we added the foot thats what made us the #1 seed so basically sticky stuff rules