Pitfalls of having a "wide" robot?

[wilsonmw04]

Because of various design issues and the "80 inch rule," we are thinking about turning our frame side ways and putting the drive wheels on the short axis. We are looking at a frame 36" wide by 26" long. With a far shorter wheelbase, are there going to be problems with turning something this wide. is there a disadvantage to powering all four wheels?

[MrForbes]

Having a wide 4 wheel drive skid steer robot makes for easier turning than a narrow one.

But it affects how easy it is to tip over....look at the distance between where the wheels contact the floor. With a normal configuration, this distance is similar for both directions, while a wide robot has a very short wheelbase, and is much more likely to fall over if bumped near the top, especially if it's top heavy to start with.

Some teams have used this design with an extendable "wheelie bar".

[Travis Hoffman]

Originally Posted by wilsonmw04

Because of various design issues and the "80 inch rule," we are thinking about turning our frame side ways and putting the drive wheels on the short axis. We are looking at a frame 36" wide by 26" long. With a far shorter wheelbase, are there going to be problems with turning something this wide. is there a disadvantage to powering all four wheels?

If anything, turning will become much easier due to the shorter wheelbase. Assuming your wheels are standard "grippy" wheels and you power all of them, it's easier to turn a wider robot with this configuration than it is a longer bot.

However, you must consider other drawbacks to using a wider design - first and foremost, how stable will you be if you have an arm that reaches high in the air? Remember, you should also consider external bumper zone forces from other robots in your design. If "tippiness" is a problem, you may choose to incorporate a simple extendable wheelie bar in the front and/or back of your robot (can be as simple as a pneumatic cylinder pointing at the ground with a PVC endcap attached to the end of it - 48 did this in 2003 to stabilize our short wheelbase robot and minimize the risk of tipping over when driving up the ramp).

You must also consider that you will be a "wide load" when driving around the track - you will take up more track width and are therefore more likely to block traffic - you are also more likely to be blocked by other traffic, as you aren't as easily able to squeeze through tight spaces.

[wilsonmw04]

thanks for the replies. We have ditched the arms this year and going for a low profile machine. The tallest part of the robot will be the top of the ball. I was concerned with the power needed to turn and the "jumping" while it skids. You have put them to rest. thanks again.

[Mr.Rush]

yet another team opts for a push bot speed demon....our paper weight is doomed ^-^

[Daniel_LaFleur]

Originally Posted by wilsonmw04

Because of various design issues and the "80 inch rule," we are thinking about turning our frame side ways and putting the drive wheels on the short axis. We are looking at a frame 36" wide by 26" long. With a far shorter wheelbase, are there going to be problems with turning something this wide. is there a disadvantage to powering all four wheels?

Driving 36" wide will make turning a lot easier. In addition, it will make the robot less tippy while turning. You will need to take care because you will be tippy while accellerating. If you have problems while accellerating, I'd suggest a wheelie bar or moving some heavy objects within the robot forward in the chassis.

We are driving wide this year as well, and we've had excellent success the last 2 years in this configuration.

Powering all 4 wheels is generally recommended as well as running chains between them, although this will add a lot of weight to your drivetrain. This gives you good pushing power and accelleration. If you use grippy tires you should be able to corner well in this configuration.

[Tytus Gerrish]

the further corners are from the center of the bot the more leverage you have to push it arround.

you can't get more extreme than this when it comes to wide robots

[wilsonmw04]

Originally Posted by Mr.Rush

yet another team opts for a push bot speed demon....our paper weight is doomed ^-^

We aren't pushing, we're grabbing :-)

[Rosiebotboss]

Originally Posted by wilsonmw04

thanks for the replies. We have ditched the arms this year and going for a low profile machine. The tallest part of the robot will be the top of the ball. I was concerned with the power needed to turn and the "jumping" while it skids. You have put them to rest. thanks again.

The tallest part of your robot should be the top of the flag holder at 51 inches per <R017>.

http://www.usfirst.org/uploadedFiles...Robot-RevC.pdf

[wilsonmw04]

Originally Posted by Rosiebotboss

The tallest part of your robot should be the top of the flag holder at 51 inches per <R017>.

http://www.usfirst.org/uploadedFiles...Robot-RevC.pdf

I always forget about that when talking about the Robot. You are right and it is the tallest portion of the robot.