AndyMark AM14U Chassis Error?

Hey guys, this is my first post on Chief Delphi and I’ve got a question concerning the chassis included in the KOP, the AM14U. We got it on Thursday (we’re from Chile, so we get things later :frowning: ) and built it the same day. We also got the basic electronics mounted and programming on the cRIO, so we started driving straight away. We tested it and found out that the frontal wheels were slightly lifted up from the ground. So our CAD subteam sketched the chassis in Inventor based on the files from the AndyMark webpage and realized that the ToughBox shaft was 0.14" higher than the center of the outer wheels. Is this a design error, or is it intentionally designed in that way?

Yes, it has a dropped center drivetrain to make turning easier.

It was intentionally designed that way to allow it to turn about a point. All six wheels on the ground would have caused lots of friction potentially stopping you from rotating.

It’s intentionally designed that way, if there wasn’t a “center drop,” a six wheel drive with just rubber wheels wouldn’t turn very well if any at all.

Hey. Welcome to Chief. This design is intentional. The center wheel is dropped for turning; instead of attempting to go in a circle on a dime with 6 wheels, there are only 2 attempting to spin on a dime when you turn quickly. This is what’s known as “West Coast Drive”.

Your front and rear wheels should be slightly lifted from the center ones. this allows for turning with 6wd. It’s awesome that you already have a driving chassis!! Great job!:smiley:

I think it’s designed that way. 6WD with a lowered center wheel is a very typical drivetrain–it gives better maneuverability than having 4WD with the wheels on the corners. Every Kitbot I can think of has had a dropped center wheel as an option.

If that doesn’t suit you, you could remove the center wheel on each side; however, that may result in difficulty turning.

Its intentional, it allows you to turn the robot easier. If all the wheels were at the same level, turning would be extremely difficult due to wheel scrub.

EDIT: Wow, 6 responses in the time it took me to type this. Welcome to CD. =P

Be sure to test on carpet. The friction is quite different, causing flat robots, especially long ones, to be unable to turn without tripping breakers.

Greg McKaskle

Thanks everyone for the quick answers!!! Our mechanical team was quite surprised, but now we know how these drives really work! :eek:

If you ever want a bit of entertainment, build a long 4WD base with traction wheels and try turning it, fully weighted, on carpet.

It’s not a pretty sight.

In 2012 we ended up with 4WD base with 10in pneumatics and a gear ratio that was to high along with max weight, it wasn’t pretty. :eek: