# Team 1727B presents Sekhmet

here is a summer reveal for our nothing but net robot -Sehkmet

we have also made a video going over all the parts of our robot in detail, and one going over the physics we used to design our robot

Enjoyed the music, lighting, & smoke/fog

The drive is an interesting choice

What drove you (no pun intended) to choose the banshee drive over the holonomics that most teams (ourselves included) are using?

Banshee? What is a banshee drive? I’m sorta confused.

In the video they called their drive a banshee drive. It has 4 mecs and 2 traction wheels

I know its the obvious question that everyone is thinking about, so I just gonna ask it. ELEVATION?

Also, why didn’t you build the robot to hold 4 balls at once? How hard would it be for you guys to modify that?

What is the motor distribution for your drive? There are 6 wheels and 4 motors…

I noticed that in one of the demonstrations of the intake mechanism the ball didn’t go up the center. Are you working on this problem? How will that affect the entrance and trajectory of the launching?

ok, so the “bashee” drive, is actually and innovation we stole from our FRC team, as far as I know our FRC robot in 2014 was the first to use that drive, and so the head of our drive and chassis team at the time named it the banshee drive because it “turned like a banshee(demon)” as explained in one of the other videos on the channel, the banshee drive is unique because the way we lay out the wheels, when we turn, the vectors form a perfect box. We could not strafe laterally with this wheel lay out, but the arrangement allows us to turn with 100% of our drive power. Because we cannot strafe, we add the traction wheel in the middle to aid with traction. This drive can turn with more force than any other drive, in a standard traction wheel drive, the only thing that drives turning is the fact that the wheel vectors are off-set, in this drive, the actual rotation of the wheel gives power, so with this drive, we can out turn/maneuver any convectional drive, and out push and holonomic drive

we do have plans for elevation, at this point that consists of a ramp of the front of the robot, we would pull robots up it with a hook and winch, and then raise the plate with pistons

we are working on holding four balls at once, the robot is very compact so we are looking at ways to make that happen without having to raise the shooter into the air and build a support structure for it

yep four motors 6 wheels, the back two wheels are chained together

as for the offset ball, yes we will fix that, the plates show into the video will be extended upward along the ramp, however the ball being off center does not actually effect trajectory in a major way, if the ball hit one wheel first it will start to spin, so it’s velocity relative to the other wheel is greater, so the other wheel puts more force into the ball, canceling out the spin

in a standard mecanum drive, only 50% of the force from wheel rotation goes into the forward direction, or goes sideways when strafing, the addition of the traction wheel put more force directly into the forward direction, because all of the force from that wheel goes directly into the forward direction. It also stops slipping or free spinning problems inherent to mecanum or Omni-wheel drives.

In terms of turning, the robot pivots around the traction wheels, which provides a good stable turning point. the mecanum wheels unlike a standard drive, put force directly into turning, where in a standard drive, only the offset wheel forces drive turning.

does it turn quite as well as a mecanum drive? no

does it have as much direct power as an all traction drive? no

but it provides a very good balance between the two, it is also more stable than a standard mecanum drive

Almost nothing you just said in your most recent post is correct.

how so, the drive does have advantages from each of the drives to borrows from, it also has some disadvantages, it a balance between two drive designs

And I thought there was no drive worse than the hipster drive.

the drive works, and it works well, our drive was one of the best in the 2014 regional we attended in FRC, and we are happy with how the drive is preforming for vex

The drive doesn’t really take the advantages of either drive, just the disadvantages. You are gaining basically no force in the forward direction from the middle wheels and you lose both the strafing and turning capabilities of the mecanums. In addition, placing extra wheels in the middle of a mecanum drive will not increase the stability.

I think you will find a lot can be done in FRC that can’t be done as well in VEX (I mean, have you seen 118?)

Oh, you should try a normal tank drive, it performs really well.

hehe I see what you did there

The addition of a traction wheel does increase both traction(which by extension increases the amount of force the drive can apply. having 6 wheels as opposed to four does give us a more stable platform

the physics of how it works are the same, just different scales

while a tank drive would have more power it has less turning ability and maneuverability

wat. (10 char)

I think what everyone is trying to say is there is no reason to over-complicate the drive train, the part you want to be simple and reliable. A “regular” tank drive could do everything your drive system currently does.

and different parts