Vex Clutch Ulterior Use

VEX V5 General Discussion Technical Discussion
1

In an effort to brace some cantilevered axles, I have found an ulterior use for the Vex clutch. Here is an excerpt from our design notebook:

In my efforts to find a way to brace the cantilevered axles in my transmission, I came to an ulterior use of the plastic overdrive clutch Vex sells. To understand my solution, one must first understand the way the Vex clutch works.

The clutch consists of seven parts: major housing, minor housing, compression spring, geared o-ring, geared axle holder, two posts. The major housing connects to one axle. The minor housing mates into the major housing. These housing components are secured together with two posts on either side. Inside the minor housing rests the geared axle holder, which features a slot for an axle and upward facing gear teeth. Above this lies the geared o-ring, an o-ring shaped part with downward facing gear teeth and two plastic keys jutting out of either side, both of which interface with the major housing. The gear teeth on these two components mesh. Above these two components is the spring, which forces these components into each other, increasing the stability of their mesh. On the outside of the assembly, two posts enter the major housing, pass through the minor housing, and exit the major housing, acting as keys to keep the assembly together. When the clutch makes a “clicking” noise, the gear teeth on the o-ring and the gear teeth on the axle holder pass over each other and slightly round off, before being forced back into a mesh by the spring above them.

I have modified the Vex clutch to change its behavior. Instead of “giving way” when too much rotational force is applied, the clutch now allows free rotation of both engaged axles. I have done this by flipping the o-ring so its downward facing gear teeth now face upwards, by shortening the compression spring, and by lubricating all the internals. Now, when two engaged axles rotation with different speeds, the axle holder’s gear teeth rub on the back of the o-ring, and the o-ring’s gear teeth rub against nothing. The compression spring has been left in to provide structural support for the axle holder (to stop it from rotating along both axes perpendicular to the axis along which an axle falls).

This modification will allow me to brace the cantilevered axles in my transmission because it allows me to connect them in such a way that they can rotate freely while still being connected.

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Has anybody else has the same thought? I find this to be quite useful for applications of securing axles which may turn at different speeds relative to one another.

2

I had the thought to leave it as is but, sand the teeth on the axle holder down to allow a slight force to cause the Clutch to slip. Is this legal?

3

Pretty sure it’s legal, but why?

4

I was thinking to make a two motor Differential transmission with a Pneumatic piston to shift speeds.

5

I don’t see the benefit of this…

But nice job @Octogonapus with your remake of the clutch!

6

To do somthing like this…

7

But what is the benefit?

8

Ideally, you’d have torque whenever you needed it, and speed otherwise. I don’t see many situations this year where you’d need a transmission, since you won’t be pushing your partner around usually. My team’s just gone with a 6-motor drivetrain geared really quick.

9

I wont to have a high range and a low range.

10

The benefit is that I can zip across the field vary fast and be able to slow down to a 1:1 Standard gearing.

11

The slowing down that you’re talking about could easily be accomplished with a lot of practice. Also, if you’re going fast and you suddenly slow down (non-gradually), the robot will receive a jerk, which could mess with your robot significantly. The fact of the matter is that a transmission isn’t really that useful for this year. It adds too much weight to solve something that practice can solve. The only fairly complex thing I see being used this year would be a ratchet.

12

The game field’s half the size of what it was last year (for each alliance). Thus, each alliance has less room than usual to work with on the field. While speed is still important, there really isn’t a need for transmissions this year on the drive train, or anywhere else on the robot.

13

I agree. @Inventer bots, if your goal is slowing down, all you have to do is have a button in your code that cuts your motor speed in half. This year you don’t need the extra torque provided by a transmission. You can just have fast drive and slow down your motors and you should be fine. Transmissions are educational, but beyond that they aren’t helpful this year.

14

The transmission I am talking bought, doesn’t callus the robot to “jerk”,(like a conventional transmission) because the speed of the output shaft will be varied by a sprite motor, or Pneumatics .

15

Also when the motors are slowed down (say half power) they will not run at half speed because the *voltage * is low enough that the current required can’t get to the motor. The power of a brushed motor at low speed is much lower than at high speed (a Brushless motor has constant power, the timing is what changes) . That is ware the transmission comes is to the picture, it allows the motor to work at higher speeds, giving more power while the robot moves slow.

16

I realize that. In a normal game, a transmission is used to zip around the field really fast with low torque (“power” or “strength”), then when you get into a shoving match with your opponent you switch to low speed/high torque mode to shove them out of the way. I’m saying you don’t need that much torque for this game. Your opponent is on the other side of the fence, so you don’t need to shove them out of the way. The only advantage of slowing down is that it gives more control. To do that you just make your motors spin slower without changing the gear ratio at all.

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