Pros and Cons of A Transmission Design

VEX Robotics Competition Discussion VRC > Starstruck (16/17)
1

Hi! I am designing a dumper for the Starstruck competition, and I am having trouble deciding whether or not I should use a transmission this year. The idea is that I use 6 motors for the drive, but also have the motors be able to power the lift, which is accomplished by the transmission. However, I am also debating if simply using 4 motors for the drive, and 4 motors for the lift is the better option.
**The Disadvantages of Transmission ( as far I can tell):
**1. Cannot drive while using the lift so we sacrifice flexibility in matches
2. More Complex ( some of my team members are relatively new to Vex)
**The Advantages: **

  1. Save motors for other systems (intakes etc)
  2. More speed in drive (not too sure about this, I am assuming that using 6 motors will give the drive more speed compared to 4 motors)
  3. More torque in lift ( similar logic to above)
2

I would not do it because:

  1. It will be really complex
  2. it will create a lot of friction and drastically reduce the energy efficiency of your robot
    3.the ability to use the dumper and drivetrain simultaneously is crucial due to the severe time constraints, also switching gears will take time
  3. what do you need those other motors for really? the stars and cube are too big to be using a motorized intake, a simple scoop will work great
3

@Mr.Constructor
Thanks for the feedback! The first 3 points were extremely helpful, and I needed some advice from someone with experience. However, number 4 may not be true. I see some potential in side rollers this year.
Here are some links to side roller videos
https://vexforum.com/t/reveal-albas-open-source-starstruck-robot/35945/1

Note: This isn’t a side rollers conversation. Please keep this post relevant to transmissions.

4

I really don’t think a transmission is useful this year in the manner that you want to use it. It sounds like you would need to use pneumatics, in which case you lose the 2 motors, which I honestly believe is crucial this year. I know that other people have already said it, but efficiency is key and you sacrifice that when you can’t drive and lift at the same time.

(As an added note, IMO side rollers aren’t as efficient either because of how long they take to dump their load)

5

I agree with the previous posters that the transmission you’ve proposed doesn’t sound like it will be super effective. However, not all hope is lost for a transmission - one idea we considered but ultimately decided against was to use a transmission for our hanging mechanism. In that case, you could transfer your dumper/catapult’s motors to power your hanging mechanism at the very end of the match, and thus get a pretty fast hang with the power of 4/6/8 motors.

6

I considered that also.:wink:

7

We are using a transmission for the catapult with a 27:1 gearing and we are able to drive and lower it.