Two motor drives?

With the emphasis on launching this year, do you think we will see robots with two motor drives?

2 motor drives are very slow, very few teams will have a 2 motor drive and they will almost certainly not be good as you must quickly drive around and pick up all the balls off the field. It also doesn’t take 6 motors to launch those balls, simple launchers with 4 motors not finely tuned can already launch across the field.

Two motor drives are possible, but if you want to play out in the field where the bonus balls are, you will probably want some speed and some ability to resist being pushed around by robots with more motors on their drives. However, if you think you can score from around your starting position and make up your losses with climbing, etc. then nobody is going to disparage your design if you win. :slight_smile:

I foresee more two motors drives to give more motors to climbing and shooting.

If you can use all the match loads and preloads into the goal from the starting area, then climb on your partner for a high elevate, you can have a ton of points without moving much.

But if your strategy is to get the floor elements, speed will be a good thing to have. Push using a non-concave surface to your goal corner and scoop 4 at a time into the low goal or load them back on to your partner who is constantly shooting at the goal.

Drives are going to be very important this year. Teams will want to be both fast and capable of engaging in aggressive back and forth.

Your drive is worth it

For my first prototype out of two, im testing different drive set ups. The first once has a 8 motor drive with alot of POT (transferring power to other places).

If you want to be a full court shooter, than a two motor drive could be an option, but I still believe for this game where the bonus balls are in the middle of the field, at least a four motor drive would be the best.

Does anyone have polar charts of speed and power as a function of the driving direction for the various drive types?

I thought it would be one google search away, but the best results seem to be pointing back to VEX: Team 80 blog, mecanum thread, motor control thread,… Those all are great resources, worth rereading, but none have actual graphs.

Ideally, there would be three plots for each drive system: speed, pushing power (active), and pushing power (resisting).

I must be using wrong keywords to search.

Edit: Actually found some

X-Drive @ AURA blog http://www.aura.org.nz/archives/1141 in this thread

What about PTOs and transmissions?

We are looking at the option of a 2 motor drive. In order to have enough motors to intake, shoot and lift it seems only sensible to give it a go.
You also need to consider that the robots this year should be much lighter without the need to high lift, so 2 motors might be ok.

I have also successfully built and won regional comps (in NZ with the Roarbotics team and Elevation game) with a 3 motor drive using a differential on the back to 2 wheels. It gives you a little more power and speed, still saving one motor.

Have you considered that this game will have a lot more physical contact than this past game? 2 motors will die instantly against a 6 or 8 motor drive.

Are you a VexU team? because a 6-8 motor drive robot isn’t going to be capable of much else in the High school devision where we only get 10 motors.

Our considerations are this with our teams designs.
2 motors for either of our launch systems.
1-2 motors for an intake.
4 motor to lift (realisitically we think we need the power to lift a robot in less than 30 seconds, with gearing and a bit of mechanics it could be done for less and maybe this is the next development for us to get back to 4 motor drive).
Current though this only leaves 2-3 to drive (depending on the intake).

As yet we don’t have pneumatics… but not sure I’d use them for a launch anyway.

4 motors dedicated to lifting isn’t a good idea. You need those motors for the rest of the match.

This is just our initial thoughts, we have only built a launcher which uses 2 motors at this stage, Robot lifting will be the last part we work on. So we will try to do it with less and use elastics or another method to get the power.

My opinion is, if there is a strategic advantage of strong pushing ability, conserve your motor and slam as many as you can on your base. I do see that knocking your opponent out of position the moment they get ready to shoot can be advantageous, and this needs some power in the base.

Plus, with most of the motor mounting structures possibly being stationary relative to base motor this year, rock on the insane transmission guys!

Skyrise is perhaps the only year in which base didn’t matter too much; Engineering division champion captain 7797C had a 2 motor base, I believe.

There are ways to lift your alliance partner without any motors at all. Creative ways to save motors are my favorite part of VRC.

Unless you choose to play the game in a different way.

Green Egg in Toss Up had a six motor base, 2 motor side roller intake, 2 motor 1:7 lift, and they could high hang in auton within 2 seconds.

Don’t say impossible so fast. It is only the very beginning of a season.

2 motor drive is definitely not the way to go. NBN is all about getting the contested game objects in your goal first, and for that you need drive speed. My b team had a 2 motor 1:1 drive for a large part of the season, and that thing would burn out even with no robot on robot contact. Just do a PTO off of the drive or the flywheel for the lift.

Is this what you’re talking about?

https://vexforum.com/showpost.php?p=358762&postcount=55

This is purely theoretical. For things like active pushing force vs. passive resisting force, you would need to do empirical tests, which are harder.

The polar chart for mecanum wheels would look similar to the one above. The function for power is the same. The functions for both speed and force have the same diamond shape as the X drive, but for both speed and force the points are at 1 on each axis.

on topic: 2-motor drive is probably fine for certain specialised robots (such as robots that mostly shoot match loads and elevate their partner). However, I don’t think launching mechanisms will require all that much motor power and intakes definitely won’t, meaning most teams should have a lot of leftover motors for their drive (even without using pneumatics). Even if your robot could function with a 2-motor drive, you will probably have enough motors that you don’t need to do it.