Gateway Drive

VEX V5 General Discussion General Forum
#1

What do you guys think the Best Drive for Gateway would be and why?:slight_smile:

What would the gear ratio be why?:slight_smile:

What would be the advantages and disadvantages with the drive?:slight_smile:

Thanks

#2

Personally, I don’t think that holonomic drive will be all that useful this year. The main question will be whether you intend to be mainly playing in the isolation or interaction zone. Isolation robots do not need to be fast, so perhaps 4 269’s or 3 wire motors will suffice, unless you feel the need for holomonic. But for an interaction robot, there can be a considerable distance covered; it will probably be very common to see teams with four 393’s on their drivetrain, with the high speed internal gearing. Personally, i do feel that about 1.5:1 or 1.6:1 (393’s with speed internal gears) is appropriate. But i would not like to go below 6 motor drive on a robot that is playing predominantly interaction zone, as it will be very important to be able to position yourself, or, shall we say, “deposition” your opponents.

#3

i agree on the 1.6:1 ratios
2:1 is too fast for this field setup and provides too less torque

i think there will be some torque monsters in the interaction zone that has “out of the box” features"
but for the isolation zone, a “round up” robot (motor distribution wise) would suffice

and too bad this forum doesnt have a “rep” button, i would totally have repped the OP for creating such interesting discussion! :slight_smile:

#4

Hey,

I like the idea alot because that will be adding a little speep but not alot.
Can you guys try to answer these questions

What would the gear ratio be why? Like would it be 393 high speed option (direct to motor):slight_smile:

What would be the advantages and disadvantages with the drive? Like will u be a competitve robot with this drive:)

#5

Using four 393’s is a good option, as it give you plenty of speed, and good torque for most situations. One on the benefits of doing this is that you still have six motors the other mechanisms on your robot!

Also, it is very simple to make, because, as you said, you can put the wheel directly into the motor. I;m sure many people will be successful with this this year, just like they were last year

#6

I think 6 wheel tank would be good. Simple, reliable, easy to drive, can provide a good amount of torque.

I don’t think anything with a 1.6 is very necessary though. If you had a good robot it would clear the isolation zone within the first minute forcing you to seek game pieces from the interaction zone (or to pursue some other strategy).

We’re shooting for a drive thats between 1:1 and 1.33:1. Want to limit the risk of tipping as much as possible, shorting breakers as much as possible, and have that ability to plow through the sea of game pieces (when they’re all knocked down and on the floor as seen in the first matches of this year) with ease.

#7

There is no “best”. It depends entirely on your goals and what you’re trying to do with your robot.

#8

I feel like for a change you would actually want torque over speed. Or even just use a minimal amount of motors on your drive and focus the rest on the scoring mechanism.

I believe one of the 254 teams one year had a pneumatic transmission. letting them swap between 2 different levels of speed/torque. you could do that to give yourself an isolation speed and an interaction speed. so you would be ready either way.

#9

One of the people our team planned on building a robot only has a RWD and focuses the remaining 8 motors on scoring.

EDIT: No. the robot didn’t plan for us. My bad for the early grammar mistake.

#10

I personally like driving all the wheels weather it is with gears or chain from a “central” power source or direct drive. But that’s just me…

-Andrew

#11

I agree that for most average-sized robots a 4 393 drive in speed config is probably a good option. Having less motor power generally requires a lighter robot to prevent tripping breakers, or a slower speed. 6 motors is usually good enough for everything other than drive: 4 motors on lift, 2 motors on intake. If you spread your motor power around much more, it becomes too little to do much.

I don’t feel that having unpowered wheels is a good idea because if your robot gets caught on something and only the unpowered wheels are touching the ground, you are stuck for the rest of the match unless your partner helps you.

Wheel guards are fairly vital to not getting caught up on game pieces lying around. If you have a piece of lexan or metal in front of the wheel so that you are pushing objects rather than gripping them and trying to drive over, it makes a big difference.

#12

Driving over game pieces shouldn’t be too much of a problem. They’re so large…

#13

In our experience it’s not just driving over the objects but running into them at all. I think what happens is that when an object contacts the front of the wheel it can generate a good amount of friction which can prevent the wheel from spinning as easily. We had problems with this at worlds and it caused our drive motors to overheat and stall. Because of this experience our drive train for this year is completely covered on all sides.

#14

Hey,

Yea that happened to us at worlds too this year. We had a claw and when we can up to score with our four bar we got a ring stuck under us and we happened to go forward and flip backwards idk but i was driving one second and the next the robot was on its back (we lost that match).
But anyways our team has decided to go and use the 393 motors on speed option for our drive and have all wheels linked with high strength chain and sprockets.
We want to be a fast scorer so if this doesnt perform the best then we will switch it to a bit more speed ratio.

#15

A few things to keep in mind when designing a drive:

The isolation zone is small, so it would be good to keep a small turning radius. For 4WD tank drives, this may pose problems.

A really good isolation robot can conceivably finish early and move into interaction.

Interaction-based robots will likely have powerful drive trains. If you plan to play in interaction, think about having power.

If all else fails, a powerful drive can make you a valuable defensive partner. Don’t skimp on the drive unless you’re sure the manipulator will work.

#16

I agree, unless you’re in the college division your drive is the most important part on the robot. If you can’t move around the field you really aren’t that much use.

For interaction your also going to want that power because of all the strewn game pieces. Skimp out on power and you might see yourself tripping circuit breakers. I say in general, make sure your drive train is the most solid and reliable part on your robot. Who knows if you can play the zone you want?

#17

do you think that for an h drive, it would be good for an interaction robot to have 3 393’s powering the two forward wheels, and the middle wheel, then another 2 2wire 269 motors for the back wheels. is that not enough power, just right, or is it not good to have mix and matched powered wheels?

#18

I assume you mean 1 269 and 1 393 on each side of the drive, and a 393 on the strafe? This is, in my opinion, a very good configuration. Gearing the forwards on 3:2 or 5:3 for speed would make this a very agile robot

#19

I think that the answer is that question is meaningless unless you know more about what you are trying to accomplish and how your robot is designed. Any team could use this list to start a drivetrain design checklist:

  1. Long wheelbase or short? The shorter the wheelbase, the less power you need to turn.

  2. How fast do you need to go? Forget gear ratio, motor count, and wheel size UNTIL you have gone to the VEX speed charts and picked your target top speed. Once you’ve done that, you can design a drive train. For example, if you decide you only need to go 1.1 feet per second, I can guarantee that you won’t *need *any 393s at all, although you may want them for maximum torque.

  3. How heavy is your robot? Team 417 in 2009 had the lightest VEX robot I’ve ever seen playing at World Championship level, and they only had four 3-wire motors geared for about 3.6 feet per second. If their robot had weighed more than 7.5 pounds, they would have had to either gear down to go slower or add more motors.

  4. What kind of wheels are you using? If they are all omniwheels (and in a slide drive they would be all omnis, right?) you will turn more easily and need less power.

  5. Do you plan to try to shove other robots around? If so, plan on lots of motors and not going fast.

So, to give someone meaningful advice, you need to fully describe your robot’s weight, strategy, drivetrain layoug, how fast you want to go, and what kind of wheels you plan on using. There are no simple answers.

#20

I agree. For the new drive for 24C we were thinking of a 1:1.5 (speed) gear ratio using two 2-Wire 393 Motors and two 3-Wire Motors on the drive. (one of each motor on each side) Then have two 3-Wire Motors for our strafing wheel, geared at 1:1, most likely. Definitely not gearing the strafing wheel up, but don’t think we need to gear it down – it won’t be used as much as the other drive wheels most likely.

Figuring the robot will weigh around 13 lbs.

~Jordan