Drivetrain, High or Low?

This year we are encountering something that we have not seen in the previous game season. The field objects are a real pain to drive over and around. During gateway many if not all teams tried to get there robot as low to the ground as possible to help with tipping problems. This year such a base will simply not work. My team has already begun testing and has found all of our gateway bases get sacks trapped beneath our drive trains and cant move. So one of the obvious fixes is to simply lift yourself up so you can roll over the sacks without them getting stuck between your metal and the floor. But my team thinks it would be better to build some sort bent metal piece to keep the sacks from getting underneath your drive in the first place. What are you all’s thoughts?

My team is settling for a mixture of the two, all braces between wheels and other parts of the chassis will be high enough for objects to slide under, but my wheels will be surrounded by a low “skirt” to stop objects getting under the wheels, which has the added advantage of keeping your intake low to the ground, by stopping it getting lifted by objects.

you can really go either way. if your using 4" wheels you cn mount them to the top hole in the 5x c-channel which will make it very low to the ground and it would act more like a “plow”. or you can put the wheel on the bottom most hole which would make it very tall so that i would be easier to drive over. it all depends on your preferences.

I think the low drive train will be the best for those who want to get under the troughs. We have made it a priority to accomplish this so we want to save vertical space anywhere we can.

Let’s get Real Radical here!!!

Use a variation of the NonaTread with the Wheel Legs, deployed with Pneumatics.


Modify the Wheel Legs, Cut Off, ( or Shorten Significantly ) Two of the Legs, on Opposite sides of the Axel. Place them Outboard on the Front ( and Rear ) of the Robot.

Use them like the iRobot Packbot’s Flippers. With their Long Configuration parallel to the Ground, and then Rotate to lift the Front ( or Back ) of the Robot over the Sacks…

Our chassis is going to have a low skirt to push the sacks and keep them out of our drivetrain. That way, if we need to, we can score mass amounts in the floor goals.

Do sacks scored in the floor goals have to be physically touching the ground or can they be staked up if you had a lot?

This question is up on the official Q&A. Karthik will be getting to it when he has an answer.

Karthik answered your question:

I will be using a 6wd with a base ~2 inches from the ground to always drive over sacks. It seems that with a low “skirt”, if sacks ever get under your robot there’s no chance of escape.

I agree with this. Way back in elevation, my team had a robot that NEVER got stuck on cubes… until it did in division semi-finals at Worlds…

I do believe that I’m going to try a low-skirt + plow first. There’s gotta be a way to solve the problem with both methods, so we’ll trouble-shoot that idea until we give up and just raise the base.

Something to add.

If you plan on going under the trough, you will most likely want to have a low drive. That way you will be able to have a bigger tower for your lift and what not.

There are trade offs for being high, and low. I think low out weighs the high drive though.

Is it true that Mecanum’s eat bean bags for breakfast?

Yes. We’ve been attempting to enclose the mecanum wheels as much as possible and still the sacks seem to manage to slip in. We noticed it happens mainly when you have a wheel on or near a sack and make a quick motion.

Possible solution - have some of your buttons on your joystick programmed to run only one wheel to unjam the sack.

Or just avoid running over sacks if possible.

Mecanums are going to be tricky this year. I think we are going to see a lot of speedy drives that get a sack stuck in it and can’t unjam them. Experiment with speed vs. torque now during the summer months. Our experiments have lead us to go the torque route this year.

You will drag if you mount it to the top hole. 4" wheels radius is 2" and the C-Channels width is 2.5". The furthest up you can mount it is in the 2nd hole from the top.

Can you link to or post your own video of this hapening.

I would surround your wheels/drivetrain with metal so that when you hit the sacks they are just pushed out of the way. However, the metal would have to be completely surrounding the drivetrain so that there is no risk of any sacks getting stuck under your robot.

I will get one of the students to take video of this during the week and hopefully get it posted up here soon.

There are some of our initial test videos on our build blog, see the link in my signature.

I should also note that drive trains geared for speed will not be able to push a clump of sacks very easily. The amount of weight that can be located near one spot and the overall density of a pile of sacks make them extremely hard to move with a drive geared for speed.

Thanks. :slight_smile:

A few wheels using these should have more than enough clearance for whatever gets thrown at it.

Additionally, the low or high factor might also have an impact on the design. The significance of this impact is dependent on the design, but it’s something to keep in mind.

  • Sunny G.