Don't Get Stuck! Design YOUR drivetrain to clear the corner.

#1

As I mentioned in the recent Day 9 148 Build Blog Post, this year’s field has an obstacle that can be deceptively tricky.

THE RAMP CORNER!

As everyone is designing their drivetrains, I hope you take the time to check whether you have sufficient clearance.

While the game theme is 2-dimensional, the playingfield is not.
As with most ramps, the corner provides the worst-case for drivetrain clearance.

Take it from the Robowranglers - you don’t want to end a match (or event) with your robot stuck.

As part of the 2015 Build Blitz, I wrote a whitepaper describing the keys to designing a drivetrain to handle bumps. It was written for 2015, and a lot of it does NOT apply now, but there is still some good stuff in there. Give it a read.

You can always tell your driver “don’t drive up the corner”… but that has never worked out for me. You’re probably luckier than I am.

Hopefully this gentle reminder didn’t matter to you, because you’re already on top of it. As always… Good luck with your season!
-JVN

#2

I’m about 99% sure this is why the bumper zone was moved up. As it originally was defined a continuous front/rear bumper as depicted in JVN’s diagram (above) would hit the ‘double-bevel’ if your track was above something like 16-20in (ish).

#nobeachedwhales

#3

We tested this out with an old practice robot carcass this past weekend as we were testing out different wheels and configurations. Our decision came easy after testing that particular situation.

#4

Also consider the possible need to drive up onto a ramp robot. We played with the various angles that would be needed for ramp robots and found these to have even tighter constraints than the platform. Ultimately, this drove our design.
Even if you plan to climb or be a ramp, there may be alliance situations where you are the robot to go up a ramp. We are not one of the best teams that will get to dictate alliance roles, so we design for flexibility.

#5

Also, John, please check out my latest post in your JVN calculator thread (https://www.chiefdelphi.com/forums/showthread.php?t=140667&page=3) there seems to be an error that may or may not have been slightly costly (depending on if our order got squared away at the robot space)

#6

I’m glad you brought this up. We did this analysis yesterday, and the style of how we’re building our frame has changed somwhat from most of our prior years. Let me put it this way, our WCD Stronghold 2016 robot with 7.5" wheels did not fully clear this ramp in every way that we wanted it to. Be careful with your design choices folks!

#7

I love how the WCP folks released a video almost FLAUNTING how well they solved this problem on the same day I posted this.

WCP MCC Robot 2018. (Relevant section is 1:18 to 1:37).

#8

No the reason was that if you use the bumper brackets supplied with the KOP chassis per the instructions the top of the plywood would be at 7" leaving no room for the fabric, stack of layers of fabric and velcro, and/or the legal angle aluminum.

The plus side is that it gives you the ability to have another 1/2" of ground clearance increasing the approach and departure angle that can be achieved.

#9

I encourage teams to use 6” wheels and mount their bumpers at least 2” off the ground. It is also important to leave as much ground clearance as you can under your robot.