Large or small ground clearance? was: Low Drive-train

My robot is high off the ground to go over the sacks, but lately I’ve been seeing teams that have a low drive-train. What are the benefits of having a low drive train? What are the benefits of having a high drive-train? Which one is overall better?

Benefits of a well designed very Low Drive chain/low profile:
*]Ability to push objects around (can score sacks in low goal)

Benefits of a High Drive chain:
*]Can drive over sacks easily/faster than pushing sacks
*]Easy to make
*]Unlikely anything from the ground will stop it

Winner - Depends on your needs

we have a reasonably high drive base, this was designed so we could drive over the sacks … the other team at ours has a drive base which is extremely low to the floor, and they are having problems with driving with the sacks, so they are putting guards around the wheels to try and push away the sacks …

In my opinion a high wheel base is better. It is harder than it seems to push the sacks, as they have a high amount of friction on the ground. Also there is not a big advantage to pushing them as they are worth five times as much in the trough than on the tile.

My team originally had a low drive base and had a whole bunch of problems with sacks getting stuck underneath the drive train, making us unable to move for large portions of matches.
After our first competition we quickly changed to a higher drive base and it interacts with sacks a whole lot better.

I would highly suggest building a higher drive base, from our experiences it causes more problems then it’s worth.

One advantage I see with a low drive chain is being able to put more weight down low. From what I’ve seen, robots with high drive chains tend to fall over.

Thats true, however that can easily be prevented through driver practice, slew-rate programming, and some extra wheels in the front/back.

at the competition i was at yesterday, i also have noticed that robots with low drivetrains (less than .5") still tend to get stuck
and robots with higher drivetrains just drives over the sacks as if nothing happened

Thanks! How high would be sufficient? Would a 4" wheel at the lowest hole of a 5 C-channel suffice.

That would be about the ideal height in my opinion. My team has the C-channel dropped down one more so that it’s the 2nd lowest, but either would work fine. We find with ours being a little bit closer to the ground, any grouping of sacks might have a little bit of difficulty going under the chassis

Really? I haven’t noticed that so much, I figured that problem was due to some other reasons. I don’t think the balance would be altered THAT much by just having a high chassis vs low chassis… Having been in a team that has tried both, there was never any difference for us (of course there would have been, just not a noticeable amount).

Personally, I say go with a high chassis, with plenty of room underneath. The biggest downside I see to a low drive train is what if your robot does tip slightly (or something else happens) and a sack gets itself underneath?

If you do try a low drive train, a message from my team, please don’t attempt to drive over sacks. It gets messy. Or at least don’t try in a match :wink:


i have also noticed that some bots are designed to be exactly 15" in order to go under the trough
but usually, there are sacks underneath the trough
and the extra .5" is just enough for the robot to get caught under the trough
so keep that in mind :wink:

We are running a bot on 2.75 double omnis. How about skirting the drive train with polycarbonate to get a zero clearance?

you will end up just (maybe) pushing the sacks, which is not a good thing to your drive
and the sacks will somehow get stuck under it :stuck_out_tongue:
its much easier to raise your drive train
unless you are up to “doing it right” with a 0 tolerance skirt :stuck_out_tongue:

I wonder if chain will eat up sacks…? Haven’t had a problem yet!!! hopefully…

One of our teams has tried this before. You have to be careful because as you intake sacks or if sacks get stuck on top of your drive train, the weight can push your drive train into the foam mats. A zero clearance drive train seems risky. In my opinion, a well-built high riding drive train can have no issues with either driving over sacks or tipping.

i measured ours today, it is around 1-1/2 inches of the floor, and it works fine (runs over sacks fine) :smiley:

i would go for a higher drive change.

We must be “doing it right” then, because we have a chassis with about .25" of clearance, and in all our hours of vigorous testing it hasn’t gotten stuck on anything. It pushes up to 8 sacks at one time. We have also tried to make the robot tip itself over, but the skirting stops that from happening.


It seems to me that the title and content of this thread is a little confusing (at least to me :slight_smile: ). I have seen the terms drive train, drive chain and even drive change used to explain whether or not the robot has a low chassis / skirting fitted. The drive train is the group of components that generate power and deliver it to the foam tiles. To me, this suggests that the height of the drive train is determined by the wheel radius, as the axles need to be supported by some kind of structure at this height. You could have a low chassis / skirting, even when using large wheels and having a high drive train.

My opinion - if you design your robot to push sacks, rather than drive over or around them, you are going to load your drive motors more. This will require lower gearing (slower robot) and/or more motors on the drive than you might otherwise have used. Skirting is a good idea if you consider the ability to push sacks to be a priority, for example a strafing robot.

Cheers, Paul

Sorry about that. I didn’t know what to title the thread. Whoever changed it, thank you.