Uneven Center Drop? Does it work?

Technical Technical Discussion
#1

Hello Everyone,

I’ll spare all the details but for a project I’m working on I want to know if anyone has ever used an “uneven” center drop in their drivetrain?

The way I have the drivetrain setup I have one wheel on the center-line of a section of VersaFrame. The other wheels are on VersaBlocks so I have (measured from the side of the frame closer to the ground):

Back wheel 1" high on the VersaFrame
Middle wheel 15/16" high on the VersaFrame
Front wheel 1 and 1/16" high on the VersaFrame

I apologize for the lack of pictures. Any information on how a drivetrain like this would actually work is appreciated. I’m inclined to think that it wouldn’t be that different than a regular center dropped drivetrain but that might be very incorrect.

#2

Presuming you’re using same-sized wheels, and the holes are spaced evenly, you’ve just described a drive train where the frame is slightly angled with respect to the ground. You can do the math for the angle given the distance from your front to back wheel. Think about the geometry and gravity acting here. You just have a straight line when that’s under gravity on the ground.

If the center wheel is offset, you have the angling effect but possibly with a bit of the drop center effect. I’m a bit less confident in what would be going on in this situation. The equivalent drop would likely be the distance from where the center axel is to where it would be on the lime, I think. I’ll have to olay around with CAD to see if my instinct is right in this configuration.

#3

We have done this with Versablocks and it works the same. We found there was too much drop when the 4 corner Versablocks were in the same orientation so we just flipped the front blocks. I’d say our resulting drop was around 0.09". This does angle the frame, but over the length of the wheelbase, it’s barely anything.

#4

You can run a multitude of combinations of drop. Last year we centered our drive CIMs and battery between our front and middle wheels then ran those wheels with the same drop and the rear wheel slightly higher (3/32). Effectively made our turns bias to that end of the robot similar to what a 2+2 would do but not as dramatic. Just keep in mind that your robot will sit on 2 sets of wheels so you should be conscious that you’re not tilting your hole robot and then end up out of package.

#5