Hi, right now I'm designing an intake system for FRC (FIRST Robotics Competition). Basically, there are the totes: (For one tote): Dimension: 26.9" x 16.9" x 12.1" Weight: 7.8 lbs Now I'm designing something to suck the totes in, something similar to this: See at the bottom the subsystem with the two wheels? Now in my design these will be able to articulate, but it will be held in place with a spring load. I want to figure out the maximum spring load I can put in so that the friction between the wheels and the end of the tote can still overcome the springs, but it has to be a strong enough load so that the wheels can still have enough friction and force to suck the totes in from either side. Sorry if this is a little confusing, so please ask any questions to clear things up. I'm not asking for any calculations to be done for me, but just some guidance on how I go about doing this. Thanks, Shashank R.