pic: 1736 Robot Casserole Offseason WCD
 

Some details:

3.5" Colson wheels, 1/8" drop
Ratio Low gear: 11.03
Ratio High gear: 5.1

Speeds around 7.5 ft/sec in low and 14.3 ft/sec in high.

Designed side bumper mounts to be 3D printed with provisions to add McMaster latches. Can fall back to vertical 2x1 aluminum if we have strength issues.

https://workbench.grabcad.com/workbe...9BfERSw3el_QBL

Re: pic: 1736 Robot Casserole Offseason WCD
 

Interesting design. What is the weight? Also, what made you guys choose colsons over blue nitrile tread wheels?

Re: pic: 1736 Robot Casserole Offseason WCD
 

I've estimated around 37 pounds as shown. If we drop back to 4 cims, that'll put us around 31 pounds. As for wheels, it's possible we may try blue nitrile, but the main concern is that the increased traction may lead to more brown outs.

Re: pic: 1736 Robot Casserole Offseason WCD
 

Are you planning on adding a bellypan? They greatly increase the stiffness of the chassis, but if you've run without on in the past that would be intersting.

Re: pic: 1736 Robot Casserole Offseason WCD
 

Plenty of great reasons to use Colsons over blue nitrile, but if you're concerned about brownouts then 6 CIMs is far more of a risk factor than the wheel choice.

Re: pic: 1736 Robot Casserole Offseason WCD
 

I would imagine in most cases when a belly pan is not in the model they just didn't model it, not that they aren't going to have one.

Re: pic: 1736 Robot Casserole Offseason WCD
 

Can you add more detail about your bumper mounts? Unless you make all four sides as one piece, wouldn't the draw latches tend to flip the bumpers upwards? Or is there a secondary support I can't see?

Re: pic: 1736 Robot Casserole Offseason WCD
 

The strongest way to make bumpers is to make them as one piece. This is most likely what they're doing. They'll probably have a hard stop so the bumpers can only go down so far, then the latches will pull the bumpers in and down against the hard stops.

Re: pic: 1736 Robot Casserole Offseason WCD
 

This is really what I wanted to do on our 2014 bot since we had a one piece bumper.

Re: pic: 1736 Robot Casserole Offseason WCD
 

Plan is for a one piece bumper to slide on from the top. Still need to add a latch or two on the front and back.

And yes, we'll have a belly pan. I don't know the exact details as the electrical team takes care of that aspect, but it's similar to the pre-drilled polycarbonate.

Re: pic: 1736 Robot Casserole Offseason WCD
 

I understand that 6 cims at stall is likely a problem. Has anyone confirmed we can stall 4 cims without being worried about a brownout?

Re: pic: 1736 Robot Casserole Offseason WCD
 

I believe the ultimate goal is to design so you are traction limited so you can't stall your motors, but I'm no engineer so don't that that as law.

Re: pic: 1736 Robot Casserole Offseason WCD
 

I can pretty much confirm that if you stall 6 CIMs, you will brown out. Brownouts happen pretty early with the roboRIO. We were seeing brownouts with 4 CIMS in high gear accelerating from a stop towards the middle to end of the match.

Re: pic: 1736 Robot Casserole Offseason WCD
 

This confirms my theory, 4 cims may be "safer" from a brownout, but that alone may not avoid a case of the brownout blues. Better to make sure you are traction limited or have some form power limiting implemented.