pic: 1736 Robot Casserole Offseason WCD

[jeremylee]

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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

[KohKohPuffs]

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

[jeremylee]

Originally Posted by KohKohPuffs

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

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.

[asid61]

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.

[Chris is me]

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.

[notmattlythgoe]

Originally Posted by asid61

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.

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.

[nuclearnerd]

Originally Posted by jeremylee

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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.

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?

[Ty Tremblay]

Originally Posted by nuclearnerd

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?

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.

[notmattlythgoe]

Originally Posted by Ty Tremblay

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.

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

[jeremylee]

Originally Posted by nuclearnerd

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?

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.

[jeremylee]

Originally Posted by Chris is me

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.

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?

[notmattlythgoe]

Originally Posted by jeremylee

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?

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.

[AustinSchuh]

Originally Posted by jeremylee

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?

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.

[jeremylee]

Originally Posted by AustinSchuh

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.

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.