Off-season chassis

[Michael 4499]

This is the grabcad for last year's offseason chassis that my team worked on and built. It is designed to weigh around 25-30 lbs with all of the hardware on it.


EDIT: IN THE GRABCAD OPEN THE ASSEMBLY CALLED TB2_base.asm I hope this works

[asid61]

The assembly is not showing up for me on GrabCAD. Could somebody double check that it's not just me (or GrabCAD + Creo)?

[Chak]

Most WCD I've seen have the chain or the belt behind the wheels. I've always assumed that the intent is to protect the chain or wheel from caught when the robot is hit from the side. Are you concerned about that?

Edit: I'm going by the picture, I can't get the CAD either

[Michael 4499]

Originally Posted by asid61

The assembly is not showing up for me on GrabCAD. Could somebody double check that it's not just me (or GrabCAD + Creo)?

I just uploaded the folder with all of the files, I think it should be in there.

[asid61]

The picture you have is enough, although the model doesn't load for me; kind of odd.
Building on what Chak said, you may have trouble mounting bumpers on there without extending the front/back rails.
I love the lightening pattern (seems strong but light), and the use of what appears to be 2x2 tubing everywhere. Have you considered adding a bellypan for stiffness?

[Michael 4499]

Originally Posted by Chak

Most WCD I've seen have the chain or the belt behind the wheels. I've always assumed that the intent is to protect the chain or wheel from caught when the robot is hit from the side. Are you concerned about that?

This robot is not FRC legal, it is just a simple bruiser bot and it will have bumpers on the side of it. One problem I can see in this chassis is after enough wear the belts might stretch too much and come off of the pulleys.

[Michael 4499]

Originally Posted by Chak

Most WCD I've seen have the chain or the belt behind the wheels. I've always assumed that the intent is to protect the chain or wheel from caught when the robot is hit from the side. Are you concerned about that?

Edit: I'm going by the picture, I can't get the CAD either

Originally Posted by asid61

The picture you have is enough, although the model doesn't load for me; kind of odd.
Building on what Chak said, you may have trouble mounting bumpers on there without extending the front/back rails.
I love the lightening pattern (seems strong but light), and the use of what appears to be 2x2 tubing everywhere. Have you considered adding a bellypan for stiffness?

Close, it is 2x1-1/2 tubing everywhere and although not in cad there will be a carbon fiber plate on the belly of the chassis.

[z_beeblebrox]

Originally Posted by Michael 4499

Close, it is 2x1-1/2 tubing everywhere and although not in cad there will be a carbon fiber plate on the belly of the chassis.

Nice work!


Why carbon fiber over "cellulose fiber"? Wood tends to be nearly as strong and light, but is far cheaper and easier to machine. And the frame is plenty sturdy to make up for any loss in strength?

[Michael 4499]

Originally Posted by z_beeblebrox

Nice work!


Why carbon fiber over "cellulose fiber"? Wood tends to be nearly as strong and light, but is far cheaper and easier to machine. And the frame is plenty sturdy to make up for any loss in strength?

We really like to use the carbon fiber that is thin (1/16") and it is still strong enough to support an electronics board. With would it isn't possible to go as thin as you can with carbon fiber.

[mrnoble]

Originally Posted by Michael 4499

We really like to use the carbon fiber that is thin (1/16") and it is still strong enough to support an electronics board. With would it isn't possible to go as thin as you can with carbon fiber.

I know what you mean. We did carbon fiber last year and it was a little lighter and thinner than a wood belly. We mostly did it so our kids could have the experience of creating the layup, because the gains were small and were offset by other factors (cost especially). Still, you guys were the coolest team in Colorado last year, so I ain't gonna try to advise you. Looking forward to what you come up with this year!

[Michael 4499]

Originally Posted by mrnoble

I know what you mean. We did carbon fiber last year and it was a little lighter and thinner than a wood belly. We mostly did it so our kids could have the experience of creating the layup, because the gains were small and were offset by other factors (cost especially). Still, you guys were the coolest team in Colorado last year, so I ain't gonna try to advise you. Looking forward to what you come up with this year!

Thanks a lot, you guys had an awesome robot last year and your team did very well in the tournament. We have a carbon fiber fanatic on our team it is really not an option to go back to a wooden belly. I hope to see you guys at the competition this year, best of luck.

[RyanCahoon]

Originally Posted by Chak

Most WCD I've seen have the chain or the belt behind the wheels. I've always assumed that the intent is to protect the chain or wheel from caught when the robot is hit from the side.

It also shortens the moment arm of the cantilevering force on the axle. On this chassis, the tension force carried by the belts will have ~5x the ability to bend the shafts compared to if the belts were right against the chassis rail. Also, when the shafts do deflect (either from the belt tension, or force on the wheels), the pulleys will move ~5x as much, which means your belts will be more out of alignment.