1114 Inspired Chasis

[Gregor]

Originally Posted by apalrd

We (33 2013) use our gearboxes to span the chassis outer and chassis inner, as well as bridge the chassis inner rear and front panels (they are not continuous panels, the outers are).

Could you provide a picture of this?

[apalrd]

Originally Posted by Gregor

Could you provide a picture of this?

Here are some pictures of the prototype. I don't have any good pictures of the in-season chassis, plus it's painted black and hard to see detail on.

The four pictures are:
-Gearbox assembled, upside down. Secured to chassis inner on front face and bottom flange with bolts, significant structure to chassis inner. Secured to chassis outer with four bolts/spacers on front face, bolts on bottom flange to chassis outer flange. I'm not sure we actually bolted the gearbox outer to chassis outer on the bottom flange, we might have thought the four bolts were enough.
-Gearbox assembled, another view. It's just an AM shifter with 22t output sprockets and new plates. Prototype was servo shifted, production was pneumatically shifted.
-Prototype chassis assembled, with electronics tray and servo shifters. This later saw the bandsaw and became the practice robot chassis (we literally removed the rear chains and bandsawed it to 27" long). Talons also tested, performed admirably without fans.
-Chassis inner assembly without chassis outers or ends. Gearbox inner plates temporarily put in for fit-up, not yet folded. The top hat above the gearbox does very little, almost all of the loads in that area go through the gearbox. In fact, it's the only thing that bridges the inner and outer chassis in the middle of the span.

There were a few changes between this chassis and the production one, mostly in ride height (added 1/4" ride height) and chain tensioning (slotted all 6 wheels instead of only inner wheels). we also moved the battery for cg and placed the arm gearbox in the battery space.

[BJC]

Originally Posted by apalrd

Here are some pictures of the prototype. I don't have any good pictures of the in-season chassis, plus it's painted black and hard to see detail on.

...

Just to clarify several things. The chassis Andrew showed pictures of is misleading. He talked a lot about stiffness and then posted a picture of one with very little. That's because that chassis is specifically designed to reduce weight and increase packaging space by intentionally being flimzy. It makes use of all the manditory things in a drivetrain like the gearboxes and axles for structural support but uses its bumpers (which don't count towards the robot weight) as the "meat" of the frame providing almost all of the stiffness.

I attached a .pdf to better explain it. I just didn't want anyone looking at it to get the wrong idea.

Regards, Bryan

[Billfred]

Originally Posted by BJC

That's because that chassis is specifically designed to reduce weight and increase packaging space by intentionally being flimzy. It makes use of all the manditory things in a drivetrain like the gearboxes and axles for structural support but uses its bumpers (which don't count towards the robot weight) as the "meat" of the frame providing almost all of the stiffness.

For ten years now, I would often look at 33's robots and wonder "How the heck do they make weight?!"

Now that I know how that pans out, I'll have to ask "How the heck do their bumpers make weight?!"

(Mind you, I find their approach fantastic and truly next-level work within the rules. )

[mman1506]

Originally Posted by BJC

Just to clarify several things. The chassis Andrew showed pictures of is misleading. He talked a lot about stiffness and then posted a picture of one with very little. That's because that chassis is specifically designed to reduce weight and increase packaging space by intentionally being flimzy. It makes use of all the manditory things in a drivetrain like the gearboxes and axles for structural support but uses its bumpers (which don't count towards the robot weight) as the "meat" of the frame providing almost all of the stiffness.

I attached a .pdf to better explain it. I just didn't want anyone looking at it to get the wrong idea.

Regards, Bryan

Does the box tube bumper frame force you to give the robot a smaller perimeter?

[Billfred]

Originally Posted by mman1506

Does the box tube bumper frame force you to give the robot a smaller perimeter?

From the looks of the prototype they showed, it doesn't look like a big sacrifice.

I would imagine the outward-bent flange is to define their FRAME PERIMETER and provide a mount for the box, since their hard parts can't extend more than an inch beyond the FRAME PERIMETER (under 2013 rules, mind).

Considering the AndyMark C-Base is 1.13" wide (and you can't really mount things on the outer face with the present frame perimeter rules), I doubt it's much of a loss of usable space. If you needed to mount something on the outer flange, I believe you could still hog out part of the box tubing on the upper face to provide room for a bolt or rivet. How much strength you give for that I'll leave to the pros.

[AllenGregoryIV]

Originally Posted by BJC

Just to clarify several things. The chassis Andrew showed pictures of is misleading. He talked a lot about stiffness and then posted a picture of one with very little. That's because that chassis is specifically designed to reduce weight and increase packaging space by intentionally being flimzy. It makes use of all the manditory things in a drivetrain like the gearboxes and axles for structural support but uses its bumpers (which don't count towards the robot weight) as the "meat" of the frame providing almost all of the stiffness.

I attached a .pdf to better explain it. I just didn't want anyone looking at it to get the wrong idea.

Regards, Bryan

Bryan, this is absolutely amazing, thank you for posting this. Are you sitting on any other awesome presentations you want to share.

[mman1506]

Originally Posted by Billfred

From the looks of the prototype they showed, it doesn't look like a big sacrifice.

I would imagine the outward-bent flange is to define their FRAME PERIMETER and provide a mount for the box, since their hard parts can't extend more than an inch beyond the FRAME PERIMETER (under 2013 rules, mind).

Considering the AndyMark C-Base is 1.13" wide (and you can't really mount things on the outer face with the present frame perimeter rules), I doubt it's much of a loss of usable space. If you needed to mount something on the outer flange, I believe you could still hog out part of the box tubing on the upper face to provide room for a bolt or rivet. How much strength you give for that I'll leave to the pros.

I'm guessing that it will stay the same (2013 bot does not have a flange) as the robot perimeter is measured without the bumpers.

Since bumpers are measured on there own, the 2" box tube would be measured as the attachment device.

I would like to see someone from team 33 to chime in on this manner.

[BJC]

Originally Posted by Billfred

For ten years now, I would often look at 33's robots and wonder "How the heck do they make weight?!"

Now that I know how that pans out, I'll have to ask "How the heck do their bumpers make weight?!"

(Mind you, I find their approach fantastic and truly next-level work within the rules. )

Thanks, this is actually the first year we've done something like this. The prototype was designed in the fall and built mostly over winter. The actual bumper box frame is comparable in strength and weight to a west coast frame like 254 makes every year (before we add the plywood for the bumpers.) Because we only have one set of bumpers and use Snap-On covers we didn't have a weight problem. A lot of our ability to make weight for the last 10 years was dependent on using thinner materials then most teams do. We make up for this by using stronger/harder-to-bend aluminum then most teams/shops use and bend it ourselves. This has its pros and cons.

Originally Posted by mman1506

Does the box tube bumper frame force you to give the robot a smaller perimeter?

The 2x1 aluminum box frame fits within the frame perimeter, however, because we have an outward facing flange we can still mount stuff over the box beam. We can't mount stuff underneath it because the one piece bumper is removed via bottom of the robot.

Originally Posted by Billfred

From the looks of the prototype they showed, it doesn't look like a big sacrifice.

I would imagine the outward-bent flange is to define their FRAME PERIMETER and provide a mount for the box, since their hard parts can't extend more than an inch beyond the FRAME PERIMETER (under 2013 rules, mind).

Considering the AndyMark C-Base is 1.13" wide (and you can't really mount things on the outer face with the present frame perimeter rules), I doubt it's much of a loss of usable space. If you needed to mount something on the outer flange, I believe you could still hog out part of the box tubing on the upper face to provide room for a bolt or rivet. How much strength you give for that I'll leave to the pros.

Yes, the flange is important in order to bolt the box bumper frame to the robot frame in two planes (basically making them one.)

Actually, instead of drilling the box beam out to mount stuff we just mount stuff to it via rivnut. Our entire arm and arm structure was basically bolted through the outboard 0.05" thick flange into the 1/8 box frame. It was also attached to the actual frame via 4 small rivets to maintain legality. This was both the strongest way to mount it and made it easy to remove the entire top of the robot if need be (there was never a need.)

Originally Posted by mman1506

I'm guessing that it will stay the same (2013 bot does not have a flange) as the robot perimeter is measured without the bumpers.

Since bumpers are measured on there own, the 2" box tube would be measured as the attachment device.

I would like to see someone from team 33 to chime in on this manner.

The 2013 robot does have a outboard flange. Simply attaching a box frame to the outside of your frame would be illegal. If anyone attempts a drivetrain like this I strongly encourage them to go over the 2011, 2012, 2013 bumper rules with a fine tooth comb.

Originally Posted by AllenGregoryIV

Bryan, this is absolutely amazing, thank you for posting this. Are you sitting on any other awesome presentations you want to share.

Thank you, I attached a paper I created last year around this time basically detailing my "drivetrain philosophy" but never published it. I'm not sure its awesome but is relevant.

All of this is pretty off topic from the thread except to say that if you want to design a new chassis make sure you understand why you are doing what you are doing. Always design with a purpose/problem in mind and revisit that problem frequently as you go. If you do this at the end of it all you can’t help but to have solved the problem you set out with (then iterate to more elegantly solve the problem).

I’m sure Jim will post the 2013 CAD sometime in the near future. Perhaps it would be better to hold questions until that thread, create a new one (I can talk about design decisions/implementations for hours), or PM me if you’re still curious about the WASPdrive.

Cheers, Bryan

[Cash4587]

Update:
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-Thanks for all the feedback

[lynca]

Originally Posted by Cash4587

Update:
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-Thanks for all the feedback

Looking sharp ! This is a great summer exercise, let us know if you need help getting sheet metal parts made.