23-01-2012 10:31

Taylor

Re: pic: Team 1325 Sheetmetal Chassis 2012

Nice work. Note: Dark chassis on dark background makes it a bit hard to see.
Assuming the white cylinder on the left side is an intake roller, I hope you have a system to get the basketballs up before they hit the CIMs.

23-01-2012 17:40

Dr Theta

Re: pic: Team 1325 Sheetmetal Chassis 2012

You may want to add some standoffs in your wheel channels; if that get's hit in the side it may be liable to bend.

23-01-2012 18:00

Feroz1325

Re: pic: Team 1325 Sheetmetal Chassis 2012

Thanks, what do you recommend in terms of stand-offs. I was thinking bent sheetmetal brackets, but i want to give our shop the least amount of work possible. Would bolts with spacers be strong enough to survive competition impacts?

23-01-2012 18:02

roystur44

Re: pic: Team 1325 Sheetmetal Chassis 2012

Add another return flange on the back panel to stiffen the rear.

On the mounting panels for your roller put the flange on the top and mount the panels to the inside of the frame or flip the bend. This will give you 2 more inches of intake.

Consider cutting a 45 deg angle on the front and back of your robot. This will give your wheel clearance when it goes up the ramp. The bottom back/front won't drag on the carpet when the robot goes up at a angle.

Cutting the triangles takes longer than just punching a circle. If you are concerned about time go with a simple hole paterrn instead of the fancy triangles.

23-01-2012 18:05

BlacksmithWoods

Re: pic: Team 1325 Sheetmetal Chassis 2012

Are you planning on going over the bump? How is this frame able to do so? From what I see it looks like the chassis will hit the bump before the wheels.

23-01-2012 18:13

Feroz1325

Re: pic: Team 1325 Sheetmetal Chassis 2012

Thanks guys!
First of all, Team 1325 will not be crossing the bump (its a strategy thing...we plan to be the best feeder bot north of the border!). As for cutting the sheetmetal, we only have access to a CNC mill to cut these parts. With this in mind, wont cutting a circle and a triangle take the same amount of time?
Also, could you explain what a return flange is? This is my first time with sheetmetal and im not really sure what your talking about (sorry)

23-01-2012 23:19

BJC

Re: pic: Team 1325 Sheetmetal Chassis 2012

Is there anything connecting the two chassis halfs besides the back cross piece and the front roller?

I think you need a nice 3/4" plywood bellypan or a nice strong cross member supporting the chassis forward of the middle of the robot -- or both. This robot would have terrible tortional stiffness without something else bracing across it.

Regards, Bryan

23-01-2012 23:30

tim-tim

Re: pic: Team 1325 Sheetmetal Chassis 2012

I think the OP mentioned that the center support and baseplate were not in this model because the intake/conveyor system was not finalized.

For the most part I would say it looks good. Out of curiosity what bend radius are you using for the .090 5052? Do you plan on riveting or the conventional bolting for this? As someone else mentioned, you may want to add some stiffeners between the wheel channels. I think a few bolts with spacers would work, but would be more work than bent sheetmetal flanges. The flanges required for those are relatively simple and could probably made in house by hand (just another option)

Edit: After looking at 842's frame picture, it lead me to another option. You could also use a series on small "L" angle and flat sheet

23-01-2012 23:42

BJC

Re: pic: Team 1325 Sheetmetal Chassis 2012

Ah, my mistake, quite right.

24-01-2012 16:25

Feroz1325

Re: pic: Team 1325 Sheetmetal Chassis 2012

Thanks for all your comments....to answer some of the questions:
First of all i hope to use riveting to secure the frame members, however some people on my team prefer bolts, we shall see who wins .
For the bend radius...im actually not sure, i used the presets in Autodesk Inventor and i believe it is 0.09 inches?
At school we have a sheetmetal brake, so I was wondering if it would be okay to get the parts CNC'd and then bend it on our brake? This would save us a lot of time as it wouldn't need to be shipped out to a sheetmetal shop. Any thoughts?
Also, yes we will be adding a plywood baseplate and another cross member.

24-01-2012 16:34

Akash Rastogi

Re: pic: Team 1325 Sheetmetal Chassis 2012

If you are doing the sheetmetal in house, you really should have someone who knows what they are doing with sheetmetal. Each material and thickness has its own bend allowance formula and all shops have their own specific minimum bend radii.

Please make sure you talk to a sheetmetal shop for help before you continue.

24-01-2012 18:06

Nuttyman54

Re: pic: Team 1325 Sheetmetal Chassis 2012

If you have a sheetmetal shop that is willing to do this for you, most likely they would be more than happy to cut it all for you. I doubt many shops would willingly take parts that were cut elsewhere to bend. Each shop has their own practices for bend tolerances, relief cutouts and other minor details that you would not have if you cut it yourself.

CNC (I assume you are milling this) is not going to cut thin sheet well, and I would not recommend it. Fixturing will be a big issue, and milling puts forces on the sheet that will likely warp it in ways you don't want unless your material is thick enough. Even with 1/8" plate (which is really getting towards the upper limit of what you could probably bend well on your school's brake), you will likely get lots of vibration and tool chatter. If you absolutely must mill it, use a straight flute endmill to help keep the sheet from being pulled up.

Bending parts precisely on a brake is not an easy task, and requires a fair bit of experience to do well and/or an automated setup. It is highly likely the parts will not be precise enough for all of your holes to line up well if you pre-drill them.

All said, if you want to do a sheet metal design, you should aim to do it with the proper tools or your design won't be able to realize the benefits of sheetmetal. If you have a local sheetmetal shop, ask them if they'd be willing to sponsor you.

24-01-2012 18:06

akoscielski3

Re: pic: Team 1325 Sheetmetal Chassis 2012

Please make sure your sheet metal break is big enough to hold a piece and bend it. We almost did that for our prototype, our break wasn't bug enough to bend the metal. Instead we got it bent at our sponsors place.

See you in Toronto!