How to CAD belly pan weight reduction pattern?

Hey CD

On my team, we have more familiarity of designing unique parts that do not incorporate many patterns. With all of these 775 pro drive trains, it got me thinking how can I design my own. Does anyone have any tutorials or tips on how to create a weight reduction pattern for a belly pan in Fusion 360? Any tips will help!

My boy Andrew made a pretty good tutorial on this:

Check out the Vent tool in SolidWorks. It can save a huge amount of time. Fusion 360 may have something similar (or just switch to SW)

Looks pretty… but how do you mount anything to it?

Just make it thinner?

To expand: here is a 0.032in thick belly pan with some beads rolled into it. Worked like a charm!

Andrew’s tutorial is fantastic. We’ve used it in 2016 and 2017 with much success.

I know this is backwards from how teams should do gearbox pocketing, but we size out and pocket the bellypan first, transfer over the electronics/mounting layout next, and create mounting geometry off of the remaining web. Picture of our PDP and talon mounting in CAD below.

This last step is far more tedious than the actual pocketing if you follow the tutorial linked to above, but 100% worth it to have nice and solid mounting for electronics.

We pocket our diagonals from corner to corner so there is an uninterrupted tension member between the far corners of our bots.

Essentially what Jeremy said. I’m actually teaching my current students how to make bellypans right now so maybe I’ll make a video about it, but the main concept is to make the base diamond structure by itself and then add the mounting holes in a different sketch. Once I have my diamond bellypan I take the following steps:

1: In a new sketch, model the mounting holes for my electronics components on the bellypan.
2: Add material around the holes (typically an offset of the mounting circle).
3: Extrude the material into the bellypan (note: some of the material may exist in empty space between the diamonds - that’s okay).
4: Cut out any of the holes that may intersect the diamond strands.
5: Connect the extruded material to the diamond strands for proper support.
6: Fillet everything.

Always room to consider using wood for bellypans… My team started using wood after spending >18 hours making our 2015 bellypan, and our bellypan this year took 5 minutes on a laser cutter! Even on a router, wood use when there is not heavy structural need (covered by the rest of your drivetrain frame for example) cuts down your manufacturing time a lot and can make iteration cycle time much faster.

I would advise against using MDF.

Wood != MDF. Plywood can be quite good.
I should mention that 299 broke a couple of plywood bellypans due to various errors, including ramming the gear arm into it at full speed. Apart from things like that plywood bellypans are great.
Make sure you paint it though. Unpainted plywood does not look great IMO (cue picture of 4183’s robot) especially if the rest of your robot is bare aluminum.

We use all baltic birch, 3 or 6mm. It has been a great decision for our team, using it in lots of places that aren’t taking too much stress. Really cuts down machining time and makes iteration cycles so much faster! Lets try to avoid turning this into an argument about wood on robots, but my point is wood on a bellypan (assuming you attach well and use high quality wood) can be a huge help and save you some grueling machine/design time.

This. 0.25" (6mm) baltic birch makes a great and light bellypan, no pocketing needed. Definitely worth the machine and CAD time saved.

We have used perforated polycarbonate for the past two years and it is very effective. Advantages of it are the holes are already there for electrical, the holes also help with weight reduction, and if it does take a hit it won’t break like cheap wood can.

In terms of design and manufacturing effort to reward, thick / lightened metal belly pans are pretty low on the list of priorities. They force you to figure out your electronics mounting in advance, they require fairly specific manufacturing resources, and they aren’t really THAT much better than a 1/4" baltic birch bellypan even in terms of structure.

Perforated polycarb is definitely a nice low effort solution for electronics mounting, but it is not useful as a structural element in this specific application since it is not very rigid at that thickness.

228 would always use VHB to attach electronics, which made us partial to a solid belly pan. A lightened belly pan would need a thin Lexan cover sheet for us to use VHB.