West Coast Drive: Bellypan

[AdamHeard]

Originally Posted by BJC

Interesting, our analysis suggests that it is actually quite inefficient as a structural member. What you are saying pretty much corresponds with where my head was on bellypans: they are nice, but not mandatory. At least in our sheet metal construction, another well placed cross-member is probably a more effective use of weight. I do really like the use of the bellypan as a welding jig though, that makes perfect sense for a stick construction method.

Thanks for the info!
Regards, Bryan

They are very good at connecting the frames corner to corner in tension. Most other types of loading are handled pretty well with "West Coast Drive" frames.

[BJC]

Originally Posted by AdamHeard

They are very good at connecting the frames corner to corner in tension. Most other types of loading are handled pretty well with "West Coast Drive" frames.

While it certainly keeps the robot square I still think that a similar or more effective result could be achieved with some triagular corner brackets and perhaps even corner to corner cables in tension. There is definatly a good deal of bellypan that isn't actually doing much and I would still contend that as a structural piece it is not as efficient as it could be. We built a west coast drive in 2011 and like you said, it handles most types of loading very well. I think if I were to do a west coast drive again I would use a 1/16 waterjeted bellypan to use as a jig when welding and a low electronics mounting point. Because, as you said, the stick frame handles the tortional loads 1/16 should be fine for corner to corner in tension (try pulling apart a piece of sheetmetal, it can be bent, but not stretched or compressed without bending.) As a bonus, lighter material means less pocketing and less machining time.

In any case, it's only my opinion, take it with a grain of salt.
Regards, Bryan

[IKE]

Originally Posted by NickE

... Furthermore, when the frame tubes are riveted to it, it acts as a welding jig and holds the frame tubes nice and square. It helps make the competition and practice bots closer to identical. ....

I hadn't thought of doing this for welded assemblies, but I really like the idea. Often we end up adding gusset straps to butt joint welds anyway. Why not put them in place before the welding begins in order to hold everything true.

[roystur44]

Here are a couple shots of our belly pan. We used the belly pan as the main design element to hold the frame together. We use rivets to join the pieces together and once joined the frame is lightweight, very stiff and strong. The material we used was .090" 5052 aluminum. The frame is 12 lbs total. No welding required.

We used a CNC punch press to cut the metal. Notice the basic shapes circle and square. The punched frame takes only minutes to produce but requires a bit of up front programming. The tolerances for the frame are very high. Hole to hole tolerance is +-.010" . We used a staggered perforation pattern to lighten the belly pan. A staggered pattern can reduce the weight by 50%-60%.

We laid out our electronics prior to punching. By taking the CAD model of the the electronics and extrude the mounting holes through the belly pan we come up with all the mounting holes. We used a 10-32 .250 thk. Pem standoff, a plastic isolator and a nylon screw to mount the electronics. Once installed we cut off the remaining thread and makesthe bottom surface smooth.

The proper use of the belly pan can reduce your build cycle considerably. It can be used to fixture other parts of your frame. It can be used to mount electronics. It can be used to strengthen and stiffen your frame. It can be bent up in the front and rear to allow the wheels to climb over field elements.

https://picasaweb.google.com/1045493...18089428878706


https://picasaweb.google.com/1045493...18315802523202

[Adam.garcia]

Thank you to everybody who commented.

Our team has decided that we will buy a sheet of Garolyte for the time being. We did not know that fabricating the bellypan would be such a time/resource sink.

I fully agree that there are other parts of the drivetrain to improve upon first.

By the end of this summer, we will have a solid drive train, and will start the iterative process of improvement. I'm not yet sure when we will get to the custom bellypan, but that's the beauty of having another season to improve.