Good Material For Bottom of Chassis

It allows us to allocate more weight to other parts of the drive if we want. For example, saving some weight in the bellypan lets us use steel axles and #35 chain or even allocate more weight to the gearbox.

Baltic Birch plywood is my recommendation. Easy to work with, not resource intensive (other than the cost), lightweight, adds a lot of rigidity, easy to add things later if your design changes… lots of advantages. We got two 5’x5’ sheets for $43ea from a local hardware store.

In theory, weight and stiffness down low is very important.

In general, a few pounds is a few pounds and can be a whole new feature.

As an inspector, peg board tends to get fall apart around 4 or 5th match unless very well supported structurally (IE not a 4 zipties…). By the way, ziptieing your control board with pretty much any material seems to be a big likelihood of it falling apart. My biggest recommendation is use button head fasteners pointing up (so the round head faces the carpet) and fender washers to help support it in several locations.

Use some angle pices to support your battery and a good strap to hold it down. Hint, if your robot accidentally flips upside down, your battery should stay put.

Amazon is also a good source for Baltic Birch plywood in a variety of sizes and thicknesses.

While it is pretty typical our experience might be useful for someone. We used a piece of 1/16 aluminum sheet on our WCD which is quite a bit thinner than most teams use (254 uses .1 so they can tap it I believe) which was nice as we didn’t have to pocket it which would of taken a lot of water jet time. We were worried about it breaking especially around the battery but it worked great. It also added ton of rigidity to the chassis which improved handling IMO.

I’m going to toot my own horn for a moment…

We’ve done

  1. 1/16" G-10/FR4 Garolitem (2009, 2009 offseason, 2010, 2012)
    -Looks darn good (glossy black)
    -Very Stiff/strong
    -Easy enough to drill, but vacuum the mess!
    -Waterjet delaminates it, so they pierce 3-4" away from final cut and feed over. We did some external slots to act as rivet holes, then match drill rest on robot.

  2. 6mm (~1/4") 5 ply baltic Birch (2012 offseason, 2013 season, 2014 offseason, 2015 season)
    -Easy to cut
    -Very HIGH stiffness to weight
    -Can thread fasteners right into it for components
    -When painted, looks nice enough.
    -Ignorant teams look down on it. This is fine, it just points out their lack of understanding of material properties and basic math :wink:

  3. .125 6061-T6 diamond pattern (Waterjetted/lasercut). (2011 season, 2011 offseason, 2014 season)
    -Forces you to do layout
    -Expensive resource wise
    -Not as stiff as the other 3 items
    -One and done, no mods

  4. .25 ABS (if you count 294). This is similar enough to (2007 season)
    -It’s really just a heaver version of plywood. I’d use plywood over this.

I highly recommend the wood, no need to laminate or do anything to it. Just use it as is. If your frail ego can’t handle the wood, garolite is a great option at 1/16" thick but requires more tools to work with.

The diamond bellypan is nice… but in nearly all cases is a huge resource waste. Many subsystem gearboxes and gussets could be cut in the same time.

I’ve never understood the diamond belly pan thing is their any other advantage over a thinner sheet besides being able to tap it?

We like that it makes it super easy to zip tie wires down. You can do this with wood too, but you have to drill a hole wherever you want to put a zip tie in.

No need to drill holes through the wood.

Drilling holes through wood is so hard :wink: Instead I will waterjet GIANT holes :wink:

In the cases where we are replacing stuff in the middle of competition I like to be able to easily add and remove cable ties. Clearly it doesn’t matter that much, but it’s the only reason we’ve continued to do metal bellypans on our comp bot.

We use this stuff:

It’s often called “twin-wall” or corrugated polycarbonate. I believe McMaster sells it but I’m not sure what variety they have. We typically aim for a thickness between 1/4th and 1/8th. Anything less than an 1/8th can be too flexible.

It’s lightweight and reasonably priced from our local vendors. It’s also easily machined… and by machined, I mean you can drill holes into it or cut it with a knife/razor. I highly suggest learning how to cut it and mount it to take advantage of it’s inherit perpendicular strength (perpendicular to the inner walls that is).

We’ve been very happy with it over the years.

Would something like this work fine?
Or does it have to be baltic birch?

We have a sponsor willing to cut a pan out of sheet metal for us this year. Does any team use sheet metal instead of aluminum? If so what gauge? Or does any team use stainless steel. Just wondering short of the electrical issues that could occur if we were not careful, are there any other downfalls to using sheet metal. We normally use .25 lexan and have really not had any issues with it but it is expensive. and a pain to cut :frowning:

I agree with other posts further up: say thank you to the sponsor, but use plywood.

You can also use this stuff. It’s good enough for our entire chassis, so an electronics board will be no problem. Has a very nice finish.

The nominal 1/2" and 3/4" sizes of that plywood is what we used to make all of the PNW’s road cases that are used to transport the field and all of the production equipment. It is nice stuff.

I like a nice piece of aluminum or steel/stainless. We’ve been doing 1/4" aluminum lately.

But I’m a control panel guy, I’m pretty attached to my metal back plates and my Greenlee DTAP kit.

We used carbon fiber for a few years… however we did have a sponsor that just gave it to us for free which is nice because it can be very expensive. The only issue we had was that it was conductive so we velcroed electronics down. It was super light and we had the right stuff to cut it with.