Good Material For Bottom of Chassis

[snoman]

we use aluminium road signs that were donated to us. we have been careful mounting our components and haven't had any issues. there are non conductive paints out there and we may try some this year to be safe.

[wireties]

We use polycarb to mount the electronics (thicker stuff for cRio than for the motor controllers etc) except for the battery. Lately our sheet metal sponsor is making fancy battery trays for us but in years past we used aluminum angle to stick-build reliable battery trays.

Being flexible with the battery location is a plus. If you can move it around a little (as the last design step) you can get the robot's COG just right.

[philso]

Originally Posted by Qbot2640

Be careful interchanging the terms "Birch" and "Baltic Birch". The former is just an appearance grade plywood with a birch veneer for cabinet making. What you really want for a strong bellypan is the latter - Baltic Birch. The core layers are solid birch as well as the outer veneer, and with no voids. This material is excellent for many robotics applications. It is light, strong, and holds screws extremely well. "Just plain birch" plywood is attractive, but the inner cores are made of a cheaper grade of wood and can contain voids and imperfections.

Also worth noting, American plywood is getting thinner - often you will see 23/32 rather than 3/4. The Baltic Birch is a European product, thus it is usually available in mm sizes...the 9mm is a great thickness for bellypan - a hair thicker than 3/8.

Probably the best way to purchase Baltic Birch is to find a specialty hardwood supplier where you live (Houston Hardwoods and Clarks Hardwoods in Houston, TX). Rockler sells 24" x 30" pieces as well as 12" x 30" pieces in 1/8", 1/4", 1/2" and 3/4" thicknesses. Lee Valley Tools also sells thick Finnish Birch Plywood in 3mm x 25" x 25". Lastly, you can try a local hobby shop that serves the model airplane builders but they are likely to be more expensive and they might only carry small pieces.

[Anupam Goli]

This seems like a good thread to ask these questions:

For those of you who have used Garolite, I was thinking of purchasing 1/16th" Machineable grade Garolite from Mcmaster-carr to use as the bellypan of our chassis this upcoming season. I had some questions about machineability, mainly with drilling holes. I'd like to use a waterjet to cut the patterns I need out, but I'd imagine the impact of the water would be too much for the Garolite. Should i go about manually drilling out any holes, or look for CNC routing options?

Also, would 1/16" be enough to hold the battery and other various electrical components without sagging, or should I go for a thicker sheet?

[Mike Marandola]

Originally Posted by Anupam Goli

This seems like a good thread to ask these questions:

For those of you who have used Garolite, I was thinking of purchasing 1/16th" Machineable grade Garolite from Mcmaster-carr to use as the bellypan of our chassis this upcoming season. I had some questions about machineability, mainly with drilling holes. I'd like to use a waterjet to cut the patterns I need out, but I'd imagine the impact of the water would be too much for the Garolite. Should i go about manually drilling out any holes, or look for CNC routing options?

Also, would 1/16" be enough to hold the battery and other various electrical components without sagging, or should I go for a thicker sheet?

Just to let you know, I only have firsthand experience with G-10. I am not sure about waterjetting Garolite, but 1/16" would be too thin even with supports, especially when you put holes in it. I would go up to 1/8" and have a battery carriage mounted to the frame to prevent sagging.

[Mr V]

Originally Posted by Anupam Goli

This seems like a good thread to ask these questions:

For those of you who have used Garolite, I was thinking of purchasing 1/16th" Machineable grade Garolite from Mcmaster-carr to use as the bellypan of our chassis this upcoming season. I had some questions about machineability, mainly with drilling holes. I'd like to use a waterjet to cut the patterns I need out, but I'd imagine the impact of the water would be too much for the Garolite. Should i go about manually drilling out any holes, or look for CNC routing options?

Also, would 1/16" be enough to hold the battery and other various electrical components without sagging, or should I go for a thicker sheet?

I would think that water jetting it would work fine. Water jetting is used for many delicate items because it doesn't damage them. It's all about the right settings for the material.

[Tom Line]

We use expanded / foamed PVC. Isolated, easy to cut and drill, stiff and lightweight. It also comes in a number of colors. Your local plastic or sign shop will usually have it in 4x8 sheets.

[Gdeaver]

Garolite comes in many classes. G-10 and G-11 are probably what you want. 1/16 is a little thin, 1/8 is probably a min. You could get the thinest g-10 and glue it to both sides of some structural foam. Could also do it with some honeycomb material. This would give a strong composite board with out the hassle and mess of laying up a composite board.
Woodcrafters carries Baltic Birch.
http://www.woodcraft.com/family/2004113/plywood.aspx
What ever board you use, Get some nylon hardware to mount stuff.
http://www.mcmaster.com/#machine-screws/=v8em46

[electroken]

Originally Posted by Tom Line

We use expanded / foamed PVC. Isolated, easy to cut and drill, stiff and lightweight. It also comes in a number of colors. Your local plastic or sign shop will usually have it in 4x8 sheets.

We use this stuff too, in a 6mm thickness.

[IndySam]

Originally Posted by Tom Line

We use expanded / foamed PVC. Isolated, easy to cut and drill, stiff and lightweight. It also comes in a number of colors. Your local plastic or sign shop will usually have it in 4x8 sheets.

I have access to as much of this stuff as I want for free but I would be very hesitant to use it on a FIRST robot. It will crack easily under impact, especially when drilled trough.

I can see how it may be useful in this situation but I always hesitate to use something this fragile on a competition robot.

[Joe G.]

In the past, my team has had the resources to do an aluminum diamond bellypan. But for those who don't, I highly, highly recommend this stuff. I use it for several applications in my high power rocketry endeavors (fins, mostly). A bit pricey, but it has very good strength, and much better stiffness than plastics of comparable thickness, all at almost unbelievably low weight. It consists of two pieces of very thin G10, with a honeycomb structure joining them.

[MrForbes]

As usual, I'm baffled as to why so many teams go to so much effort to keep weight off the very bottom of the robot. The belly pan is the perfect place to let there be some heavy, stiff, strong material.

But this thread has shown us several neat lightweight materials that I'd be eager to use higher up on the robot.

[Michael Hill]

Originally Posted by MrForbes

As usual, I'm baffled as to why so many teams go to so much effort to keep weight off the very bottom of the robot. The belly pan is the perfect place to let there be some heavy, stiff, strong material.

But this thread has shown us several neat lightweight materials that I'd be eager to use higher up on the robot.

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.

[tim-tim]

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.

[IKE]

Originally Posted by MrForbes

As usual, I'm baffled as to why so many teams go to so much effort to keep weight off the very bottom of the robot. The belly pan is the perfect place to let there be some heavy, stiff, strong material.

But this thread has shown us several neat lightweight materials that I'd be eager to use higher up on the robot.

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.