Good Material For Bottom of Chassis
 

What is a good covering for the bottom of the robot chassis to mount things like the control system, battery, compressor, pneumatic manifold, motor controllers, etc.? Last year was my team's rookie year and be used a piece of pegboard (something like this). Probably needless to say, it didn't really hold up too well under the weight of heavier items (mainly the battery) and started to fall apart from the stresses of competition. I was wondering what other teams liked to use and what their experiences with different materials were.

Re: Good Material For Bottom of Chassis
 

Baltic birch plywood, if you can find some, cuts well and looks nice--and it's an insulating material. It's also pretty light.

Re: Good Material For Bottom of Chassis
 

I know many teams use some forms of plastic, mostly polycarbonate.
I've also seen teams use aluminium plate with nylon bolts for attaching parts.

Re: Good Material For Bottom of Chassis
 

Plywood will work fine, as long as you make sure it is adequately supported around the battery area. We used 3/16" for the belly pan (as well as the rest of the chassis) and it holds up fine.

Re: Good Material For Bottom of Chassis
 

I have heard of teams using birch plywood, G-10 or garolite, and perforated polycarb. Just as a side note, we have used 1/16" perforated 3003 aluminum sheet for our bellypan and I would not recommend it. It sagged and bent around the edges like crazy. Maybe go thicker if you can find it, or 6061, but that is very expensive.

Re: Good Material For Bottom of Chassis
 

1/4 to 1/2" plywood usually works ok, although you need to provide some extra bracing under the battery unless it's right at the edge of the robot. Pegboard is not very strong....plywood is stronger. If you want to get fancy, you can use plastic or metal, but you might find that plywood gives you more stiffness for the weight, and is easy to attach stuff to, and the insulating is a good thing as well. It's not quite as "high tech" looking as other materials, for whatever that is worth.

Re: Good Material For Bottom of Chassis
 

You'd do best to avoid placing the battery directly on the bellypan/electrical board without other framework. The best thing to do would be to integrate some sort of specific case for the battery with the rest of the framework on the robot.

Re: Good Material For Bottom of Chassis
 

For the past 2 years at least, Team 20 has used Garolite for the past two years to cover the bottom of our chassis, as well as to mount the majority of our electronics. I cannot remember the thickness we used, probably 1/8". So far, it has worked well for us, since it's lightweight and relatively strong.

Re: Good Material For Bottom of Chassis
 

1/4" plywood is what I recommend. To stiffen it up a piece or two of 1x1 angle placed on the top works well to support the battery. If you space it just slightly larger than the battery so the edges of the battery rest on it then you've got the battery constrained in one axis. Use a small piece of the 1x1 angle to make a bracket to attach it to the frame on each end.

Re: Good Material For Bottom of Chassis
 

Can you machine on garolite easily? I've been thinking about using it, but hear bad things like delaminatione can happen.

Re: Good Material For Bottom of Chassis
 

I'm not too sure about the machinability, but as far as I know, we haven't had any major issues as of yet.

Re: Good Material For Bottom of Chassis
 

We used 1/8" polycarbonate sheet last year and it worked great. More commonly available at Home Depot, Lowes, and Menards than birch plywood, which can be somewhat of a specialty item. Polycarbonate sourced there is cheaper than the sheets that AndyMark stocks.

I would avoid using construction grade SPF plywood in a 3/8" thickness, as its quality varies widely and won't hold up as well as birch, which has more glue in it.

You'll find that acrylic sheet is also available and cheaper, but you shouldn't use it. It breaks too easily, and the broken pieces are quite sharp.

Re: Good Material For Bottom of Chassis
 

We're experimenting with a custom carbon fiber composite belly pan. We're taking a thick foam core and CNC'ing grooves for strength, for a battery holder, and for mounting electrical components. Then we layer this in sheets of glass fiber and carbon fiber, epoxy it, and vacuum out the excess air while it cures. This takes more time and more planning, but has given us a much better result than the 1/16th aluminum that we used last year.

Re: Good Material For Bottom of Chassis
 

Plywood, polycarbonate, and sheet aluminum are all going to work well for this. Plywood and polycarbonate are a bit better than the aluminum in my opinion. The reason for this is it makes sure any electronics you mount to it are electrically isolated from the frame. Though, this is almost as easily done with double sided tape or Velcro. The take away from this is, use what ever material meets your budgetary and aesthetic needs.

One thing to note, If you want to use this as an element to stiffen up your chassis, use more screws than you would think. More smaller screws are better in this regard. One 10-24 screw every 4 inches or so around the perimeter works pretty well. Much better than just securing the corners.

Re: Good Material For Bottom of Chassis
 

The 2015- control system does not have any components with grounded cases that require isolated mountings.

Re: Good Material For Bottom of Chassis
 

My team used to mount the battery to a section of the frame and use smaller pieces of aluminum angle to make sure it couldn't move/slide. A velcro wrap was then used to secure it in the battery holder (think like a cup holder).

For most of the electronics, we would use corrugated plastic (often used for yard signs) because it was light and cheap as well as sturdy enough. Usually we had sections for different parts of the electrical system and the sections could be removed to get to specific areas of the robot. They were all held on with velcro

Re: Good Material For Bottom of Chassis
 

Even so, the frame isolation requirement (R37) is likely to return for 2015 -- it has been part of every FRC Manual that I can recall. Many instances of isolation failure that I have seen, while inspecting FRC robots, have been caused by poor wiring -- and were therefore intermittent.

Also, a non-conductive wiring substrate will not produce conductive chips when you drill it at the last minute to re-position control system components.

Re: Good Material For Bottom of Chassis
 

Doesn't the axis camera have a grounded enclosure?

Re: Good Material For Bottom of Chassis
 

The 206 does, but Axis doesn't make them anymore. The M1011 and M1013 screws and enclosures are isolated.

Re: Good Material For Bottom of Chassis
 

Good catch. I've never had much time to play with the new ones yet, and just figured they were the same.

Re: Good Material For Bottom of Chassis
 

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.

Re: Good Material For Bottom of Chassis
 

A material 857 has used for a couple years is HDPE (high-density polyethylene). We have an absolutely enormous sheet and have been slowly working through it. Machines similarly to polycarbonate, and is opaque.

Nothing really special about it, but it's different than the other materials mentioned and has worked well for us.

Re: Good Material For Bottom of Chassis
 

How thick is your foam?
What kind of foam? (Make, model)
Are you trying to do this in one pass? I ask this since I've found that doing wet layup in 2-3 steps is a much easier process (and less stressful). We have much less retained epoxy. Peel ply is now a good friend.

Re: Good Material For Bottom of Chassis
 

On the most recent iteration we had a flat core (either 1/8th or 1/4th, don't know where we got it from) that we did one big lay up on. Not completely sure on the foam type, but it looks pretty similar to http://www.aircraftspruce.com/catalo.../lastafoam.php. We then made ridges separately and epoxy'd them on after the first lay up. This worked fine but doing the ridges separately took a bit of work. We haven't gotten to the CNC'd foam core quite yet, but we plan on making it with 1" foam core. We haven't had any issue with doing it in one pass, and we don't really want to have to wait for multiple lay ups to dry.

Re: Good Material For Bottom of Chassis
 

For several years now we have been using 4mm or 1/4" Baltic birch plywood laminated with a layer off 5.7 oz plain weave carbon on both sides. The panel is a structural member of our frame. S2 glass or Kevlar cloth could be used if the conductivity of carbon bothers one. It has not been a problem for us. Last year a sponsor laser cut the panel including mounting holes. We do not laminate the practice bot panel and it does not have the durability or stiffness of the carbon panel. Each year it ensures that the team receives some experience in composite construction.

Re: Good Material For Bottom of Chassis
 

Thanks.

We've had good success using HDPE for a mold material and directly CNCing the mold shape (we have a router-based gantry-style CNC). Then doing a layup of carbon x3, peel ply, perforation film, breather/bleeder, and vacuum bag. After curing, the next night we did a second layup of core (1/4 nomex honeycomb), 3x carbon, etc. A carbon part in 3 days was the most efficient recipe we've developed or executed.

This recipe could be adapted to cut foam opposite to the mold, adjusting to the thickness of the first layup.

Scott

Re: Good Material For Bottom of Chassis
 

My team during our rookie year used plywood and try to not use a too thick of wood because then the bolts under it would scrape the ground. Other than that it works great, didn't even crack until this summer when we were doing an outreach and took it off the cart at an angle.

Re: Good Material For Bottom of Chassis
 

We've used 3/16" black ABS plastic for the last few years with great success. Pretty much indestructible and easy to cut into odd shapes. We know Baltic Birch would be a good, and probably lighter, material. We avoid it because some scouts in the pits have been known to look down upon robots with lots of wood (for no good reason.) If we do use it we paint it to make it look less obviously, well, wooden.

Re: Good Material For Bottom of Chassis
 

If you spray it black it's no big deal.

Also, I wouldn't be too bummed about not playing with a team that looks down on wood like that. Their loss.

Re: Good Material For Bottom of Chassis
 

We've used plastic pegboard recently to good effect; we don't have to drill nearly as many holes. We usually mount the battery box and compressor directly to the frame, and put the cRIO over some additional support; not sure if the roboRIO will require this.

I absolutely agree that the control board should be non-conducting. It doesn't really matter when everything is done correctly and nothing comes loose, but it reduces the chance of a jolt or a short when things don't go quite right. For example, we are salvaging last year's drive as a base for prototyping this year. This involved pulling off the manipulators, and several of the now-spare controllers. The kids left the supply wires for a couple of the talons in place, with breakers still in the PDB. Since they were sitting on a non-conductive board, there were no ill effects. If they had been on an aluminum board, I could only hope that the breakers would have tripped immediately!

Re: Good Material For Bottom of Chassis
 

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.

Re: Good Material For Bottom of Chassis
 

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.

Re: Good Material For Bottom of Chassis
 

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.

Re: Good Material For Bottom of Chassis
 

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?

Re: Good Material For Bottom of Chassis
 

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.

Re: Good Material For Bottom of Chassis
 

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.

Re: Good Material For Bottom of Chassis
 

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.

Re: Good Material For Bottom of Chassis
 

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

Re: Good Material For Bottom of Chassis
 

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

Re: Good Material For Bottom of Chassis
 

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.

Re: Good Material For Bottom of Chassis
 

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.

Re: Good Material For Bottom of Chassis
 

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.

Re: 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.

Re: Good Material For Bottom of Chassis
 

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.

Re: Good Material For Bottom of Chassis
 

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.

Re: Good Material For Bottom of Chassis
 

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

Good Material For Bottom of Chassis
 

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.

Re: Good Material For Bottom of Chassis
 

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)
Pros
-Looks darn good (glossy black)
-Very Stiff/strong
-Easy enough to drill, but vacuum the mess!
Cons
-Expensive
-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)
Pros
-Easy to cut
-Cheap
-Very HIGH stiffness to weight
-Can thread fasteners right into it for components
-When painted, looks nice enough.
Cons
-Termites
-Ignorant teams look down on it. This is fine, it just points out their lack of understanding of material properties and basic math ;)

3) .125 6061-T6 diamond pattern (Waterjetted/lasercut). (2011 season, 2011 offseason, 2014 season)
Pros
-Hypetrain
-Forces you to do layout
Cons
-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?

Re: Good Material For Bottom of Chassis
 

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.

http://m.homedepot.com/p/Commercial-...5665/202520055

Re: Good Material For Bottom of Chassis
 

Drilling holes through wood is so hard ;) Instead I will waterjet GIANT holes ;)

Re: Good Material For Bottom of Chassis
 

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.

Re: Good Material For Bottom of Chassis
 

[quote=AdamHeard;1417870]

3) .125 6061-T6 diamond pattern (Waterjetted/lasercut). (2011 season, 2011 offseason, 2014 season)
QUOTE]

Don't you want to go back to Einstein? Lol. I'm sure 973 will do fine without the fancy belly pan.
Dumb question, why do you switch from year to year?

Re: Good Material For Bottom of Chassis
 

We use this stuff:

http://www.piedmontplastics.com/land...ate-sheet.aspx

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.

Re: Good Material For Bottom of Chassis
 

Would something like this work fine? http://www.homedepot.com/p/Unbranded...1178/203183010
Or does it have to be baltic birch?

Re: Good Material For Bottom of Chassis
 

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 :(

Re: Good Material For Bottom of Chassis
 

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

Re: Good Material For Bottom of Chassis
 

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.

http://www.homedepot.com/p/Unbranded...9023/100073744

Re: Good Material For Bottom of Chassis
 

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.

Re: Good Material For Bottom of Chassis
 

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.

Re: Good Material For Bottom of Chassis
 

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.