Good Material For Bottom of Chassis

[alicen]

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

[Richard Wallace]

Originally Posted by cgmv123

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

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.

[Jared]

Originally Posted by cgmv123

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

Doesn't the axis camera have a grounded enclosure?

[cgmv123]

Originally Posted by Jared

Doesn't the axis camera have a grounded enclosure?

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

[Jared]

Originally Posted by cgmv123

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

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

[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.

[Christopher149]

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.

[s1900ahon]

Originally Posted by Bryce Paputa

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.

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.

[Bryce Paputa]

Originally Posted by s1900ahon

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.

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.

[Gdeaver]

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.

[s1900ahon]

Originally Posted by Bryce Paputa

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.

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

[RomeroFRC5012]

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.

[Dale]

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.

[AdamHeard]

Originally Posted by Dale

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.

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.

[GeeTwo]

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!