In preparation for the new control system, I have done some work to make sure that the new roborio is a bit safer. In order to help cover the large amount of open areas on the board in an effort to prevent board frying, I designed this simple two-piece protective case. The bottom part is a 3D printed plastic base which holds the roborio in place and provides room for a clean velcro attachment between the roborio and the case. The top is a 1/16" thick polycarbonate sheet that acts as a transparent cover to the system that protects the roborio from debris while allowing the roborio to remain easily visible. The corners have clearance holes for 10 bolts to fit through to bolt the assembly to the bellypan with 6.125" C-C spacing between the holes (not diagonally). There are about 2" of clearance space between the roborio and the polycarb to allow wires to run in and out of the system, and the top is easily removable for access.
If anyone is interested in the CAD files, message me and I’d be more than happy to share them with you.
I am not expert in CAD, but I am really interested to see a stress analysis of this case. I do not have CAD on this laptop because it is not powerful enough to run the software at a manageable level.
If you’re going to post a CAD file of a case, the least you can do is strength test it in software
There are quite a few definitions of “strength” in the engineering world (sorry not bored enough to list them…). Which one(s) do you have in mind?
I am mostly just interested in the amount of force required to break the polycarbonate sheet, as that is the most probable place of impact.
The case seems like it’d serve its purpose, to protect the roboRIO, I was just wondering how good of a job it really does. The worst case scenario the past few years would be either the 2014 game ball landing directly on it, or a Frisbee deflected into it. The latter has the potential to have a lot of force. FRC games are tough. You have to design durable parts.
I’m a programmer, but I’m willing to bet money on if you design something for industry, you have to extensively stress test it in software before implementation is ever thought of. It’s kind of like with code, only it’s called unit testing then. Bill Gates got so much free programming time because someone who wrote the login info to computers back then they didn’t unit test their code. When prompted to put time, he simply put a letter, and the software couldn’t make sense of it so he got to use the computer for free.
NASA wouldn’t have gotten to where they are today if it weren’t for extensive stress testing, in software and in the lab.
I think it would be a good habit to get into the ensure what you design can serve its purpose in the worst case scenario. What if brakes of a new car failed after 10,000 miles? What if pacemakers fail after 4 years?
It may seem silly for a little case, but it pays off. It gets you experience, and isn’t what this is all about?
This is a bit off topic, but I had an interview today for an internship for developing software. One of the questions was how I unit test (stress test) my code. It is important to do, and it could be the difference between getting a job or not. You never know.
And if you really don’t want to do it, I’m sure there exists some program online that allows you to upload a cad file (I don’t even know what extension they have…) and it will do it for you, or you could figure out how to do it in whatever software you designed it in.
I could easily see the quality award going to a team that has documentation about their robot’s durability (and of course a good robot) How much the frame will deflect during a collision, stuff like that. It shows good engineering practice.
Good engineering practice is to not over engineer or overanalyze things. If this case was protecting components for manned space exploration, on which lives depend, and was something never-before-done, then yes, extensive stress testing would definitely be in order.
This is not going into space. It is a simple protective cover for a relatively replaceable component in a robot designed to play games, for a robot whose operational lifespan will be measured in hours, using materials the designer has almost certainty used in similar applications dozens of times, in an application that is highly weight sensitive. Given these constraints, stress analysis is a waste of the designer’s time, and overbuilding the case to withstand any freak accident imaginable in FRC is poor use of resources.
Nice case! Have you considered implementing cable retention into the base piece?
I hope you don’t mount your electronics where a big 2lbs ball or a supersonic (exaggerating here) frisbee could hit it!
I bet that it would protect it from most things, especially if you 3d print it properly. I don’t think stress testing is necessary, and if this case goes through more than a little stress, shame on you
I for one think this is a very good idea. Although this is akin to the sidecar, which is typically mounted deep within the structure. If your design necessitates mounting to an exposed surface, this thing will shrug off a bouncing rebound rumble ball.
It is made out of ABS and a 6.25" square of 1/16" polycarb. Anyone who has touched either of these materials could attest to their properties.
Will it survive a frisbee or a yoga ball? Ask yourself this: would a naked rRIO survive better?
You guys are really being harsh. My count is near nil for CAD files posted on CD that get berated for lack of stress testing. What about that thing that jammed into the 8-slot cRIO to hold a sidecar, or the Tower of Talons thing.
Yeah it won’t survive a worst case scenario. It wont even stop a freight train. Perhaps consider casting it from pure Adamantium.
For example, designing it to withstand a combination of hits that sheared a 1/4-20 bolt. That’s a LOT of OUCH! And, yes, I have seen that happen. It also happened to be a bolt that was holding a battery holder on. The battery was plainly visible shortly afterwards, and the robot wasn’t moving.
A more reasonable test would be bouncing a Frisbee or a ball off of a robot’s side panel that was made of similar material, several times, as hard as thought to be reasonable (grab a freshman and tell him to break it using X, but stop after half an hour, for example). If it breaks early, redesign. If it doesn’t break (probably won’t), you should be OK.
There’s a time and a place to do analysis. A case to try to keep FOD out of the controller, you pretty much need enough strength to hold it together. A robot frame, you need a bit more for some reason…
A 1/16" sheet of polycarbonate will not shatter no matter what you do to it.
Are the standoffs 3D printed, or are they aluminum or steel? Even with the 10/32s running through them, that would be the only part I’d have any concern about. It looks great and my team would totally use something like it. We’ve already printed a mock up of the roboRio for our off season bot, so we’re right there with you.
Wasay, I’m feeling more like Digiorno right now.
Thank you! It wasn’t in my original design, but as Electronica1 mentioned below, it’s definitely possible to.
The standoffs are printed as well (they are a part of the base - they don’t come off), but with a decent enough wall thickness to hold their own (it’s an odd number due to the wall thicknesses driving the overall dimensions of the case, I forget the exact number). I’m sure aluminum standoffs could be used just as well.
It definitely can include something like that. There’s plenty of room.
That is a cool idea. It looks like it should be able to sustain an impact from pretty much any game piece. A robot arm would be a different story but it would not be considered debris either.
From your description, it seems that you intend that the #10 screws used to attach the polycarb cover also holds the case onto the electronics panel. If so, removing the cover would detach the case from the bellypan. You will likely need more than 2 inches of space between the top of the Roborio and the cover in order to insert the various wires and cables. This design also requires screws that are longer than 2 inches, which will be harder to find. Four #10’s in a more common length would be perfect for holding the case onto the bellypan. Four more short #10’s could then be screwed into the pillars to hold the cover on.
Is each Roborio meant to be permanently attached to a case? It may be difficult to remove the Roborio if a lot of Velcro is used. Some holes in the bottom of the case would allow the Roborio to be pushed out of the case.
Alternatively, use the case to clamp the Roborio to the bellypan and dispense with the Velcro.
Please consider adding some strain relief features to the case to allow the various wires and cables to be secured to the case with zip-ties. Pairs of ridges on the vertical cylindrical parts would be just one way of doing this. Allowing the wires to be tied down would, hopefully, encourage the people installing the wiring to do a neater job overall.
Please also consider a version of the cover with a flap on each of the 4 sides of the cover may help keep debris out of the Roborio. Is it as prone to getting debris in it as the old Jaguars? The flaps can leave holes near the pillars for the wires to exit or the flaps can be custom trimmed for each application.
With this concept, it would be possible to “bury” the Roborio in the robot and gain access through the removable cover. The case would be mounted upside down so the top of the pillars would be touching the bellypan. You may have to make a larger version so that there is room to work on the connections.
Yes, please consider adding features like the one Electronica1 linked.
Agreed, if you are going to all the trouble to print what amounts to something that could be made out of plywood and wood glue you might as well take advantage of the 3D printers abilities, like some sort of cable management on all sides.
Also, the 2+ in long steel bolts and nuts could be removed if you made the holes in the standoffs a bit smaller and tapped them from both ends (or tapped from just the top and just velcro the entire thing to the robot)
Well, if you’re going to enclose the Roborio somewhat anyway, what about getting some rubber/flexible 3d printing filament and making somewhat of an otter-box for the Roborio?
This retrospective, observational study found that “the 4-year survival rate of device battery was significantly worse for Medtronic devices compared with devices from other manufacturers (94% for Boston Scientific, 67% for Medtronic, and 92% for St Jude Medical, P <0.001).”
Anyways, my point with that is… know the expectations for the part you are designing, and do your due diligence accordingly. An electrical enclosure like this is designed to shield the part from debris like metal shavings, not from robot-robot impacts. If your roboRio is exposed to impacts from other robots, this enclosure won’t protect it.
