Second layer

Our second layer mounting on top of the first layer is going to be made of 1/2" thick plexiglass. The mentors are saying we should just go ahead with it. Is this going to be a problem?

Could you post images or better describe your situation? I’m not exactly sure what you’re asking.

For general robot applications, ensure the “plexiglass” is polycarbonate and not acrylic.::safety::

The reason for this STRONG recommendation is that acrylic plexiglass very easily shatters. Many teams have used acrylic plexiglass, but they almost always use it just once, then they learn.

I’m sorry: Did you say 1/2"? as in 0.5 inches thick? :eek:
Goodness that’s overkill, way too thick for anything I can think of. I think the thickest POLYCARBONATE (not acrylic! Never!) we use is just under 3/16, and that’s a major structural element of the robot.

Print this thread out and show it to your mentors. We’re sure it is overkill.

Oh, and not plexiglass. Not ever. Even 1/2" thick.

It’s confirmed that we have acrylic plexiglass. We used a dremel on it and had some minor hallucinations from the smell. It’s a half inch thick. I don’t think we have a chance on getting a substitute for it by bag and tag day. We’ll probably be practicing with for a bit and get a copy of it with polycarbonate by our regional.

I don’t know exactly what you’re using it for, but is there any possibility you could use plywood instead?

Probably a good idea. Two things:

Lexan is very strong, and it bends instead of breaking. 1/8" lexan is about as strong as 1/16" aluminum. So you could not possibly need Lexan thicker than 1/4".

Also, take careful notes on that piece of plastic, so you can pre-drill and cut things, making it an easy retrofit at competition.

I can think of something. Though even then it was only 1/4". http://www.chiefdelphi.com/media/photos/21476

Oh, and we were thinking of using plexiglass (or rather, “unidentified clear plastic”) on the robot this year. A quick “smack! test” from a mentor left several pieces on the floor, and we found something else right away.

Amazon.com is an good source of small sheets of polycarbonate. Much of it ships Prime.

You can buy Lexan/polycarbonate on McMaster-Carr and ship it next-day air, too…

But at this stage in the game, I’d much rather use thin plywood than thick acrylic plexiglass. Plexiglass is a “no, no, no, no, never, never, NEVER” item in our workshop. Acrylic plexiglass shatters easily when subjected to FRC-level forces. .5" wouldn’t give me the slightest bit of reassurance over .25".

Lexan good. Plexiglass bad.

Heh. 1075 built our electronics on a plexiglass panel in our rookie year. That was the last time plexiglass ever made an appearance on a 1075 bot.

Home Depot usually stocks a good selection of both acrylic and polycarbonate (lexan) in their windows section if you need something fast. Yes acrylic will shatter but with a piece 1/2" thick it’s going to take an aweful lot of force. If you have the weight allowance I would say go for it if you have it in stock. If not, home depot for lexan/polycarb.

It is not clear to me what application you are using this for. It sounds like an outside layer of something that you would want to see through, so the suggestions here of lexan are good. We use 1/8" for side panels all the time. It will bend a lot in impact but rarely breaks, and when it does break it doesn’t shatter.

If you don’t need to see through it, corrugated plastic is a nice alternative as well. We often use 1/2" corrugated and it is light, sturdy stuff. We had a slide made of it last year that stuck out about 13 inches past its attachment on the frame members. You could whack that extension with a hammer and not do any significant damage.

So the acrylic broke today when one our members tried dremmeling hacksawing and hammering it to get it the right shape. It’s all for the good now because we bought half inch plywood which is much lighter. We’ll get us some lexan or polycarbonate and trace around the plywood after the deadline. Our second layer on top of the electronics needs to be clear so that the inspectors can see our circuit board. Thanks for the help!

Hooray! Better now than in a collision on the field!

Okay new problem. My mentors (and me) are fairly new to FRC. This being our second year and only one mentor has technical experience with cars. They seem fine with 3/8"lexan which we already have. I feel that’s way overkill given its weight and how much prefabricated materials we can bring. The thickest at home depot is 0.093in. Is that suitable for taking FRC level hits?

Could you post a photo of your application? There is much more to knowing if a material will work than it’s thickness and a benchmark of “FRC level hits”.

If weight is not an issue (i.e., you are underweight) then go with what you have.
Otherwise 0.093" Polycarbonate is quite strong and, more importantly, tough - it takes a beating without breaking. FRC “hits” are not all that bad since everyone has bumpers. This isn’t battlebots. You’ll see.

We use .125 Lexan because it’s the thinnest we can get at cost from a sponsor, but would use .093 if we could.