Has any team or anybody made a 80% - 100% lexan bot?

[Alex Cormier]

I'm looking for pictures and any details on a robot that is made of lexan or any other material then metal. It goes with all these posts.

**I'd like to add a note this is for my senior project and it will be done before the start of the season and i will be doing extensive testing on the durability of the materials chosen, since we will be going to 3 competitions this year.

6 wheel bot

Belt Drive

Drive the 6" wheels

thanks!

pictures if possible

[Cory]

I believe 1038 had a frame made of lexan in 2003.

[Steve Howland]

Here's a picture of it...it was acrylic and was apparently not used because of "design flaws."
http://www.chiefdelphi.com/forums/sh...threadid=17366
Hope this helps.

-Steve

[Greg Perkins]

190 made their 2003 chassis out of lexan, it was SICK! they had no problems until battlecry when the lexan split right down the middle of the robot


that was an easy 6-7 events before they had a fatigue problem.

[Andrew Rudolph]

SPAM team 180 has mad robots, even the gear boxes were out of lexan i believe. I belive this one below was called lexy.

[Arefin Bari]

Originally Posted by Greg Perkins

190 made their 2003 chassis out of lexan, it was SICK! they had no problems until battlecry when the lexan split right down the middle of the robot


that was an easy 6-7 events before they had a fatigue problem.

One reason i am against using lexan as the chassis... it may break. example was given by greg...

Edit- andrew, spam is a great team. and yes they have made 3 robots out of lexan. none of the robot broke during the competition. the past three years (2002, 2003, and 2004) they used aluminum as their chassis. for a game like we had in 2003 (Stack Attack) i wouldnt build a robot using lexan. but still you never know, you might be able to come up with something very solid.

[JVN]

Originally Posted by Arefin Bari

One reason i am against using lexan as the chassis... it may break. example was given by greg...

Any material can break.
Engineering is about designing such that the materials used can withstand the forces applied.

It's true, a robot chassis made out of graham crackers (my default, "weak material" for examples) probably wouldn't hold up. However: lexan, aluminum, steel are all TOTALLY doable.

Lexan's main advantage is it bends quite a bit before exceeding the elastic point. However, this is also a disadvantage when it comes to chassis design. Aluminum is much more rigid, and rigidity is important for some chassis applications.

Enough rambling... my point is:
Lexan is a totally viable chassis material, and I'd be more worried about it bending and throwing a chain or something than worried about it breaking.

John

edit:
Despite it's "bendability" (there's a fun fake word) Lexan can STILL be used effectively. Check out the above picture of 180 and see how they got around it. Note the cross bracing and box stucture (very high rigidity). Good stuff.

[JamesCH95]

Originally Posted by Arefin Bari

One reason i am against using lexan as the chassis... it may break. example was given by greg...

I agree. Plus Lexan is expensive. I'm on 95, and we hardly spend any money on our 'bots. We use 9-layer baltic plywood becuase i can absorb damage much more easily. Plus it's really easy to mount things to. But Lexan does look pretty cool.

[Max Lobovsky]

I don't have any numbers off the top of my head, but I'm pretty sure lexan is horrible in most strength(tensile strength, etc)/weight ratios compared with aluminum. I'd venture to say a good quality plywood will even exceed polycarbonate.

[JamesCH95]

Originally Posted by Max Lobovsky

I don't have any numbers off the top of my head, but I'm pretty sure lexan is horrible in most strength(tensile strength, etc)/weight ratios compared with aluminum. I'd venture to say a good quality plywood will even exceed polycarbonate.

I would tend to agree. It certainly has terrible performace/cost ratio. We only have about 900 extra dollars to spend on our bot every year, so every dollar counts.

[ahecht]

Originally Posted by Max Lobovsky

I don't have any numbers off the top of my head, but I'm pretty sure lexan is horrible in most strength(tensile strength, etc)/weight ratios compared with aluminum. I'd venture to say a good quality plywood will even exceed polycarbonate.

Really? I've always been told that aluminum and lexan have almost identical strength/weight ratios. However, as it has been stated before, lexan is much more springy than aluminum, and will bend and flex (which led to 190's 2k3 bot throwing lots of chains).

Also, I agree that lexan is much more expensive than aluminum, and 190 would probably not use it if we didn't get it donated every year. In fact, in 2003, the lexan that was donated to us was Hyzod AR, which is a pain to work with due to its abrasion resistant coating, and normally costs $300-$500 for a 4'x4' sheet (about twice what normal lexan costs).

[JVN]

Originally Posted by Max Lobovsky

I don't have any numbers off the top of my head, but I'm pretty sure lexan is horrible in most strength(tensile strength, etc)/weight ratios compared with aluminum. I'd venture to say a good quality plywood will even exceed polycarbonate.

Max,
What you posted doesn't "mesh" with what I thought to be true. Can you go to www.matweb.com and get the actual values, and report back your results?

I'd do it, but I'm working on something else right now.

Can anyone out there do this for me? I'd really appreciate it.

Maybe a comparison between 5052 H34 aluminum or 6061 aluminum, and whatever common grade of Polycarb McMaster-Carr sells?
That would be awesome.

Real enginerding -- you betcha!
Thanks,
John

[Arefin Bari]

Originally Posted by JVN

Max,
What you posted doesn't "mesh" with what I thought to be true. Can you go to www.matweb.com and get the actual values, and report back your results?

I'd do it, but I'm working on something else right now.

Can anyone out there do this for me? I'd really appreciate it.

Maybe a comparison between 5052 H34 aluminum or 6061 aluminum, and whatever common grade of Polycarb McMaster-Carr sells?
That would be awesome.

Real enginerding -- you betcha!
Thanks,
John

is this what you wanted John?...


http://www.matweb.com/search/Specifi...snum=MA5052H34 ... thats for 5052 H34 Aluminum...


here are few examples of 6061 Aluminum...

http://www.matweb.com/search/Specifi...ssnum=MA6061AO

http://www.matweb.com/search/Specifi...assnum=MA6061A

here is an example of lexan....

GE Plastics LEXAN EM1210 Polycarbonate
http://www.matweb.com/search/Specifi...snum=PGE8NA117

[Max Lobovsky]

I was already on it, and would have had it posted before you, John, but Firefox crashed

I used ultimate tensile strength as other websites have suggested it is the standard for strength-to-weight calculations. I would have thought yield strength is more appropriate, but I can't find that data for Lexan.

GE Lexan (clear, no glass) ---72 MPa -----1.2 g/cm3----- ratio 60
Aluminum 6061-T6 ---------310 MPa -----2.7 g/cm3 ---ratio 114

for comparison:

very strong titanium ------- 320


steels have an incredible range of like 40-250 but as far as I can tell (I'm not sure what are the most common types), structural steel is in the 80-110 range.

Amazingly enough, a high quality piece of wood (European ash, is good, apparently) can have a ratio as high as 320! in the direction of the grain though it is a mere 12 perpendicular to the grain.

I'm trying to find some good data on plywood, but it looks to be approximately equal to PC (but of course it is bidirectional, unlike regular wood.)



carbon fiber ----------------3200

kevlar----------------------2100

I know that what is generally considered the strongest material ever created was carbon nanotube fiber (spun by some of my dad's former co-workers ) but that is using some other measurement of strength (I believe Young's modulus).

Note that the properties of these extremely high tensile strength fibers aren't simply comparable with steel and aluminum. You can't build a robot 20 times lighter out of carbon fiber.

[JVN]

Originally Posted by Max Lobovsky

I was already on it...

Cool!
Thanks a lot. It is always nice to see someone back up their argument with numbers. Props to you, AND to Arefin for taking the time to do some research (Which is very important when doing design and analysis.)

You guys rock,
John