Is your frame tough enough for FIRST?
 

I was cadding up our last years frame up and a thought hit me. How many pounds of force actually hits your bot? Weak hits, medium hits and the hardest hit possible. So i need some help finding out the forces.

Thanks
CD

Re: Is your frame tough enough for first?
 

I would like to think so... and hard, harder, and hardest
mike d

Re: Is your frame tough enough for first?
 

The speed at which the collision occurs, as well as the angles and location of the hit, and how effective the bumpers are, etc will play a big part. For weight, figure 150 lbs to make it easy.

Some materials absorb impacts better than others...for example, fiberglass tends to bounce back, while some aluminum shapes get bent easily.

Re: Is your frame tough enough for first?
 

Thatz what i was figuring, but i wasn't sure. What do you think composite sides

Re: Is your frame tough enough for first?
 

I don't know the forces involved, but there are dents on the front of our robot that would be tough to make with a hammer.

Re: Is your frame tough enough for first?
 

Our hardest hits this year were when hybrid went awry. 15 ft/s into the wall is tough. Turns out the wall is a flexible member. Other than that, bumpers help a lot. We have some pretty vicious scars from years past.

As a little bit of how bad can it really get, I recently saw a vehicle go to 10 G's during a 5mph impact with a wall. 15 ft/s is almost 10mph. For a little math let's assume that your robot collides with a stiff wall at 3 m/s (approximately 10 ft/s). bumpers are about 3 inches thick or rough .1m Let's assume the bumpers are perfectly balanced and do an ideal deceleration.

Therefore d=V*t-1/2at^2 which is really d=V*t-1/2*V*t therefore d=1/2Vt
or t=2d/V=.2/3=1/15 second.
V=at therefore a=45m/s^2 or about 4.5 G's. This would be if the bumpers had perfect crush causing constant deceleration. If you assumed a linear rate of decel from 0 then the peak will get closer to 10G's. You can continue playing this game and second guessing it quite a bit. Overall having it survive a 10 G impact is probably pretty reasonable. You shouldn't see a lot of those, but you may likely see a couple a season.

Re: Is your frame tough enough for first?
 

I agree, those robots can take a beating! But, no matter how many numbers you run, your probably never come close to those freak incidents. So, always throw in a hefty safety factor.

Re: Is your frame tough enough for first?
 

We didn't use bumpers our 07 season and all the chassis aluminum is bent in.

Re: Is your frame tough enough for first?
 

One thing to keep in mind is that dents and dings aren't always a bad thing. They absorb impact energy that could go elsewhere. If your robot is still fuctional consider it good energy management. If your robot was incapacitated. Make it stronger.

Re: Is your frame tough enough for first?
 

we did our robot with an 80/20 frame this year.. the same chassis lasted from NJ to Chesapeake to atlanta. our hardest hit was in atlanta first elimination match our autonomous goes crazy and we hit the wall soo hard the entire wall is moved... the bumpers arent there our robot steering mechanism is toast... turns out the force angled one of the beams so the connecting point to the main chassis went from 90 degrees to say 65-70... neways our robot weighed 130 with bumpers and top speed which is what it hit the wall at was 25fps.

other than that the 80/20 frame has held up very well.

Re: Is your frame tough enough for first?
 

Squirrel from 1726 can attest to the toughness if 1662's frame. We were pretty busted up in 05 & 06. We totally redesigned the frame. We have ran it into a wall at full speed to test it. It passed. Pic is on CD

Re: Is your frame tough enough for FIRST?
 

I'm not sure about force, but at the Pittsburgh regional hitting another robot caused our 1/4 in plexi to shatter into 5 pieces.

Re: Is your frame tough enough for FIRST?
 

oooh, any pics?

Re: Is your frame tough enough for FIRST?
 

Was the "plexi" acrylic or polycabonate (Lexan)?

The reason I ask is that while they look similar, acrylic can shatter like glass, whereas polycarbonate is much stronger and normally it should never shatter (unless you spill Loctite on it). The only "downside" to polycarbonate is that it is more expensive than acrylic.

On both the teams that I mentor, acrylic is almost never used on a FIRST robot with only a few very limited exceptions, as polycarbonate is the preferred "plexi" material.

Re: Is your frame tough enough for FIRST?
 

For the good of the order (since I can't think of any such cases), what are those limited exceptions where acrylic is used? (1618 used it as side panels its rookie year, but wised up quickly following that.)

Re: Is your frame tough enough for FIRST?
 

We used acrylic last year to cover up our electrical board. Lexan would probably have been better. The plexiglass cracked due to improper hole drilling. It worked though. If you saw last year's robot you would understand. :D

-Vivek

EDIT: Our frame has always been plenty strong for us. I don't care what anyone says, the kitbot frame is a beast.

Re: Is your frame tough enough for FIRST?
 

We used the kitbot frame this year and it held up well. The frame suffered virtually no damage, but our bumpers sure got ripped up at the Kettering Rookie Competition (the judges at Buckeye were very surprised by how much damage we had from it; it was brutal, and we were tipped a few times with no penalty called).

However, I know it can withstand a good blow without bumpers since I was test driving it after we/I got the drive code running, and I went in full reverse . . . into a metal column in our school lobby. The battery casement came off (secured with one screw at that time, but that was fixed), but the pole suffered a chip and the frame had no damage.

Re: Is your frame tough enough for FIRST?
 

On 467 we used a unibody design this season that used the skin to support the internal components without a frame. it worked pretty well as it was light weight and durable. It took the force of being flipped twice at the Connecticut
regional without any dents or damage, our bot was so light that we had to bolt
a 14.1 pound steel plate to the bottom to stabilize it.

Frame, pre-construction:

http://www.team467.org/gallery/main...._itemId=512177

Final Bot:
http://www.team467.org/gallery/main...._itemId=512365

Re: Is your frame tough enough for FIRST?
 

I'm pretty sure it was polycarbonate but i'm not sure. It didn't shatter exactly but it cracked apart.

Re: Is your frame tough enough for FIRST?
 

Good way to distinguish between polycarbonate and plexiglass:

Place a corner of it on the end of a table, clamp down the other side, and have a good whack at it with a hammer (hard). If it didn't break, it was polycarbonate.

-Vivek

Re: Is your frame tough enough for FIRST?
 

Or try to cut it with a jig saw and if it cracks then its plexi

Re: Is your frame tough enough for FIRST?
 

Haha. Real efficient Vivek... I like it.

We used acryllic as our electrical panel. We have a laser on campus that we can use to cut acrylic which takes the error out of drilling holes. We can model it up exactly as we want the board in CAD and then send it straight to the laser. We can even do etching with it if we want.

Re: Is your frame tough enough for FIRST?
 

190 used an acrylic tube for the inside of its custom built high power slip ring, because we needed a plastic tube with an ID equal to the OD of the aluminum tube used for the elevator. This piece of acrylic was merely to mount the copper rings on and to act as an insulator.

Re: Is your frame tough enough for FIRST?
 

Low impact areas where cost is a factor. Electrical panels, covers, etc... are great uses for acrylic.

Re: Is your frame tough enough for FIRST?
 

I would assume acrylic is a lot more common for rookie and some of the less better off teams because of the inexpensiveness and availability as compared to acrylic.

Heck, I hadn't even heard of the goodness that is polycarb until this year and we have yet to use it outside of the toughboxes on our bot.

-Vivek

Re: Is your frame tough enough for FIRST?
 

Everyone is talking about aluminum and plexiglas, does anyone use an all steel frame other than us?

Re: Is your frame tough enough for FIRST?
 

Steel, while being very durable and relatively inexpensive is heavier than aluminum and polycarb. Most teams prefer these alternative materials because it gives the a larger weight allowance for other parts of the robot such as the drive train or the manipulator

Re: Is your frame tough enough for FIRST?
 

I believe both 269 and 1501 have used welded thinwalled (.035" sounds about right iirc?) chromoly tubing for frames before. \

The thing is, to get steel tubing to be light enough, it has to be very thin. This makes it a lot harder to work with in general.

Re: Is your frame tough enough for FIRST?
 

Yeah i prefer to use aluminum tubing instead of steel.

Re: Is your frame tough enough for FIRST?
 

I believe we had a significant amount of steel on our superstructure... someone on our team decided it was a good idea. Next year I'll be pushing for a lighter material: we barely came in at 119.2 after lightening, but it was 119.9 before elimination rounds.

Re: Is your frame tough enough for FIRST?
 

Let's see if I can get this in under the radar...

As soon as our prototype frame was completed with all components assembled, I intentionally ran it 10 fps into the concrete wall of the high school with no bumpers. Other than a ding on the outer aluminum frame at the impact points, everything was ok. Then for the production frame, we rearranged some of the 1" aluminum extrusion to allow for an open front. Again, the same quality assurance test was completed, but this time at 12fps and testing was only done on frontal impacts. The result was a small dent in the front exposed tubing, but nothing severe like we had our first year.

During front impacts of the competition season, these aluminum bars became more and more crushed, which leads me to believe they served as a crush zone that made up for the lack of bumpers. In hindsight I'm glad we had them because that meant there was less shock force delivered to the rest of the components. While I don't condone running full speed at a wall to test your frame, I definitely think quality assurance tests are quite helpful. Plus they make for great videos...

Re: Is your frame tough enough for FIRST?
 

We used Ultrasteel (thin-wall steel sheet, dimpled for added strength, bent by the manufacturer into 8"-wide C-channel) for our ramps in '07. It allowed us to make ramp panels with a very minimal aluminum frame underneath (strickly for hinge mounting). Worked great, plus it was easy to repair if it got bent--just hammer them out.

We usually use welded aluminum for our base frame. Using steel as a base frame would be too heavy--maybe small pieces to strengthen joints that aren't being welded.

Re: Is your frame tough enough for FIRST?
 

Any link to the ultrasteel???

Re: Is your frame tough enough for FIRST?
 

http://www.dietrichindustries.com/ultrasteel/menu.asp

We had always wanted to use a locally-manufactured product on our robot to further gain community interest in our program and FIRST. A parent of one of our students works at Dietrich in Warren, OH and helped us aquire a supply of framing members.

Re: Is your frame tough enough for FIRST?
 

When it come to frames, your number one enemy is impulse (force x time). Even you most violent collision inside of first cam be modeled by

F = (2*(M*∆V))/t + M

So when design a frame you need to consider ways to maximize the time over which the impulse occurs. This reduces the force applied and thus the stress in the element. Bumper are just one method to reduce the total force acting on a frame. Rubber Cushioned Pillow Block are another.

I recommend using iso clipping inside of your cad package to check to see the effect that impulse has on your frame.

Re: Is your frame tough enough for FIRST?
 

On our 2007 bot we used acrylic to hold omniwheels laterally in place since we could use a very thin sheet, had a laser cutter for it, and couldn't find any other fender washers that would do the job. Since they were omnis the acrylic never saw and force and we never had a piece shatter, even after we destroyed the wheels that were being held in place.

Re: Is your frame tough enough for FIRST?
 

Does anyone have pics of their super cool frames???

Re: Is your frame tough enough for FIRST?
 

http://www.phxhs.k12.az.us/images/pa..._id=1203612925

this was our frame

Re: Is your frame tough enough for FIRST?
 

Going into the season this year we had a very pretty frame... but now that the season is over its not so pretty. We used 1/16 wall 1x1 tube for our frame. It held up pretty good for us all year. the bottom rails aren't so pretty anymore from robot arms and appendages getting under the bumpers and hitting the frame, also the bumpers were just high enough so if we accidentally hit the dividing wall in hybrid or teleop the bottom supports for the overpass would get under there and beat our frame up pretty bad... Ill have to see if i can get some pics of it tomorrow?!

Re: Is your frame tough enough for FIRST?
 

Here's a photo of Team 190's 2008 base chassis. I's not a good general all-purpose frame; rather it was highly customized for our design strategy.

http://img142.imageshack.us/img142/7225/1003436io0.jpg

It's four motor (3 CIM, one Globe), 4WD drive (two custom omni, two Colsons). It's designed to allow our robot to drive right up against a wall, then drop the rPOD to scoot sideways into it, in order to position ourselves perfectly for our "unique" trackball strategy. ;)

Re: Is your frame tough enough for FIRST?
 

our robot's gyro freaked on us, and pushed a 250+ pound table that was not meant to move. It took two adults to just push it back!:yikes: ... and the other day at the 4-H fair, we built a robot that you can ride on. the only kill switch that worked was on the actual bot itself (in the form of a breaker, the switch on the remote would only make it lose the signal.) We were unpacking our trailor, and i was using the bot to haul around crates (approximately a 100 lb. load ) when the gyro also freaked on us. It ended up taking out 2 and a half boothes. Luckily no one was there due to the fact that it was before the fair started.

I know you are thinking about why the kill switch on the remote did not work. it was because we were using a vex Robot Controller so it was never meant to operate on such a big scale.

Re: Is your frame tough enough for FIRST?
 

Do you have any pics of the robot itself?

Re: Is your frame tough enough for FIRST?
 

blue painted pultruded fiberglass channel, with a riveted on sheet aluminum bellypan and corner gussets.

http://photos.project1726.org/thumbnails.php?album=28

Re: Is your frame tough enough for FIRST?
 

Team 467 Unibody Chassis. Although it has no real frame the unibody grants us an extremely light-weight and durable body.

Pics:
Construction:

http://www.team467.org/gallery/main...._itemId=511138
http://www.team467.org/gallery/main...._itemId=511236

Chassis with Skin attached:
http://www.team467.org/gallery/main...._itemId=512219
http://www.team467.org/gallery/main...._itemId=512201
http://www.team467.org/gallery/main...._itemId=512177

Final Product:
http://www.team467.org/gallery/main...._itemId=512353
http://www.team467.org/gallery/main...._itemId=512356
http://www.team467.org/gallery/main...._itemId=512365

Re: Is your frame tough enough for FIRST?
 

we call this the "Magic Carpet"
we built it in 3 days at the 4H fair using a vex controller. It was the one that took out the boothes. (it had heavy tubs on it at the time)

http://i213.photobucket.com/albums/c...picture048.jpg

And this is our 2008 robot. it was the one that pushed over the heavy table.

http://i213.photobucket.com/albums/c...8c5211e3fe.jpg

Re: Is your frame tough enough for FIRST?
 

That's a very cool looking frame :cool: Not sure as to its practicality, but I like the roundedness of it. Very slick indeed.

What kinda paint did you use? The blue adds a nice touch.

Re: Is your frame tough enough for FIRST?
 

Hachiban, we used Rustoleum metal finish paint. You can get it in almost any color at your local hardware store. As for durability, our unibody survived being flipped over twice, being rammed by another alliance, and being slammed around in a truck bed on the way to the WPI Battlecry off-season event without any dents and just minor wearing off of the pretty blue paint. Also, being 14.1 pounds underweight with the battery installed is a pretty useful feature. The only caveat is all of the riveting we had to do to attach the skin.

Re: Is your frame tough enough for FIRST?
 

I might suggest you get a new scale :cool:

CIM = 4(2.75)
Battery = 13 +/-

Total = 20 +/-

Unless of course you're hiding some baloons in there...

a lot of baloons...

Re: Is your frame tough enough for FIRST?
 

You should've seen the mayhem reeked on our copper pipe game layer... Not pretty.

Re: Is your frame tough enough for FIRST?
 

The benefit of using the unibody is that because the skin acts as a frame it is quite a bit lighter than the standard frame design. We actually had to bolt on a 14.1 pound steel plate onto the chassis to stop the bot from flipping over in high gear. Also on the bottom of the chassis we have many, many flanged holes.

Re: Is your frame tough enough for FIRST?
 

Makes sense to me, he said 14.1 lbs underweight.... Not 14.1 lbs.

Re: Is your frame tough enough for FIRST?
 

Oh, my bad. I appear to have been confuzled

srsly u guys

Re: Is your frame tough enough for FIRST?
 

Well...

A lot of people might be quick to put off plywood as a chassis material. However, depending on the plywood, it can be tough stuff. Our plywood chassis have survived everything from stack attack to overdrive, and all of the robots in between still live to today. Worst hits that I have seen a robot of ours take was a wall, and another robot, at 17-20 fps during hybrid. These robots did have bumpers (some of them), yet they still have surprising durability, in that they have survived some tough pushing games, and tipping.

I guess if you want more proof that plywood's strong enough for whatever FIRST throws at us, ask someone on RAGE. I hear they've made some pretty successful wooden bots...

Re: Is your frame tough enough for FIRST?
 

I forget the name but a team based out of L.A. built their robot's frame out of bamboo which is incredibly strong and lighter than aluminum.

Re: Is your frame tough enough for FIRST?
 

Also bamboo is the also used in baseball bats, a lot better than aluminum. Nice way to use bamboo, any pics?