Weight Reduction
 

While in the computer lab at midnight last night, thinking about how much weight fasteners will add to our robot, I figured it might be a good resource for some teams if we made a sort of "Weight reduction - How to do it" thread.

So if your in the mood to share, feel free to tell us all how you make your robot lighter. Anything from the smallest task of say, making your spacers have as thin a wall as possible, up to say, removing an arm.

Re: Weight Reduction
 

I've said it before:

This was already discussed here: http://www.chiefdelphi.com/forums/sh...ad.php?t=44155

Re: Weight Reduction
 

Replacing steel bolts with aluminum versions. Very light and still strong enough for most purposes.

Re: Weight Reduction
 

1618 hasn't gotten into the weight-reduction business (their past two robots have been far underweight, and this year's is still obviously in the pipeline), but I do remember a few tricks from 1293:

-Switching out our 1/8" aluminum hopper for a thinner stainless one
-Hacking off most of our tower (not because we were overweight, but because the weight was high up)
-Gratuitous use of the slugbuster (a hydraulic device for poking large circular holes in sheetmetal)
-Cutting the team numbers into our covers, causing us to lose weight for a required feature rather than gain it
-Rivets, rivets, and more rivets (and rivet nuts for places we needed to get in and out of)
-Running as short a wire as we could safely use (something I'm sure Al Skierkiewicz is happy to see as well)
-Thin-walled metal spacers on our Kitbot axles
-Going from six polycord runs on our ball pickup to four (and ultimately zero with the top getting chopped, but that's a whole other ball of wax)
-Plastic belt pulleys instead of metal
-Plain paper and Velcro for attaching school and sponsor information. (It works, I swear!)

Re: Weight Reduction
 

Replace Aluminum bolts with Nylon ones.

Even better for some applications.

You don't really need a steel or aluminum bolt holding down the RC now do you? ;)

Use 2 screws on muffin fans instead of all 4 corners.

TRIM THOSE WIRES!!! You don't need 1' of cable going from your battery to your quick connect if the battery is right next to the breaker.

ONLY SWISS CHEESE THE BOT IN WEEK 6!!!!!!
None of this "speed holes in week 1" nonsense!!!!

You can't put material back as easily as you can remove it if you need to mount anything, even something as simple as a potentiometer, limit switch, or a sensor of some kind.

Re: Weight Reduction
 

Rivets, we were able to take almost 5 pounds of bolts off our robot last year by replacing them with rivets. Also choose your materials wisely, sheet metal is your friend, too much extruded aluminum is not. Even if you are not at the cheesing stage yet with your build, plan our where you can reduce weight if you have to, and expect to have to take apart your robot a couple of times throughout the season (keep welding till you know your weight).

Re: Weight Reduction
 

Corrugated lexan (green house material) instead of lexan for side shields, and coverings..

Re: Weight Reduction
 

Heres a fun story from the Nu-Tron from around 4-5 years ago:

They brought the bot up to inspection and placed it on the scale. The scale read 130.0....130.1....130.0....130.1 (for all you youngens back in the day the limit was 130 pounds WITH a battery). Eventually the scale stopped at 130.1. One of the team members decided to check the air tanks, they were full so he released all the air pressure...the scale dropped to 130.0 and they were good to go. Moral of the story: EMPTY YOUR AIR TANKS!

Re: Weight Reduction
 

This year Team 1323 was able to cut 11 lbs of our basic chassis by welding our frame together it was a task our team was shooting for since the end of last year when we invested in a tig welder.

Re: Weight Reduction
 

We've used some fairly large bolts in the past to mount various mechanisms, wheels, etc... A 1/2" bolt is typically overkill in terms of strength, but the diameter has been our requirement. So, we've actually drilled out the center of our larger bolts in order to reduce the weight of this large hardware, and it definitely works.

YMMV, good luck.

BEN

Re: Weight Reduction
 

We have a saying that we use over and over when looking for weight reduction;

Steel parts first, then alluminum, then plastic.

Cutting/drilling holes in a 1/8" lexan side plate for instance is pretty inaffectual. On the other hand, putting a gear or sprocket in a lath and taking some "meat" off it can pay big dividends.

Re: Weight Reduction
 

Our team is working hard to actually predict weight of the final design in order to avoid the problem we had last year. Every piece is being designed with speedholes included, so hopefully when it all goes together it will be underwieght.

In case anything is heavy and still has room for holes at the end of the build, we have a Rotex punch which can be used to speed up the cheesing process.

Re: Weight Reduction
 

Well one of our experiences last year was that we were 12oz overweight at tech for the regional. This was already AFTER drilling and trimming the snot out of the robot before we shipped.

So one of the engineering mentors goes around the robot with 2 of the students and tells them which bolts, nuts and washers to remove. After about a 1/2 hour he stood there with 2 hands FULL of "extraneous, unnecessary hardware" that weighed.....you guessed it - 3/4 of a pound. Much of it came fro the KOP frame joints where 1 fastener was just fine due to our design last year.

Assign a couple of team members to monitor the weight of everything you put on a robot. It will help you during week 6. Remember, everything weighs something (even paint).

Re: Weight Reduction
 

This year it already looks like we are having weight issues so we have been taking the weight of EVERYTHING (components, motors, spikes) and adding them into an excel file. Then for things that arn't built yet like the chassis, wheels and stuff we have done extrememly acurate Solidwork models of them and these give us the weight.

#1 tip to avoid overweight issues:

Plan/design everything first then build. dont design as you go.

Re: Weight Reduction
 

weight relieve every sprocket, pulley, gear, and gear box that you can. weight relieve all aluminium and lexan plates. These are some of the densest things on most people`s bots. also, make sure you are using gears belts or chain that is appropriate (not overkill), as jumping up to the next strongest category can mean doubling the weight of these components.

Re: Weight Reduction
 

to avoid this?

Re: Weight Reduction
 

Another thing to keep in mind;

If the component that you designed is still strong enough after you have drille the cheese out of it, it is possible that you could have just used thinner material to start with.

Re: Weight Reduction
 

Our robot last year was allmost all pollycarbonate. We were more than 40 pounds overweight. We spent week 5 and thursday of our first competion drilling the holes in the frame larger, trimming corners off of pieces and many speed holes. 3 in hole saw works well but this year we have acess to even larger ones. My advice - allways keep weight into consideration.

Re: Weight Reduction
 

Adding some fiber to your robot can work wonders for weight.

Re: Weight Reduction
 

Just as a funny story although it wasn't funny then. When i was with a now defunct team we had an engineer who insisted we had to use 1/4 in thick aluminum for our sides. This was several years ago when you could only weight 130 with your battery. I told him many times it wasn't necessary to go with something so heavy. He still insisted. When we finished the robot we weighed it and came in at a whooping (are you sitting down!!) 217 lbs:ahh: . What could I say other then I told you so which of course I didn't. Shaking my head and handing out the sawzalls we made it down finally to 130 on the dot. It only took us 9 days of making swiss cheese out of EVERYTHING. Needless to say that engineer was never seen nor heard from again. :D

Re: Weight Reduction
 

Programmers: Get rid of that White space, no comments. Those extra electrons are killing us

file everything smooth, I havent teste4d it but im sure of you filed everything on the robot to a smooth surface almost a half pound of dust would be removed.

Re: Weight Reduction
 

What to do:
-Mill your chassis. This might not come in to the minds of rookie teams or people who just haven't done it, but it can shave off a lot of weight, oh, and it can even make handles on your robot (but I don't suggest that).
-Speed holes in week 5/6. Cheese-grater robots are still robots.
-Calculate everything. You won't need to make speed holes if you figure it all out beforehand and get it taken care of.
-Use thinner material, or use it smarter. I'll leave this for you all to figure out.
-Lop off excessively long shafts or bolts. It might add up to that crucial pound or two.
-Use lighter parts. Aluminium sprockets, thinner gague wire where thick stuff isn't needed, etc.
-Plastics are your friends. Lexan/Polycarbonate/Plexiglass instead of actaul glass (why would you want it?) or aluminium.
-Minimize Pneumatics. They're heavy and ineffecient.
-Minimize Chain. It might not weigh a bunch on it's own, but it will add up.
-If all else fails, Nitroglycerin. Sure, you might not have anything competition-worthy afterwords, but you'll be under the limit.

Tools you will need:
-Drill
-Angle Grinder
-Dremel
-Nibbler (Maybe?)
-Mill (CNC, Precision, or otherwise)
-Files. Lots of files. Straight files, round files, cylindrical files. Single cut. Double cut. Bastard.


That should help. Oh, and good doses of common sense will help you out, too.

Re: Weight Reduction
 

Wow, the resemblance is uncanny!

We were in the same boat as your team as well, but we only had two days to shave 30-40 pounds. I'm sure you saw the other picture of our robot in a heap on a piece of plywood. We're planning ahead this year, so hopefully that won't happen again.

Re: Weight Reduction
 

Not always. If a team uses 1/4in Alu. for the frame and cheeses it, it might be stronger than say, solid 1/8in Alu. it also depends on the structural rigidity as a whole.

If you swiss the frame and it doesn't seem to be affected, you'll be sadly wrong the first time some other team's robot meets your frame up close and in person.


That is one of, if not, the coolest looking robot I've seen. You should have had LED's at the bottom (red and blue) and changed the color based on what alliance you were on then frosted the whole robot. You could change the color of your bot on a whim.



Adding does not take weight off. Replacing does. If you make something out of plywood, it'll be heavy. If you make it out of Carbon fiber and Aluminum, it'll be much lighter.



Heh. I see no problem with 1/4in Aluminum for frames, but then again, I've only been in FIRST for a year now so...



Filing? Half a pound? Are you crazy?

Filing will do more than make it flat. Filing will take more off. Lapping would make it perfectly flat (assuming you're using 2000 grit or better). However, I severely doubt that all the alu. you will file off will even be close to a half pound. A quarter, hell, even an eighth of a pound, maybe. But a half? no.

Re: Weight Reduction
 

Thinwall square tubing for stuff that doesn't need to take hits. Our shooter frame last year was mainly 3/4" square x 1/16" thick tubing, save for the support frame for the drive for the shooting wheel (1" square x 1/16", IIRC.) Problem is, you can't take much weight off. (But it will hold up as well as L-angle, 1x1x1/8, at least for some purposes, and weigh less.) Wouldn't reccomend it for the drive frame, though.

Re: Weight Reduction
 

I totally agree with this.. swiss cheesing is the way to go to lose weight and give your robot a new look:D but do not do this until later in the season like around week 4 or 5

Re: Weight Reduction
 

When you are designing, if you know that you are going to be overweight, it is easier to drop the wall thickness on stock instead of cutting holes in it. To take out the same amount of weight in holes as going from 1x1 tube with 1/8 inch walls to 1x1 tube with 1/16 inch walls would take lots of holes and time.

Re: Weight Reduction
 

Whatever you do, don't drill speed holes in the pneumatics system. :eek:

Re: Weight Reduction
 

We traditionally mirror polish many components of our robot, and the parts become noticeably thinner in some places. That might have some bearing on weight.

I see all this stuff about changing out bolts and such coming before using lighter materials. As a mountain biker, I should technically be counting the weight of my bike in grams. There are people out there that switch out their water bottle cage bolts from aluminum to titanium just to shave a gram off. But the best way to shave weight is to not put heavy stuff on there period. I switched out my wheelset for a lighter, stronger one, and took two whole pounds out of my weight. I replaced my handlebars, stem and seatpost for lighter alloys (and carbon fiber!) and took off a pound and a half. I can shave off another three by changing my mountain tires to my road slicks (but this only is ridable on roads). My bike was 35 pounds when I first got it, and I've knocked the weight down to 30 when riding mountain and 27 when I ride on the roads. If you thought FRC was OCD about weight, you should see the mountain bike community. The sky's the limit when it comes to weight reduction. Sad thing is, unless you're really one with your bike, shaving off 5 pounds actually isn't that noticeable on the mountain.

Moral of the story: when you build, keep weight in mind. It's better to save weight in pounds than to remove in grams. You've got a lot of grams to go when your robot weighs 150 pounds (or your bike weighs 40). Save the desperate stuff like bolt switching and speedholes for last.

Re: Weight Reduction
 

Oh, and another piece of advice: Remove functionality only as an absolute last resort. With enough slugbusting and materials replacing, we were able to go from 4 pounds overweight to 2 pounds under without giving up anything last year. Now, some teams have dropped major systems of their robot and still gone on to win regionals (1251 comes to mind), but as a rule....don't do it.

Re: Weight Reduction
 

Just as a funny story although it wasn't funny then. When i was with a now defunct team we had an engineer who insisted we had to use 1/4 in thick aluminum for our sides. This was several years ago when you could only weight 130 with your battery

Team 190 had their robot a couple of years back where pretty much the entire chassis was made of Lexan.

You can do some pretty cool stuff with Lexan........

Re: Weight Reduction
 

Yes, you can! Just keep in mind that the modulus of elasticity is around 30 times less than aluminum, which means you have to have a good design to keep deflection down, but it also allows you to have that deflection if you need it for your design.

Re: Weight Reduction
 

Why not? Then you would save the weight of the metal AND the air. :)

Re: Weight Reduction
 

very true, we chopped off our shooter and ball gathering device, granted our robot was roughly 60 pounds overweight if I'm not mistaken. The tough part was redesigning the robot to become a dumper on practice day at UCF, good time, good times.

Re: Weight Reduction
 

i admit it! thats what TOTALLY happened to us last year. It ws our rookie year. This year we are trying to avoid it with what i said earlier! lol.

Re: Weight Reduction
 

After reading this thread I have an inexplicable desire for some swiss cheese.

I wonder why. :D

Re: Weight Reduction
 

Words of warning:
Two years ago, MORT built the infamous plastic fantastic end effector out of lexan, acrylic, and polyurethane foam. It was about 30 lbs over weight. The moral: light materials are not a cure-all. If the engineering is flawed, the material won't save you.

Oh yeah. And don't forget that Lexan doesn't break, but it flexes easily, so don't use it for anything that needs to be rigid.

Re: Weight Reduction
 

yeah, we were in the pits next to you in Phoenix and at Atlanta, I was impressed with your team's ability to deal with some serious challenges.

Re: Weight Reduction
 

I love Lexan and HDPE. That stuff is great lightweight strong and it bounces back into place. It can also be welded. Every year I purchase sheets of this stuff store it outside then cut off a chunk of it when needed