Weight Reduction

[robotguru1717]

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.

[RichardJames]

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.

[maltz1881]

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 . 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.

[Cuog]

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.

[Brian C]

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........

[MrForbes]

Originally Posted by Brian C

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

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.

[FourPenguins]

Originally Posted by Brian C

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

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.

[Otaku]

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.

[Otaku]

Originally Posted by MattB703

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.

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.

Originally Posted by AJ R

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.

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.

Originally Posted by Gdeaver

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

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.

Originally Posted by maltz1881

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 . 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.

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...

Originally Posted by Cuog

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.

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.

[EricH]

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.

[geeknerd99]

Originally Posted by Otaku

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.

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.

[Billfred]

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.

[Cowmankoza]

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.

[MrForbes]

Originally Posted by robotguru1717

#1 tip to avoid overweight issues:

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

to avoid this?

[MattB703]

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.