Our Robot weight woes.. to rebuild or not to rebuild

[viperred396]

As mentioned in this thread http://www.chiefdelphi.com/forums/sh...=102188&page=5

Our robot when we just weighed it was ~148 lbs (without bumpers and battery)

We are trying to see where to take all the weight off but we just cant see how to while keeping structural integrity (see robot below)



So out question is, what if we did something crazy! such as make a new robot!?!

out shooter works great so if we kept that and rebuilt everything else could we manage in ~9.5 hours?

Thought? Plans? Suggestions?

Thanks,
2240

[DominickC]

You want to rebuild a robot and integrate a functional system into it in 9.5 hours?

I don't understand where you're getting the majority of your weight from. It appears to be quite a small, compact little bot. How much does your drive train and shooting mechanism weigh?

[viperred396]

Originally Posted by DominickC

You want to rebuild a robot and integrate a functional system into it in 9.5 hours?

I don't understand where you're getting the majority of your weight from. It appears to be quite a small, compact little bot. How much does your drive train and shooting mechanism weigh?

we aren't really sure where all the weight is coming from.. we think its the motors and electronics

4 CIMs
2 window
2 throttle
3 Banebot775

plus the electronics
cRio2
6 Jags
3 victor
2 spikes
Kinect
small laptop (for image processing

plus the 4 andymark pneumatic tires

Originally Posted by viperred396

we aren't really sure where all the weight is coming from.. we think its the motors and electronics

4 CIMs
2 window
2 throttle
3 Banebot775

plus the electronics
cRio2
6 Jags
3 victor
2 spikes
Kinect
small laptop (for image processing

plus the 4 andymark pneumatic tires

Weigh the laptop and kinect together and see what they weigh. We have more electronics and motors than you, yet we still aren't that heavy.

[wireties]

Originally Posted by viperred396

we aren't really sure where all the weight is coming from.. we think its the motors and electronics

4 CIMs
2 window
2 throttle
3 Banebot775

plus the electronics
cRio2
6 Jags
3 victor
2 spikes
Kinect
small laptop (for image processing

plus the 4 andymark pneumatic tires

the extraordinary piece (weight-wise) is the laptop and the Kinect! Is that necessary? Can you move vision-tracking to the cRIO? or remove it all together? (better than not playing at all)

Have you tried the Kinect on the robot? I thought teams were having trouble making that work as a rectangle tracker.

[DampRobot]

We changed almost all our steel screws and nuts that held our frame together to steel rivirs, and saved 5 or so pounds. Steel is much heavier (about 3 times) than aluminuim. Keep in mind, if you do decide to redesign, lightening holes don't matter that much, unless they are huge, in steel or thick aluminuim. The best way to lose weight usually doesn't include holes, and does include thickness, material, design, or even strategy changes.

[EricH]

The cardboard concrete tubes... well, those things can be pretty heavy. Start there with lots and lots of holes or other patterns to lighten the robot.

[wireties]

Hmmm - it does not look crazy heavy. Are you sure your scale is accurate?

Are those plates on top solid material? Do they need to be?

Are the vertical support pieces solid? Will lighter extrusion work?

What are the red things in the middle?

Is there any steel on the robot? Can you substitute aluminum of similar dimensions?

[viperred396]

Originally Posted by wireties

Hmmm - it does not look crazy heavy. Are you sure your scale is accurate?
We took it to the local PetsMart scale so its fairly accurate

Are those plates on top solid material? Do they need to be?
Yes solid 1/8 Aluminum, maybe not

Are the vertical support pieces solid? Will lighter extrusion work?
No they are 1x2 Aluminum extrusions, possibly switch to 1x1

What are the red things in the middle?
they are 8in concrete cardboard tubes used to hold the balls once they are captured

Is there any steel on the robot? Can you substitute aluminum of similar dimensions?

nope, all Aluminum, the only steel is the 2 3/8in rods on the shooter

[Mk.32]

How thick is the metal you are using? 1/16th inch is often plenty and half the weight of 1/8. Also solid plates are usually over kill, we saved like nearly 2 lbs by pocketing out a a 17inch circle of alum.

You could swap to 6inch wheels [loose some bump abilities...] and save some weight off those pneumatic tires.

And as said above check to see if your scales are correct, weigh a person who knows there weight[safety first though] to see if it is off.

This late in the game rebuilding large portions of your robot is probably to late... best try finding parts you can swap or take off. Large pieces of metal are a good place to start. Figure out what needs strength and what doesn't. And don't be afraid to loose some functionality. Lesser under weight robot is always better than a over weight robot of any caliber.

For starters: Wheels

Those pneumatics look kinda heavy to me, so maybe switch them out for 8" plaction wheels, or maybe even 6" ones. You should be able to get away with going over the bump with them.

If you're really pressed for weight, and want a competable robot, I'd put serious thought into not going over the bump at all. Take out the lift kits, and replace the pneumatic wheels with smaller, light ones. Re-organize your strategy to work on one side of the field. There are so many successful strategies using only one side of the field, and that could be a major benefit to you (PM me for examples of such strategies, we can talk).

That's a nice turret you have there. Take it off. A stationary shooter has worked extremely well for us, and from what we've seen at our practice day worked way better than the turreted ones.

Like said above, double, if not triple check your weight. You don't look heavy, but if you are, these are some steps to follow.

[DominickC]

Originally Posted by SuperNerd256

That's a nice turret you have there. Take it off.

I laughed at that

SuperNerd has some pretty good ideas. I'd also consider swiss-cheesing your top aluminum plate, if not replacing it with polycarb/plywood. The polycarb would look wicked nice, but plywood weighs less.

Take a look at the on-board computer you've got. Can you strip any parts off of it or replace it's battery with a smaller one?

[Garret]

We were worried about weight on our robot so we dropped the thickness of the sheetmetal we were using in a lot of places; or you could switch to plastic all together. Not only is the thinner stuff lighter but its way easier to machine and cut. Also what size bolts are you using, we dropped ours down to #10-32 to just about everything and saved a ton of weight.

[wireties]

Originally Posted by DominickC

I laughed at that

SuperNerd has some pretty good ideas. I'd also consider swiss-cheesing your top aluminum plate, if not replacing it with polycarb/plywood. The polycarb would look wicked nice, but plywood weighs less.
?

Swiss-cheese that top plate, reasonable-thickness polycarb won't support that shooter.

[Kevin Sevcik]

Welcome to the wonderful world of weight loss! We recommend that you weigh in early and often so you won't come back to visit next season.

Unless you know where all that extra weight is coming from, building an entirely new robot in 9.5 hours isn't going to save you. You're just as likely to end up with a second overweight robot. If you DO know where all the extra weight is coming from, then you should be looking at removing those systems/parts to make your weight.

Looking at your picture, it's difficult to see where all of that weight is actually coming from. Until you can provide more and closer pictures of the robot, I'll throw out some general purpose weight loss guidelines:

1. Steel is heavy. Anywhere there's steel on your robot is a place to reduce weight by removing it or replacing it with Aluminum.
2. Flat sheet and plate are heavier than thinner sheet and plate with a tube supporting it. Look for large expanses of thick plate material and see if you can replace it with thinner material with a tube or beam supporting it. (I'm looking at that Lexan electronics board).
3. Motors are heavy. If you're using a bigger motor than you need for a task, look at swapping in a smaller, lighter one.
4. Pneumatics can be heavy. If you're using pneumatics, make sure you're using the lighest, smallest cylinders possible, and look at using plastic air tanks and keeping the compressor off-board.
5. Subsystems are heavy. Seeing as how a subsystem is guaranteed to have a combination of all of the above, subsystems are very heavy. The absolute quickest way to lose weight and become legal is to ditch an entire subsystem. Which system you ditch would depend on your priorities and the relative weights of the systems. Offhand, I would suggest that a turret on an overweight robot is about as useful as a bicycle for a fish. If I could ditch everything for the turret and have a fixed shooter on a legal robot, I would do that in a heartbeat.