We're trying to lose weight...
 

We're over weight by quite a lot and were wondering if we could take out some of the unused cRIO module-thingies...? They don't seem to really serve a purpose that I can see... unless there's like some base code that runs in them in the background that I don't know about....? We weighed them and with the three extras removed we could lose around a pound, which would be good....

Re: We're trying to lose weight...
 

The only modules that you need to leave installed on the cRIO are the 9201 Analog module in slot 1 with the battery monitoring jumper (<R64>) and the Digital module in slot 4 with the sidecar attached to run the Robot Signal Light <R58>.

All other modules can be removed if your team is not using them.

Re: We're trying to lose weight...
 

How much is quite a lot?

Re: We're trying to lose weight...
 

I see no problem with removing the extra cRIO slot things, but how much overweight are you exactly?

Re: We're trying to lose weight...
 

Just in case:

Remember, the battery + bumpers are not weighed. :)

Re: We're trying to lose weight...
 

Yeah we're still like eleven pounds over last time it was counted... And that was without the bumpers and battery. > . > Been careful not to add too much stuff on it from the beginning, but didn't take into account all the lexane or whatevertheheckit'scalled stuff that we had to put around the electrical board and all, which is what's going to put us over....

Re: We're trying to lose weight...
 

For the future, you should remember to plan out your weight from the beginning of the season and the design process. Allot for the drivetrain, the electronics, and everything else you're planning to add. Try to keep the estimated total around 100 lbs because you're always going to end up needing extra weight in the end. (:

For now, if removing the unused modules is only saving about a pound, you should work through the entire robot design with the team and see where you can save weight.

Re: We're trying to lose weight...
 

Does your team have an air compressor on your robot? If yes you could consider removing it if you can find a way to have enough air for an entire match stored in your air tanks. Also you may want to consider removing air tanks if possible.
Another thing you may want to consider if you are using an Andymark toughbox or an Andymark supershifter is converting the large spacer block to aluminum standoff spacers.
If these solutions do not apply or are not sufficient enough, to help us help you can you please post a picture of your robot so we can see what other lightening options are available?

Re: We're trying to lose weight...
 

11 pounds of lexan is a LOT of lexan. Our basket has solid lexan sides right now and weights in at 10.6 pounds. I think it might be some other things that put you overweight, or you need to check your weight estimates.

Wetzel

Re: We're trying to lose weight...
 

Some general weight loss tips:

The accumulation of steel nuts, bolts and washers can be significant. Since robots cannot extend past the bumper perimeter this year, you may find that 1/8" aluminum rivets will suffice to fasten surfaces together that won't provide much structural strength. Aluminum bolts are lighter but more expensive, though my team has never used them. If you're using a lot of corner brackets, those can be pretty bulky. You could buy some 1/8" thick aluminum strap, 1" or 2" wide, drill holes and/or bend into an L, and they will do a good job in many instances. As far as aluminum bar stock, T-slot extruded aluminum is about 2 feet per pound, whereas hollow square tubing is about 3 feet per pound (both at 1" square).

I don't know how thick the lexan you're using is, but to mount and shield your electronics you can probably go as thin as 1/8". This is the first year that my team has varied from 1/4", we are using some 1/8" thick and some 1/2" thick for places we need the strength (1/2" thick lexan is still lighter than 1/4" thick aluminum plate, methinks).

Finally, there are always good old speed holes. Just don't go overboard and damage the structural integrity. Figure out the volume you'd be drilling away, look up the density of the material, and think if it would be worth it.

Overall, since robots cannot extend past the bumper perimeter, my team has the feeling that we can be a little less RTAD (Robust To A Degree).

Re: We're trying to lose weight...
 

another thing you can do is bore out the center of the toughbox axles, you can save a little that way, but you need a very good drill press for that. also this year the wheels do not need 6 of the screws to hold them to a hub or a sprocket, because you can not torque the wheels very much. we only have 3 bolts holding the wheels to the sprockets. another thing you can do is step down to 1/4 pitch chain.

Re: We're trying to lose weight...
 

Lots of great suggestions, plus you have two weeks still to figure it out!

Pictures of your robot would be a great help, if you are looking for more specific ideas about easy ways to lose weight.

Re: We're trying to lose weight...
 

We have used them in the past on 461, and it does help a bit, but you have to be very careful--they are quite a bit weaker than their steel counterparts, so you want to be careful to only put them in places where the load won't overwhelm them.

Re: We're trying to lose weight...
 

I'm not sure what it's called but there is a plastic material that is in a cardboard like arrangement (two sheets with vertical supports in between). My team used this last year to save wight it weights 1/5th as much as lexane (used before). That should save some weight. (6 pounds roughly) Then you need to trim about 2 pounds...

Re: We're trying to lose weight...
 

Along with the types of bolts, think about the length as well. If you only need a 1" bolt for full engagement with a nut, there is no reason to have a bolt longer than 1". You can either shorten the bolt by replacing it or taking a hacksaw and elbow grease to it.

Re: We're trying to lose weight...
 

If you can, replace as many 1/4-20 bolts with smaller bolts as possible. 228 used to use 1/4-20 for everything, since they were easy to pick up at Home Depot. Then I calculated that by dropping to #10/32 for almost everything, we could save almost 3 pounds; now we exclusively use #10/32 button and socket cap head screws.

Lighten the gears in the Toughbox. Turn pockets into them on a lathe, and/or drill six 7/16" or 1/2" holes through them. This can cut their weight in half.



Don't use 4 CIM motors on a drive train. Use 2 CIM motors, and use chain to connect the other wheels. CIM motors weigh 2.75 lbs each.

Take a second look at material choices. You can do a lot with 1/16"-wall aluminum box tubing and 1/16" polycarbonate (Lexan) without breaking the weight budget.

Using pneumatics? Only use one or two accumulators. They weigh a pound each.

Edit: But most importantly, treat this as a weight-per-effort knapsack problem. That is, go after the densest materials first that take the easiest amount of effort to remove a relatively high amount of weight. Then keep working downwards towards the parts where it'll take a lot of effort to only remove a little weight.

Re: We're trying to lose weight...
 

Corrugated plastic/matroplast. It's used in signs a lot. It's tough enough to support a robot's full weight over a 36" square, supported only on the sides. That's 1/4" thick stuff, IIRC, for that purpose. There might have been some 1/8" plastic on the ramps leading to that...

It's almost as strong as Lexan, but doesn't have quite the puncture resistance. On the plus side, you can get it in one of your team colors.

Re: We're trying to lose weight...
 

Remove unneccessary hardware. (got a 1/4-20 bolt holding on a lexan shield? Remove it and replace it with a ziptie/barlock)

Back in 06 I made a few students nervous when I went around the robot pointing at various nuts and bolts, telling them to take them off because we didn't need them. Took off about 2 pounds worth of 1/4-20 bolts that way . . . only then did the drilling begin. :eek:

Re: We're trying to lose weight...
 

We like to use #8 and #10 hardware for holding things onto the robot, 1/4" for things that need be held on really well. This year we have some 3/8" and 1/2" bolts because it's the easy way to support a roller with a bearing at each end...no shaft required.

We use a lot of 5/32" rivets, they're a lot stronger than 1/8" and don't weigh much more.

Plywood is a wonderful material for robots, but you have to think differently.

Re: We're trying to lose weight...
 

I agree, a picture of the bot in question would be nice so we know what you could potentially lighten or cut.

What are you using for your hopper? It doesn't have to be solid, it could be as simple as some cord (http://www.chiefdelphi.com/media/photos/32582?)

How many wheels do you have? I know this is drastic but you could cut from 6 wheel down to 4 wheel.

Barring any of those, what are you putting over your electronics? I know 397 probably won't put too much over them this year. Actually last year we left them exposed in the middle of our robot (right under our launcher) and never had a problem.

Re: We're trying to lose weight...
 

Thanks for the replies!

I think that we are going to be okay weight wise... Our finished robot weighs about 127lbs with the lexan shielding and everything. I think that we have a good idea on how to remove that extra weight!

Re: We're trying to lose weight...
 

Do I hear....swiss cheese?

Re: We're trying to lose weight...
 

We have used 030 Polycarbonate (lexan) for shielding velcroed on for many years. If your shielding is much more substatial than this you might want to ask yourself if it needs to be. As Grant Imahara points out in Kicking Bot.
"You can reduce 25% of the weight of a 1/4 panel by going to 3/16. To do the same with "lightining holes" will dramatically reduce the integrity of your armor". A good example would be drilling 1/2" diameter holes in a 1" grid (1" square minus (0.25)^2*pi=about 1-3/16) pattern on the 1/4" plate will reduce the mass by 3/16. You can reduce it 4/16 by going from 1/4 to 3/16 thickness (best of all no holes!).

P.S. We get hit by other robots a lot and this shielding has always worked well.

Re: We're trying to lose weight...
 

smart idea... or order the aluminum lighter ones...

But i think il be doing this soon... very smart

Re: We're trying to lose weight...
 

Don't overlook the small things like extra wiring. Good general practices has only what is needed on the robot.

A couple of little tweaks add up to real weight.

Re: We're trying to lose weight...
 

You can start to swiss cheese you bot. We have resorted to that in the past when we ran into this same problem.

Also have you tries Jenny Craig?

Re: We're trying to lose weight...
 

i saw a team one year that was overweight one year with a lot of lexsand the jail birds i think.. they drilled a rediculous amount of wholes in it until they where under.

Re: We're trying to lose weight...
 

Let me just put out 1 point of caution when 'swiss cheesing' your robot.

Please know and understand the forces that will be affecting the area that you are 'swiss cheesing' lest you end up with a bent frame (or worse) when you recieve an impact.

Re: We're trying to lose weight...
 

Yea, that was us in 06 . . Lots of holes in lots of 1/8 in. Lexan.

The team found out that a UPS store scale is not very accurate @ 120 lbs.
We got a good digital scale the year after that. I think it ended up being about 20 pounds overweight. Removing the pneumatic system improved it significantly, the rest was hardware/holes.

In hindsight, the construction method for our hopper that year made it a bit heavy. (1/8 in. Polycarb where 1/16th would suffice).