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).