weight advice

[Brian Savitt]

Look for heavier pieces of material on your robot and think what you could replace it with that would make it lighter, and there is always the option of drilling a million holes

Brian Team 56

[bigqueue]

Originally posted by Chris Hibner
I forgot another thing: Lexan (and other plastics).

Wherever possible, substitute Lexan instead of aluminum. This is advisable only when the part you're substituting doesn't carry much load (if it carries a lot of load, you'll need to do some calculations to see if it will survive and not bend too much). For instance, all of our control system parts last year were mounted on an aluminum plate. We replaced the aluminum with Lexan and saved about 2 lb. The heat conduction properties of aluminum was nice, but the matches only last 2 minutes so it's not that necessary. You may need to reinforce the Lexan with a couple of thin aluminum strips to keep it from sagging too much, but overall, you can save a lot of weight.

Also, a lot of bearings can actually be replaced with delrin bushings. I would keep the bearings in your drive wheels, or other areas that cary an enormous amout of load, but delrin bushings are adequate for most spinning shafts that don't carry a lot of loading.

Just remember that you don't need to design your robot for infinite life. As long as it lasts a few months, it will be fine.

And then if you find Lexan too dense for your weight budget, you might want to look into Luan Plywood.

Luan Plywood is 1/2 the density of Lexan.....sure, it isn't as strong, but there is alot of lexan use that is simply there to things like ball containment....not requiring so much for strength.

-Quentin

[CaptainPlaid]

Expanded aluminum is also a good option for things like ball containment and even for supporting top and side loads if you give it a bit of support. Last year we used it as the deck on our robot and it worked wonderfully. It would support humans and robots. Essentially it is plate aluminum with more holes drilled in it than you could possibly do on your own.

[Neill Means]

Practical Weight considerations for Rookie Teams!

A Note from a Veteran:

If your 'bot weighs 130.0 lbs, my suggestion is to get it down to
129.5 lbs. The difference is small, but the difference between your shipping scale and the USFIRST shipping scale could be the difference between 1/2 pound (about 0.5%)

According to the rule books, the USFIRST scale at checkin is the "absolute" authority, so if you are 0.1 lbs over, they will not let you compete until you are 130.0 lbs by THEIR scale. There is NO debating with the officials about the accurracy of their scale at the competition. NONE!

If you want to live on the bleeding edge of a 0.5% margin of error, then show up with a 'bot at 130.0 and bring power tools for cutting.

Rookie teams should probably bring their 'bot in at 129.5 lbs. Use a recently certified shipping scale that has a weighing platform at least as big as your robot is. The shipping scale will be a monster! Bathroom scales will give you false readings.

Neill Means
Team 933
P.S. Do you know that Earth's gravity changes according to where you are in the world? So, different masses (your robot) can have different weights in different parts of the world (small differences).

[Wayne Doenges]

I agree with Neill. Get the weight below 130 lbs. We use the wrestling scale at the school. Very accurate. Still our bot gained a 1/2 pound from regional to the championship.

Wayne Doenges

[ChrisH]

I don't know about this year, but the scales used last year also had a slight variation depending on where on the platform you placed the robot. As I recall it was definitely to your advantage to get the robot CG centered on the scale. Note: depending on your robot design that may not be the center of your robot.

For us it was the difference between making weight and getting out the drills

[Wetzel]

Originally posted by ChrisH
I don't know about this year, but the scales used last year also had a slight variation depending on where on the platform you placed the robot. As I recall it was definitely to your advantage to get the robot CG centered on the scale. Note: depending on your robot design that may not be the center of your robot.

For us it was the difference between making weight and getting out the drills

As a wrestler, I am familar with this. The scale at are school, you could shave 1.5 lbs by putting all the weight towards the left edge of the scale, and similar type things on the other scales at the diffrent schools. Don't know why, but thats just they way it is.

[Matt Reiland]

I wish first would let the robot weight be 131 pounds

Ohh well we came in at 131 fully loaded and we were actually able to shave off 4lbs off the electrical system if you can believe it. The terminal strip and a huge amount of 10 ga. wire is now on the floor and we have more weight now for armor. By far the biggest weight cam from gears, we were able to reduce most of the larger 20 pitch gears by 70 % by turning down hubs and drilling holes, and in steel terms thats alot of weight sometimes over a 1lb at a time. Also look into the fastners on the robot, we found BOSCH gussets in places they were not needed and extra t-nuts where they weren't needed. Heck we welded a bunch of parts to make them lighter also.

[Wetzel]

I wish we could weld....

[Patrick Wang]

This is just the slightest bit ironic since I just finished 4 and a half days of welding for our ball mechanism.

Welding 0.049 wall aircraft tubing is not fun. Makes you also have to bend your body in the wierdest of ways. All while TIG welding.

I'll say it was a challenge, but certainly not the most fun thing I've had to do heh.

[AdamT]

Uggg!! 20-25 pounds over. Must dump components. Crap...stupid planning.

[Radiant Phoenix]

Dude, we were almost 70 pounds over at one point, and we were incredibly worried that we'd never get down to 130. We have to drill so many hole in our steel, and we lost half our treds to casters. Almost there though.
Remodeling was a last resort, but last resorts are often necessary. ::sighs::
Good luck on the Robot diets Minna-chan!!!
Athena

if youve got so much steel you might want to try aluminium or titanium if you can afford it

[dets002]

Put the controls system close together and especially have the thermal breakers close to the battery, because the six gauge wire is very heavy. Try to position electronics so that you use the least wire as possible. Thats how our controls team dealt with weight.

[Andrew Dahl]

carefuly placed holes in teh battery



(that joke gets better every year)

dahl