Ok, so our team just came across a huge problem, our robot is 20 lbs over weight, so we are going to ship it to heavy. So our question is, do we have time during the off season to work on a replacement part for our heaviest component? We were told that last year there was 10 hours allowed to build spare parts between the ship date and the regional, and that you could put it on then? Is this applicable this year and situation?
The rules this year are:
You can keep 40 lbs. back from your shipped robot (Withholding Allowance). You can make spare, replacement, or upgrade parts for your robot with time limited only by the calendar (<R26>). You can take the weight out at the event, as well as doing any other work that can be done onsite (<R27>).
Don’t forget that you can work on your robot all weekend at an event. You can experiment with weight reduction after the build season, and then bring the raw materials with you and assemble them on site at the regional. If you need help, please check in with your lead inspector. They are there to help and can introduce you to other teams that have experience in weight reduction and design.
Both Eric and Al have given you sound advise. I’ll take it a bit further…
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You can bring as much raw, unmodified, COTS material with you as you wish to your event. You are limited to 40 pounds of modified or machined assemblies (this includes items withheld from the robot shipment). Note that the operator interface is not counted in this 40 pound weight allowance.
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I would contact an area veteran team ASAP. Many veteran mentors will be glad to come to your next meeting and discuss your issues in person. Show them pictures and/or CAD drawings of your robot and plan your attack of the problem.
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When you get to your regional, bring your robot up to the lead inspector ASAP and ask to weigh your robot. Do this for two reasons. (1) Your school scale may not be accurate with respect to the official event scale. (2) As Al said, the lead inspector can help you get the weight out and/or introduce you to veteran teams who may be willing to assist you.
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Do not give up! I have seen teams lose 90 pounds (no kidding) on a single Thursday at the competition.
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Many places to lose weight may not be obvious. As an example, Are you using all of the modules in the cRIO controller? My team pulled 3 modules (we kept the analog in slot 1 and the digital in slot 4) and saved over a pound right there…
Good luck,
Mike
Yeah never give up. Our rookie year, we shipped the robot without a an arm. The Thursday practice day we built it and were over weight. We had the second match the next morning, and were over by like 15 lbs. We dropped the weight and later qualified for finals, where we were overweight again, but we made it, anything is possible hang in there.
For the past two years, Team 1676 has not had a weight problem. However, in the past the best thing we thought we could do was “Swiss Cheese” the robot to make weight. 20 LBS is a huge weight to overcome, but the combination of that plus perhaps bringing lighter-weight COTS materials to the competition with you can help…
Good Luck!
I won’t say that this will never happen but don’t plan on playing on Friday or in the finals on Saturday without meeting all of the inspection process.
We were over by 9 pounds at 4am of ship day this year. We went home slept a couple hours came back and were 1 pound under by noon.
I am not a big fan of swiss cheesing a robot. I am a much bigger fan on taking 1/8 materials and swapping it down to 1/16th. Costly, Yes, but you reduce the weight by 50%. We dropped 4 pounds for $40. Think about it.
Remeber the bylaws of weight reduction:
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Do the math. Have a plan on how to get there. The reason we were able to drop the weight was that at 4 am we took some measurements and made a plan for when we came in. While the swiss cheesing seems to have a lot of glamor to it, figure it out. If you drill a 3/4" hole every inch in an box tube you will loose most of the weight of that hole (some shavings will cling). Let’s do the math. (.75)^2*pi/4 is equal to .44. Thus 1-.44 is .56 material left.on a 4 foot struct of 1x1 box, this is 47x4 holes or 188 holes. :ahh: Reducing the material thickness by 1/2 is a 50% reduction and usually less work.
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Attack the dense materials first. If it is steel, can it be replaced with AL plastic or wood?.
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Can you use a thinner material? Switching 1/8 box to 1/16 wall box is a 50% reduction in weight (see example above). Attack large surface area panels. If you switch for 1/8" Lexan to .060", you reduce it by 50%. Better yet if it is just a cover use 030 and attach it with velcro instead of bolts.
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Be prepared to swiss cheese. Have a corded drill, an extension cord, a good uni-bit or step drill, tape measure, and a center punch. Also cover your electronics as you are about to make a giant mess.
The reason for the corded drill is that you will drain battery drills too fast with this process. Nothing more depressing than trying to make a fix with a dead battery. -
Decontent. Decide what is necessary to compete vs. what you wanted. Do you really NEED 4 drive motors or will 2 do. Do you really need that extra arm, or can you do something else and remove it. This year you will need to move, but you don’t necessarily have to do anything else.
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Keep on the lookout for good weight savings ideas. Maybe you can find a couple other pounds with a fresh set of eyes, and then ad the arm back on.
This is great advice. When you are at your regional, maybe you can snag a few members/mentors from other teams who aren’t busy (is that possible though? 
) That’s what I plan to do if our replacement parts don’t bring us underweight like we calculated.
Lead Inspectors will help you do that. They have a good idea of which team has extra people and who generally brings enough material and tools to help build your ideas as well.
Start with a brianstorm of everything on the robot, and then rate items and systems by what is most important, and then question everything. To lose that much weight, you may need to drop a whole system or motor set.
Try to get an idea of the weight of the components so you know where the big hitters are.
Good targets (in addition to the ones listed above) -
CIMs
Pneumatic pump and related hardware (if you only use a few pneumatics you can create a system that does not need the pump)
Reserviors
Smaller chain (can you go from #35 to #25)
Good luck - and i am confident you will find help at your regional.
All good ideas here. One thing to keep in mind is that swiss cheesing a part will reduce it’s weight, but it may not be a good thing. When you start drilling big holes in your robot, you might inadvertently create structural problems that could cause a piece to bend, break, crumple, or otherwise distort during competition. Always go in with a plan, and do the math ahead of time to figure out where you can afford to lose weight.
This year the Robettes are pretty close to the weight limit, but we know exactly where to shave a few pounds if we need to. We have about 15 pounds worth of steel plates that could easily lose some weight without hurting the robot 