2014 FRC's Biggest Loser

[BoilerMentor]

With the current position HBR has found themselves in, I thought this might be a fun thing to look at.

Share your robot weight situation and describe your remedy.

Let me start by saying the number on the scale shocked me. I have 9 years of FIRST experience and I've never seen a robot look so light, but weigh so much.

Initial Robot Weight: 138.4lbs
Final Robot Weight: TBD
Anticipated Weight removal (based on list of remedies): ~21 lbs
Remedy:

• Replace 4 Mini Cims with 3 RS550's in Cimile gearboxes (~8 lbs.)
• Rebuild interface frame replacing 1/8" wall 1x1 tube with 1/16" wall (~5 lbs.)
• Replace 40" of steel 1/2" hex shaft with 1/2" aluminum hex shaft (~1.4 lbs.)
• Replace 2-1.75" bore 12" stroke cylinders with 1.0625" bore 12" stroke cylinders (~1.4 lbs)
• Rebuild intake roller with polycarbonate tubing and delrin endplates to replace 3" PVC roller (~2.2 lbs.)
• Remove excess length from any hardware or replace with a lighter option. (~.25 lbs)
• Remove webbing from the robot back plate (~2.5 lbs.)
• Remove 4 unneeded standoffs from drive modules (~.6 lbs.)

EMERGENCY NUCLEAR WEIGHT LOSS OPTION:

• Remove 2 CIMs from the 6 CIM drive (~7 lbs.)

[wilsonmw04]

Originally Posted by BoilerMentor

EMERGENCY NUCLEAR WEIGHT LOSS OPTION:

• Remove 2 CIMs from the 6 CIM drive (~7 lbs.)

I would do this first.
I fail to see the significant benefit of 7lbs. vs. what 6 cims give you.

[EricDrost]

Originally Posted by wilsonmw04

I would do this first.
I fail to see the significant benefit of 7lbs. vs. what 6 cims give you.

Acceleration.

I tend to agree with you, that would be a good place to start for a lot of teams. But without knowing their strategy, it's hard to know what their best place to lose weight is.

Accelerating quickly might be very important to their strategy and hence, not a great place to start removing weight.

[Chadfrom308]

Right now we weigh around 116-117lbs

Our frame without anything on it is only 10 lbs

We have 6 cims and 4 mini cims, 3 banebots or andymarks(I cant remember) and a compressor

I thought we would be way over, but we designed our robot to be as light as possible

We just have to add Plexiglas around the sides for sponsors and a couple of lights

I hope we stay under!

BTW, 6 cims on your drivetrain is definitely an advantage, I would also take them off last.

Aslo: Maybe swiss cheese your robot? Ours is swiss cheesed for two reasons:
Save weight and to have somewhere for cables to run

[Jon Stratis]

Weighed ours on Saturday, and I was surprised how much it weighed - 120lbs exactly, with a battery on board. Our proposed solution: 13lb steel block

[Exla357]

We're currently less than 90 pounds. That's right. 84.7 pounds. Four CIM, eight wheel tank drive.

Our secret?

HOLES.

A. Crap. Ton. Of. Holes.

Look's like we'll need to find ways to ADD weight this year.

lololol

[Oblarg]

So, last year we were ditching wire guides at competition to get under the weight limit, so we at 4464 were admittedly a bit apprehensive about weight this year.

However, we weighed our robot, sans compressor, tanks, solenoids, and electrical board for the first time last night. Came in at 67 lbs. We've got a 6-CIM drive, two PG188's, one RS550, and four 1.5'' bore, 8'' stroke cylinders. We are very pleased. About half of our superstructure is 1/16'' aluminum tube, and the other half is 1/8''. We've actually overbuilt a lot of our mechanisms, it's just that our design is very simple and doesn't call for all that much actual stuff.

Here's a pic:

[DELurker]

Originally Posted by Chadfrom308

We just have to add Plexiglas around the sides for sponsors and a couple of lights

Hoping you mean Lexan/polycarbonate/Makrolon... Plexiglas is prone to shattering.

[BoilerMentor]

Originally Posted by wilsonmw04

I would do this first.
I fail to see the significant benefit of 7lbs. vs. what 6 cims give you.

The drive train is geared for 6 CIMs. That is precisely the problem with removing them. It is also a surprisingly large amount of work to remove them as well. You can't get at them from the outside of the gearbox, so we'd probably have to remove our drive modules, remove the transmissions from those, split the transmission, remove the motors, then reassemble. Compared to most of the other items on the list it is much more difficult.

Also, it would hurt our strategy pretty severely and go completely against an important lesson the team learned last year regarding the value of defensive play.

Lastly, the robot should cross the field (calculated including wheel slip with all six cims) in 3.25 seconds. In the case we have to cycle by ourselves they will be fast cycles.

[DELurker]

Originally Posted by BoilerMentor

With the current position HBR has found themselves in, I thought this might be a fun thing to look at.

Share your robot weight situation and describe your remedy.

On paper, with the battery, 6 lbs of bumpers, and without bolts or wires (we're not going to model them), we're at 102 lbs. Our method was lightweight parts, thin Lexan, and perforated PVC panels. That, and an intense desire to break the three-year trend of being within 0.5 lbs of the upper weight limit at weigh-in ... since our shop scale broke.

[BBray_T1296]

Originally Posted by DELurker

Hoping you mean Lexan/polycarbonate/Makrolon... Plexiglas is prone to shattering.

Regolith.

According to our BOM (we don't actually have the whole robot built to weigh it for sure) we are going to clock in at about 110lbs with what we currently have planned.

[droswell]

In 2010 we guessed our weight to be around 110lbs. Never could get it on a scale.

Showed up to the WPI regional and weighed in at 142

Spent the first hours of practice day changing the wheels and drivetrain and cutting everything off. Then measured the frame. It was out of square by 1/4", and wouldn't fit in the box. Spent the rest of the day shortening the frame bu cutting sections out by hand with a hacksaw and re-assembling the robot.

We learned a valuable lesson about being 2" under frame size and ALWAYS weight your bot _before_ showing up to a regional.

[Christopher149]

Weighed ours the other day (with a couple of bumpers on), and the scale read like 80 lbs. It's a decently accurate scale since it tells me I weight ~120 (I do). Also, the bot is essentially done.

We haven't been this underweight since Lunacy.

PS. And it's made of C-channel and 1" 80/20.

[DELurker]

Originally Posted by droswell

We learned a valuable lesson about being 2" under frame size and ALWAYS weight your bot _before_ showing up to a regional.

Our current weighing method is to take two students, weigh them on a pair of bathroom scales, then weigh them while they are both holding the robot. Subtract out the student weights and you get the answer +/- 1 lb. If you then rotate the robot 90 degrees and repeat, you could actually figure out the location of the center of gravity of the robot in the horizontal plane. I'm not a fan of turning the robot on its side to get the vertical axis of the CG...

[c.shu]

Last we checked we were sitting at around 103 lbs with everything on the robot.