2014 FRC's Biggest Loser
 

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.)

Re: 2014 FRC's Biggest Loser
 

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

Re: 2014 FRC's Biggest Loser
 

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.

Re: 2014 FRC's Biggest Loser
 

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

Re: 2014 FRC's Biggest Loser
 

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 :)

Re: 2014 FRC's Biggest Loser
 

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

Re: 2014 FRC's Biggest Loser
 

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:

Re: 2014 FRC's Biggest Loser
 

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

Re: 2014 FRC's Biggest Loser
 

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.

Re: 2014 FRC's Biggest Loser
 

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.

Re: 2014 FRC's Biggest Loser
 

Regolith. :p

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.

Re: 2014 FRC's Biggest Loser
 

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 :ahh:

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.

Re: 2014 FRC's Biggest Loser
 

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.

Re: 2014 FRC's Biggest Loser
 

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...

Re: 2014 FRC's Biggest Loser
 

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

Re: 2014 FRC's Biggest Loser
 

One of our students suggested last night that we weigh our robot....so I'm bringing in a scale today. My guess is around 90, we'll see.

Re: 2014 FRC's Biggest Loser
 

Our robot weighs 72.75 pounds. If anyone would like to send us weight go right ahead

Re: 2014 FRC's Biggest Loser
 

You guys are making me feel self conscious about our robot weight... :rolleyes:

Re: 2014 FRC's Biggest Loser
 

We are at 80.1 lbs, with a 6CIM drivetrain, a pickup, and a shooter. We still have to put on a 2 in stroke cylinder, and that shouldn't add too much weight.

Re: 2014 FRC's Biggest Loser
 

Yes, I couldn't think of the name for it!

Re: 2014 FRC's Biggest Loser
 

we weighed systems last night and are coming up with 120 lbs... We're still missing some important items like the sponsor panel, which is also the entire front of our robot.

Luckily, we designed in some weight savings opportunities should the need arise. looks like we'll be diving into that.

On a completely unrelated note :rolleyes: , anyone know where we can get a 26" long 1/2" keyed aluminum shaft? The longest I can find right now is 24"

Re: 2014 FRC's Biggest Loser
 

If you end up a bit over and are not using them elsewhere switching 2 of the cims to mini cims will save you 1.3lb. I have heard they can be used in 3 cim gearboxes like this with the same gearing.

MOE is unable to find one either, we may need to get one keyed with a mill, is switching to hex an option for you?

Re: 2014 FRC's Biggest Loser
 

It's an option, it would just require a little more tear-up and a few parts we don't have (but I think could acquire). I'm looking at the churro tube from AM if we go that route. My recollection is that it's loose in the hex hubs, which could cause a problem, so we'll have to check on it.

Re: 2014 FRC's Biggest Loser
 

We're currently at about 85lbs. Much better than we've done in previous years

Re: 2014 FRC's Biggest Loser
 

We weighed in at 110lbs fully loaded.

I would be tempted to stick two chunks of shaft together with a ferrule insert to couple them, using a key to ensure that the two shafts' keyways lined up.

Like this:

Re: 2014 FRC's Biggest Loser
 

I am not quite sure what this is, but it got me thinking, you could get 2 pieces of shaft, tap the ends of both and connect them with a piece of threaded rod. Same concept I think.

As for hex shaft, I have found that the Vex hex shaft is extremely high quality and precision, you may want to look into that.

Re: 2014 FRC's Biggest Loser
 

Unfortunately, I have found that the probability of a vex hex bearing fitting on a vex hex shaft without issue is about 50%, though I might just have really rotten luck.

Re: 2014 FRC's Biggest Loser
 

That's a technique for sticking carbon fiber tubes together to make longer carbon fiber tubes.

It is the same concept, but there are two reasons to not use a threaded rod. First, the keyways would have a negligibly small chance of lining up with each other. Maybe a problem, maybe not. Second, you would have to make darn sure that threading never came apart, or even loosened a little bit. If it did, you'd have threading in bending, and that is a very bad time.

Re: 2014 FRC's Biggest Loser
 

(joking in this post)

Being 1747 alumni, I see some things never change (minus 2010).

Look at some pictures of your 2007 robot (whose name escapes me). To call that robot cheeseholed would be an understatement. It was (from what I was told at the time) accidentally made from 1/8" wall 1" square tubing (not 1/16") and even cheeseholing the frame, (if I remember right) they had to cut the tubing into angle irons to make weight. Even one frame section as cut and replaced by a carbon fiber member...

More seriously, I agree with the list... specifically the hex shaft. Usually AL is a better material than steel for hex shafts. The lone exception was the shooter shaft in Seagriffin (the 2009 robot). Being the student machinist who made the 2nd and 3rd shafts, that one had some gnarly vibrations with aluminum that steel seemed to fix. But otherwise, AL hex seems to be strong enough (although in the past, a bit less than precise when being used for pressed hubs).

Re: 2014 FRC's Biggest Loser
 

Our 2nd year, 2012, our robot came in, 3 days before ship day, at 150 lbs....to this day I have no idea how we shed 30 pounds without sacrificing any major systems at all.

This year we are set to come in right under 90 lbs! :D

Re: 2014 FRC's Biggest Loser
 

First try deburring the edges. Then just sand down the hex shaft. You loose the fancy paint, but it fits!


As for the long shaft source, you could go with McMaster, which sells some .500 aluminum rod with the "ground and polished" finish. This will be the exact diameter, but doesn't have the keyway cut into it. You could then cut your own keyway, use a roll pin, or make some flat parts on the shaft, and use a set screw.

Re: 2014 FRC's Biggest Loser
 

Oh, trust me, I've got plenty of experience sanding down hex shaft. Don't exactly have enough money to just buy new bearings until we get ones that fit ;)

Re: 2014 FRC's Biggest Loser
 

huh. seventy six pounds. I guess we need to go on a high carb diet

Re: 2014 FRC's Biggest Loser
 

As in high carbon steel? :D

Weighed in on Sunday out of curiosity (it is my first year as a coach) and we only weighed 87lbs. A few more parts to add but should finish under.

Re: 2014 FRC's Biggest Loser
 

The math I did for our robot put us at around 140lbs. So we spent a whole day planning out how we would cut weight. A little over half way through the day we decided to actually weigh the robot. The scale said the robot weighed 93 lbs. Now I thought the scale had to be way off because my math is never wrong. So the my best explanation was that the weight loss fairy had come over night and taken 47 lbs off our robot. So I think 4607 is the biggest loser so far this season. Then again my math could have been wrong. But I did the math on that and the odds were that my math was right. (Obviously meant to be funny pleased don't take anything I said seriously)

Re: 2014 FRC's Biggest Loser
 

Our CAD said the robot would weigh something like 1000lbs. But this was including a ball and bumpers that were both solid aluminum

Re: 2014 FRC's Biggest Loser
 

Our Robot , yet I=to be named from Team 1075 weight is about 92 lbs all in. We have 4 Cim " not be release " hardly ever seen style of drive with interior tough box gear changes 14 and 24 tooth. we use 2 more cims for shooter our ball, one fisher price for ball pick up along with 2 van motors for the arm mover. base frame id 1by3 tube 1/8 wall, arm is 1x1 channel, removalable shooter frame is 1x2 channel, arm is 1x1 channel and tube. WE control everything with 7 Talons ( Expensive ). I think the secret is our welding student who can held aluminum like no tomorrow. Pics later in the week. Good luck teams.

Re: 2014 FRC's Biggest Loser
 

Our robot hit 110 lbs on a very old bathroom scale today, which is almost exactly what our CAD said. We plan to acquire a better scale, but we had some people with known weights "calibrate" that one. Our structure is pretty simple but is mostly heavy 2x1x.125" tubing and we're using all 6 CIMs, 4 miniCIMs, and a pair of AM 9015s on the PG-71 gearboxes (no, we don't plan to pop the breaker every match :yikes:)

The tubing is mostly solid so we may try to make some sort of jig to swiss cheese our unbagged parts. Life would probably have been much easier if we used the thinner Vex tubing, but they were out of stock until the day we placed our order. We may also switch out the miniCIMs with banebots motors in versaplanetaries or CIMiles if we can afford it.

Re: 2014 FRC's Biggest Loser
 

We've probably seen about forty linear feet of Vex hex shaft and hundreds of their hex bearings. Literally none of them didn't fit on the shaft properly the first time around, no filing or nothin.

Re: 2014 FRC's Biggest Loser
 

Time to delete autonomous! if that does not work go to a party store and request a "metric crap ton of helium"

Re: 2014 FRC's Biggest Loser
 

I'll never forget weighing in at 137 lbs 4 days before ship day in 2006.
We ended up chopping the top half of our robot which was a nightmare, trying to redo all the functions with a different design.

I bought car scales soon afterwards and we weigh as we build since then.

Re: 2014 FRC's Biggest Loser
 

Rookie team here and we WAY over built (the team takes durability way too firmly). We are at 110lbs and do not shoot. We are using 3 by 1.5 in double extrusion for arms which weigh in at 50 lbs. And do not have much to save weight in. On the plus side, we can *accidentally* be a battering ram.::ouch::

Re: 2014 FRC's Biggest Loser
 

A metric ton of crap
Is still a metric ton. I don't see the difference. /sarcasm/

Re: 2014 FRC's Biggest Loser
 

Well, if you want to get technical, helium doesn't have negative mass, it is just less dense than air. A metric ton of helium is a metric ton of stuff, but it's still gonna float.

Re: 2014 FRC's Biggest Loser
 

Compressing 1 metric ton (of mass) into a 112" circumference, 60" tall cylinder will NOT float.

At STP, 1000kg (mass) of Helium will occupy 5.6 million liters of space. Compressing that to ~980 liters (cylinder above) will increase the density from 0.1786 g/L (STP) ("lighter" than air) to over 1 kg per liter (much, much "heavier" than air [1.29g/L])

The most current price I can find on helium is $5.2 per 100 grams (if it is out of date, helium is only getting more expensive) You would have to drop 52 grand on helium, which is definitely illegal.

Also the pressure would be 15,000 PSI, definitely not legal, and unbelievably dangerous

Re: 2014 FRC's Biggest Loser
 

Weighed in at 66.7 pounds without subsystems. Should be about 80 pounds all in .

Re: 2014 FRC's Biggest Loser
 

My team likes to wait until the competition to realize our robot is too heavy. Makes things more exciting!

Re: 2014 FRC's Biggest Loser
 

:( And if we ever meet on the field I sure hope you are full of Gracious Professionalism, because this comment is not what first is about, and as a rookie team you will not go far with this type of comment. I wish if I was a robot inspector in your regional you never make it to the field if I had seen this post.

Re: 2014 FRC's Biggest Loser
 

116 lbs as of yesterday with full functionality retained. After all our weight loss the robot came in at 114 lbs. We had to change one 550 back to a mini cim after it literally shot fire during driver testing. Minor things to add. We should be in good shape moving forward. We're very excited to attend the rookie event at Central Illinois and our home turf at Boilermaker. Good luck at the competitions. Reveal video to come.

Re: 2014 FRC's Biggest Loser
 

You missed it a bit as well. FIRST volunteers are far to gracious and professional to preclude a team from competing because of a member's silly post on chief. There are however, possible card issuances for behavior within the arena this year, off of the field. Eventually he'll figure it out, don't you worry. They'll go up against another bigger, badder robot and find out that they aren't quite as tough as they thought. Defense is absolutely a part of the game this year. Everyone should be prepared to take some hits. With a totally open field the possibility of high speed collisions skyrockets. You need to build a robust robot, but they need to not intentionally damage potential alliance partners. Nuff said. Good luck at competition.