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#16
02-16-2018, 01:08 AM
 Ian Curtis Best Available Data FRC #1778 (Chill Out!) Team Role: Engineer Join Date: Feb 2005 Rookie Year: 2004 Location: Snohomish Posts: 2,601
Re: OVER WEIGHT

Quote:
 Originally Posted by RoboChair You should learn to be friends with 1/16th wall tubing!
We are.

I didn't do that math, because it's twice as depressing.
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CHILL OUT! | Aero Stability & Control Engineer
It is much easier to call someone else a genius than admit to yourself that you are lazy. - Dave Gingery
#17
02-16-2018, 06:59 AM
 TechWaffle What did I do this time... AKA: Brett Gallagher FRC #0225 (TechFire) Team Role: Mechanical Join Date: Oct 2015 Rookie Year: 2016 Location: York, Pennsylvania Posts: 19
Re: OVER WEIGHT

Seems liek you're going to be tasting the bitterness of Swiss Cheese (-ing your robot)
#18
02-16-2018, 07:57 AM
 MrForbes Registered User AKA: Jim FRC #1726 (N.E.R.D.S.) Team Role: Mentor Join Date: Feb 2006 Rookie Year: 2006 Location: Sierra Vista AZ Posts: 6,401
Re: OVER WEIGHT

Quote:
 Originally Posted by Ian Curtis Aluminum weighs about 0.1 lbs per cubic inch. Take how overweight you are, multiply it by 10, and that's the volume of aluminum you've got to remove. If you are drilling 1" holes in 1/8th inch aluminum, you've got to drill 10 holes to get 1 cubic inch of volume.
Maybe 13 holes per cubic inch? (holes are not square)

If you use thin wall tubing to build your robot, you are not likely to be so overweight, but you also soon discover that reducing weight should be done on other parts of the robot, that are really causing the problem.
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Jim
#19
02-16-2018, 08:03 AM
 IKE Not so Custom User Title AKA: Isaac Rife no team (N/A) Team Role: Mechanical Join Date: Jan 2008 Rookie Year: 2003 Location: Michigan Posts: 2,287
Re: OVER WEIGHT

A paper I put together from "Back-in-the-day".

Robot Weight Watchers

In general replacing pieces with thinner gauge reduces wieght much better than wearing out drills and drill bits drilling holes. You are also a lot less likely to fill your electronics with shavings.
#20
02-16-2018, 08:20 AM
 Kevin Sevcik (Insert witty comment here) FRC #0057 (The Leopards) Team Role: Mentor Join Date: Jun 2001 Rookie Year: 1998 Location: Houston, Texas Posts: 4,146
Re: OVER WEIGHT

Quote:
 Originally Posted by IKE A paper I put together from "Back-in-the-day". Robot Weight Watchers In general replacing pieces with thinner gauge reduces wieght much better than wearing out drills and drill bits drilling holes. You are also a lot less likely to fill your electronics with shavings.
But if the electronics are smoked because of swarf, you don't need them on the robot anyways.
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#21
02-16-2018, 08:23 AM
 IKE Not so Custom User Title AKA: Isaac Rife no team (N/A) Team Role: Mechanical Join Date: Jan 2008 Rookie Year: 2003 Location: Michigan Posts: 2,287
Re: OVER WEIGHT

Quote:
 Originally Posted by Kevin Sevcik But if the electronics are smoked because of swarf, you don't need them on the robot anyways.
Yeah, but I have found teams like to leave those dead electronics on their robots and blame the field controls instead. Plus shavings in electronics means the weight is just transferred, not removed...
#22
02-16-2018, 08:53 AM
 Old Guy Registered User no team Join Date: Apr 2014 Rookie Year: 1992 Location: New England Posts: 5
Re: OVER WEIGHT

From a previous post....

24 Hours before a competition
77 lbs.
65 lbs. weight limit

Lessons learned
Attached Thumbnails

#23
02-16-2018, 09:35 AM
 pfreivald Registered User AKA: Patrick Freivald FRC #1551 (The Grapes of Wrath) Team Role: Mentor Join Date: Jan 2007 Rookie Year: 2001 Location: Naples, NY Posts: 2,454
Re: OVER WEIGHT

We just added 16.70 lbs of steel ballast to the back of our robot.
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#24
02-16-2018, 09:40 AM
 bjtheone Design and Fab guy AKA: Brad Warkentin FRC #2706 (Merge Robotics) Team Role: Mentor Join Date: Jan 2016 Rookie Year: 2011 Location: Canada Posts: 185
Re: OVER WEIGHT

Quote:
 Originally Posted by chadr03 Mini-Cims are .6 lbs lighter than Cims and if you can live with 2/3 the power are an easy swap
And 775Pros are even smaller.

CIM - 2.82 lbs
MiniCIM - 2.16 lbs
775Pro - 0.8 lbs

The advantage is they have basically the same power as a full CIM. They actually perform better when run at full power than a CIM (will run way longer before they overheat), due to the active cooling. We have seen this when running our practice bots continuously. Probably not as big a deal when you are running real matches, with cool down periods in between. The weight savings is huge though, and they are easier to package since they are so much smaller.

However, they DO NOT deal with stall, as they rely on the motor spinning to provide the active cooling rather than the motor casing acting as a heat sink. A CIM is rated for around 30 seconds of full power stall before it suffers catastrophic failure, a 775Pro around 3 seconds. Makes them a great candidate for intake motors - huge weight savings on a mechanism you are likely having to lift high in the air, and winch style climbers. Not so great for main drive and elevator lifts.

We saved 6 pounds on our design using them... that is a lot of holes.

Alternatively, blame the software team.
#25
02-16-2018, 09:47 AM
 bjtheone Design and Fab guy AKA: Brad Warkentin FRC #2706 (Merge Robotics) Team Role: Mentor Join Date: Jan 2016 Rookie Year: 2011 Location: Canada Posts: 185
Re: OVER WEIGHT

Quote:
 Originally Posted by pfreivald We just added 16.70 lbs of steel ballast to the back of our robot.
Hopefully, we will be doing the same. So far, the design calculations have us coming in around 89-95 pounds, with the plan being to add the weight back in as low as possible to move our CoG down, and balance the robot fore/aft.

However, at this point we still have much assembly to complete, and are still at the hoping all the students got their CAD correct so our weight estimate is sane stage.
#26
02-16-2018, 10:03 AM
 rich2202 Registered User FRC #2202 (BEAST Robotics) Team Role: Mentor Join Date: Jan 2012 Rookie Year: 2012 Location: Wisconsin Posts: 1,498
Re: OVER WEIGHT

Quote:
 Originally Posted by VIKotic Dave 2) smaller font in programming
Programmers forgot to periodically empty the bit bucket, so the mechanical people drilled a hole in it.
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#27
02-16-2018, 10:07 AM
 CEF Registered User FRC #5607 Join Date: Nov 2016 Location: Raleigh, NC Posts: 163
Re: OVER WEIGHT

Mechanum? Those wheels can be heavy -- Andymark's 6" Mechanums are 2.2 lbs each.

If you have Andymark, switch to Vex -- their 6" Mechanums are only 1.25 lbs each.

God help you if you did something bigger than 6" Mechanum -- AM's 10" Mechanums weigh in at 9 lbs each.

If that's not enough, you could ditch mechanum altogether. Non-mechanum wheels are under 1lb from either AM or Vex.

You might also look at all the hardware on your robot. We switched to mostly aluminum rivets this year which saved weight (in addition to being faster).

If you do swiss-cheese, be sure to protect your electronics. Yeah, you shouldn't have any bare wire. But, you'd be amazed at where tiny little pieces of metal can go.
#28
02-16-2018, 10:23 AM
 unie01 Registered User no team Join Date: Feb 2018 Location: ohio Posts: 1
Re: OVER WEIGHT

subscribed, this seems like a very interesting thread
#29
02-16-2018, 10:25 AM
 hrench mechanical build mentor AKA: Bob Hrenchir FRC #1108 (Panther Robotics) Team Role: Mentor Join Date: Jan 2012 Rookie Year: 2010 Location: Paola, KS Posts: 376
Re: OVER WEIGHT

If you have pneumatics, consider running at 30 pounds instead of 60. That'll save 30 pounds.

Seriously, if you're that heavy, you probably should consider removing some systems or if you have any systems that perform the same function, you might get rid.

For instance, if you have a cube intake that both actively rolls in and uses a clamp too, you don't need both.

Someone else mentioned. wheels. If your mecanum, A four-wheel tank works too and is much lighter.
#30
02-16-2018, 10:37 AM
 Seth Mallory Registered User FRC #0192 (GRT) Team Role: Mentor Join Date: Mar 2007 Rookie Year: 2003 Location: Palo Alto, CA Posts: 282
Re: OVER WEIGHT

Replacing screws, bolts, and nuts with aluminum rivets save a lot of weight. They are quick to remove if you to just drill the head off and use a punch to push the rest out. You can convert your robot by removing the bolt and drilling the hole to the size for the next larger rivet. Python is over weight.
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