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Unread 02-16-2018, 01:08 AM
Ian Curtis Ian Curtis is offline
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Re: OVER WEIGHT

Quote:
Originally Posted by RoboChair View Post
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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Unread 02-16-2018, 06:59 AM
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Re: OVER WEIGHT

Seems liek you're going to be tasting the bitterness of Swiss Cheese (-ing your robot)
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Unread 02-16-2018, 07:57 AM
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Re: OVER WEIGHT

Quote:
Originally Posted by Ian Curtis View Post
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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Unread 02-16-2018, 08:03 AM
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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.
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Unread 02-16-2018, 08:20 AM
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Re: OVER WEIGHT

Quote:
Originally Posted by IKE View Post
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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Unread 02-16-2018, 08:23 AM
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Re: OVER WEIGHT

Quote:
Originally Posted by Kevin Sevcik View Post
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...
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Unread 02-16-2018, 08:53 AM
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Re: OVER WEIGHT

From a previous post....

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


Lessons learned
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Unread 02-16-2018, 09:35 AM
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Re: OVER WEIGHT

We just added 16.70 lbs of steel ballast to the back of our robot.
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Unread 02-16-2018, 09:40 AM
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Re: OVER WEIGHT

Quote:
Originally Posted by chadr03 View Post
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.
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Unread 02-16-2018, 09:47 AM
bjtheone bjtheone is offline
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Re: OVER WEIGHT

Quote:
Originally Posted by pfreivald View Post
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.
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Unread 02-16-2018, 10:03 AM
rich2202 rich2202 is offline
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Re: OVER WEIGHT

Quote:
Originally Posted by VIKotic Dave View Post
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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Unread 02-16-2018, 10:07 AM
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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.
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Unread 02-16-2018, 10:23 AM
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Re: OVER WEIGHT

subscribed, this seems like a very interesting thread
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Unread 02-16-2018, 10:25 AM
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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.
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Unread 02-16-2018, 10:37 AM
Seth Mallory Seth Mallory is offline
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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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