Close Inspection

[ZackCraig]

Did anybody have an inspection where you barely passed?

Our robot was 119lbs and fit the square space perfectly.

[TubaMorg]

At first we barely DIDN'T pass. We weighed 120.8 lbs. and were 1/16th of an inch to tall. Didn't take much to fix though and ended up short enough and 119.3 lbs.

BTW does anyone know why lbs. is an abbreviation for pounds?

[Tristan Lall]

One hint for everyone who builds a robot that fits "perfectly": build it one inch smaller in all directions next time. Ask yourself how much of an advantage you gain by keeping that inch, and consider what happens if your frame gets twisted, or you want to add something, or the inspection box is undersized (and nobody notices). Also remember that you can't be pushing on the walls of the bounding box (or the virtual walls, in the case of this year's sizing box); you must fit inside unconstrained.

There are probably cases where you need to build your robot almost exactly to the maximum size, but realistically, most maximum-sized robots aren't examples of this.

Also, as we're on the topic, remember to keep track of weight. There was one team at GTR which arrived something like 37 pounds overweight (due to their own malfunctioning scale). Don't let that happen to you!

Originally Posted by TubaMorg

BTW does anyone know why lbs. is an abbreviation for pounds?

It's from the Latin, librum, for scale.

[Dan Zollman]

At Philly, we were around a pound over the limit, so we cut off a few inches of the middle support of our ramp (taking away 30% of its support, but it still worked out), and landed exactly at 120 lbs.

Originally Posted by TubaMorg

BTW does anyone know why lbs. is an abbreviation for pounds?

Interesting question...

Originally Posted by Wikipedia

The word “pound” comes from the Latin word pendere, meaning “to weigh”. The Latin word libra means “scales, balances" and it also describes a Roman unit of mass similar to a pound. This is the origin of the abbreviation “lb” or “℔” for the pound. The “s” at the end of “lbs” simply denotes the plural form.

Edit: Tristan beat me.

[IndySam]

We design to be 1" shy on all dimensions and it is amazing how things always seem to grow during build season and we end up being close to max size.

This year we had zero problems with dimension or weight for the first time ever.

Having a weight budget spreadsheet is a must!

[Billfred]

Ours was painless--102ish pounds, in by a good half-inch all around. I don't know of anyone who had size or weight problems at Palmetto, though I did inspect size issues at UCF and Chesapeake. (Some Palmetto teams did get burned on other issues, like not having the Rockwell block.)

[EricH]

Originally Posted by IndySam

We design to be 1" shy on all dimensions and it is amazing how things always seem to grow during build season and we end up being close to max size.

This year we had zero problems with dimension or weight for the first time ever.

Having a weight budget spreadsheet is a must!

We take 1/4" off all sides and the top. Minimum. This is to allow room for bolt heads and the like.

Weight budget: with us everything goes on it individually, and we use it for our BOM. Hey, it works, and it needs less work.

[Mister_Juggles]

I remember last year (06) our robot was weighing in at a tenth of a pound or so overweight. We let the air out of the pneumatics and it put us *just* under 120

[Gabe]

Originally Posted by TubaMorg

BTW does anyone know why lbs. is an abbreviation for pounds?

In Spanish libra means pound, originating from Latin as mentioned before.

[Tristan Lall]

Originally Posted by Mister_Juggles

I remember last year (06) our robot was weighing in at a tenth of a pound or so overweight. We let the air out of the pneumatics and it put us *just* under 120

That shouldn't have worked. Assuming that you have two Clippard AVT-32-16 tanks with 16 in³ each at 120 psi, and four 24 in stroke, 2 in bore Bimba Cylinders on board (realistically, that's way more than you'd expect, even neglecting the tubing), at 120 psi and 60 psi respectively, the amount of air on board is only about 0.06 lb.* If you went from 120.1 down to 119.9 ("*just* under 120"), there's a leftover 0.14 lb to be accounted for. More likely, you just got lucky with the error in the scale.

And here's a question to which I don't really want to know the answer: do you need to weigh the robot with or without its compressed air?

*This assumes an air temperature of 21°C; in reality, the air is probably hotter than this due to being mechanically compressed. And that lowers the density even more.

[Wayne Doenges]

We let the air out of the pneumatics and it put us *just* under 120

That happened to us this year at Boilermaker. We were 120.2 pounds. We were told to let the air out of our three clippard tanks. We than weighed 120.0 We have to have our tanks filled because we use the air to back fill our cylinders to keep the gas struts compressed
We also always build 1" short of the width and length dimensions. We have never been too big but we have removed plexiglas from the box due to bolt heads