What scales to weight robot?

[Jaine Perotti]

Originally Posted by Me

We also tried using this REALLY old one that came out of BD (one of our sponsors), but it ended up being WAY off once we double checked it with the aforementioned scale. This caused us some problems, as we were suddenly overweight...

Here is a picture of the REALLY OLD scale that I mentioned.
It's the big thing jammed up against the wall to the right.

[suneel112]

That looks a lot like the scale we used to weigh the robot. In my opinion, the competition should use my home weighing scale. It will display the bot as 5 pounds less than it really is. I guess we CAN use a winch now.

[Hunter]

We got really lucky and in return for a short demonstration at the "Fur Barn" here in North Bay, Ontario, Canada, they let us use there industrial scale that gets certified all the time because they have to accuratley weigh their furs before they ship them out all over the world. It was within .1 pounds of the competition scale at both the Canadian regionals and the Nationals, and it has a large platform that we easily fit our robot on since it is designed to weigh stuff as big as bear pelts.

Have to love northern Canada, who else can say that they get to hang out with a bunch of trappers to get your robot wieghed.

[BaldwinNYRookie]

Just a couple of days before we had to ship, someone realized the robot was 50 pounds over the weight limit. Of course that night it was decided that only a select few would be permitted into the shop, we had to get the weight off. I think I remember (before I was kicked out, trying to take pictures) they put each wheel of the robot on regular bathroom scales.

[Justin1636]

we use our wrestling teams scale it has a huge platform it is like 3 feet by 2 feet but it was like 800 dollars

[UlTiMaTeP]

At 710, after our rookie year finding out we were 15 pounds overweight, with our wonderful bathroom scale and pieces of wood, it said we were right at 130. Thinking we were safe we got to competition and found out we were 15 pounds overweight. "Say what" yes 15 they said. We proceeded to rip off the mobile goal hooks, then the drilling started with the 1 inch dremming bits, and the massive aviation snips. It wasn't till 500 holes later that we made weight. We realized at that point it was imperative to have a very accurate scale. So in 2002, I said no more guessing, and I took the project on myself to find an accurate scale that we could get accurate weights that the bot could actually sit on without large 4x4's supporting it, because if your not centered, your weight could be off by 5 or more pounds easily. The bathroom scale with the little platform or the feet shaped platform just wasn't cutting it for us. I search long and hard to find something accurate and finally, there was something within our budget accurate enough, and the hardest thing was, the big platform. I then found the best possible price for it. I learned a lot about scales during my search, counters, legal, gram, how they work. I finally found a group of scales that fits exactly the amount of accuracy we needed and the budget for it. Ohaus had the best scales for this application. The series I chose was the ES series and the model was:



Ohaus ES100L its specs, are 220lbs capacity with a tolerance of 0.1 but the selling point of this scale was the fact that it has such a large base for a bench scale. The lowest price I found for it was 289$.




The one I debated only other model I looked at that was somewhere near the price range with a large base was the Ohaus multi-function CQ100L31 , its specs are a 250 pound capacity with a tollerance of .01 I liked this one better because I could use it to accurately weigh small items to get a general weight during the design phase of the robot. But since we already had a accurate 2000 gram scale it didn't make any sense to buy a super accurate scale, and also the base is smaller than the ES model. The selling price for this scale the lowest I could find is 678$.


One of the things I learned about scales was their tolerance changes by weight, its the most accurate in the middle of its spectrum. For instance a 30 pound max scale is a bad choice for FIRST because it would be too close to its max. You want to chose one with at least a 30 pound difference between its max weight and your robots max weight to get an accurate reading.

Both scales I cited came from the same company www.discountscales.com I have bought from them before and they are a trustworthy company.

[Joe_P.]

we just used the wrestling team's scale... and i would have hated it if the scale had broke because then the wrestling team would hunt me down, drag me on the mat, and we would have an impromptu match... good thing the scale didn't break *shudders*

[Mike]

Originally Posted by BurningQuestion

Here is a picture of the REALLY OLD scale that I mentioned.
It's the big thing jammed up against the wall to the right.

Heh, like Jay said. We have a farm scale that's from the late 1800's, I'll see if I can find a pic of it.

[KTorak]

We use our Wresting Team scale, meaning we have to navigate through the locker room to get it. But, we don't know how accurate it is so we try to go around .5 lbs under 120..and pray we make weight at competition, lol.

[Justin_302]

Get a scale for a close measurement. We used a digital scale that was about 30 bucks. Once you get to the competition, you need to reweigh it. Every competetion our weight changed. As soon as we pulled it out of the box, we some how weighed 120.4, but at the regional before were at 120 exactly. We also found out that factors such as wind blowing at the scale can change it so be careful

[Biff]

This year we used a small digital 30lb postage scale, spread sheet, and a digital bathroom scale. As complete assemblies were built and lightened, we weighed them and removed the individual items from the quantities part of the spread sheet. The spread sheet also served as our cost accounting for inspection. Entering down real costs (used items) and book cost (what it would cost if new). We recored all weights in ounces, and in ounces per linear or square foot.
Our robot was a flop down so it was pretty easy to stand it up on a small board on the bathroom scale. As shipped I figured we were a few pounds over and the scale at Buckeye confirmed this. We wound up taking our arm with the window motor and grabber off and going with a lighter and simpler tee bar and single part last arm. Due to issues with not getting a space to build early in the season and taking longer to get parts designed and built, We spent almost all of Thursday finishing, Just to break several sets of shear pins in our lowest transmission in the last practice match.
In past years we have used the wrestlers scale. We had a Doh moment when we figured out we could bring the scale to the shop instead of dragging the robot upstairs to the wrestlers locker room.

[StephLee]

I don't think anyone has said this in this thread, but sorry for repeating if they have.

You could just weigh the individual components before putting them together, and keep track of how much it all weighs together. That might not get you an exact weight, but it should keep you within reason so you can get enough weight off to compete without hacking off too much.