What scales to weight robot?
 

What scale does your team use to weigh the robot? We're trying to find one but the only ones in a good price range had a platform which is too small.

Thanks!

Re: scales
 

We use a scale with a small platform. It is a digital scale, so we set a piece of plywood on it then zero out the scale then weigh the robot. Works very well.

Re: scales
 

1 of my teams uses the shipping scale at the factory in which they work

the other team uses a bathroom scale with a modified platform on it so it can support the robot...


i would say for an inexpenive solution you can use a bathroom scale and then for the final meausrement take it to a shipping store UPS or FedEx and they can give you an accurate weight

Re: scales
 

I think the folks at PBR (our main sponsor last year) did the weighing. Then when we really had to figure it out fast, we just hauled it all over to the gym and weighed it on the scales that the athletic department has. Worked fine for us this year.

Re: scales
 

We also use the school's gym scale. I figure if they can handle those 300 pound wrestlers they can handle our puny little 135 pound (hopefully less) bot. :p

Wayne Doenges
ex-Team 535
Soon to be a Rookie again :eek:

Re: scales
 

Our team this year used two different scales. The main one we use at the high school's woodshop is an old farm scale. It's about 100 years old and I believe it's original use was to weigh grain. This one has different weights you can add to it and the scale is mounted on wheels so you can roll it around. It's made of cast iron (very heavy) with oak boards for the weighing platform and makes one heck of a noise when you roll it down the ceramic tile in the hall! :yikes: Just don't try to sneak up on anybody with it. :p The second one we used was at one of our sponsors shops. We met there when the school was closed due to snow or the extreme cold we had back in January (how can anybody forget?! :rolleyes: ). This scale was a digital scale used in the shipping department. Both these scales worked quite well, and we even weighed ourselves. :D

Re: scales
 

wow all these high tech and alarmingly low tech but still effective scales! for the past two years we've used a bathroom scale from a mentor's house, and usually we try to find a balance point on the robot so we can weigh it without it touching the ground. failing that, we have someone hold the robot while standing on the scale and we weigh it that way. naturally this is just for a rough estimate and whenever we can we take it to be weighed, i believe we've used vet scales in the past before. course all the scales in the world wont help you if you're 135lb two nights or a night before ship :ahh:

Re: scales
 

I would not recommend using a traditional needle bathroom scale. We have found ours to be up to 8 lbs (!) off depending on the surface the scale is sitting on and how you load the mass. If you must use a bathroom scale, be sure to calibrate it with water or lifting weights but even then I wouldn't trust it to more than about +/- 2lbs.

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we just guessed :D and the night before shipping we were finally able to borrow the wrestling team's and found out we were quite overweight... which is why we ended up with many many holes

Re: scales
 

You can get a good digital scale from Office Max or Office depot. The scale has a range to 200 lbs or the KG equilv. All in 1/4 lb increments.

All ypou have to do is make a platform (plywood surface. If the plywood is in place when you turn the scale on it zeros out and you are ready to go.

Cost? It was about $35

Re: scales
 

Back when I was on 992, we would just drive the parts down to the local FedEx office, where they were more than happy to help us with our unusual request (they only asked that we come after 7pm, when they aren't as busy).

If you want to buy a scale, I would recommend a scale with a wired remote. This will allow you to place a plywood platform over the top (you could even make up a nice wooden cover that fit the size of the scale if you wanted), and still be able to read the numbers.

The price of such a scale really depends on the accuracy you are looking for. Costco has a Digital Shipping Scale with wired remote for $50 that is good to 310 pounds, but the accuracy is (+/-1.0% + .22 lb), which translates to +1.52/-1.08 pounds for a 130 pound robot.

For a more accurace scale, such as this Health-O-Meter H349KL, which is accurate to ±.2%, or ±.26lbs @ 130 pounds, you will need to spend around $250.

Re: scales
 

Most high school gym scales can be tilted depending on the loading. The one at our school, we could drop 3 lbs at weigh-in by standing at the back of the scale. We could drop a lot more if we hung off, but that was suspicious looking to hang off the back of the scale.. :rolleyes:


Wetzel

Re: scales
 

In 1998, we used a needle bathroom scale, and ended up needing to lose 30lbs when we weighed with a real scale at nationals.

Re: scales
 

We tried a digital scale we bought, and it was off by as much as 18 pounds, I believe.

we tried the scale the school uses for wrestlers, and it was off by 8 lbs.

We used a series of weights from the weightroom to test the accuracy of the scales.

The funny thing is the scales were never off by the same amount. It always got progressively worse as you added weight.

We found out we had to shave 30 lbs off our bot last year. It looked like swiss cheese when we were done

Re: scales
 

We used a vet hospital (for large animals) scale...it worked great and was within a pound of the competitions scale. I think a vet place is easy to find and usually have a scale big enough for a robot and a much better solution compared to a bathroom scale.

Re: scales
 

In 2002 we took the robot to the airport and used the luggage check-in scales, they're pretty accurate and, if you have nothing better closer to you, it's a very good option.
In 2003 we didn't weight the robot - ended up adding ballast to increase traction, a robot builder's dream ;)
This year we only had to take a pound off the robot, despite our somewhat "ghetto" weigh in techniques... :p

Re: scales
 

another answer :
Dont!
Wait until the competition then find out your massivly overweight (yes, we did that lol, had to remove our forklift mechanism....) ..
proper planning etc.....

Re: scales
 

Scales tend to be off by percentages rather then x amount, so that makes sense.

Wetzel

Re: What scales to weight robot?
 

Heh, I think we must have the most ghetto way of weighing a robot...

We use a digital bathroom scale with someone carrying the robot while standing on the scale. Then we subtract the person's weight and we have the robot's weight. :cool:

Re: What scales to weight robot?
 

We use a digital scale that that measures up to the hundredth place in pounds. Really nice since the plate is about three feet by three feet.

I would not really rely on bathroom scales because of the very small weighing surface area. I would even recommend bringing your robot to Publix and have it weighed in their spiffy scale (accurate to half a pound).

Re: scales
 

Speaking of weight, we found out that we were 138 on thursday night at florida regional... feel the stress?

we use a scale that motorola has in thier facility... its aobut 5 ft. by 5 ft. and its digital... :)

Re: scales
 

That... is... awesome.

I never thought about using a balance type scale to compare the "new" robot weight to that of an old (hypothetically 130lb) robot.

I'm sure it's not the most tremendously accurate method, but heck... I give it bonus points for ingenuity.

JV

Re: What scales to weight robot?
 

We got this really cool industrial scale from a local surplus supply shop. It is great, it measures weight to the 100ths of a pound and has a nice large surface area.

The funniest thing we did when we first got it was that members of the team, would weigh themselves, go to the bathroom and then weigh themselves again (a mentor started this) and see how much weight they lost from going to the bathroom.

Pretty crazy if you ask me.

Re: What scales to weight robot?
 

Vernier Force Scale type deal.

Re: What scales to weight robot?
 

we use the scale from our wresteling team, it reads to the thousands place so its accurate for our purposes, hell, one of the guys sneezed on it and i weighet .012 lbs

lol

Re: What scales to weight robot?
 

I just want to thank you for that mental image! :eek:

You should have waited 'till later to post this. Like when I'm eating dinner. :p

Re: scales
 

I didn't know they were that accurate :eek:
We "steal" our school's wrestling team's scale :p much to their consternation...
but it is the most accurate scale we have available. 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...
it is a good idea to use multiple scales to check. Better safe than sorry :ahh:

Re: What scales to weight robot?
 

lol That's even more accurate than the FIRST scales.

Re: What scales to weight robot?
 

We use our wresting team's scale for weighting. It's free, it's easy to use, and it's always available. But I wouldn't be the fool to have to tell them we broke it, I mean, they *ARE* wrestlers! :ahh:

Re: scales
 

We'd used a bathroom scale to weigh our robot..

That was after we'd drilled a ton of holes in it, too. We thought we were underweight (good thing!) but when we went to regionals and used their scale, we were still a good couple of pounds overweight (baaad!).

We ended up spending the periods between each practice round on the practice day filing the robot like mad, and trying to drill more holes wherever we could. Our area was full of aluminum shavings. It was fun :rolleyes:

After some very tedious work, though.. we'd finally gotten it down to EXACTLY 130 lbs. I think we're gonna pay much more attention to the weight factor while designing and building this year than before :o

Re: scales
 

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.

Re: What scales to weight robot?
 

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. :D

Re: What scales to weight robot?
 

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. :cool:

Re: What scales to weight robot?
 

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.

Re: What scales to weight robot?
 

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

Re: What scales to weight robot?
 

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.

Re: What scales to weight robot?
 

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*

Re: scales
 

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.

Re: What scales to weight robot?
 

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.

Re: What scales to weight robot?
 

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

Re: What scales to weight robot?
 

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.

Re: What scales to weight robot?
 

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.