We are looking for a way to weigh our robot and were wondering how everybody else does it. Do you just use 4 scales(one under each wheel)…a large shipping scale?
Thanks
Do not use a standard dial bathroom scale. They are very inaccurate. We use a 50 lb shipping scale (dial) to weigh individual pieces and assemblies. When we need to weigh the whole robot, we go to the local pet hostpital and use their big (electronic) dog scale.
We have a digital scale with a 276 pound capacity a sponsor bought us. We have no idea what they paid for it, but it’s really awesome.
We use one of those standard counterweight scales every gym has. Step exercise platforms are perfect for holding your robot on the scale :). During, build, we use a 1oz x 22lb kitchen scale for weighing sub assemblies.
our sponsors, have this large shipping scale that i think goes up to 500lbs. it works for us, and we dont need to take apart the robot.
We use the shipping scale at Visteon. We have gotten it well over 1000 lbs 
Our lead mentor is also our school’s wrestling coach. The wrestling room is less than 100 feet from our garage, and when we need to weigh something we just go grab the big scale they have in there for weighing wrestlers.
It’s a nice setup.
What about the good 'ol fish scale 
Rob
check this thread from earlier this Fall.
http://www.chiefdelphi.com/forums/showthread.php?t=30211&highlight=costco
I followed the advice regarding the purchase of an office supply store postal scale. We purchased one that has a 14" square base which we place a 48" square of 1/2 plywood. The display is detachable and uses a coiled cord so that we can still read the weight. That has been a big plus for us this year.
We can check weight any time and not have to haul the 'bot up to the nurse’s office and support it on the small pedastal and slide weights on the balance.
I think it was $120, maybe less. It was one of several pre-season supply purchases. Others included, aluminum, shaft encoders, chain, nuts and bolts,…
Here’s a way to weigh your robot with stuff you have in the shop right now. I’ll describe how to make a “beam scale” which is pretty accurate, but not exact.
*** DISCLAIMER: Be very careful in the process of putting a “lifting sling” on your robot lab ceiling as well as in the process of lifting the robot off the floor.
Steps:
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Get three sections of PVC pipe you were using for practice goals (the longer tetra pieces). They should be 60" long.
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Tape them together with lots of duct tape
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Drill one hole through all three pipe sections about one inch from the end. Thread a nylon cord through these three holes, tie tight and make a hanging loop
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Measure EXACTLY TWO INCHES AWAY from these three holes and repeat the three hole process with a new nylon loop.
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Attach the “inner” nylon cord to the STURDY, RIGID ceiling beams of your shop area. Do NOT attach the the suspended ceiling tile grid, etc. It MUST be able to support 150 lbs.
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Now, go and fill two 2-liter soda pop bottles (the big ones) FULLY with water.
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Attach one bottle to the END of the PVC where you had the first nylon loop.
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Attach the 2nd one-liter bottle onto the other end of the beam, and SLIDE it towards the middle until the beam balances.
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Measure the distance between where the sliding bottle balanced and the center hanging point.
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Mark this SAME spacing (ever 2") along the PVC pipe out to well beyond the 55" mark. Make marking IN-BETWEEN these marks; namely EVERY inch for the full length of the PVC.
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Now, attach your robot under the “short” end of the beam, tighten the harness until the PVC pipes are angled upwards, and place the adjustable water bottle onto the PVC pipe bundle until it balances. do NOT lift your robot too far off the floor; only enough so it hangs freely.
*** The number of inches away from the centerline is your robot’s weight (approximately) in KILOGRAMS.
The robot must weigh less than 54.43Kg (120 lb.) WITHOUT the battery.
Good luck; remember that this is just a testing method.
PetsMart (providing you have one nearby) locations usually have a veterinarian’s office in them and they have a nice big flat scale that they let us use when we ask nicely.
And, if you’re totally strapped for cash, you can use the CA Robotics Poor Roboteer’s Scale™:
Take a scale (your standard scale, that is). Tip the robot so the CG is over a single side (we tip it forward, so that the outermost front metal bar is resting on the center of the scale. Tip it so that it is basically free, use your arms just to keep it from falling over, not to hold it up. The reading you get on the scale will be close to the weight of the scale.
Note: this is highly inaccurate, because a) bathroom scales have a tolerance of something like +/- 5% (?) and b) it’s hard to get the robot exactly balanced so that all of the weight is resting on the scale.
We use this during build season, and if we are really close then we run it to the bus depot to use their baggage scale, which has a much better tolerance but has the same tipping problem.
We will probably run it over to GE/Fanuc again this year and use their big scale, just before we ship it. Not that we would be able to correct for it right then, but if we were over we would know what to expect on Thursday the 3rd.
Hope this helps,
Jonathan
We use an Intercomp CS200 “hanging scale.” You could call it a
“fish scale” but it is a strain gauge scale accurate to 0.1 pounds.
It is very convienent to hang a whole robot with ropes, major
components with ropes, or a set of parts in a plastic bag.
We could not get through a build period without it…
Does your school have a wrestling team? We use our Wrestling team’s scales. Works great.
hehe, yep! Except the wrestling coach runs woodshop and the scale is onto of a flight of stairs…but today it was down in the wreslting room so we had to carry the robot over the mats since we couldn’t roll the cart over them.
Motorola Shipping Dock Scale (It’s good to be in a facility that used to manufacture all Nextel phones and ship them to nextel in large crates).
It would be hard to get your hands on, but the best way to measure a robot, is to buy a four point scale. It will tell you the distibution of wieght if you serious about this stuff thats the only way u can go you rnot serious without one.
We have a 150 year old calf weighing scale that our school has had forever… It’s made almost all out of wood and iron, but it seems to work fine.
My team (447) uses my fathers Longacre 4 pad scales. They get within 1/10th of a pound. He uses them for Soap Box Car Setups, and I get to talk him into letting us use them. They are very nice, but VERY expensive. I suggest them if you team can afford them.