Weighing rockets
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I use to take mine to the post office & use the scale they have in the front & then I ended up buying a digital food scale from Walmart. It's pretty accurate and will weight up to 15# rockets.
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I've found a fish/luggage type of scale - one with a handle on top and a hook on the bottom - to be handy for larger rockets. I use it to weigh each section of the rocket individually.
Oh ... and I prefer a mechanical one (though it may not be as accurate). Whenever I needed it, the battery was always dead in the electronic one.
-- Roger
Oh ... and I prefer a mechanical one (though it may not be as accurate). Whenever I needed it, the battery was always dead in the electronic one.
-- Roger
Huh... I never thought of using my fish scale! Thanks man!!!
I can sympathize with you for HPR. Obviously, one could buy a scale like the ones RSOs use to weigh rockets at inspection. I have two scales, and neither is directly useful for my bigger rockets. The postal scale stops at 10 pounds, and the bathroom scale starts at 20 pounds. :rant:
One thing you can try is to weigh yourself, then weight yourself holding the rocket, and subtract the difference. Of course, this is a ballpark weight accurate at most to a half-pound.
One thing you can try is to weigh yourself, then weight yourself holding the rocket, and subtract the difference. Of course, this is a ballpark weight accurate at most to a half-pound.
ParrytheWind
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I tape everything together and using a digital luggage scale and bungee, I hang the rocket from the fin can.
I fill the bathtub halfway with water and mark the level of the water on the side of the tub. Then I push the rocket under the water, making sure to get all of the rocket under but not any of my hands or fingers, and mark the new level. Then I calculate the volume of the difference. From there I can convert to weight knowing how much that water will weight.
Fool proof and highly accurate.
Fool proof and highly accurate.
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You can use one of those fish scales to weigh the water. Just dip the hook into the water and lift the scale. Go slowly and be careful to keep the water from slipping off the hook before you get a good reading.
(BTW ... you're measuring the volume of the rocket, not its weight.)
-- Roger
jrkennedy2
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I have this $10 scale that supposedly handles 100 lbs. Got it from Amazon, item H-110. I load up all the parts and find the cg as well as the weight for a given motor...
I had one of the scales go bad right after I got it but they replaced it pretty quick.
I had one of the scales go bad right after I got it but they replaced it pretty quick.
woferry
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I have a pair of scales I use both at home and bring out to the field and I'm quite happy with both. For very small items I got this scale (weighs up to 10.5 oz), and for heavier things I got this scale (weighs up to 55 lbs). Within the overlap range the numbers I get on both scales match, obviously the resolution on the bigger one isn't as good as the smaller one. Both can be battery powered, though I've found the bigger scale if you leave the batteries in it kills them very quickly (I even had a set explode after only being in for a few months), so I take the batteries out except when I'm using it on the field, and use the wall-wart at home. I've left the batteries in the smaller one with no trouble. But I keep pretty detailed weight measurements of each rocket component to use when I make my .ork files, so anything I can measure with the smaller scale I do, only using the larger one for heavier or bulkier things. The postal scale even has a 'letter/tube stand' which flips up which is handy to keep the rocket from rolling-off the scale, the smaller scale has a lid that can be used for similar capturing of small items. They came out to less than $50 shipped for me, looks like both of the items cost a bit less now than when I ordered them last year.
I tried that, but you have to slice the displaced water off the top of the rest of the water first, and sticking your knife in there to cut it messes with the height the water goes.
I'm measuring volume first, and converting that to weight. The last sentence I mentioned that "From there I can convert to weight knowing how much that water will weight."
Construct_VA
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I use my wife's digital Kitchen scale. Works like a champ.
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But your rocket is not made entirely of water. Consider the case of weighing a balloon in two ways. First use your method with the balloon empty and limp. Then repeat with it blown up and tied off. You will get two weights, neither of them correct.
Of course you and jadebox may be trolling for a laugh, too. (See what I did there?)
N
Of course you and jadebox may be trolling for a laugh, too. (See what I did there?)
N
Good point. So instead of converting the volume of water to weight using density of water, I should first find out the density of rockets and use that. To find the conversion factor for water to rocket density I'll need to start with a large wooden badger, then I'll put....
321_BlastOff
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Volume will do nothing for weight. If I filled my rockets nose cone with lead (say 100lb) the volume would still be the same.
watermelonman
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I like the bathroom scale for yourself, then self plus rocket, and subtract method. I use it for bicycles all the time.
As for precision, if you have an 8lb rocket you are still doing better than the 20% variance allowed on motors!
terryg
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I use this scale. The detached display is really handy for larger or odd shaped rockets.
https://www.amazon.com/gp/product/B00KYA0RC2/?tag=skimlinks_replacement-20
https://www.amazon.com/gp/product/B00KYA0RC2/?tag=skimlinks_replacement-20
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OH MY GOD!! People here can't understand sarcasm I guess. I was trying to be funny, but failed miserably. Not sure if it was me or the audience, but I'll accept responsibility.
Here's some non-sarcastic explanations of my previous posts:
1) Putting a cardboard rocket under water will destroy the rocket, so that's a horrible way to attempt to measure anything about it anyway. I knew this when posting my first reply to this thread thinking this fact alone would clue builders in that this was a non-serious method to how to weigh a rocket.
2) I stated "foolproof and highly accurate" because I knew when posting it that it was neither of those. And to be clear, I mean that it was not a foolproof way to measure weight, nor a highly accurate way (as pointed out a few times already).
3) Bathtubs rarely have sides that are exactly vertical, so it would be seriously difficult to calculate volume of the change in water level. Another hit at the "highly accurate" claim I made.
4) You can't really slice off a top layer of water. Nobody actually tried to tell me that this wouldn't work - yet. But I thought I'd clear it up for those that are figuring out the best way to phrase their reply.
5) The large wooden badger was only a reference to a scene in a Monty Python movie, and not actually an item used to determine the density of rockets.
6) There would be no single density of rockets, as they're made of several different materials used in different quantities.
Here's some non-sarcastic explanations of my previous posts:
1) Putting a cardboard rocket under water will destroy the rocket, so that's a horrible way to attempt to measure anything about it anyway. I knew this when posting my first reply to this thread thinking this fact alone would clue builders in that this was a non-serious method to how to weigh a rocket.
2) I stated "foolproof and highly accurate" because I knew when posting it that it was neither of those. And to be clear, I mean that it was not a foolproof way to measure weight, nor a highly accurate way (as pointed out a few times already).
3) Bathtubs rarely have sides that are exactly vertical, so it would be seriously difficult to calculate volume of the change in water level. Another hit at the "highly accurate" claim I made.
4) You can't really slice off a top layer of water. Nobody actually tried to tell me that this wouldn't work - yet. But I thought I'd clear it up for those that are figuring out the best way to phrase their reply.
5) The large wooden badger was only a reference to a scene in a Monty Python movie, and not actually an item used to determine the density of rockets.
6) There would be no single density of rockets, as they're made of several different materials used in different quantities.
dixontj93060
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The_Lone_Beagle
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My weak attempt at a joke:
"I'm from California, so we just use the scales we weigh our marijuana with to also weigh our rockets."
It's not that far from the truth, I bought a cheap scale from Amazon to weigh my low- and mid-power rockets (and the component parts)...it will weigh up to a kilogram, is digital, and highly accurate (I bought the 500g calibration weight).
Well, reading the reviews of the thing...it appeared to me that pretty much everybody else was buying the same scale to weigh *their* marijuana with.
I like the fish scale idea...no batteries required. When I was a kid, I had a had scale that would measure up to 1 oz, it was perfect for weighing my mini-rockets.
"I'm from California, so we just use the scales we weigh our marijuana with to also weigh our rockets."
It's not that far from the truth, I bought a cheap scale from Amazon to weigh my low- and mid-power rockets (and the component parts)...it will weigh up to a kilogram, is digital, and highly accurate (I bought the 500g calibration weight).
Well, reading the reviews of the thing...it appeared to me that pretty much everybody else was buying the same scale to weigh *their* marijuana with.
I like the fish scale idea...no batteries required. When I was a kid, I had a had scale that would measure up to 1 oz, it was perfect for weighing my mini-rockets.
Construct_VA
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When I first read your original post, I was like WTF! But then I caught on.....Yay me!
EXPjawa
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I thought it was funny - it seemed pretty clear to me that you were making a joke. I just didn't get here in time to add in a "if it weighs the same as a duck..." sort of comment.
