Some kind of weight system?

[Goldfish4209]

We need a weight system for a trebuchet. Last time we tried it, we used bench press weights from the Y, and that scaled up to about 1200 pounds. We have a pretty small budget, so what can we get that will scale up further to 1500-200 pounds? We don't have the budget to get a ton of lead or DU, so crazy things like that are out of the picture.

Ideas?

 

[QuixoticOne]

Water is about the safest, cheapest, easiest to move / get rid of / acquire (in some cases), and heaviest material there is. Pump it, drain it, don't worry quite so much if you drop it on your foot (depending on the container and so on), et. al. 1000kg (around 2.2 tons) / cubic meter density isn't too bad; even solid rock / metal isn't more than about 2-4x that density.

Of course the next easiest / cheapest thing to use is (probably moist or rocky) dirt / sand / rocks. Usually you can get into the 2000-3000kg/cubic meter density range that way, and you can get the materials free and dispose of them without too much mess / difficulty. Obviously a little more danger of dropping it on your foot.

Mini black holes work well too, but they're usually considered too dangerous and expensive to work with, though maybe the Large Hadron collider can sell you some cheap surplus ones.

 

[PlasmaBomb]

Do you really want to play with DU?

Quixotics ideas sound good

 

[Gibsons]

go to a junkyard, an old engine block can probably be had pretty cheaply. Not so easy to move around.. .

I like QuixoticOne's idea about water, though, just get a very large bucket or two.

 

[QuixoticOne]

Scrap metal (steel, iron, copper, aluminium) is expensive these days.. like $0.50-$3 / pound or something depending on the metal and situation. Only really iron/steel are particularly heavy anyway. Not what I'd want to pay for by the ton if rocks / water would do.

 

[QuixoticOne]

Yeah we can all claim co-inventorship of the bathtubuchet / tubuchet, bathlista, jacuzzapult,
weapons of mass dowse-truction...
One could achieve some very clean victories with this....wash away your opponents...pond them into dust..

"Cry havoc and let slip the rubber duckies of war..."

"Once more unto the beach, dear friends, once more!"

Actually, I think it has been done commonly with H2O IIRC.

Originally posted by: Gibsons
I like QuixoticOne's idea about water, though, just get a very large bucket or two.

 

[Goldfish4209]

Well, previously, we used gym weights and that worked pretty good. Would it be pretty cheap to build a giant bucket? It'll be swinging around, and we don't want it to be slopping all over the place.

Of course, if we had the means/sheer will to get DU, we'd probably go for DU.

 

[QuixoticOne]

Pretty cheap, certainly compared to the cost (and difficulty) of filling it with metal.

You'd need about the same strength of container whether it held water, rocks, metal, after all, a ton is a ton is a ton and if you swing it around in a flimsy rigging / container, you'll have problems.

All kinds of cheap water tanks are available, collapsable / inflatable, metal, plastic.
You could use surplus 55 gallon drums (55G H2O = 458#, x4 = 1832# of H2O + the weight of the drums and framework).

Obviously a dumpster or similar container would be trivial to line with a pond liner and could contain more water than you'd really want to use.

If you close the top with a lid or pond liner or whatever it isn't going to slosh / leak much, especially if you add some extra space in there to allow for it to slosh a bit and not go over the side.

If you want to spend $1000+ for steel weights or whatever I'm sure you could use those... I don't really see the point compared to something that is much cheaper and easier to handle / get / transport / get rid of.

Originally posted by: Goldfish4209
Well, previously, we used gym weights and that worked pretty good. Would it be pretty cheap to build a giant bucket? It'll be swinging around, and we don't want it to be slopping all over the place.

Of course, if we had the means/sheer will to get DU, we'd probably go for DU.

 

[TonyG]

Well, when a few friends and I built a trebuchet we used an assortment of weights totaling 2000lbs at one point. We used a large quantity of old wheel weights purchased from a tire shop for almost nothing, along with plate weights from the high school we were in at the time, and tractor weights. I built a large basket which held all of the weight, and would have easily accommodated quite a few 5 gallon buckets full of water.
Granted we also had free access to a large quantity of scrap metal.

When the arm was standing straight up it was approximately 30ft at the highest point, and had rungs welded to the side of it so one could climb up it and attach the wrench cable to pull it back down.
This is the only picture that I have of it anymore, and no that is not me in the picture.
Trebuchet

Edit:
What are you using for the throwing arm and the pivot?

 

[Goldfish4209]

Yeah, but we had borrowed weights from the gym, and welding together a few metal bars together to put them on wasn't too hard. Would this be more cost effective? (That's the main question, along with scalability if the gym runs out of weights).

I appreciate the help anyways.

The arm is an aluminium I beam and we have a 2 inch steel rod to hang the weight on, I dunno what the pivot is, but there shouldn't be any problem holding all we can throw at it.

 

[TonyG]

The counter weight box that I built was massively overbuilt for the weight that we had it in it, and I am thinking that if you could find some sort of metal bin you could rig some straps to it and hang it off your arm. Maybe a steel truck toolbox, as you should be able to find an old one for very little money though it might pose a small challenge in to rig it up. A truck toolbox would be easily filled with dirt, rocks, bricks, busted up concrete or whatever else you could find. I am just unsure of how much weight you could actually get into it, though you could weld some bars on top of the box to slide the plate weights onto. It might be worth calling scrapmetal places and explain to them what you are doing and see if they would give you a discount on some scrap lead if you allowed them to come out and watch while you launch it.

 

[QuixoticOne]

Speaking as an occasional diver, I can tell you that in general lead is quite expensive even from scrap yards. Occasionally you may get a deal on stuff free / cheap from somewhere that doesn't usually deal in the material and doesn't really know / care what it is worth on the usual channels. Usually, though, it is costly. What's more, you may not WANT a bunch of scrap lead or even some kinds of scrap metal depending on the nature of it you may have limited local options to dispose of it properly; most landfills won't accept it or will charge you money to do so as either special category trash or environmentally hazardous trash. Only a pretty regular scrap metal type dealer or similar will either pay you or freely take it off your hands when you're done with it.

 

[TonyG]

If you are wanting to be able to hang the weights directly you might look at building some sort of sandbags with handles so you could hang them. We have some sandbags at work that are made from car tire inner tubes that were cut into sections, filled with sand, and closed off on either end by screwing a block of wood to both sides of the tube. The blocks of wood have holes cut in them for handles, and are very easy to hang. I don't know if that makes any sense, but it requires 4 pieces of wood per sandbag, two of them can be smaller strips and two of them can be cut with handles in them, or just one with handles in your case. The handle goes on the front of the sandbag and the strip goes on the back of the sandbag and is screwed to the front strip to effectively sandwich the inner tube between two pieces of wood on either end. Should be cheap enough to build and be fairly effective for additional weight, without taking up too much space.
I am just trying to come up with some cheap and easy options for adding weight. If you have the room for and can add some sort of basket it would be a lot easier to do, though I understand the low budget bit. If we did not have access to lots of free scrap metal we could not have built ours on the same scale.
Our throwing arm was a 5 inch heavy walled pipe which we ended up snapping on the short end when one of the pivot points broke free and the arm bound up momentarily halfway through the swing.
We were throwing 12lb bowling balls which we had epoxied a large eye bolt into one of the finger holes and attached a steel cable to the eyebolt, which had a loop on the other end to go over the hook on the throwing arm. You can normally get an old bowling ball for free from a bowling alley.

 

[Juked07]

Dumpster dive and run baby.

 

[CycloWizard]

I have a 2400-pound car you can have if you can tow it. I'll be donating it to charity otherwise. You can use it for dead weight, a projectile, or even the target.

 

[cheesehead]

Use four 55 gallon drums. Filled with water, you'll have a hair under 1950 lbs.

 

[WoodButcher]

If your using water an old household oil tank, 250 gal, it's steel so hangers or a pivot can be welded on easily. An acrylic window could be installed to view the level and calculate weight. fill and drain valves could be installed and the whole thing could be had cheap.