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Step 4: Weight

The last big step was building the weight. I purchased two lead diving weights and hung it to the throwing arm with a piece of leather belt and metal plates cut from the same bicycle chainguard as the sling release pin.

I cut the belt and attached the metal plates to it, estimated the height of the weight from the bottom to the upper fastening holes and subtracted that amount from the distance between the axle and the base. Then I subtracted a few centimeters (just to be safe) to get the distance between the weight fastening holes and the axle.

You absolutely DO NOT want to MELT LEAD! http://en.wikipedia.org/wiki/Lead#Health_effects

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yeah, everyone has room on their DESK for a DESKTOP trebuchet of this size
You obviously need a better job. :)
nah, im 14. besides, this thing is a freakin behemoth. nobody has room on their desk for this, let alone office codes of conduct would prohibit such devices.
Our office code mandates that fire shall be fought with fire.
so by what you just said, in event of a fire, use a flamethrower? lol xD
by the way, it seems neat, just a bit misnamed. oh , and lets see how long we can make this reply tree!
It shall go on forever
 yes it must!
 It must never end
Yay, im helping!
This was a thing of beauty but it has now fallen to ruin and has been forgotten
can someone convert measurments plz
you do realize this is a trebuchet, don't you?<br />
I'm 75% finished a similar trebuchet - but mine's made with the front forks rather than the back. Forks were removed from the headtube and wedged into a slab of wood as a base (can fit wheels later if the damn thing actually works) I also cleaned and used the hub from the front wheel - cut off all the spokes from the rim and unthreadded from the hub. (saved for some future use) Biggest problem I have currently is attaching the boom to the hub.... currently its off-centered which will probably throw the whole action out of whack. Also, the end of my boom is off-set so the purse comes alongside the shaft, rather than through the forks. Also need to source some kind of weight which will fit through the forks properly - there's not a lot of room for error.
You could always make a heavy lead weight by using the technique in <a rel="nofollow" href="http://www.instructables.com/id/E6QSBN2Z30ES9J4834/">my instructable</a><br/>
That is going to need a lot of solder. One can use other metals too. I have a smaller trebuchet where I used two large sacrifical zing pieces (those used to protect steel boats from corrosion).
Uranium is probably the heaviest metal out there. I hear there a storage problem, so you might get some dirt cheap!
where d'you find the weights? of course, i could use sometthing lying aroud that happens to be heavy enough.... a large electric motor?
just go to our local tire place ask for 2kg of old tier lead alloy u then melt down in a old kitchen pot and cast into foil try like u get fore one serve of lasagna
I bought the weights from a diving shop.
This is great. I've always liked hurling machines AND repurposing junk around the garage. This does both with one SWOOP!
I'm going to make one tonight because I've got nothing else to do.
Well done! Perhaps I missed it in the Instructable but what kind of range are you getting? The pictures are very good, I think, but a video for a project like this is a must! I've built several small trebs as well as one large one but never considered the use of a bicycle frame; I think it's quite creative.
I have not fired it outside yet, so I do not know the maximum range. It shoots a golf ball sized (soft) ball across our office 8 meters with a very flat trajectory. Should do 15 meters outside.
add weels and you git better range
Medieval office warfare - sounds like the right kind of work environment. Nice job!
Wow! What an amazingly awesome idea! I'll have to think a little bit and see if I can convert this idea into a FAT type.
How would you create the tracks for a floating arm treb if you're sticking with parts from a bike?
That's what's going tot take some thinking ;) I have an idea for tracks, I'm just trying to come up with a way to make the weights slide properly :)
Very nice. I was thinking whilst I read this was that if I had a broken bicycle, I will possibly have a unused spindle from the wheel, If I was lucky the quick release type. That would make a great axle. Good job

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