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Bolts That Fly Straight Answered

I just made a crossbow from Lego (not much fire power but it works) and I have been firing pencil from it but they hardly go straight. i tried adding cross fins and even an elevator hoping that it would be stable but it isnt working so if anyone has any ideas fire away.

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blckthng
blckthng

13 years ago

i put staples in the front even tried a little potters clay dosent seem to work also its a little hard to get longer bolts since im already using the 25 cm ones

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NachoMahma
NachoMahma

Reply 13 years ago

. For your application, bolt length is not that critical, but a longer bolt will usually be a heavier bolt, which should help. . I doubt if you can get enough staples in the end of a pencil to do much good - they're awfully light and there's not much space. Try a ball of clay about 1/2-1" (1-1/4-2.-1/2cm) in diameter. You probably don't have enough velocity to worry about making the ball very aerodynamic, but a slight point may help. . You want the CoG as far forward as possible, with a slight drag from the fletching. For your application, the rotation imparted by the fletching on hunting arrows shouldn't be that important - try to get some rotation, if you can, but don't obsess over it.

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Kiteman
Kiteman

13 years ago

Make a bolt from scratch - roll a paper tube, wedge a bolt into the business end.

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blckthng
blckthng

13 years ago

and yeah how exactly do i make the fletchings i tried the metal from the floppy's and a sanded out pcb.

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NachoMahma
NachoMahma

Reply 13 years ago

. Fletching can be made from stiff paper, thin cardboard, plastic, &c. Google "fletching". Make the fletching as light as possible, to keep the center of gravity forward.

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killerjackalope
killerjackalope

13 years ago

Pencils have little weight to them, need weight up front...

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NachoMahma
NachoMahma

13 years ago

. Move the center of gravity of the bolt as far forward as possible. Adding weight to the tip oughta do it. . You probably need more fletching. . Probably need a longer bolt.