coilgun barrel questions

[saladtossser]

you guys know the camera flash coil guns everyone likes? would barrel length affect performance at all?

and does a coil 1" long and 0.5" or 0.75" in diameter around a drinking straw/pen sound like a good plan? from the looks of other coilguns on the internet, thats about right.

[Hotwired]

Yes it does.

A simple coilgun loses energy in a long barrel because the projectile just gets one very short kick from the coil to get it moving. Any contact with anything after that will use up its energy.

However if you can stuff enough energy in to not be bothered about that then a long barrel will increase accuracy.

Sounds fine. Stuff a pencil down the straw so you don't squash it while winding

[Recruit]

If you have a drill that can turn slow insert a pencil or other thing in the straw and use the drill to wind it quickly.

I think you got the idea down so good luck.

[saladtossser]

i got something more rigid than a straw, its a plastic tube 3/8" od and about 3/16" id, i read about how air gaps negatively affect performance but will a thicker wall affect anything?

and will putting metal washers to sandwich the coil affect performance? or should i use plastic washers?

edit: http://www.oz.net/~coilgun/theory/externaliron.htm says using metal washers is better, and putting the coil in a iron pipe is good, but a iron barrel is bad