Coil gun with aluminium coil

[thedark]

I plan to make a coil gun with a capacitor approx 400v 6800uF charged at 300v but I have not found copper wire to do it, how efficient would it be to use aluminum strip wire?

[Weston]

Aluminum has ~ 1.6x the resistance of copper. At high frequencies where the skin effect comes in to play the difference is less.

You probably wont see much of a difference in performance. A bigger challenge could be making a good electrical contact to the ends of the wire because you cant solder to Aluminum.

Is this insulated wire? Aluminum can have a mildly insulating oxide coating, but I would not trust it for electrical insulation. At least in the USA, Aluminum wire for electrical use is pretty rare.

[davekni]

A bigger challenge could be making a good electrical contact to the ends of the wire because you cant solder to Aluminum.

Not easily, but aluminum can be soldered by working under a small puddle of oil (or sometimes even flux):
   

/>About 50 years ago I purchased a small coil of aluminum solder which worked reasonably well.  However, I now read that such solder usually contained cadmium, so isn't generally available.

At least in the USA, Aluminum wire for electrical use is pretty rare.

It is rare for branch circuits within buildings due to reliability problems with connections to outlets and switches and light sockets.  (Common in houses built in the later 1960's and early 1970's, but since banned by most codes due to the resulting problems.)  Aluminum is almost universal in high-voltage transmission lines (with steel core for mechanical strength) and common down to the wires leading to building main breaker panels.  For such high power uses, the cost and weight savings of aluminum justify necessary connection technology.

[thedark]

Is this insulated wire? Aluminum can have a mildly insulating oxide coating, but I would not trust it for electrical insulation. At least in the USA, Aluminum wire for electrical use is pretty rare.

The aluminium wire it use in a old arc welder transformer for the insulation double masking tape?

[davekni]

The aluminium wire it use in a old arce welder transformer for the insulation double masking tape?

Masking tape is probably fine, especially given the short duration of voltage.  As Weston pointed out, conductivity is only 60% that of copper, but better than no wire at all

[klugesmith]

Aluminum magnet wire with "painted on" insulation is common, as in MOT's and the arc welder.
Check out this item (soon) on ebay.com: 255717927827.
Or search for "aluminum magnet wire" on ebay or amazon etc.

Connections tightened with screws will be fine for a coilgun.

>>the cost and weight savings of aluminum justify necessary connection technology.

Every few decades, there are papers published about electrical conductors made of sodium metal.
There are obvious problems with corrosion when exposed to air.
But sodium is far ahead of both copper and aluminum, in cost and weight for a given conductance.
Sodium is the cheapest metal on the planet, by volume, when ordered in rail-car quantities.