Track chambers based on precision drift tubes housed inside 30 mm mylar pipe

We describe drift chambers consisting of 3 layers of 30 mm (OD) drift tubes made of double sided aluminized mylar film with thickness 0.125 mm. A single drift tube is self-supported structure withstanding 350 g tension of 50 microns sense wire located in the tube center with 10 microns precision with respect to end-plug outer surface. Such tubes allow to create drift chambers with small amount of material, construction of such chambers doesn't require hard frames. Twenty six chambers with working area from 0.8 x 1.0 to 2.5 x 2.0 m(2) including 4440 tubes have been manufactured for experiments at 70-GeV proton accelerator at IHEP(Protvino).