This is a drawing of a D-cell; 
Putting the tube over the cell approximates to this; 
So there needs to be something to support the cell within the tube, idealy this would be a perfect fit but there wasn't one. Though clearplastictube.co.uk. They sold tubes in shorter lengths but not the blue one with that particular pipe wall thickness. 
with an inside dia of 34mm and outside dia of 40mm gives a 2.5mm gap which could be filled in with epoxy resin.
Next there needs to be a washer which can be cut from 5mm acrylic sheet and have a 10mm hole drilled in centre for the +ve terminal of the battery to poke through.
