Upgraded to better batteries and double the number... to 4 batteries..
XTAR 18650 2600mAh 3.7V Protected Sanyo Li-ion cell inside Rechargeable Battery (2-pack)
From Amazon £11.99 for two.
Longer Tube, 4 batteries in a 2S2P confguration and positive take off from the centre maintaining the 8.4v but at ~5200mAh. Burn time achieved = 3hrs approx...
Slight issue with the new tube I ordered, it was supposed to the same size as the one I ordered before but there appears to be a variance on the diameter so the original rubber bungs were too small.
So, new test tube is made up of ( off ebay) :-
21mm solid Rubber Stopper (rubber bung)
21mm 1 Hole Rubber Stopper (rubber bung)
25mm x 2mm CLEAR Acrylic Perspex Plastic TUBE Pipe 1M
The holes in the rubber bung had to be drilled out a bit to accept the cable..Cable thread through the hole with silicon sealant smeared over the cable/bung and left to dry.
Mounted between the wing and cylinders:
The old one and new one..
Wired up to the torch head.